\\houw33883\sstaffor$\temporary\welding inspection\chapter08.doc TableWeld NDE Requirements – ASMEPartial Penetration Branch Conn. Structural Circ. Butt Longitudinal & Sockets/ Full Penet. Permanent & Branch4 Butt Fillets Corner Welds3 Attachments1 NB-5220 NB-5210 NB-5260 NB-5243 NB-5262 Nuclear Class 1 RT 100% + MT or PT ext. & accessible int. surfaces adj. base mtl. for at least 1/2” either side of weld RT 100% + MT or PT ext. & accessible int. surfaces adj. base mtl. for at least 1/2” either side of weld MT or PT 100% OD >4” - RT or UT 100% plus MT or PT OD £4” - MT or PT all ext. and accessible int. & surfaces MT or PT 100% for all perm. attach. to pressure retaining mat’l NC-5222 NC-5212 NC-5261 NC-5242 NC-5262 Nuclear Class 2 RT – 100% RT – 100% MT or PT 100% OD >4” - RT 100% OD £4” - ext. weld surface & access. int. weld surface – MT or PT 100% MT or PT 100% for permanent attach. to pressure retaining mat’l ND-5222 ND-5212 Nuclear Class 3 MT or PT or RT 100% for greater than 2” NPS For welds in greater than 2” NPS see ND-2500 Not Required ND-5222 MT or PT or RT 100% for greater than 2” NPS Not Required 1 – Permanent Attachments – e.g., hangers 3 – F2 – Nonstructural & temporary attachments – e.g., nameplates, lugs 4 – F
e 8-1 E Section III – (Piping Welds Only) (As shown in NX-4436) Nonstructural Special Welds Attachments & Temporary Weld Metal Hard Tube to Weld Edge to Piping Attachments2 Cladding Surfacing Tubesheet Preparations After Testing NB-5272 NB-5273 NB-5274 NB-5130 Per NB-5000 None except removal of same req. 100% MT or PT PT 100% PT 100% except: none req. for valves with inlet connections £4” NPS PT 100% Weld edge prep surfaces in mat’l 2” or more in thickness shall be examined by MT or PT 100% rule as applicable NC-5272 NC-5273 NC-5274 NC-5130 Per NC-5000 None except removal of same req. 100% MT or PT PT 100% PT 100% except: none req. for valves with inlet connections £4” NPS PT 100% Weld edge prep surfaces in mat’l 2” or more in thickness shall be examined by MT or PT 100% rules as applicable ND-5272 ND-5273 ND-5274 Per ND-5000 Not Required PT 100% PT 100% except: none req. for valves with inlet connections £4” NPS PT 100% Not Required rules as applicable Full penetration corner welds, e.g., weld-o-lets, half-couplings Full penetration butt welds; e.g., sweep-o-lets, sock-o-lets (NB-5242, NC-5242(a), ND-5242)
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-0 Page 9.1 GENERAL ................................................................................................ 9-1 9.2 TYPE OF DEFECTS................................................................................. 9-1 9.2.1 Arc Strikes................................................................................................. 9-1 9.2.2 Undercut.................................................................................................... 9-2 9.2.3 Porosity ..................................................................................................... 9-3 9.2.4 Slag Inclusions........................................................................................... 9-5 9.2.5 Tungsten.................................................................................................... 9-7 9.2.6 Cracks........................................................................................................ 9-8 9.2.7 Crater Cracks............................................................................................. 9-10 9.2.8 Incomplete Fusion...................................................................................... 9-11 9.2.9 Inadequate Joint Penetration ...................................................................... 9-13 9.2.10 Unconsumed Insert .................................................................................... 9-15 9.2.11 Concave Root Surface................................................................................ 9-17 9.2.12 Drop-Through............................................................................................ 9-18 9.2.13 Mismatch ................................................................................................... 9-19
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-1 9.1 GENERAL Some discontinuities, or imperfections, that are small or insignificant are permitted by material specifications, codes or standards. The evaluation of discontinuities is an important part of a welding inspector’s job. The following pages cover various types of weld discontinuities, some of their basic causes, their effects on various types of welds and the images they produce on a radiograph. Discontinuities are imperfections in materials. All metals and welds have imperfections that exist in varying degrees. An imperfection which exceeds the acceptable limits is called a defect. Some discontinuities have no effect on the base metal as long as they do not interfere with the welding process, or become large enough to cause the item to fail when in service. The following four items should be evaluated when judging whether an imperfection is to be regarded as an acceptable discontinuity or a defect: 1. Type 2. Size 3. Location 4. Service 9.2 TYPE OF DEFECTS 9.2.1 Arc Strikes Arc strikes are inadvertent changes in the contour of the finished weld or base material resulting from an arc generated by the passage of electrical energy between the surface of the finished weld or bare material and a current source, such as welding electrodes or magnetic inspection prods. (ASME Section IX, QW-492) Many codes and standards do not address arc strikes. Some codes impose specific requirements. Arc strikes are not necessarily harmful. The significance of arc strikes is whether or not the required material thickness is reduced below design requirements, and whether or not cracks have resulted. Most of the engineering materials used for welded construction in power plants have been selected because of their weldability. Because of their good weldability, they are resistant to cracking induced by arc strikes. Most arc strikes are harmless. It should be noted that nondestructive examination equipment may cause arc strikes. This examination method would not be required by the various codes if arc strikes were a major concern. The greatest concern is for arc strikes on the more hardenable, alloyed steel material with medium to high carbon content. These materials are more susceptible to cracking. Austenitic stainless steels are relatively immune to arc strike cracking.
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-2 Surface Arc Strike 9.2.2 Undercut Undercut is another fairly common discontinuity, and is usually caused by the welder using improper techniques, such as too much welding current, faulty electrode manipulation, incorrect electrode size, or incorrect electrode angle. Undercut produces stress risers that can create problems under impact, fatigue, or low temperature service. For non-impact, non-fatigue service, this may be an innocuous discontinuity which can be evaluated on a simple strength of materials basis. Photomacrograph of Undercut on the Outside Diameter
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-3 Depiction of Undercut on Fillet Weld Undercut at Fillet Weld Toe 9.2.3 Porosity Next to slag inclusions, porosity is probably the most commonly seen discontinuity. Porosity is caused during the welding operation by trapped gas in the weld metal before it solidifies. It usually appears round, but may also be cylindrical or elongated in shape. Porosity normally suggests that the welding process is not being properly controlled or that welding consumables are contaminated with gas producing elements. Some of the causes may be insufficient shielding, excessive heat, excessive moisture in electrodes, damp flux, oil, rust, too long of an arc or excessive air movement. On a radiograph, porosity appears as dark spots, or circles, which can be uniformly scattered, in a cluster, or in a line as shown.
