Precision rolling pipe is one of the higher grades of seamless steel pipe products.It has the characteristics of high precision and surface finish requirements, especially the quality requirements of seamless steel tube for oil cylinder are higher than other varieties.There are very few domestic manufacturers that use cold drawn pipe as the blank of fine rolling pipe. Most manufacturers adopt the production process of two-high cold rolling mill and three-high cold rolling mill.According to the existing equipment conditions, the steel pipe factory provides the billet for the fine rolled pipe through the cold drawing method, and finds out a more reasonable production process. The product, as the fine rolled pipe billet, can produce high-quality seamless steel pipe for the cylinder.
Features of finishing - rolled pipe editing
1. Cold-rolled precision steel tube has high tolerance dimension accuracy, product accuracy is controlled at + / -0.05mm, good inner and outer wall finish, no oxidation layer on the surface.
2. Cold-rolled precision steel pipe has excellent comprehensive performance, can withstand high pressure, cold bending, flaring and flattening without cracking or wrinkling, and can do all kinds of complex deformation and mechanical processing.
3. The promotion and application of precision seamless pipe can save steel, improve the processing efficiency, reduce the investment in processing procedures and equipment, save costs and greatly save machining hours, improve the production capacity and material utilization rate, as well as improve product quality and reduce costs.
The purpose of finishing rolling pipe editing
Cold-rolled precision steel tubes are widely used in automobile, motorcycle, electric vehicle, petrochemical, electric power, ship, aerospace, bearing, pneumatic components, middle-low pressure boiler and other fields .
In order to ensure the provision of qualified pipe billets for cold rolling and meet the requirements of finishing rolling pipe billets, the original cold drawing process was improved:
1. Drill - oblique holes in itd after heading to create conditions for pickling and cleaning the inner surface of steel tubes;
2. After acid cleaning, carry out fine cleaning for many times to ensure the inner surface of the steel pipe is clean and create conditions for phosphating.
Reduce defects such as internal scratches caused by cold drawing;
3. Adopt multi-pass short mandrel drawing and conical internal mold for the first time before the finished product to increase the deformation of the inner surface of the steel pipe.
Ensure uniform deformation of inner and outer surface of steel tube;
4. Change the heat treatment system and adopt complete annealing for intermediate heat treatment of semi-finished products and recrystallization annealing for heat treatment of finished products.
To ensure the surface finish and mechanical properties of the steel tube after finishing rolling
The key points of production process are as follows:
1. The pickling - H2SO4 concentration of 10% to 15%, the temperature of 55-65 ℃, ferrous content of 100 g/l or less, pickling time for 30 min.
2. Multiple cleaning is required to clean the residues in the pipe;
3. Conical outer mold and cylindrical inner mold were used for the first few times of cold drawing, and curved outer mold and conical inner mold were used for the first time of finished products.
All internal molds adopt "metal infiltration internal mold" among
4. Adopting full annealing heat treatment, annealing temperature is 850-880 ℃, time of 15 min.
Finished product by recrystallization annealing heat treatment, removal of residual stress, annealing temperature is 630-670 ℃, the time for 10 min;
5. Perform normal processes in other processes