Production of cold-drawn precision seamless steel tubes
Production of cold-drawn precision seamless steel tubes
The cold-drawn precision seamless steel pipe has the characteristics of no oxide layer on the inner and outer walls, no leakage under high pressure, high precision, high finish, no deformation in cold bending, no cracks in flaring and flattening, and anti-rust treatment on the surface. It is mainly used for mechanical structures. , Hydraulic equipment and pneumatic or hydraulic components of automobiles and motorcycles, such as air cylinders or oil cylinders.
The basic process flow of cold drawing is: hot rolled capillary—>capillary inspection and grinding—>capillary pickling—>re-inspection after capillary pickling—>cold drawing—>straightening before finishing pass—>pickling, lubrication —>Fine drawing —>Pre-processing of finished products —>Warehousing.
Pay attention to control in production:
1. Blank tube
The wall thickness of the blank tube should be uniform, and the internal and external surface defects should be few; external surface polishing and internal hole defect cleaning equipment should be equipped.
2. Re-inspection
Compared with ordinary cold-drawn steel pipes, the production of cold-drawn precision seamless pipes adds a hot-rolled blank tube pickling and re-inspection process, which is mainly to ensure that the outer surface of the capillary tube is free of folds, cracks and other defects, and eliminates the presence of folds and severe scratches on the inner surface Defective capillary such as thread and pitted surface.
3. Tools
Generally, the surface finish of the tools used in the production of cold-drawn precision seamless steel pipes is required to be above Ra0.4, the dimensional accuracy is above H3, and the hardness is required to be above HRC70. At the same time, it is required that the plug or die sticking to steel should not occur during the drawing process.
4. Annealing
Annealing is a very important process in all cold drawn pipe production. The quality of annealing affects both the performance of the steel pipe and the removal of scale. Cold drawn precision steel pipes need to be equipped with non-oxidizing bright annealing furnace equipment.
5. Pickling
In the process of sulfuric acid pickling, precision seamless steel pipes are prone to form "black slag" mainly composed of Fe2O3 and Fe3O4, which will form black spots on the surface in subsequent production. Fe2O3 and Fe3O4 are easily soluble in hydrochloric acid. To prevent the formation of dark spots, add 5-10g/l of NaCl to the acid pool.
6. Lubrication
Cold drawn precision seamless steel pipes should use resin as lubricant. This kind of lubrication is obviously different from phosphating and lubrication (saponification). The drawn steel pipes present the true color of iron matrix, which has both high smoothness and coldness. Beautiful appearance and color like a rolled tube.
The industrial control of the production of cold-drawn precision seamless steel pipes includes mold design, annealing, pickling, lubrication and other conditions. At the same time, it is necessary to do a good job in capillary quality inspection and refurbishment.
