Cold-drawn Precision Seamless Steel Pipe Matters Needing Attention

Cold-drawn precision seamless steel tubes have the characteristics of inner and outer walls without oxide layer, withstand high pressure, no leakage, high precision, high finish, no distortion after cold bending, no nicks after flaring and flattening, and the surface has been treated for anti-rust treatment. It is mainly used for mechanical structures. Pneumatic or hydraulic components such as cylinders or cylinders for hydraulic equipment and car/motorcycles.

The basic process of cold drawing is: hot-rolled capillary -> capillary inspection, grinding -> capillary pickling -> capillary pickling -> cold drawing -> fine straightening - before pickling, lubrication —>Drawing —> Finished product —> Storage.

Production requires attention to control:

1, capillary

The wall thickness of the capillary tube should be uniform, and there should be less internal and external surface defects; external surface polishing and internal hole defect cleaning equipment should be configured.

2, review

Compared with ordinary cold-drawn steel tubes, the production of cold-drawn precision seamless tubes increases the pickling process of hot-rolled capillary tubes. The main task is to ensure that the external surface of the capillary tube is free from defects such as folding and cracks, and the inner surface is free from folding and severe scribing. , pits and other defects of the capillary.

3, tools

The surface smoothness of the tools used in the production of cold drawn precision seamless steel tubes is generally Ra0.4 or higher, the dimensional accuracy is above H3, and the hardness is above HRC70. At the same time, it is required that the head or mold sticking steel phenomenon cannot occur during drawing.

4, annealing

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 oxide scale. Cold-drawn precision steel pipes need to be equipped with non-oxidation bright annealing furnace equipment.

5, pickling

In the process of sulfuric acid pickling, precision seamless steel pipes tend to form “black slag” mainly composed of Fe2O3 and Fe3O4, and form black spots on the surface during subsequent production. Fe2O3 and Fe3O4 are easily dissolved in hydrochloric acid. In order to prevent the formation of dark spots, 5-10 g/l of NaCl is added to the acid pool.

6, lubrication

Resins should be used as lubricants. There is a clear difference between this lubrication and phosphating plus lubricating (saponification). The drawn steel tube shows the true color of the iron matrix, which has both a high finish and a beautiful appearance like a cold rolled tube. Color.

The industrial control of production of cold-drawn precision seamless steel tubes includes mold design, annealing, pickling, lubrication, and other conditions control. At the same time, good work should be done on capillary tube quality inspection and refurbishment.