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-4 Scattered Porosity (Surface) Radiographic Image of Scattered Porosity Photomacrograph of Porosity
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-5 Radiographic Image of Porosity 9.2.4 Slag Inclusions The most common cause of this type of discontinuity is due to the welding technique used by the welder or failure to properly clean off the slag of previous weld beads. As an example, if a welder does not manipulate his arc correctly, the slag may not float to the surface, and become trapped between passes. Normally, slag entrapment is caused by improperly shaped weld beads. Slag inclusions in a radiograph appear as irregularly shaped dark areas or lines. Surface Slag Inclusion
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-6 Depiction of Slag Inclusions (Subsurface) Photomacrograph of Slag Inclusion
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-7 Radiographic Image of Slag Inclusion 9.2.5 Tungsten Tungsten inclusions occur from the gas tungsten arc welding process when the electrode occasionally touches the work or the molten weld metal and transfers particles of tungsten into the weld deposit. Since tungsten is a very high temperature melting element and is approximately twice the density of steel, it normally is discovered by radiographic examination and is revealed as a very low density (white) spot on the radiographic film. Typically round in nature, the tungsten represents a weld discontinuity which is proper to evaluate by porosity acceptance standards. Photomacrograph of Simulated Tungsten Inclusion
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-8 Radiographic Image of Tungsten Inclusion 9.2.6 Cracks A crack is defined as a fracture-type discontinuity characterized by a sharp tip and a high-ratio length- and height-to-opening displacement. Cracks are linear ruptures of metal under stress. They are often very narrow separations in the weld or adjacent base metal, and usually little deformation is apparent. Weld metal cracks are the result of many factors. For example, cracking occurs when a joint is highly restrained. Also, welds which are too small in size for the parts that are joined may crack when the shrinkage strains during cooling fracture the least ductile location. Cracking also results from poor welding practice, improper preparation of joints, and improper electrodes for matching base material. Inadequate preheat during welding of low-alloy carbon-steel materials promotes cracking of the weld metal or heat-affected zone (HAZ). Cracks in the HAZ are promoted by high restraint of the joints and improper electrode control. (Low-hydrogen procedures are necessary for most low-alloy steels.) High-alloy, austenitic materials such as stainless steel, are more crack resistant than low-alloy carbon steel; however, contamination of the weldment with compounds, such as sulphur, or the selection of the wrong filler material can produce microfissuring and/or centerline cracking. It must be recognized that other types of cracks can form during the service life of a component or weldment. Cracks can be generated by overloading, metal fatigue, intergranular and transgranular stress corrosion, and stress rupture mechanisms, to mention only a few. The radiographic and ultrasonic examination response of such flaws is dependent upon the size and orientation of the flaw.
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-9 Throat Crack Photomacrograph of Crack Radiographic Image of Crack
Section 9 Defects m:\temporary\welding inspection\chapter09-01.doc Welding Inspection Handbook 9-10
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-10 9.2.7 Crater Cracks Crater cracks are shrinkage cracks which occur in the crater of a weld bead. This condition is caused by improper filling of the crater before raising the electrode away from the weld puddle, or by stopping the arc suddenly. Crater cracking is commonly called star cracking, but these cracks can also take the form of centerline, or transverse cracking. Depiction of Crater Cracks Crater Crack
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-11 Longitudinal Crack Propagating From Crater Crack 9.2.8 Incomplete Fusion Incomplete fusion, or “lack of fusion” as it is frequently termed, is described as fusion that is less than complete. It is the failure of adjacent weld metal and base metal or weld metal and weld metal to fuse together. This condition can be caused by improper weaving, low welding current, or too fast a welding speed. Failure to obtain fusion may occur at any point in the weld. Incomplete fusion results when base metal or previously deposited weld is not raised to the melting temperature at the point of weld deposit-prior to weld metal solidification. Failure to remove slag, mill scale and oxides from weld joint surfaces can also prevent the deposited metal from fusing. Incomplete fusion is usually elongated in the direction of welding and may have either rounded or sharp edges, depending on how it is formed.
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-12 Photomacrograph of Incomplete Fusion at the Root Depiction of Incomplete Fusion Photomacrograph of Interbead Incomplete Fusion
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-13 Photomacrograph of Side Wall Incomplete Fusion 9.2.9 Inadequate Joint Penetration Inadequate joint penetration is defined as joint penetration which is less than specified. Although this is the preferred definition, the condition is often referred to as “lack of penetration.” The condition is created when the penetration and fusion of the weld nugget into the joint cavity fail to reach the specified depth within the base metal cross section. For full penetration joints, this can be caused when insufficient root gap is provided during fitup operations or when weld shrinkage causes the established gap to be closed. Another common cause is that an excessive root face or land is provided during joint preparation which precludes penetration to the back side of the joint. For joints welded from both sides, inadequate backgouging prior to welding the second side will result in lack of penetration.
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-14 Depiction of Inadequate Joint Penetration Photomacrograph of Inadequate Penetration
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-15 Radiographic Image of Inadequate Penetration 9.2.10 Unconsumed Insert An unconsumed insert results from preplaced filler metal that is not completely melted and fused in the root joint. This condition is caused by low welding current, improper weaving procedure, improper joint design, and/or welding speed. Considerable welder technique and skill must be developed to assure high quality root beads using inserts, with the gas tungsten arc welding process. Proper welding variables and sufficient skill of the welder will produce melting and fusion of the insert and the side walls of the joint preparation. This results in a satisfactory root bead profile. The next figure shows one common insert shape which has not been fused. There are other insert shapes, rectangular, round and Y, which are commonly used.
