Shandong Xinhe International Trade Co., Ltd. is a large-scale manufacturer specializing in stainless steel products. High quality and low price, the main business scope includes stainless steel seamless pipe, stainless steel coil, stainless steel sheet, stainless steel rod and so on.
In the welding operation of stainless steel welded pipes, we face three common problems in the market, unqualified seams, incomplete penetration or burn-through, cracks and pores. Let's follow Shandong Xinhe International Trade Co., Ltd. to understand the causes and solutions of these problems. Let's master the correct welding technology, so as to complete the welding task scientifically, safely and efficiently.
(1) Unqualified welds. Unqualified welds are due to improper selection of welding process parameters or unskilled operation techniques, resulting in different heights and widths of welds, poor weld formation, and concave welds on the back. Causes the weld to be weakened too much and the weld strength is not enough.
(2) Not fully welded or burned through. Incomplete penetration is mainly due to the following reasons: one is that the current is too small, the other is unskilled operation technology, the welding speed is too fast, the butt gap is small, and the third is that the arc is too long or the arc is not aligned with the welding seam, etc. When the metals are not fused together or partially in the welded metal, repair welding should be carried out in time for this part. The reason for burn-through is that the welding current is too large, the temperature of the molten pool is too high, the welding wire is not added in time, the butt gap of the strip is too large, and the welding speed is too slow, etc., resulting in single or continuous perforation on the weld. The strength of the weld is weakened and it is burned through.
(3) Cracks and pores. The frequency of cracks is very high. Generally, cracks are divided into two types: hot cracks and cold cracks. During the solidification process of the liquid metal or at a temperature slightly lower than the solidus temperature, thermal cracks with oxide color will be formed on the fracture along the intergranular boundary. Phase transition occurs in the solid state, or diffusible hydrogen exists, and under the action of excessive welding shrinkage stress during cooling, cold cracks with transgranular properties, bright fractures and no oxidation color will be generated. If the welding wire is not up to standard, the high temperature stays for too long during welding, resulting in oxidation, overheating and excessive grain size growth, the material itself has many impurities, or the material itself is prone to cracks when it is easy to harden. However, in the case of oil, scale, rust, etc. on the surface of the weldment and welding wire, or welding in a humid environment, or the purity of argon gas is low, or the argon gas shielding gas is not good, and the molten pool is oxidized and splashed at high temperature, it is easy to produce pores.
The welding of stainless steel welded pipes requires operators to understand the characteristics of different types of stainless steel in detail. In addition, they must also be proficient in the specific methods of stainless steel welding technology. Therefore, manufacturers should further strengthen the technical training of operators.
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