Precautions for the production of cold drawn precision seamless steel pipe

Finished steel pipe is also called cold drawn precision steel pipe, which is a production process of seamless steel pipe. 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 after cold bending, no cracks when flaring and flattening, and anti-rust treatment on the surface. Mainly used in mechanical structures, hydraulic equipment and pneumatic or hydraulic components of automobiles and motorcycles, such as cylinders or oil cylinders.

The basic process of cold drawn seamless tubing is: hot-rolled capillary—capillary inspection and grinding—capillary pickling—>reinspection after capillary pickling—cold drawing—straightening before fine drawing—pickling, lubrication—finish drawing - Pre-processing of finished products - storage.

Production requires attention to control:

1. Capillary

The wall thickness of the capillary should be uniform, and the internal and external surface defects should be few; the external surface polishing and internal hole defect cleaning equipment should be equipped.

2. Recheck

Compared with ordinary cold-drawn steel pipes, the production of cold-drawn precision seamless pipes adds a hot-rolled capillary pickling re-inspection process. The main purpose is to ensure that there are no defects such as folds and cracks on the outer surface of the capillary, and to eliminate the capillary with defects such as folds, severe scratches, and pockmarks on the inner 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 should be above H3, and the hardness should be above HRC70. At the same time, it is required that the plug or die stick to steel during the drawing process.

4. Annealing

Annealing is a very important process in the production of all cold-drawn pipes. 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

Precision seamless steel pipes tend to form "black slag" mainly Fe2O3 and Fe3O4 during sulfuric acid pickling, and form black spots on the surface in subsequent production. Fe2O3 and Fe3O4 are easily soluble in hydrochloric acid. To prevent the formation of black spots, add 5-10g/l NaCl to the acid pool.

6. Lubrication

Resin should be used as lubricant, which is obviously different from phosphating plus lubrication (saponification). The drawn steel pipe presents the true color of the iron matrix, with high finish and beautiful appearance and luster like cold-rolled pipe.

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

Note: The seamless steel pipe has a hollow section and is widely used as a pipeline for conveying fluids, such as octg pipes for conveying oil, natural gas, gas, water and certain solid materials.

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