Precautions for cold-drawn of 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 cylinders or oil cylinders.
 
The cold drawing process is: hot-rolled tube billet —> tube billet inspection and grinding —> tube billet pickling —> tube billet re-inspection after pickling —> cold drawing —> straightening before fine drawing pass —> pickling , Lubrication -> fine drawing -> finished product pre-processing -> storage.
 
 
Matters needing attention in manufacturing:
1.Tube billet
The wall thickness of the tube billet 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 capillary pickling and re-inspection process, which is mainly to ensure that the outer surface of the capillary is free of defects such as folds and cracks, and eliminates the presence of folds and severe markings on the inner surface , Pitted surface and other defective capillary.
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 in the acid pool.
6. Lubrication
Resin should be used as lubricant. This kind of lubrication is obviously different from phosphating and lubrication (saponification). The drawn steel pipe presents the true color of iron matrix, which has high smoothness and beautiful appearance like cold rolled pipe. Color.
　　
The industrial control for the production of cold-drawn precision seamless steel pipes includes mold design, annealing, pickling, lubrication and other conditions.