What to do if the welding part of 304 stainless steel strip used for mechanical equipment manufacturing is rusted

It is reported that some customers who specialize in mechanical equipment use 304 stainless steel strips to weld and the welding points are prone to rust during the production of certain equipment. Why does the welding part of 304 stainless steel strips used for mechanical equipment rust? What to do? There are many reasons why the welding points of 304 stainless steel strips rust after welding.

If the argon welding method is used when welding mechanical equipment, it is necessary to focus on whether the carbon content of the 304 stainless steel strip can meet the requirements of welding and whether auxiliary materials are used. If the carbon content in the 304 stainless steel strip is relatively high, it will easily cause intergranular corrosion during welding. Therefore, for customers who need welding, steels with low carbon content and higher nickel content, such as 304L stainless steel, should be preferred.

304L stainless steel, this material is a derivative steel of 304 stainless steel. Except for the carbon content below 0.03%, the other components, performance, and application range are almost the same. It also can resist intergranular corrosion that 304 stainless steel does not have and is suitable for welding processes. During welding, the lower carbon content of 304L stainless steel reduces the carbides precipitated in the heat-affected zone near the weld, effectively improving the stainless steel’s resistance to intergranular corrosion and extending the service life of the stainless steel weld. Therefore, the use of 304L stainless steel can effectively reduce welding corrosion.

However, some customers who specialize in mechanical equipment prefer 304 stainless steel. In that case, the following points should be noted during welding to avoid rust as much as possible.
1. When welding, use narrow weld automatic argon arc welding and shorten the residence time in the sensitization temperature zone. Generally speaking, the sensitization temperature range should be controlled between 450℃ and 850℃.
2. Use water to quickly cool the welding area to effectively prevent intergranular corrosion caused by welding 304 stainless steel strips.
3. Shorten the welding time and reduce the duration of the high temperature of the weld, which will help improve the 304 stainless steel strip’s resistance to intergranular corrosion and thermal cracking.
4. When performing multi-layer welding, wait until the weld layer cools to about 600 degrees before welding the next one.
5. Use a relatively small line energy. Under the same conditions, the current used should be 10-20% smaller than that of ordinary steel. The material rack should try to swing vertically as much as possible to avoid horizontal swing.
6. If conditions permit, try to use pulse welding. This welding method can reduce overheating at the welding point and help improve the corrosion resistance and crack resistance of 304 stainless steel strips.
7. Regardless of whether the welding is finished or interrupted, the arc closing speed should be slow. Note that the arc pit should be filled to prevent crater cracks.
8. When performing filler welding, the filler wire should be biased towards the arc and quickly withdrawn to avoid adhesion between the filler wire and the edge of the molten pool.
9. The surface of the weld should be cleaned to ensure that the weld position is relatively smooth and there is no unevenness. After welding, the residue should be thoroughly removed. Operators should operate correctly to avoid random arcing and spattering. Note that when welding, the back part should be protected to avoid back oxidation.