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-16 Photomacrograph of Unconsumed Insert Radiographic Image of Unconsumed Insert
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-17 9.2.11 Concave Root Surface A concave root surface, sometimes called “suck back,” is a defect caused by excessive shrinkage of the weld deposited root bead. A concave root occurs when the molten weld solidifies without sufficient filler metal being added to the molten zone to supply the volumetric shrinkage that takes place during solidification. This condition is promoted by excessive amperage, excessive root gaps, and out-of-position welding. It can be caused by improper welder technique, including too slow travel speed, too high current or not adding sufficient filler material. Photomacrograph of Concave Root Surface Radiographic Image of Concave Root Surface
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-18 9.2.12 Drop-Through Weld drop-through is an undesirable sagging or surface irregularity at the weld root. When the molten weld puddle doesn’t solidify quickly enough, it will sag. Generally this condition is caused by too wide a root gap, excessive heat, improper welding technique or a combination of these. Photomacrograph of Drop-Through Radiographic Image of Drop-Through
Section 9 Defects \\houw33883\sstaffor$\temporary\welding inspection\chapter09-02.doc Welding Inspection Handbook 9-19 9.2.13 Mismatch Mismatch refers to the amount of centerline offset of two members in a welded butt joint. Many specifications put a limit on mismatch since it can be a stress raiser and can also cause difficulty in welding. This condition is sometimes referred to as “high-low.” When the members are equal in thickness, the mismatch is equal to the offset measured at the surface; but for differing thicknesses, it is equal to the offset at the centerline and must be computed using the surface offset and the two thicknesses. For pipe, mismatch refers to the internal alignment. Photomacrograph of Mismatch
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-0 Page 10.1 ASME B31.1 ............................................................................................. 10-1 10.1.1 Requirements............................................................................................. 10-1 10.2 ASME B31.3 ............................................................................................. 10-1 10.2.1 Weld Repair............................................................................................... 10-1 10.2.2 Defective Components and Workmanship .................................................. 10-1 10.3 ASME SECTION III ................................................................................. 10-2 10.3.1 Defect Removal ......................................................................................... 10-2 10.3.2 Requirements for Welding Material, Procedures and Welders..................... 10-2 10.3.3 Blending of Repaired Areas........................................................................ 10-2 10.3.4 Examination of Repair Welds..................................................................... 10-2 10.3.4.1 Class 1 ....................................................................................................... 10-2 10.2.4.2 Class 2, 3, MC & NF Supports................................................................... 10-2 10.3.4.3 Class 1, 2 and 3 Only.................................................................................. 10-3 10.3.5 PWHT of Repaired Areas........................................................................... 10-3 10.3.6 Elimination of Surface Defects................................................................... 10-3 10.4 AWS D1.1 ................................................................................................. 10-4 10.4.1 Repair of Weld Defects.............................................................................. 10-4 10.4.2 Members Distorted by Welding .................................................................. 10-4 10.4.3 Prior Engineering Approval........................................................................ 10-4 10.4.4 Inaccessibility of Unacceptable Welds......................................................... 10-5 10.4.5 Restoration of Unacceptable Holes by Welding .......................................... 10-5 10.4.6 Surface Finishes of Butt Welds................................................................... 10-6
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-1 10.1 ASME B31.1 10.1.1 Requirements (A) Defect Removal. All defects in welds or base materials requiring repair shall be removed by flame or arc gouging, grinding, chipping, or machining. Preheating may be required for flame or arc gouging on certain alloy materials of the air hardening type in order to prevent surface checking or cracking adjacent to the flame or arc gouged surface (B) Repair Welds. Repair welds shall be made in accordance with qualified welding procedures using qualified welders or welding operators (see Para. 127.5), recognizing that the cavity to be repaired may differ in contour and dimension from a normal joint preparation and may represent different restraint conditions. The types, extent, and method of examination shall be in accordance with Table 136.4. For repairs to welds, the minimum examination shall be the same method that revealed the defect in the in the original weld. For repairs to base material, the minimum examination shall be the same as required for butt welds. (127.4.11) 10.2 AMSE B31.3 10.2.1 Weld Repair A weld defect to be repaired shall be removed to sound metal. Repair welds shall be made using a welding procedure qualified in accordance with para. 328.2.1, recognizing that the cavity to be repaired may differ in contour and dimensions from the original joint. Repair welds shall be made by welders or welding operators qualified in accordance with para. 328.2.1. Preheating and heat treatment shall be required for the original welding. See also para. 341.3.3. (328.6) 10.2.2 Defective Components and Workmanship An examined item with one or more defects (imperfections of a type or magnitude exceeding the acceptance criteria of this Code) shall be repaired or replaced; and the new work shall be reexamined by the same methods, to the same extent, and by the same acceptance criteria as required for the original work. (341.3.3)
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-2 10.3 ASME SECTION III 10.3.1 Defect Removal Defects may be removed by mechanical means or by thermal gouging processes. The area prepared for repair shall be examined by a liquid penetrant or magnetic particle method in accordance with NX-5110 and meet the acceptance standards of NX-5340 or NX-5350. This examination is not required where defect removal essentially removes the full thickness of the weld and where the backside of the weld joint is not accessible for removal of examination materials. (NX-4453.1) 10.3.2 Requirements for Welding Material, Procedures and Welders The weld repair shall be made using the welding material, welders, and welding procedures qualified in accordance with NX-4125 and NX-4300. (NX-4453.2) 10.3.3 Blending of Repaired Areas After repair, the surface shall be blended uniformly into the surrounding surface. (NX-4453.3) 10.3.4 Examination of Repair Welds 10.3.4.1 Class 1 The examination of a weld repair shall be repeated as required for the original weld except that when the defect was originally detected by the liquid penetrant or magnetic particle method, and when the repair cavity does not exceed the lesser of 3/8 in. or 10% of the thickness, it need only be reexamined by the liquid penetrant or magnetic particle method. (NB-4453.3 (a)) 10.2.4.2 Class 2, 3, MC & NF Supports The examination of a weld repair shall be repeated as required for the original weld, except that it need only be reexamined by the liquid penetrant or magnetic particle method when the unacceptable indication was originally detected by the liquid penetrant or magnetic particle method and when the repair cavity does not exceed the following: (1) 1/3 t for tw £ 3/4 in. (2) 1/4 in. for 3/4 in. < tw £ 2-1/2 in. (3) the lesser of 3/8 in. or 10%t for tw > 2-1/2 in. Where tw equals the thickness of the weld. (NX-4453.4)
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-3 10.3.4.3 Class 1, 2 and 3 Only When repairs to welds joining P-No. 1 and P-No. 3 materials require examination by radiography, but construction assembly-prevents meaningful radiographic examination, ultrasonic examination may be substituted provided: (a) the weld had been previously radiographed and met the applicable acceptance standards; (b) the ultrasonic examination is performed using a procedure in accordance with Article 5 of Section V to the acceptance standards of NB, NC, ND-5330 as applicable. (c) the substitution is limited to Category A and B welds in vessels and similar type welds in other items. The absence of suitable radiographic equipment is not justification for the substitution. (NB, NC, ND-4453.4) 10.3.5 PWHT of Repaired Areas The area shall be heat treated in accordance with NX-4620. (See Section 14 of this handbook for PWHT requirements.) (NX-4453.5) 10.3.6 Elimination of Surface Defects Weld metal surface defects may be removed by grinding or machining and need not be repaired by welding, provided that the requirements of (a) through (c) below are met. (a) The remaining thickness of the section is not reduced below that required by NX-3000. (b) The depression, after defect elimination, is blended uniformly into the surrounding surface. (c) The area is examined by a magnetic particle or liquid penetrant method in accordance with NX-5110 after blending and meets the acceptance standards of NX-5300 to ensure that the defect has been removed or the indication reduced to an acceptable limit. Defects detected by visual or volumetric method and located on an interior surface need only be examined by the method which initially detected the defect when the interior surface is inaccessible for surface examination. (NX-4452)
