Cutting and process of wear resistant steel plate
1. Steel plate cutting methods include cold cutting and hot cutting.
Cold cutting includes water jet cutting, shearing, sawing or abrasive cutting.
Thermal cutting includes oxygen fuel flame cutting (hereinafter referred to as "flame cutting"), plasma cutting and laser cutting.
2. Cutting test
The general characteristics, cutting parameters and cutting thickness range of various cutting methods of steel plate are mastered through relevant process tests.
3, flame cutting of wear-resistant thick steel plate
The method is as simple as that of ordinary low carbon and low alloy steel, but cracks should be prevented when cutting thick steel plates. The following suggestions should be followed when cutting thick steel plates:
Cutting Cracks: Cutting cracks in steel plates are similar to hydrogen-induced cracks in welding. If a crack occurs at the edge of the steel plate, it will occur within 48 hours to weeks after cutting. Therefore, the cutting crack belongs to delayed crack, the greater the thickness and hardness of steel plate, the greater the tendency of cutting crack.
Preheating cutting: the most effective way to prevent cracks in steel plate cutting is to preheat before cutting. Before flame cutting, the steel plate is usually preheated. The preheating temperature mainly depends on the quality grade and thickness of the steel plate. The preheating method can be carried out by flame burner, electronic heating pad or heating furnace. In order to determine the preheating effect of steel plate, the temperature should be added on the hot spot surface. Note: During preheating, the whole steel plate should be heated evenly to avoid local overheating in the area where the heat source is contacted. If the whole plate can not be preheated, the local preheating method can be used instead.
Low speed cutting: another way to avoid cutting cracks is to reduce the cutting speed.
Using low speed cutting method to prevent cutting cracks is not as reliable as preheating. We suggest that the cutting strip should be preheated several times by flame gun before cutting, and the preheating temperature should reach about 100 C. The maximum cutting speed depends on the grade and thickness of the steel plate.
Specifically, the combination of preheating and low-speed cutting method can further reduce the occurrence of cutting cracks.
Slow cooling requirement after cutting: Whether the steel plate is preheated or not before cutting, slow cooling after cutting will effectively reduce the risk of cutting cracks. The parts with warm and warm after cutting are stacked and covered with a heat-insulating blanket to achieve slow cooling to room temperature.
The requirement of heating after cutting: heating immediately after cutting thick steel plate (low temperature tempering) can effectively eliminate cutting stress (holding time can be 5 min / mm), and is also an effective method and measure to prevent cutting cracks. The heating method can also use burning gun, electronic heating pad and heating furnace. The heating temperature should not exceed 200 degrees C.
4, measures to reduce the softening of steel plates
The softening resistance of steel depends mainly on its chemical composition, microstructure and processing mode. In hot cutting, the hardness of wear-resistant steel plate decreases when the temperature exceeds 200-250 degrees C. The smaller the parts, the greater the risk of softening the whole parts.
The best way to eliminate the risk of softening is cold cutting, such as water jet cutting or wire cutting. If hot cutting is necessary, plasma or laser cutting with relatively small input is preferred.
Underwater cutting method: Limit and reduce the scope of the effective method of softening zone, can be placed in the underwater steel cutting, can also be cut in the cutting surface watering. Plasma or flame cutting can be used for underwater cutting.
Underwater cutting has the following characteristics:
Cutting heat affected zone is small.
Prevent the hardness of the whole workpiece from decreasing.
Reduce the deformation of cutting workpiece;
After cutting, the workpiece can be cooled directly.