Process of seamless rectangular pipe:

① Main consumption processes (main inspection processes) of hot rolled seamless rectangular tubes: tube blank preparation and inspection → tube blank heating → piercing → tube rolling → raw tube reheating → sizing (reducing) → heat treatment → waste tube straightening → finishing → inspection (non-destructive, physical and chemical, bench inspection) → warehousing

② Main consumption processes of cold-rolled (drawn) seamless rectangular tubes: blank preparation → pickling and smoothing → cold-rolled (drawn) → heat treatment → straightening → finishing → inspection

Consumption process of hot rolled seamless rectangular tube

Seamless square tubes are consumed by hot rolling (about 80~90%) or cold rolling and cold drawing (about 10~20%). The billets used for hot rolling pipes include round, square or polygonal ingots, rolled billets or continuous casting billets, and the quality of the billets has a direct impact on the quality of the pipes. There are three basic processes for hot rolling pipes: ① threading ingots or blanks into hollow thick wall tubes on the piercer; ② The capillary is thinned on the extension machine and extended into a waste pipe with a wall thickness close to that of the wall; ③ Rolled on the finishing mill to the requested scrap line. The pipe rolling mill series is represented by the large outer diameter of the square pipe

Consumption technology of roll piercing forming seamless rectangular tube

The commonly used 2-roll cross rolling piercing process of the piercer is shown in Figure 2. The round tube blank is pierced and rolled into a hollow thick wall tube (capillary), and the axes of the two rollers form an inclined angle with the rolling line. In recent years, the inclination angle has increased from 6 °~12 ° to 13 °~17 °, which accelerates the perforation speed. For square pipes with a diameter of more than 250mm, secondary perforation is adopted to reduce the wall thickness of the capillary. New processes such as perforation with active rotating guide plate, perforation with rear thrust, axial discharge and circular top welded square tube have also been carried out accordingly, thus strengthening the perforation process and improving the capillary quality.

Continuous hot-rolled seamless rectangular tube consumption.

The consumption equipment for continuous hot rolling seamless rectangular pipe consists of a piercing mill, a continuous pipe rolling mill and a tension reducing mill. See Figure 1 for the process flow. The round billets are threaded into tubes and inserted into mandrels. They are continuously rolled by a two high mill with 7~9 rolls whose axes are 90 ° to each other. After rolling, the mandrel is pulled out, and after reheating, the tension reducing is stopped, and the square tube with a growth of 165m can be rolled. The annual output of 140mm continuous pipe rolling mill is 400000-600000 tons, which is 2-4 times of that of automatic pipe rolling mill. The characteristics of this unit are that it is suitable for the consumption of square tubes with an outer diameter of 168mm or less, large equipment investment, large installed capacity, a mandrel length of 30m, and complex processing and manufacturing. The limited mandrel continuous pipe mill (MPM) presented in the late 1970s forced the mandrel to move at a speed less than that of the square tube when rolling, which can improve the metal movement conditions. The long tube and large diameter square tube are rolled with short mandrel.

Consumption of extruded seamless rectangular tube

For the consumption of extruded seamless rectangular tubes, firstly stop piercing or expanding the peeled round billet, then conduct induction heating or salt bath heating, and then apply the smoothing agent on the inner and outer surfaces and send it to the extruder. The metal is extruded into tubes through the annular gap between the die hole and the mandrel (Figure 5). It is mainly used for consumption of low plasticity high-temperature alloy pipes, profiled pipes, composite pipes, non-ferrous metal pipes, etc. This method has a wide consumption range but low output. In recent years, the consumption of extrusion tubes has also been developed due to the improvement of die materials, smoothing agents, extrusion speed, etc.

Cold drawn, cold rolled seamless rectangular tube consumption.

Cold rolled and cold drawn seamless rectangular tubes are used for consumption of small diameter, thin wall, fine and profiled tubes. The consumption characteristic is a multi process cycle process. The elongation can reach 6~8 with the periodic cold rolling tube mill (Fig. 6). In the 1960s, the end to high-speed, multi line, long stroke, long billet direction. In addition, small roll cold rolling tube mills have also been developed. It is mainly used to consume ultra-thin fine pipes with wall thickness less than 1mm. The cold rolling equipment is complex, the tool processing is difficult, and the variety and specification change is not sensitive; Generally, the combination process of cold rolling and cold drawing is adopted, that is, the wall is reduced by cold rolling to obtain large deformation, and then a variety of specifications are obtained by cold drawing.