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-4 10.4 AWS D1.1 10.4.1 Repair of Weld Defects The removal of weld metal or portions of the base metal may be done by machining, grinding, chipping, or gouging. It shall be done in such a manner that the remaining weld metal or base metal is not nicked or undercut. Oxygen gouging shall not be used on quenched and tempered steels. Unacceptable portions of the weld shall be removed without substantial removal of the base metal. The surface shall be cleaned thoroughly before welding. Weld metal shall be deposited to compensate for any deficiency in size. (5.26) 1a. The contractor has the option of either repairing an unacceptable weld or removing and replacing the entire weld, except as modified by 5.26.3. The repaired or replaced weld shall be retested by the method originally used, and the same technique and quality acceptance criteria shall be applied. If the contractor elects to repair the weld, it shall be corrected as follows; lb. Overlap, Excessive Convexity or Excessive Reinforcement. Excessive weld metal shall be removed. 1c. Excessive Concavity of Weld or Crater, Undersize Welds, Undercutting. The surfaces shall be prepared (see 5.30) and additional weld metal deposited. 1d Incomplete Fusion, Excessive Weld Porosity, or Slag Inclusions, . Unacceptable portions shall be removed (see 5.26) and rewelded. 1e. Cracks in Weld or Base Metal. The extent of the crack shall be ascertained by use of acid etching, magnetic particle inspection, dye penetrant inspection, or other equally positive means; the crack and sound metal 2 in. beyond each end of the crack shall be removed, and rewelded. (5.26.1) 10.4.2 Members Distorted by Welding Members distorted by welding shall be straightened by mechanical means or by application of a limited amount of localized heat. The temperature of heated areas as measured by approved methods shall not exceed 1100°F for quenched and tempered steel nor 1200°F for other steels. The part to be heated for straightening shall be substantially free of stress and from external forces, except those stresses resulting from the mechanical straightening method used in conjunction with the application of heat. (5.26.2) 10.4.3 Prior Engineering Approval Prior approval of the Engineer shall be obtained for repairs to base metal (other than those required by 5.15), repair of major or delayed cracks, repairs to electroslag and electrogas welds with internal defects, or for a revised design to compensate for deficiencies. The Engineer shall be notified before the welded members are cut apart. (5.26.3)
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-5 10.4.4 Inaccessibility of Unacceptable Welds If, after an unacceptable weld has been made, work is performed which has rendered that weld inaccessible or has created new conditions that make correction of the unacceptable weld dangerous on ineffectual, then the original conditions shall be restored by removing the welds or members, or both, before the corrections are made. If this is not done, the deficiency shall be compensated for by additional work performed according to an approved revised design. (5.26.4) 10.4.5 Restoration of Unacceptable Holes by Welding Except where restoration by welding is necessary for structural or other reasons, punched or drilled mislocated holes may be left open or filled with bolts. When the base metal with mislocated holes is restored by welding, the following requirements apply: (1) Base metal not subjected to cyclic tensile stress may be restored by welding, provided the contractor prepares and follows a repair WPS. The repair weld soundness shall be verified by the appropriate nondestructive tests, when such tests are specified in the contract documents for groove welds subject to compression or tension stress.. (2) Base metal subject to cyclic tensile stress may be restored by welding provided: (a) The Engineer approves repair by welding and the repair WPS. (b) The repair WPS is followed in the work and the soundness of the restored base metals is verified by the NDT method(s) specified in the contract documents for examination of tension groove welds or as approved by the Engineer. (3) In addition to the requirements of (1) and (2), when holes in quench and tempered base metals are restored by welding: (a) Appropriate filler metal, heat input, and postweld heat treatment (when PWHT) is required shall be used. (b) Sample welds shall be made using the repair WPS. (c) Radiographic testing of the sample welds shall verify that weld soundness conforms to the requirements of 6.12.2.1. (d) One reduced section tension test (weld metal); two side bend tests(weld metal); and three Charpy V-notch (CVN) impact tests of the heat-affected zone (coarse grained area) removed from the sample welds shall be used to demonstrate that the mechanical properties of the repaired area conform to the specified requirements of the base metal. See Annex III for Charpy testing requirements. (4) Weld surfaces shall be finished as specified in 5.24.4.1. (5.26.5)
Section 10 Repair of Weld Defects m:\temporary\welding inspection\chapter10.doc Welding Inspection Handbook 10-6 10.4.6 Surface Finishes of Butt Welds (1) Flush Surfaces. Butt welds required to be flush shall be finished so as not to reduce the thickness of the thinner base metal or weld metal by more than 1/32 in. or 5% of the thickness, whichever is less. Remaining reinforcement shall not exceeds 1/32 in. in height. However, all reinforcement must be removed where the weld forms part of a faying or contact surface. All reinforcement shall blend smoothly into the plate surfaces with transition areas free from undercut. (5.24.4.1) (2) Finish Methods and Values. Chipping and gouging may be used provided these are followed by grinding. Where surface finishing is required, roughness values (see ANSI B46.1) shall not exceed 250 microinches. Surfaces finished to values of over 125 microinches through 250 microinches shall be finished parallel to the direction of primary stress. Surfaces finished to values of 125 microinches or less may be finished in any direction. (5.24.4.2)
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-0 Page 11.1 ASME SECTION III (CLASS 1, 2, 3 AND MC)....................................... 11-1 11.1.1 General ...................................................................................................... 11-1 11.1.2 Elimination and Repair of Defects .............................................................. 11-1 11.1.3 Defect Removal (All Product Forms) ......................................................... 11-1 11.2 ASME/ANSI B31.1 ................................................................................... 11-1 11.2.1 Examination and Repair of Material Other Than Bolting............................. 11-1 11.3 ASME/ANSI B31.3 ................................................................................... 11-1 11.3.1 Examination and Repair of Material Other Than Bolting............................. 11-1 Table 11-1 Elimination of Surface Defects (By Mechanical Means) ASME Section III.................................................................. 11-2 Table 11-2 Repair By Welding (ASME Section III)................................. 11-5
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-1 11.1 ASME SECTION III (CLASS 1, 2, 3, AND MC) 11.1.1 General ASME Section III contains the repair of base material by product form. Table 11-1 covers repair by mechanical means, other than welding. Table 11-2 covers repair by welding. Note: The requirements in this section do not apply to materials manufacturers for the product forms listed. 11.1.2 Elimination and Repair of Defects Material originally accepted on delivery in which defects exceeding the limits of NX-2500 are known or discovered during the process of fabrication or installation is unacceptable. The material may be used provided the condition is correct in accordance with the requirements of NX-2500 for the acceptable product form, except: (a) the limitation on the depth of the weld repair does not apply; (b) the time of examination of the weld repairs to weld edge preparation shall be in accordance with NB, NC, ND, NE-5130, and NF-5120 (NX-4130). 11.1.3 Defect Removal (All Product Forms) The defect shall be removed or reduced to an acceptable size by suitable mechanical or thermal cutting or gouging methods and the cavity prepared for repair. (NX-4211.1) When thermal cutting is performed, consideration shall be given to preheating the material using an appropriate preheat schedule such as given in ASME Boiler and Pressure Vessel Code, Section III, Appendix D. (NX-2539-1) 11.2 ASME/ANSI B31.1 11.2.1 Examination and Repair of Material Other Than Bolting Unacceptable defects may be repaired as permitted by the material specification. 11.3 ASME/ANSI B31.3 11.3.1 Examination and Repair of Material Other Than Bolting Unacceptable defects may be repaired as permitted by the material specification.
