Stainless steel pipes can be divided into stainless steel welded pipes and stainless steel seamless pipes. Stainless steel welded pipes and stainless steel seamless pipes can be processed by cold working – cold rolling and cold drawing to achieve higher cold processed products.
Let’s take a look at the cold rolling and cold drawing process of stainless steel tubes.
Cold working makes stainless steel pipes have the following characteristics:
1. Improve the surface and improve the corrosion resistance by improving the surface finish.
2. Further improve the dimensional accuracy of the stainless steel tube. After cold rolling or cold drawing of the core rod, not only the external precision is improved, but also the dimensional accuracy of the wall thickness can be improved.
3. It can produce stainless steel tubes with smaller diameter and thinner tube walls.
4. After cold deformation and then combined with solution heat treatment, the mechanical properties can be improved.
5, special size, special section non-standard stainless steel seamless pipe can be produced.
Cold drawing process: the diameter of the cold drawn stainless steel tube is heated or the end portion is necked at normal temperature, the surface is removed by pickling, and the lubricant is applied for cold drawing. There are three kinds of methods for cold drawing. The cold head of the finished inner diameter is called cold drawing.
The core rod with the same length as the tube is cold drawn and the core rod is cold drawn or the core rod is freely cold drawn. The core rod is cold-drawn and the inner wall is smooth, and the large deformation ratio can be completed, and the stainless steel tube with long length is used for cold drawing.
The cold drawing machine can be chain, hydraulic or hydraulic. In the chain cold drawing, two or more steel pipes can be pulled out. In order to reduce the wear between the cold drawn pipe and the die, the quality of the lubricant is important for improving the efficiency. Usually, the surface oxide scale is removed by pickling, and then a lubricant is applied for cold drawing.
Cold rolling process: Cold-rolled stainless steel seamless pipe is a cold-working method in which two rolls have a roll shape which gradually becomes smaller along the circumference, and a mandrel with a slope is internally rolled back and forth, which is called a cold pilger method. A three-roll cold rolling mill can also be used.
This method is the same as the principle of the cold pilger rolling mill. The deformation process is a compressive stress state. The alloy material of stainless steel and special material stainless steel with high hardness is difficult to cold drawing. This method can be used because of the high precision of the full circumference machining. The processing volume is large, the surface quality of the stainless steel seamless pipe is improved significantly, the efficiency is high, the roll mold price is expensive, and the change of the grinding tool is difficult.