BURNTHROUGH Possible Causes Corrective Actions * Excessive Amperage *Reduce Amperage * Improper Travel Angle * Use a Push Angle *Travel Speed Too Low * Increase Travel Speed * Insufficient Electrical Stickout * Increase Contact Tip to Work Distance Defect & Distortion in Welding
INCOMPLETE PENETRATION Possible Causes Corrective Actions * Insufficient Amperage *Increase Amperage * Improper Travel Angle * Use Less of a Drag angle * Excessive Electrical Stickout * Decrease Contact Tip to Work Piece Distance * Weld Joint Too Narrow * Increase the Opening of the Weld Joint Defect & Distortion in Welding
INCOMPLETE PENETRATION Possible Causes Corrective Actions * Insufficient Amperage *Increase Amperage * Improper Travel Angle * Use Less of a Drag angle * Excessive Electrical Stickout * Decrease Contact Tip to Work Piece Distance * Weld Joint Too Narrow * Increase the Opening of the Weld Joint Defect & Distortion in Welding
DISTORTION Distortion can pose a major problem, since the final product is not the desired shape. The following pictures describe various types of welding distortion Defect & Distortion in Welding Transverse shrinkage ◦ Shrinkage stresses leading to a shortening of the member across the toes of the welded joint
DISTORTION Defect & Distortion in Welding Angular distortion ◦ Weld zone transverse shrinkage stresses not in the plane of the neutral axis leading to rotation of one member with respect to an adjacent member.
DISTORTION Defect & Distortion in Welding Longitudinal shrinkage ◦ Shrinkage stresses leading to a shortening of the member along the principal axis of the welded joint.
DISTORTION Defect & Distortion in Welding Fillet distortion Neutral axis distortion
DISTORTION Defect & Distortion in Welding Proper Edge Preparation and Fit-up By making certain the edges are properly beveled and spacing is adequate, you can restrict the effects of distortion. Additionally, you should use tack welds, especially on long joints. Tack welds should be spaced at least 12 inches apart and run approximately twice as long as the thickness of the weld
DISTORTION Defect & Distortion in Welding Control the Heat Input The faster a weld is made, the less heat is absorbed by the base metal An intermittent weld (sometimes called a skip weld) is often used instead of one continuous weld. When you are using an intermittent weld, a short weld is made at the beginning of the joint. Next, you skip to the center of the seam and weld a few inches. Then, you weld at the other end of the joint. Finally, you return to the end of the first weld and repeat the cycle until the weld is finished.
DISTORTION Defect & Distortion in Welding Preheat the Metal To control the forces of expansion and contraction, you preheat the entire structure before welding. After the welding is complete, you allow the structure to cool slowly. Limit the Number of Weld Passes You can keep distortion to a minimum by using as few weld passes as possible. You should limit the number of weld passes to the number necessary to meet the requirements of the job.
DISTORTION Defect & Distortion in Welding Use Jigs and Fixtures Since holding the metal in a fixed position prevents excessive movements, the use of jigs and fixtures can help prevent distortion. A jig or fixture is simply a device used to hold the metal rigidly in position during the welding operation. Allow for Distortion To reduce distortion, you angle the parts to be welded slightly in the opposite direction in which the contraction takes place. When the metal cools, contraction forces pull the pieces back into position.
DISTORTION Defect & Distortion in Welding
END OF LESSON ….. DJJ1043