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-2 Table 11-1 Elimination of Surface Defects (by Mechanical Means) ASME Section III Code Class Product Form NB Plate (A) Unacceptable surface defects shall be removed by grinding or machining, provided the requirements of (1) through (4) below are met. (1) The remaining thickness of the section is not reduced below that required by NB-3000. (2) The depression, after defect elimination, is blended uniformly into the surrounding surface. (3) After defect elimination, the area is re-examined by the magnetic particle method in accordance with NB-2545 or the liquid penetrant method in accordance with NB-2546 to ensure that the defect has been removed or the indication reduced to an acceptable size. (4) Areas ground to remove oxide scale or other mechanically caused impressions for appearance or to facilitate proper ultrasonic testing need not be examined by the magnetic particle or liquid penetrant test method. (B) When the elimination of the defect reduces the thickness of the section below the minimum required to satisfy NB-3000, the product shall be repaired in accordance with NB-2539. (See Table 11-2) (NB-2538) NC, ND, NE Plate (A) Unacceptable surface defects may be removed by grinding or machining provided the requirements of (1) and (2) below are met. (1) The remaining thickness of the section is not reduced below the minimum required by the design; (2) the depression, after (continued) defect elimination, is blended uniformly into the surrounding surface. (B) When the elimination of the defect reduces the thickness of the section below the minimum required by the design, the material shall be repaired in accordance with NX-2539. (See Table 11-2) (NX-2538) NB Forgings (A) Unacceptable surface defects shall be removed by grinding or machining, provided the requirements of (1) through (4) below are met. (1) The remaining thickness of the section is not reduced below that required by NB-3000. (2) The depression, after defect elimination, is blended uniformly into the surrounding surface. (3) After defect elimination, the area is re-examined by the magnetic particle method in accordance with NB-2545 or the liquid penetrant method in accordance with NB-2546 to ensure that the defect has been removed or the indication reduced to an acceptable size. (4) Areas ground to remove oxide scale or other mechanically caused impressions for appearance or to facilitate proper ultrasonic testing need not be examined by the magnetic particle or liquid penetrant test method. (B) When the elimination of the defect reduces the thickness of the section below the minimum required to satisfy NB-3000, the product shall be repaired in accordance with NB-2539. (See Table 11-2) (NB-2548)
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-3 Table 11-1 (Cont’d) Code Class Product Form NC, ND, NE Forgings (A) Unacceptable surface defects may be removed by grinding or machining provided the requirements of (1) and (2) below are met: (1) the remaining thickness of the section is not reduced below the minimum required by the design; (2) the depression, after defect elimination, is blended uniformly into the surrounding surface. (B) When the elimination of the defect reduces the thickness of the section below the minimum required by the design-, the material shall be repaired in accordance with NX-2539. (See Table 11-2) (NX-2548) NB, NC, ND, NE Pipe1 NX-2550 and NX-2560 1.0 Unacceptable surface defects may be removed by grinding or machining provided that: 1.1 The remaining thickness is not reduced below that specified. 1.2 The depression, after defect elimination, shall be blended uniformly into the surrounding surfaces. 1.3 After defect elimination, the area shall be re-examined by the method which originally disclosed the defect to assure that the defect has been removed or reduced to an acceptable size. 1.4 If the elimination of the defect reduces the wall thickness below the minimum specified, the product may be repair welded in accordance with ASME Section II, Part A, Section 8.RL. (See Table 11-2) (SA655, 9.RM) NB, NC, ND, NE Fittings2 NX-2553 and NX-2560 1.0 Surface defects may be removed by grinding or machining provided that: 1.1 The remaining thickness is not reduced below that specified. 1.2 The depression, after defect ..elimination, shall be blended uniformly into the surrounding surfaces. 1.3 After defect elimination, the area shall be re-examined by the method which originally disclosed the defect to assure that the defect has been removed or reduced to an acceptable size. 1.4 If the elimination of the defect reduces the wall thickness below the minimum specified, the product may be repair welded in accordance with ASME Section II, Part A, Section 8.RL. (See Table 11-2) (SA-652, 9.RM) 1 Includes seamless and welded without filler metal (NX-2550) and welded with filler metal (NX-2560). 2 Includes seamless and welded without filler metal (NX-2553) and welded with filler metal (NX-2560).
