The cutting of steel pipes is divided into fixed steel pipes and gas cutting of rotating steel pipes. No matter what kind of gas cutting of pipe fittings, the flame should be perpendicular to the surface of the steel pipe during preheating. After the tape is cut through, gradually tilt the cutting nozzle until it is close to the tangential direction of the pipe, and then continue to cut.
The gas cutting of fixed steel pipes (horizontal hanging pipes) generally adopts the cutting method from bottom to top, and starts preheating from the lower part of the pipe first. When cutting, the cutting nozzle first cuts along the tangential direction close to the tube. When cutting to the horizontal position of the pipe, turn off the cutting oxygen, stop cutting, move the torch to the lower part of the pipe, turn on the cutting oxygen, and continue cutting.
This gas cutting method has the following advantages:
The slits can be seen clearly;
The torch is easy to move;
At the end of gas cutting, the cutting torch is just in a horizontal position, and it is not easy to damage the cutting nozzle by the cut pipe.
Gas cutting for rotating steel pipes is different from stationary steel pipes. First, preheat the side of the tube. At this time, the cutting nozzle and the surface of the tube are nearly vertical. After cutting through, the cutting nozzle is inclined upward and forms a nearly tangential angle with the tube. During the cutting process, the torch should continuously change position to maintain this cutting angle. After cutting a section, stop temporarily, turn the tube a little, and then continue cutting. Smaller diameter pipes can be cut in 2-3 times. Larger diameter tubes can be divided multiple times, but the fewer segments the better.
The steel pipe or round pipe is placed on the rotating tire, and is driven by the rotating tire to rotate in a counterclockwise direction. The cutting torch is placed at a certain distance away from the top surface of the steel pipe or cylinder, and the distance is determined according to the following method; the tangent to the outer circle of the pipe from the cutting point is the cutting torch axis and the tangent at an angle of 15-25 degrees. The angle should be larger.
When cutting at this angle, the cutting oxygen flow forms an angle of attack relative to the front edge of the incision, and at the same time, the hot slag along the inner and outer surfaces of the pipe wall preheats the front edge of the incision to a very high temperature, which greatly accelerates the combustion reaction of oxy-iron and makes the The cutting speed is greatly improved.
When gas cutting with proper diffusion forming nozzle is adopted, the following cutting speeds can be achieved;
1) The diameter of the steel pipe is 300-1020mm, the wall thickness is 12mm, and the cutting speed is 1500-2500mm/min;
2) The diameter of the steel pipe is 700-800mm, the wall thickness is 10mm, and the cutting speed is 3500-3600mm/min;
The rapid gas cutting process is used for pipe cut-to-length cutting on spiral pipe production lines.
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