Production method and precautions of seamless steel tube

Seamless steel tube has the characteristics of high pressure without leakage, high precision, high finish, and no deformation after cold bending. How is the steel pipe produced? What details need to be paid attention to in the production process? The following seamless tube manufacturers will introduce in detail for you.

Production method of seamless steel tube:

1. Hot-rolled seamless steel tube

(1) Hot-rolled seamless tubes are generally produced on automatic pipe rolling units. After checking and removing surface defects, the solid tube blank is cut into the required length, centered on the perforated end face of the tube blank, then sent to the heating furnace for heating, and pierced on the piercing machine.

(2) The piercing is continuously rotating and advancing at the same time. Under the action of the roll and the plug, a cavity is gradually formed inside the tube blank, which is called a capillary tube. Then send it to the automatic pipe rolling machine to continue rolling. Finally, the wall thickness is adjusted by the equalizing machine, and the size is sized by the sizing machine to meet the specification requirements. It is a more advanced method to produce hot-rolled seamless steel tubes by using continuous rolling mills.

2. Cold rolling and cold drawing

If you want to obtain seamless tubes with smaller size and better quality, you must use cold rolling, cold drawing or a combination of the two. Cold rolling is usually carried out on a two-roll mill. Rolled in an annular pass formed by a conical plug. Cold drawing is usually carried out in a single-chain or double-chain cold drawing machine of 0.5-100T.

3. Extrusion method

The extrusion method is to place the heated tube blank in a closed extrusion cylinder, and the piercing rod and the extrusion rod move together to make the extrusion part extrude from the smaller die hole. This method can produce steel pipes with smaller diameters. Seamless steel tubes are long strips of steel with a hollow section and no seams around them.

Precautions for seamless steel tube production:

1. Capillary
The capillary wall thickness 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. Re-examination
Compared with ordinary cold-drawn steel tubes, the production of cold-drawn precision seamless tubes adds a hot-rolled capillary pickling re-inspection process, mainly to ensure that the outer surface of the capillary has no defects such as folds and cracks, and eliminates folds and serious scratches on the inner surface. , pitted surface and other defects of the capillary.

3. Tools
Generally, the surface finish of the tools used in the production of cold-drawn precision seamless steel tubes should 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 an 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
Precision seamless steel tubes tend to form "black slag" mainly Fe2O3 and Fe3O4 during the sulfuric acid pickling process, 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. This kind of lubrication is obviously different from phosphating plus lubrication (saponification). The drawn steel pipe presents the true color of iron matrix, with high smoothness and beautiful appearance like cold-rolled tube.