Difference between cold rolling and cold drawing of 304 stainless steel pipes

　　304 Stainless steel pipes (SS pipe) can be divided into stainless steel welded pipes and stainless steel seamless pipes according to different production processes and uses.

　　Cold drawing gives 304 stainless steel pipes the following characteristics:

　　1. Improve the surface and improve corrosion resistance due to improved surface finish.

　　2. Further improve the dimensional accuracy of stainless steel pipes. After cold rolling or cold drawing with a mandrel, not only the outer diameter accuracy is improved, but also the wall thickness dimensional accuracy can be improved.

　　3. Stainless steel pipes with smaller diameters and thinner walls can be produced.

　　4. Combined with solid solution heat treatment after cold deformation, the mechanical properties can be improved.

　　5. Non-standard stainless steel seamless pipes of special sizes and special cross-sections can be produced.

　　Cold drawing process:

　　Cold drawn 304 stainless steel pipes are heated at room temperature for pipe diameter or end necking, the surface is pickled to remove oxide scale, and lubricants are applied for cold drawing. There are 3 methods of cold drawing. Cold drawing a plug with the inner diameter of the finished product is called plug cold drawing. Cold drawing with a mandrel equal to the length of the tube is called mandrel cold drawing or mandrel-free cold drawing. The inner wall of the cold-drawn mandrel is smooth, which can achieve a large deformation ratio and is suitable for cold drawing of long stainless steel tubes.

　　The cold drawing machine can be chain-type, hydraulic-type or oil-hydraulic-type. Chain cold drawing can draw two or more steel tubes at a time. In order to reduce the wear between the cold-drawn tube and the die, the quality of the lubricant is very important to improve efficiency. Pickling is usually used to remove the surface oxide scale, and then lubricant is applied for cold drawing.

　　Cold rolling process:

　　Cold-rolled stainless steel seamless pipe is a cold working method in which two rollers are rolled along the circumference in descending passes and rolling back and forth with an inclined mandrel, which is called the cold pilger method. A three-roll cold rolling mill can also be used.

　　This method is the same as the principle of the pilger cold rolling tube mill. The deformation process is in a compressive stress state. This method can be used for alloy materials with high hardness and special stainless steels that are difficult to cold draw. Due to the high precision of the full circle processing scale, large processing volume each time, the surface quality of the stainless steel seamless pipe is significantly improved, the efficiency is high, the rolling die is expensive, and the processing is difficult to replace the grinding tool.
　　304 Stainless steel welded pipes and stainless steel seamless pipes can be cold processed - cold rolling (welding) and cold drawing (seamless) to meet the higher requirements of cold processed products.