Cold drawn precision seamless steel pipe
has the characteristics of no oxidation layer on inner and outer walls, high pressure and no leakage, high precision, high smoothness, no deformation in cold bending, no cracks in flaring, no rust treatment on the surface, and mainly used for mechanical structure. Hydraulic equipment and pneumatic or hydraulic components of automobiles and motorcycles, such as cylinders or cylinders.
The basic process of cold drawing is: hot rolled capillary tube -> capillary tube inspection, grinding -> capillary tube pickling -> capillary tube pickling after re-examination -> cold drawing -> fine pulling road before straightening -> pickling, lubrication —> fine pull —> pre-processing of finished products —> storage.
Production needs attention to control:
1, capillary tube
The wall thickness of the capillary tube should be uniform, and the surface defects on the inner and outer surfaces should be small; the outer surface polishing and inner hole defect cleaning equipment should be arranged.
Compared with ordinary cold drawn steel pipe, cold drawn precision seamless pipe production increases the hot-rolled capillary pickling re-inspection process, mainly to ensure that there are no defects such as folding and crack on the outer surface of the capillary tube, and the inner surface is excluded from folding and severely scribed. Tubes with defects such as pockmarks.
Generally, the surface roughness of tools used in the production of cold drawn precision seamless steel tubes is 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 tip or mold sticking phenomenon does not occur during the drawing process.
Annealing is a very important process in the production of all cold drawn tubes. The quality of the annealing affects both the performance of the steel tube and the removal of the scale. Cold drawn precision steel tubes require a non-oxidizing bright annealing furnace equipment.
The precision seamless steel pipe is easy to form "black slag" mainly composed of Fe2O3 and Fe3O4 in the pickling process of sulfuric acid, and forms black spots on the surface in subsequent production. Fe2O3 and Fe3O4 are easily soluble in hydrochloric acid, and 5-10 g/l of NaCl is added to the acid bath to prevent the formation of dark spots.
Resin should be used as a lubricant. This kind of lubrication is obviously different from phosphating and lubricating (saponification). The drawn steel tube has the natural color of the iron matrix, and has a high finish and a beautiful appearance like a cold rolled tube. Color.