Seamless steel pipes are very common in our lives. The application of seamless steel pipes is inseparable from the petroleum and chemical industries. Hot-rolled seamless steel pipes are generally produced on automatic rolling mill trains.

The solid tube is inspected, surface defects are removed, cut to the required length, centered on the perforated end of the tube, sent to the heating furnace for heating, and punched on the punching machine. At the same time, the perforation continues to rotate and advance. Under the action of the roller and the die, a cavity is gradually formed inside the tube blank, which is called a capillary tube.

From the processing point of view, hot rolling is hot processing, and cold drawing is cold processing. Hot rolling is rolling at a temperature above the recrystallization temperature, and cold rolling is rolling at a temperature below the recrystallization temperature;

From the appearance, it is distinguished that the cold-rolled seamless steel pipe has a bright surface, and the caliber size is smaller than that of the hot-rolled seamless steel pipe. The caliber of hot-rolled seamless steel pipe is larger than that of cold-rolled seamless steel pipe, and the surface has obvious oxide scale or red rust.

In terms of accuracy: the accuracy of cold-rolled seamless steel pipes is higher than that of hot-rolled seamless steel pipes.

It is used for hot-rolled steel pipes with low size requirements such as fluid transportation and mechanical structure; cold-rolled steel pipes are used for places with high requirements such as equipment, hydraulic systems, and pneumatics.

In terms of wall thickness, cold drawn seamless pipes are more uniform than hot rolled seamless pipes. Send to automatic rolling mill for succession rolling.

In order to obtain seamless steel pipes with smaller dimensions and better quality, cold rolling, cold drawing, or a combination of both must be used. Cold rolling is usually carried out in a two-high rolling mill. The steel pipe is rolled into an annular pass composed of a variable cross-section circular hole groove and a fixed cone. Cold drawing is usually performed on a single-strand or double-strand cold drawing machine with a length of 0.5-100T.

The extrusion process is to place the heated tube blank in a closed extrusion cylinder, and the perforated rod moves with the extrusion rod to extrude the extruded part from a smaller die hole. This method can produce steel pipes with smaller diameters, and its application range is also expanding.

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