Common problems during welding!

According to their position in the weld, welding defects can be divided into internal defects and external defects. The external defects are located on the outer surface of the weld and can be seen directly. External defects mainly include the size of welding seam is not in line with the requirements, edge bite, welding tumor, collapse, surface pores, surface cracks, burn through and so on. Internal defects mainly include incomplete welding, internal pores, internal cracks, slag inclusion, etc. The internal defects in the weld shall be found by nondestructive testing or by destructive testing. Causes of welding defects weld The weld dimension does not meet the requirements. Mainly refers to uneven weld, width and narrow, high and insufficient. Too small weld size will reduce the bearing capacity of the welded joint. Excessive weld size will increase welding workload, increase welding residual stress and welding deformation, resulting in stress concentration. Improper Angle of welding groove or uneven gap of assembly, excessive or small welding current, improper mode of transport or speed and welding Angle will cause the size of welding seam does not meet the requirements. Bite edge During welding, the groove formed on both sides of the weld and the base metal junction is called bite edge (or bite flesh). The biting edge will reduce the effective section of the base metal and weaken the strength of the welded joint. At the same time, it is easy to concentrate the stress at the biting edge, and cracks may occur at the biting edge after bearing, even causing the rupture of the structure. The causes of edging are improper operation process, incorrect selection of welding specifications, such as excessive welding current, excessive arc, improper electrode Angle, etc. flash In the welding process, the metal tumor formed by the molten metal flowing to the unmelted base metal outside the weld is called welding tumor. The weld nodules not only affect the appearance of the weld, but also cause the stress concentration. Welding gap is too large, electrode position and method is not correct, welding current is too large or welding speed is too slow, etc. Burn through During the welding process, the molten metal flows out from the back of the groove, forming a perforation defect called burn through. The main reason of burn-out is that the welding current is too large and the welding speed is too slow. Burn-out also occurs when the assembly gap is too large or the blunt edge is too thin. Not fusion Incomplete fusion refers to the part that is not completely melted and combined between bead and base material or bead and bead during welding. Or the part between the base metal and the base metal that is not completely melted and bonded in spot welding. The causes of non-fusion are as follows: the energy of welding line is too low; Arc deviation blowing; The side wall of groove has rust and dirt; Welding layer slag cleaning is not complete. Potholes, collapses and unfilled A pit is a locally low-lying part formed on the surface of a weld or on the back of a weld below the surface of the base metal. Collapse refers to the phenomenon that the weld metal overpenetrates through the back of the weld due to the improper welding process during the melting welding on one side, which causes the front side of the weld to collapse and the back side to bulge. The continuous or intermittent grooves formed on the surface of the weld due to insufficient filling metal. slag Residual slag in the weld after welding is called slag inclusion. There are many reasons for slag inclusion, such as welding parts edge and welding layer, weld between clean not clean; Welding current is too small, resulting in melting is more rapid solidification speed, slag too late to emerge; Improper transport, slag and molten iron separation is not clear, preventing the slag floating up; Improper chemical composition of welding parts and electrode; The molten pool contains too much oxygen and nitrogen. stomatal When welding, the air bubbles in the molten pool fail to escape during solidification and remain. Stomata can be divided into dense stomata, worm stomata and needle stomata. The gas forming pores in the weld is mainly hydrogen, nitrogen and carbon monoxide. Porosity has a great influence on the properties of welding seams. It not only reduces the effective area of welding seams and reduces the mechanical properties of welding seams, but also destroys the compactness of welding seams and is easy to cause leakage. The causes of stomata are as follows: the good protection of the welding area is destroyed in the welding process; There are grease, rust and adsorbed water pollutants on the surface of the base material welding area and wire. Welding rod damp, baking is not sufficient; Welding current is too large or too small, welding speed is too fast; Welding arc too long, arc voltage is high. The crack The forming temperature of welding crack can be divided into hot crack and cold crack. In the process of welding, the weld seam and the heat affected zone metal cooling to the high temperature zone near the solid phase line are called thermal cracks. When the welding joint is cooled to a lower temperature, the welding crack is called cold crack. Welding crack is the most dangerous welding defect, which seriously affects the performance of welding structure And safety and reliability. In addition to reducing the strength of the welded joint, the crack also has a sharp gap at the end of the crack, which will cause serious stress concentration and promote the development and destruction of the crack.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods