In plasma cutting torch cutting with large thickness, it often fails due to improper cutting method when starting the cut. Therefore, we must pay attention to master the correct method and essentials of cutting.

1. Cutting method and essentials

(1) The cross section of some large castings and forgings is round or chamfered and sometimes covered with a thick oxide layer. These parts are not easy to preheat to their ignition point. Therefore, the right-angle edge should be selected as the starting point. If it is necessary to start cutting on arcs or chamfered parts, mild steel rods can be used to help lead the cutting

(2) Before cutting large thickness steel, the preheating flame must be adjusted with the cutting oxygen turned on for preheating. The preheating flame should act on the upper corner of the workpiece, and the cutting oxygen flow is close to the cutting surface. When the flame heat expands from the end to the lower part, and the gas cutting reaction starts from the upper corner, move the plasma cutting torch slowly forward, and then transfer to the normal cutting speed after the entire thickness is cut through

(3) When the thickness of the steel is very large, an additional heat source can be used for supplementary heating at the bottom of the workpiece, which can promote smooth starting of cutting.

2. Precautions during the cutting process: During the cutting process, always observe the discharge of slag from the incision to ensure the normal cutting process. If the slag sparks fly off behind the cutting, the cutting speed should be appropriately slowed down. When the cutting speed is changed sharply or the cutting machine shakes, there will be gaps on the cutting surface, so be careful. In addition, when the cutting oxygen pressure is too high or the cutting speed is slightly faster, a concave center will appear in the middle of the cutting surface

3 Attentions at the end of the cutting: When cutting to the end, pay special attention to the intact end of the cutting. At this time, there can be no back drag in the cut. For this reason, the gas cutting speed should be adjusted to make the slag sparks fly down vertically. Cutting speed is too fast or too slow, or the plasma cutting torch is tilted back will cause the uncut part of the lower part of the terminal to remain, which will affect the quality.