1. The steel plate cutting method is suitable for cold cutting and hot cutting. Cold cutting includes waterjet cutting, shearing, sawing or abrasive cutting, while thermal cutting includes oxygen-fueled flame cutting (hereinafter referred to as "flame cutting"), isoparticle cutting and laser cutting.
2. Cutting method: through relevant process tests, master the general characteristics and cutting thickness range of various cutting methods of steel plates.
3. The flame cutting method of high-grade wear-resistant steel is as simple as the cutting of ordinary low-carbon and low-alloy steel, and it is necessary to pay attention to !! as the thickness and hardness of the steel plate increase, the tendency of cracks on the cutting edge increases. In order to prevent the occurrence of steel plate cutting cracks, the following recommendations should be followed when cutting:
Cutting cracks: Cutting cracks are similar to hydrogen-induced cracks during welding, and if cracks occur on the cut edges of the steel plates, they will not appear until 48 hours to a few weeks after the thickness of the steel plate is cut. Therefore, cutting cracks are delayed cracks, and the greater the thickness and hardness of the steel plate, the greater the cutting cracks.
Preheating Cutting: The most effective way to prevent cracking in steel plate cutting is to preheat it before cutting. The plate is usually preheated before flame cutting, depending on the quality grade and thickness of the plate. The preheating method can be carried out by means of a flame burning gun, an electronic heating pad, or a heating furnace. In order to determine the preheating effect of the steel plate, the required temperature should be tested on the surface at the heating point.
Note: Special attention should be paid to preheating, so that the interface of the steel plate should be evenly heated, so as to avoid local overheating in the area in contact with the heat source.
Low-speed cutting: Another way to avoid cutting cracks is to reduce the cutting speed. If full preheating is not possible, you can use the local preheating method instead. Cutting cracks are prevented using a low-speed cutting method, which is not as reliable as preheating. It is recommended to preheat the cutting belt with a flame gun for several times before cutting, and the preheating temperature should reach about 100°C.
Special note: The combination of preheating and low speed flame cutting methods can further reduce the chance of cutting cracks.
Slow cooling requirements after cutting: Regardless of whether the cutting is not preheated or not, the slow cooling after cutting of the steel plate will effectively reduce the risk of cutting cracks. If it is not stacked with warm after cutting, it can also be covered with a thermal blanket, which requires cooling to room temperature.
Heating requirements after cutting: For the cutting of wear-resistant steel plates, heating (low temperature tempering) is taken immediately after cutting, which is also an effective method and measure to prevent cutting cracks. The cutting thickness of the steel plate can be effectively eliminated by low-temperature tempering treatment (low-temperature tempering process; moisturizing time is 5min/mm), and for the method of heating after cutting, the heating method of burning gun, electronic heating blanket and jiewai heating furnace is also used for heating after cutting.
4. Measures to reduce the softening of steel platesThe anti-softening characteristics of steel mainly depend on its chemical composition, microstructure and processing methods. For thermally cut parts, the smaller the part, the greater the risk of the entire part softening. If the temperature of the steel plate exceeds 200-250°C, the hardness of the steel plate will decrease.
Cutting method: When cutting small parts, the heat supplied by the welding torch and preheating will accumulate in the workpiece. The smaller the size of the cutting workpiece, the size of the cutting workpiece shall not be less than 200mm, otherwise the workpiece will have the risk of softening. The best way to eliminate the risk of softening is to cut cold, such as waterjet cutting. If thermal cutting is a must, plasma or laser cutting is limited. This is because flame cutting gives more heat to the workpiece and therefore increases the temperature of the workpiece.
Underwater cutting method: an effective method to limit and reduce the extent of the softening zone, using water to corrugate the steel plate and cut the surface during the cutting process. As a result, the steel plate can be cut either by placing it in water or by spraying water onto the cutting surface. Plasma or flame cutting is available using the underwater cutting method. Underwater cutting has the following characteristics:
Small heat-affected zone of cutting;
Prevent the hardness of the entire workpiece from decreasing;
Reduce the deformation of the cutting workpiece;
The workpiece can be cooled directly after cutting.
