Quality Defects and Preventive Measures of 316 Stainless Steel Pipes

When 316 stainless steel pipes are cold drawn or cold rolled, some defects are inevitable, which will affect the quality of the final pipe products, so preventive measures need to be taken for the causes of these defects. Next, Permanent Steel Manufacturing Co., Ltd will show you the quality defects and preventive measures of 316 stainless steel pipes during cold rolling or cold drawing.
 
1. Cold drawing quality defects and prevention
 
The main quality defects of cold drawing include uneven wall thickness, out-of-tolerance outer diameter, surface cracks, surface straight lines and scratches, etc. The uneven wall thickness of cold-drawn stainless steel welded pipe is affected by factors such as the wall thickness accuracy of the pipe blank, the pipe drawing method, the deviation of the drawing center line, the hole shape, the deformation process parameters and the lubrication conditions.
 
During the forming process, attention should be paid to the degree of wear of the mating draft. In addition, in order to reduce the formation of cracks on the surface of 316 stainless steel tubes after drawing, it is necessary to select suitable tube blanks, and the surface defects should be repaired. When pickling the tube blanks, it is necessary to avoid over-pickling, avoid the formation of pits or hydrogen embrittlement, and avoid under-pickling to prevent the oxide scale from being cleaned. The annealing quality should be guaranteed during use, a reasonable tube drawing method should be used, suitable deformation process parameters and tool shapes should be selected, and the adjustment and inspection of the drawing center line should be improved. Improving the pickling quality and lubrication quality of steel pipes, ensuring tool hardness, uniformity and surface finish will help reduce the formation of straight lines and scratches on stainless steel pipes.
 
2. Cold rolling quality defects and prevention
 
The main quality defects of cold rolling include uneven wall thickness, excessive outer diameter, surface cracks, wrinkles and folds. Therefore, enhancing the wall thickness accuracy of the tube blank is an important condition to ensure uniform wall thickness of the cold-rolled steel tube. Ensuring the wall thickness accuracy of the tube blank and the pickling quality, lubrication quality and surface finish of the tube rolling tools are important guarantees for enhancing the wall thickness accuracy of cold-rolled stainless steel tubes. Over-pickling or under-pickling should be avoided to prevent the formation of pockmarks or residual iron oxide on the product surface. The cooling of the tube rolling tools and the surface quality of the tools should be checked during processing, and the mandrels and rolling groove blocks that do not meet the requirements should be replaced in time.
 
Therefore, measures to reduce rolling force are conducive to increasing the outer diameter accuracy of 316 stainless steel pipes, including annealing the tube blank, reducing rolling deformation, enhancing its lubrication quality and surface finish of the tube rolling tools, etc. Use materials with high strength and hardness to produce tube rolling tools, and strengthen the cooling and inspection of tube rolling tools. If the tube rolling tools are found to be severely worn, they must be replaced in time to avoid the outer diameter of thin-walled stainless steel pipes from being out of tolerance.
 
The above content is the quality defects and preventive measures of 316 stainless steel pipes during cold rolling or cold drawing. The quality defects of cold drawing or cold rolling will cause uneven wall thickness of the pipe, excessive outer diameter, surface defects, etc. Therefore, in the production process of 316 stainless steel pipes, certain preventive measures should be taken to avoid scrapping of pipes in the later stage.