Can stainless steel rust after precision machining ?

In the machining industry, general metal materials 303, 304 stainless steel are not prone to rust. 316 stainless steel material will not rust. The 316 stainless steel materials that can be processed by Shenzhen customers last week, one is the CNC lathe processing parts, the other is the CNC machining center precision machining parts, the two parts are connected by argon welding. When the QC inspection of the quality department, it was found that there was rust in the inside of the tube!

Stainless steel materials will rust, the problem is a little dare to imagine! The company has no problems in testing stainless steel materials. Where is the problem? A little bit puzzling. Later, the reason was found in the part processing technology. If the stainless steel was subjected to high temperature or heat treatment, the material would also rust, even if it was 316, 316L stainless steel. Because of the high temperature treatment, the Cr element in the stainless steel combines with the C element to form a compound of Cr and C, which aggravates the intergranular corrosion and cracking tendency of the stainless steel. At the same time, due to the decrease in the content of Cr in the matrix, the antioxidant capacity also decreases. So it will rust inside the material tube! The best way to remove rust is of course to re-solidify at about 1000 degrees. But it is already a precision machined part. Even after remelting, it still needs high-temperature welding. The same problem may happen again. What should I do?

Through the company’s understanding of the surface treatment method, I immediately thought of oxalic acid, oxalic acid can reduce rust, let the rust turn into ferrous oxalate, and the water will shine as new. Moreover, the treated surface, the metal has been passivated, is equivalent to a thin protective film, so that the metal is not easy to rust. Oxalic acid is used to treat stainless steel materials, and the same effect!
This treatment does not solve the problem of rust after the argon welding of the stainless material. It also understands why the stainless steel is rusted after precision machining. For the company, providing quality service to customers is the permanent goal of AIXI Hardware!