Cold drawn precision
seamless steel pipe has the characteristics of no oxide layer on the inner and outer walls, high pressure without leakage, high precision, high smoothness, no deformation during cold bending, no flaring and no cracks, and antirust 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 production process of cold drawn precision seamless steel pipe is:
Hot rolled capillaries—> capillary tube inspection and dressing—> capillary acid pickling—> capillary acid pickling re-inspection—> cold drawing—> straightening before finishing drawing—> acid washing and lubrication—> finishing—> before finished product Processing —> storage.
Production needs attention to control:
1. Capillary
The capillary wall thickness should be uniform, and the internal and external surface defects should be small; equipment for polishing the external surface and cleaning the internal hole defects should be configured.
2. Recheck
Compared with ordinary cold-drawn steel pipes, the production of cold-drawn precision seamless pipes has increased the number of hot-rolled capillary pickling re-inspection procedures, mainly to ensure that the outer surface of the capillary tube is free of defects such as folds and cracks, and that the inner surface has folded and severely lined , Hemp surface and other defects of the capillaries.
3. Tools
The surface finish of tools used in the production of cold drawn precision seamless steel pipes is generally above Ra0.4, the dimensional accuracy is above H3, and the hardness is above HRC70. At the same time, it is required that the phenomenon of sticking to the head or die during the drawing process cannot occur.
4. Annealing
Annealing is a very important process in the production of all cold drawn tubes. 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
During the sulfuric acid pickling process, precision seamless steel pipes easily form "black slag" mainly composed of Fe2O3 and Fe3O4, and form surface black spots in subsequent production. Fe2O3 and Fe3O4 are easily soluble in hydrochloric acid. To prevent the formation of dark spots, 5-10 g / l of NaCl is added to the acid pool.
6. Lubrication
Resin should be selected as the lubricant. This kind of lubrication is obviously different from phosphating plus lubrication (saponification). The drawn steel pipe shows the original color of the iron matrix, which has both a high finish and a beautiful appearance like a cold rolled tube.
Industrial control for the production of cold drawn precision seamless steel pipes includes condition control such as mold design, annealing, pickling, lubrication, etc. At the same time, work should be done on capillary quality inspection and repair.