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-4 Table 11-1 (Cont’d) Code Class Product Form NB, NC, ND, NE Castings NX-2570 15.1 Unacceptable surface defects shall be removed by grinding or machining provided that: 15.1.1 The remaining thickness of the section is not reduced below that required by the specification or drawing. 15.1.2 The depression, after defect elimination, is blended uniformly into the surrounding surface. 15.1.3 After defect elimination, the area is re-examined by the magnetic particle method in accordance with RW, or the liquid penetrant method in accordance with RX to assure that the defect has been removed or the indication has been reduced to an acceptable size. 15.1.4 If the elimination of the defect reduces the section thickness below the minimum required by the specification or drawing, the casting may be repaired in accordance with ASME Section II, Part A, Sections 8 to 14 (RL). (See Table 11-2) (SA-613, 15.RM)
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-5 Table 11-2 Repair by Welding (ASME Section III) Code Class Product Form NB, NC, ND, NE Plate/Forgings Defect Removal – The defect shall be removed or indication reduced to an acceptable size by suitable mechanical or thermal cutting or gouging methods and the cavity prepared for repair (NX-4211.1). (NX-2539.1) Qualification of Welding Procedures and Welders – The welding procedures and welders or welding operators shall be qualified in accordance with NX-4000 and Section IX. (NX2539.2) Blending or Repaired Areas – After repair, the surface shall be blended uniformly into the surrounding surface. (NX-2539.3) Examination of Repair Welds – Each repair weld shall be examined by the magnetic particle method (NX2545) or by the liquid penetrant method (NX-2546). In addition, when the depth of the repair cavity exceeds the lesser of 3/8 in. or 10% of the section thickness, the repair weld shall be radiographed after repair in accordance with NX-5000. The penetrometer and the acceptance standards for radiographic examination of repair welds shall be based on the section thickness at the repair area. (NX-2539.4) Heat Treatment After Repairs – The product shall be heat treated after repair in accordance with the heat treatment requirements of NX-4620 . (NX-2539.5) NB Material Report Describing Defects and Repairs – Each defect repair exceeding in depth the lesser of 3/8 in. or 10% of the section thickness shall be described in the Certified Material Test Report. The Certified Material Test report for each piece shall include a chart which shows the location and size of the prepared cavity, the welding material identification, the welding procedure, the heat treatment, and the examination results, including radiographic film. (NB-2539.6) NC, ND, NE Material Report Describing Defects and Repairs – Each defect repair that is required to be radiographed shall be described the Certified Material Test Report. The Certified Material Test Report for each piece shall include a chart which shows the location and size of the prepared cavity, the welding material identification, the welding procedure, the heat treatment and a report of the results of the examinations, including radiographic film. (NX2539.6) NB Repair of Cladding by Welding – The Material Manufacturer may repair defects in cladding by welding, provided the requirements of (a) through (d) below are met. (NB-2539.7) (a) Qualification of Welding Procedures and Welders. The welding procedure and the welders or welding operators shall be qualified in accordance with NB-4000 and with Section IX. (b) Defect Removal and Examination of Cavity. The defect shall be removed, and the cavity prepared for repair shall be examined by the liquid penetrant method (NB-2546). (c) Examination of Repaired Areas. The repaired area shall be examined by a liquid penetrant method (NB-2546). (d) Report of Repairs. Each defect repair shall be described in the Certified Material Test Report for ..each piece, including a chart which shows the location and size of the repair, the welding material identification, welding procedure, heat treatment, and examination
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-6 results.
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-7 Table 11-2 (Cont’d) Code Class Product Form NB, NC, ND, NE Pipe1 Repair by Welding (NX-2551 or NX-2560) When permitted by the basic material specification, repair by welding may be made provided the requirements of the following subparagraphs are met: Welding Qualification, Records and Identifying Stamps – The requirements of SA-655 Sections 5.2, 5.3, and 5.4 shall apply to weld repairs. Welding Materials – The welding materials used for the repair shall be tested and certified in accordance with SA-655 paragraph 5.8. Blending, of Repaired Areas – After repair, the surface shall be blended uniformly into the surrounding surface. Examination of Repair Welds – Each repair weld shall be examined by the magnetic particle method in accordance with the requirements of SA-655, Section 14.RW, or by the liquid penetrant method in accordance with the requirements of SA-655 Section 15.RX. In addition, repair cavities, the depth of which exceeds the lesser of 3/8 in. (9.5 mm) or 10% of the nominal wall thickness, shall be radiographed after repair in accordance with SA655 Section 16.RY. The penetrometer for radiographic examination of repair welds shall be based on the wall thickness at the repair area. Heat Treatment After Repairs – The material shall be heat treated after repair in accordance with the heat treatment requirements of SA-655, Section 5.7. Material Report Describing Defects and Repairs – Each defect repair exceeding in depth the lesser of 3/8 in. (9.5 mm) or 10% of the nominal wall thickness shall be described in the Certified Materials Test Report. The Certified Materials Test Report for each piece shall include a chart that shows the location and size of the prepared cavity, the welding material identification, the welding procedure, the heat treatment, and the examination results, including radiographic film. (SA-655, 8.RL ASME Section II, Part A) NB, NC, ND, NE Fittings1 Repair by Welding (NX-2553 or NX-2560) When permitted by the basic material specification, repair -by welding may be made provided the requirements of the following subparagraphs are met: Welding Qualifications, Records, and Identifying Stamps – The requirements of SA652, Sections 5.2 and 5.4 shall apply to weld repairs. Welding Materials – The welding materials used for the repair shall be tested and certified in accordance with SA-652, paragraph 5.8. Blending of Repaired Areas – After repair, the surface shall be blended uniformly into the surrounding surface. Examination of Repair Welds – Each repair weld shall be examined by the magnetic particle method in accordance with the requirements of SA-652, Section 14.RW or by the liquid penetrant method in accordance with the requirements of SA-652, Section 15.R.X. In addition, repair cavities, the depth of which exceeds the lesser of 3/8 in. (9.5 mm) or 10% of the nominal wall thickness, shall be radiographed after repair in accordance with ASME Section V, Article 2, and the acceptance standards of SA-652, Section 16 RY. The penetrometer for radiographic examination of repair welds shall be based on the wall thickness at the repair area. 1 Includes seamless, seam welded, with and without filler metal.
