Seamless steel pipe for tunnels. Seamless steel pipes are not only used to transport fluids and powdered solids, exchange heat energy, manufacture mechanical parts and containers, but also an economical steel seamless pipe for Pu’er tunnels. Seamless pipes (including casing pipes) The existing production capacity is greater than the demand. The formation of the passivation film is due to the reaction of the steel with oxygen when exposed to the atmosphere, or due to contact with other oxygen-containing environments.

The shear quality of channel steel has a great influence on the subsequent process, especially the welding quality. If there are defects such as collapse shoulder, burr, tear, and skew at the shear fracture, there will be a large gap when the channel is butted, which will affect the welding. Quality, especially the strength index, resulting in a large safety hazard. Shaped steel pipe, cold drawn profiled steel pipe, coiled pipe, elliptical pipe, conical pipe, triangular, octagonal, elliptical steel pipe, round pipe, flat ellipse, D Type tube, concave tube, H-shaped tube, semi-circular tube, hexagonal tube, mushroom tube, bread tube, armrest tube, ingot tube, T-tube, triangle tube and other metal-shaped tubes.

The outer surface area of ​​the seamless steel pipe after emptying is increased, and the surface area of ​​the inner surface is reduced, so a neutral layer appears between the inner and outer surface layers, and the outer surface and the neutral layer and all layers between them are The surface area is increased, but the outer surface is the largest increase. The inner surface and the neutral layer have the largest reduction in the inner surface.

The above-mentioned changing properties of the surface area of ​​each layer of the seamless steel pipe during the empty drawing affect the unevenness of the metal deformation. One of the characteristics is that the natural extension of each layer along the pipe wall is inconsistent, the outer extension of the seamless steel pipe is naturally minimized, the inner surface layer of the seamless steel pipe is the largest, and the inner layers of the inner layer are naturally extended from the outer surface. The layer to the inner surface layer is gradually increased. The second characteristic is that, due to the holistic relationship, the layers of the seamless steel pipe cannot be differently extended during the deformation. Therefore, the layers must be mutually restrained.

Since the metal of the outer layer naturally extends less than the metal of the inner layer, the outer layer is inevitably subjected to the inner layer during deformation, and the actual extension is larger than the natural extension, and is reduced by increasing the thickness of the extension. Conversely, the extension of the inner layer is hindered by the outer layer, which actually extends less than the natural extension and increases in thickness.

Finally, we introduce a method for manufacturing a profiled steel pipe that can be drawn without a head. The steps are as follows:
1) Round steel pipe; 2) Lubricate the surface of the round steel pipe; 3) Pull the round steel pipe into a special-shaped steel pipe: push the round steel pipe into the pushing device and push forward, during the running of the round steel pipe, The round steel pipe is kept straight, so that the front end of the round steel pipe smoothly passes through the die hole of the drawing die and protrudes 25 to 40 cm, and then is drawn and formed, and then heat-treated, straightened and sheared to obtain a finished profiled steel pipe.

Since the round steel pipe travels straight during the drawing process of the round steel pipe, the drawing of the mold can be smoothly carried out, and the drawing of the round steel pipe is facilitated. This eliminates the need for a heading process, improves production efficiency and finished product quality, and reduces production costs.