1. Cutting methods and precautions in large thickness cutting often lead to failure due to inappropriate cutting methods. Therefore, we should pay attention to grasping the correct methods and essentials of cutting.

(1) Selection of cutting position Some large castings and forgings have rounded cross-section shape or chamfer, sometimes covered with a thick oxide layer, which is not easy to preheat to their ignition point. Therefore, the right edge should be chosen as the starting point. If it is necessary to cut at arc or chamfer, low carbon steel bar can be used to help cut.

(2) Before cutting large thickness steel by cutting method, the preheated flame should be adjusted to preheat under the condition of opening cutting oxygen. 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 along the end to the lower part and the gas cutting reaction starts at the upper corner, the torch moves forward slowly and can not be turned into normal cutting speed until the whole thickness is cut through.

(3) When the thickness of steel is very large, the additional heat source can be used to supplement the heating at the bottom of the workpiece, which can promote the smooth start-cutting.

2. Notice in the cutting process. During the cutting process, the medicines often observe the slag discharged from the incision to ensure the normal cutting process. If the slag spark falls behind the cutting, the cutting speed should be slowed down properly. When the cutting speed is changed sharply or the cutting machine is shaking, there will be a gap on the cutting surface, which should be paid attention to. In addition, when the cutting oxygen pressure is too high or the cutting speed is slightly faster, the concave center will appear in the middle of the cutting surface.

3. At the end of the cutting, attention should be paid to the intact end of the cutting when it is near the end of the cutting. At this time, there can be no back drag in the incision. Therefore, it is necessary to adjust the air-conditioning cutting speed to make the slag spark fly vertically. The cutting speed is too fast or too slow, or the torch will be tilted backward will cause the remaining uncut part of the lower part of the terminal, affecting the quality.