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-8 Table 11-2 (Cont’d) Code Class Product Form NB, NC, ND, NE Fittings1 Heat Treatment After Repairs – The material shall be heat treated after repair in accordance with the heat treatment requirements of SA-652, -paragraph 5.7. Material Report Describing Defects and Repairs – Each defect repair exceeding the lesser of 3/8 in. (9-5 mm) or 10% of the nominal wall thickness shall be described in the Certified Materials Test Report. The Certified Materials Test Report for each piece shall include a chart that shows the location and size of the prepared cavity, the welding material identification, the welding procedure, the heat treatment, and the examination results, including radiographic film. (SA-652, 8.RL, ASME Section VI, Part A) NB, NC, ND, NE Castings Repair by Welding (NX-2570) Repairs by welding may be made provided the requirements of the following subparagraphs are met: Welding Qualifications, Weld Materials, Records and Identifying Stamps – Shall be in accordance with the requirements of SA-613, section 10.RL. NB, NC, Blending of Repaired Areas After repair, the surface shall be blended uniformly into the surrounding surface. Examination When repair welds require examination, each repair weld shall be examined by the magnetic particle method in accordance with the requirements of Section 19 (RW) or by the liquid penetrant method in accordance with the requirements of Section 20 (RX). In addition, when volumetric examination is specified in the order for the original casting, repair cavities, the depth of which exceeds the lesser of 3/8 in. (9.5 mm) or 10% of the nominal wall thickness, shall be radiographed after repair in accordance with Section 21 (RY) except that weld slag, including elongated slag, shall be considered as inclusions under Category B of the applicable reference radiographs. The total area of all inclusions, including slag inclusions, shall not exceed the limits of the applicable severity level of Category B of the reference radiographs. The penetrometer and the acceptance standards for radiographic examination of repair welds shall be based on the actual section thickness at the repair area. Examination of Repair Welds Inlet Piping Connection of Two Inches and Less – Repair welds in pumps and valves of P-No. I and P-No. 8 material require no examination. Other repair welds shall be examined by the magnetic particle method (SA-613; 19RW) or by the liquid penetrant method (SA-613; 20RX). In addition, repair welds in cavities the depth of which exceed the lesser of 3/8 in. or 10% of the section thickness shall be radiographed in accordance with (SA-613; 21RY). Inlet Piping Connections Over Two Inches – Each repair weld shall be examined by the magnetic particle method (SA-613; 19RW) or by the liquid penetrant method (SA-613; 20RX). In addition, repair welds in cavities the depth of which exceed the lesser of 3/8 in. or 10% of the section thickness shall be radiographed in accordance with (SA-613; 21 RY). 1 Includes seamless, seam welded, with and without filler metal.
Section 11 Base Metal Repair by (Product Form) m:\temporary\welding inspection\chapter11.doc Welding Inspection Handbook 11-9 Table 11-2 (Cont’d) Code Class Product Form ND Castings Examination of Repair Welds (All Sizes) (a) When magnetic particle or liquid penetrant examination of the casting is required, each repair shall be examined by the magnetic particle method (SA-613; 19RW) or by the liquid penetrant method (SA-613; 20RY). (b) When radiography of the casting is required, repair welds in cavities the depth of which exceeds the lesser of 3/8 in. or 10% of the section thickness shall be radiographed in accordance with (SA-613; 21RY). (c) When partial radiography of a casting is required, repairs located in an area of the casting which is not covered by radiography need only be examined by the magnetic particle method (SA-613; 19RW) or by the liquid penetrant method (SA-613; 20RX). NB, NC, ND, NE Heat Treatment After Repairs – The material shall be heat treated after repair in accordance with the heat treatment requirements of Section III of the Code, Subsubarticle NB-4620, except that the heating and cooling limitations of NB-4623 do not apply. (13.RL SA-613, ASME Section II) Material Report Describing Defects and Repairs – Each defect repair exceeding in depth the lesser of 3/8 in. (9.5 mm) or 10% of the nominal wall thickness shall be described in the Certified Materials Test Report for each piece shall include a chart that shows the location and size of the prepared cavity, the welding material identification, the welding procedure, the heat treatment, and the examination results, including radiographic film, when radiographic is specified in the order for the original casting. NB, NC, ND, NE, NF Bolts/Studs/Nuts Repair by welding is not permitted. (NX-2580; SA-614 ASME Section II, Part A)
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-0 Page 12.1 SHIELDED METAL ARC WELDING (SMAW)............................................................. 12-1 12.1.1 Advantages...................................................................................................................... 12-2 12.1.2 Disadvantages.................................................................................................................. 12-2 12.2 GAS TUNGSTEN ARC WELDING (GTAW)................................................................. 12-1 12.2.1 Advantages...................................................................................................................... 12-2 12.2.2 Disadvantages.................................................................................................................. 12-2 12.3 GAS METAL ARC WELDING (GMAW)....................................................................... 12-1 12.3.1 Advantages...................................................................................................................... 12-2 12.3.2 Disadvantages.................................................................................................................. 12-2 12.4 FLUX CORED ARC WELDING (FCAW) ...................................................................... 12-1 12.4.1 Advantages...................................................................................................................... 12-2 12.4.2 Disadvantages.................................................................................................................. 12-2 12.5 SUBMERGED ARC WELDING (SAW) ......................................................................... 12-1 12.5.1 Advantages...................................................................................................................... 12-2 12.5.2 Disadvantages.................................................................................................................. 12-2 12.6 STUD WELDING (SW).................................................................................................. 12-1 12.6.1 Advantages...................................................................................................................... 12-2 12.6.2 Disadvantages.................................................................................................................. 12-2
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-1 12.1 SHIELDED METAL ARC WELDING (SMAW) Figure 12.1 – Shielded Metal Arc Welding 12.1.1 Advantages 1 The equipment is relatively simple, inexpensive and portable. 2 The shielding gas, provided by the burning flux, is less sensitive to wind and drafts when compared to a process with an external shielding gas. 3 It is very versatile. 4 It can be used in limited access areas. 5 It is suitable for most common metals and alloys. 6 It is capable of producing X-ray quality welds. 7 Deposition rates are higher than the gas tungsten arc welding process. 12.1.2 Disadvantages 1 Deposition rate is low compared too GMAW or FCAW because of multiple stops, due to electrode length. 2 The weld is covered by a layer of slag that must be removed.
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-2 12.2 GAS TUNGSTEN ARC WELDING (GTAW) Figure 12.2 – Gas Tungsten Arc Welding 12.2.1 Advantages 1 Capable of welding thin material. 2 Controls heat input extremely well because the heat source and the filler material are separately controlled. 3 Welds can be made without adding filler material by fusing the base metals together. 4 Full penetration welds that are welded from one side only can be made. 5 Produces X-ray quality welds. 6 Recommended for materials which form refractory oxides, like aluminum and magnesium. 12.2.2 Disadvantages 1 Cost of equipment and shielding gas is high. 2 Deposition rate is slow. 3 A high degree of operator skill is required to produce quality welds. 4 Fitup tolerances are restrictive. 5 Exposure of hot filler material to the atmosphere through faulty technique, can cause weld metal contamination.
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-3 12.3 GAS METAL ARC WELDING (GMAW) Figure 12.3 – Gas Metal Arc Welding (Globular Mode) 12.3.1 Advantages 1 Deposition rate is high. 2 Costs are low because there is less electrode waste, no slag removal and welder down-time due to changing electrodes is less compared to SMAW. 3 Smoke and fumes are minimal. 4 Obtains deeper penetration than SMAW or GTAW. 5 It is very versatile. (All position process for carbon, low alloy and stainless steels.) 12.3.2 Disadvantages 1 Cost of machinery, shielding gas, and maintenance is high. 2 Accessibility to the welding joint is restrictive because of the size of the gun. 3 Shielding gas is sensitive to wind and drafts. 4 The length of the welding lead is restrictive. 5 The equipment is not as portable as SMAW.
