Carbon steel plates have good cutting properties, and there are generally no special difficulties in cutting, and no special measures need to be taken. However, for steel plates of different thicknesses, the gas cutting process used is different, which is mainly divided into a gas cutting process for steel plates according to thickness, a gas cutting process for thin steel plates and a gas cutting process for large thickness Hong Kong version. Half-thickness steel plates mainly refer to steel plates with a thickness of 4-300mm, thin steel plates refer to steel plates with a thickness of less than 4mm, and large-thickness steel plates refer to steel plates with a thickness of more than 300mm.
(1) Cutting of general thickness steel plate
Generally, the thickness of steel plate is easier to cut by gas, and the G01-100 or G02-100 cutting torch can be used. The distance between the cutting nozzle and the workpiece is roughly equal to the length of the flame core plus 2-4mm. When gas cutting steel plates with a thickness of more than 25mm, in order to improve the gas cutting efficiency, a back inclination angle of 20-30 degrees can be used. It should be noted that the length of the wind line should preferably exceed 1/3 of the thickness of the gas-cut steel plate.
(2) Gas cutting of large thickness steel plates
Usually, the cutting of steel plates with a thickness of more than 300mm is called large-thickness steel plate cutting. Since the steel plate is relatively thick, greater than 300mm, gas cutting has certain difficulties. Large-scale cutting torches and cutting nozzles can be selected. When cutting large-thickness steel plates, it is necessary to ensure sufficient oxygen supply, that is, to provide sufficient oxygen flow to the cutting area. Multiple oxygen cylinders can be used to supply gas in parallel with busbars, which can be used when necessary. Multiple sets of busbars supply air alternately.
The entire oxygen supply system, including the pressure reducer, various joints and valves, the torch inlet pipe, the diameter of the cutting nozzle, etc., must meet the corresponding oxygen supply capacity. In addition, since it is very difficult to re-cut large-thickness steel, before cutting, it is necessary to estimate all the gas consumption according to the thickness of the steel plate and the cutting length, and prepare enough sources to avoid the interruption of cutting due to the exhaustion of oxygen in the middle.
For the cutting of large-thickness steel plates, it is difficult to start cutting, so the following requirements should be followed when starting cutting; when starting to cut, the preheating flame should be large, and the preheating of the workpiece should be started from the edge of the workpiece. When preheating to the cutting temperature, gradually turn on the cutting oxygen and tilt the cutting nozzle backward. When the edge of the cutting piece is completely cut through, increase the cutting oxygen flow and make the cutting nozzle perpendicular to the workpiece, and the cutting nozzle moves forward along the cutting line. , the cutting nozzle should do appropriate lateral swing, the incision has been widened, and the slag discharge is used.
In the process of re-cutting, if there is an opaque phenomenon, the cutting should be stopped and cut again from the other end.
For large thickness cutting, the isobaric cutting nozzle and the external mixing type cutting nozzle can be used, especially the latter.
(3) Gas cutting of thin steel plates
The main problems that are prone to occur in the process of gas cutting of thin steel plates are: the slag sticks to the back of the steel plate, the front of the steel plate is cut and the back is fused together.
Because the steel plate is thin, the slag is not easy to blow off. If the parameters are not selected properly, the slag sticks to the back of the steel plate after cooling and is not easy to remove. In addition, the thin plate is heated quickly and dissipates slowly. When the cutting nozzle just passes, both sides of the cutting seam are still in a molten state. If the cutting speed is a little slow and the preheating flame is not properly controlled, it is easy to deform the steel plate too much, and the front of the steel plate is easy to deform. The water chestnuts are also melted, forming the phenomenon that the front of the steel plate is cut and the back is fused together.
When gas cutting thin plate, in order to obtain better cutting effect, the following points should be paid attention to:
The preheating flame power should be small, and the heating point should fall on the cutting line and be in front of the cutting oxygen flow;
The cutting nozzle should be tilted forward and form an angle of 25-45 degrees with the steel plate;
The distance between the cutting nozzle and the workpiece surface is 10-15mm;
The cutting speed should be as fast as possible;
Use G01-30 torch and small cutting tip
In addition, in order to smoothly gas-cut thin steel plates, BG01-0.5 manual cutting torch and stepped cutting nozzle can also be used, or 2-3 preheating holes of the smallest jet-suction cutting nozzle can be blocked with steel wire.
Because the steel plate is relatively thin and heated, the workpiece may warp and deform during the cutting process, and it is difficult to obtain the correct part shape and dimensional accuracy. For example, when cutting the slats, the plane side bending occurs. At the edge of the cutting board, the holes in the board and the forming parts are formed, which will cause the upper convex and the lower concave deformation. For this reason, for general low carbon steel plates, while reducing the preheating flame power and improving the flame concentration, it can be cut while spraying water during the cutting process for cooling, or perforated in the plate for peripheral cutting to reduce deformation .
The vertical distance between the sprinkler pipe and the cutting nozzle is 20-50mm, and the sprinkler volume is 2l/min. Excessive water volume cannot produce better results. General rubber pipes can be used for sprinkler pipes. The cutting nozzle should use the smallest size, the flame energy of oxyacetylene is more concentrated than that of oxypropane, and the flame of oxygen petroleum gas is concentrated. In order to reduce the deformation, acetylene should be used as the preheating gas instead of propane and petroleum gas.
Another method of gas cutting thin plate is to use oxygen curtain cutting nozzle, which not only has fast cutting speed, good incision quality, but also small deformation of workpiece. For the cutting of very thin plates, the stacking gas cutting process can also be used, or microbeam plasma arc cutting or even laser cutting can be used.
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