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-4 12.4 FLUX CORED ARC WELDING (FCAW) Figure 12.4 – Flux Cored Arc Welding 12.4.1 Advantages 1 Deposition rate is high. 2 Costs are low because there is less electrode waste, welder down-time due to changing electrodes is less, and one can utilize economical joint designs. 3 Compared to SMAW, distortion of the material is less. 4 Excellent profile for horizontal fillet welds. 12.4.2 Disadvantages 1 Cost of machinery and maintenance is high. 2 Electrode is more expensive than GMAW. 3 Length of welding lead is restrictive. 4 Not as portable as SMAW. 5 Produces more smoke and fumes than GMAW. 6 Slag covering that must be removed.
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-5 12.5 SUBMERGED ARC WELDING (SAW) Figure 12.5 – Submerged Arc Welding 12.5.1 Advantages 1 High deposition rate. 2 Easily automated. 3 High utilization of electrode wire. 4 Weld puddle is submerged, eliminating the need for protective clothing. 5 Little or no smoke. 12.5.2 Disadvantages 1 Limited welding positions (flat and horizontal). 2 High heat input that could be detrimental to some base metals. 3 Welding puddle not visible. 12.6 STUD WELDING Stud welding is a two-step process. In the first step, a stud is placed in the gun with a ferrule, or arc shield, then held against the workpiece until the arc heats the base metal and stud to the proper temperature. In the second step, the heated surfaces are forced together under pressure. When depressing the trigger on the stud gun, an automatic welding cycle begins and a solenoid lifts the stud off the work, creating an arc between the stud and workpiece. A timer then shuts off the current, and a main spring in the gun plunges to stud into the molten pool created by the arc. Stud welding may be used in any position, and on all types of equipment and structures. AWS D1.1 requires welded studs to show a full 360 degree flash around to stud base. Studs lacking this requirement usually must be removed, or repaired by manual welding.
Section 12 Welding Processes m:\temporary\welding inspection\chapter12.doc Welding Inspection Handbook 12-6 Figure 12.6 – Stud Welding 12.6.1 Advantages 1 It is cost effective. 2 Welding time is low. 3 Cost of equipment is low. 4 Welds are made from one side only. 5 Distortion is minimal. 6 Heat input into the base metal is low. 7 Small studs can be welded on thin sections. 12.6.2 Disadvantages 1 Only one end of the stud can be stud welded. 2 Shape and size of the stud must be compatible with the chuck. 3 Stud size is limited by the base thickness and position. 4 Disposable ceramic ferrule is required for each stud.
Section 13 Preheat and Interpass Temperatures m:\temporary\welding inspection\chapter13.doc Welding Inspection Handbook 13-0 Page 13.1 ASME/ANSI B31.1 ................................................................................... 13-1 13.1.1 General Requirements................................................................................ 13-1 13.1.2 Requirements............................................................................................. 13-1 13.2 ASME/ANSI B31.3 ................................................................................... 13-1 13.2.1 Requirements & Recommendations............................................................ 13-1 13.3 ASME SECTION III ................................................................................. 13-1 13.3.1 General ...................................................................................................... 13-1 13.3.2 Requirements............................................................................................. 13-1 13.4 AWS D1.1 ................................................................................................. 13-2 13.4.1 General Requirements................................................................................ 13-2 13.4.2 Requirements............................................................................................. 13-2 Table 13-1 Summary of Preheat Requirements......................................... 13-3 Table 13-2 Prequalified Minimum Preheat and Interpass Temperature (Table 3.2)......................................................... 13-4
Section 13 Preheat and Interpass Temperatures m:\temporary\welding inspection\chapter13.doc Welding Inspection Handbook 13-1 13.1 ASME/ANSI B31.1 13.1.1 General Requirements 1. The preheat requirements listed herein are mandatory minimum values. (131.1) 2. When welding two different P-Number materials, the minimum preheat temperature required shall be the higher temperature for the material to be welded. (131.2) 3. The preheat temperature shall be checked by use of temperature-indicating crayons, thermocouple pyrometers, or other suitable methods to assure that the required preheat temperature is obtained prior to and uniformly maintained during the welding operation. (131.3) 4. Thickness referred to is the greater of the nominal thicknesses at the weld for the parts to be joined. The nominal thickness for branch welds is defined in Figure 14-1 of this handbook. (131.4.1) 13.1.2 Requirements See Table 13-1. 13.2 ASME/ANSI B31.3 13.2.1 Requirements & Recommendations Required and recommended minimum preheat temperatures for materials of various P-Numbers are given in Table 13-1 (Table 330.1.1). If the ambient temperature is below 32°F, the recommendations become requirements. The thickness is that of the thicker component measured at the joint. (330.1.1) 13.3 ASME SECTION III 13.3.1 General It is cautioned that the preheating suggested in Appendix D of Section III (Table 13-1), does not necessarily ensure satisfactory completion of the welded joint and that the preheating requirements for individual materials within the P-Number may be more or less restrictive. Preheating may be required for the purpose of avoiding post-weld heat treatment. See PWHT section of this handbook. Interpass temperature for austenitic stainless steels is generally limited to 350’F. (Check applicable technical specifications.)
Section 13 Preheat and Interpass Temperatures m:\temporary\welding inspection\chapter13.doc Welding Inspection Handbook 13-2 13.3.2 Requirements See Table 13-1. 13.4 AWS D1.1 13.4.1 General When the base metal temperature is below the temperature listed in Table 4.2 of AWS D1.1 (Table 13-2 of this section) for the welding process and filler material being used and the thickness of material being welded, it shall be preheated (except as otherwise provided) in such manner that the parts on which the weld metal is being deposited are above the specified minimum temperature for a distance equal to the thickness of the part being welded but not less than 3 in., in all directions from the point of welding. Welding shall not be done when the ambient temperature is lower than 0°F. (Zero°F does not mean the ambient environmental temperature but the temperature in the immediate vicinity of the weld. The ambient environmental temperature may be below 0°F but a heated structure or shelter around the area being welded could maintain the temperature adjacent to the weldment at 0°F or higher.) Preheat and interpass temperatures must be sufficient to prevent crack formation, and temperatures above the specified minimum may be required for highly restrained welds. In joints involving combinations of base metals, preheat shall be as specified for the higher strength ,steel being welded. (4.2) Preheat interpass temperature and heat input for quenched and tempered steels shall be in accordance with the steel manufacturer’s recommendations. (4.3) 13.4.2 Requirements See AWS D1.1 Table 4.2 (Table 13-2).