Wear-resistant steel refers to a special plate product designed for large-area wear conditions and is widely used in parts with high wear resistance properties in engineering fields such as metallurgical machinery, machinery mining machinery, and cement machinery. Due to the high alloy content of the material, if the cutting process is unreasonable, the cracking of the cutting surface is likely to occur. The article mainly analyzes and researches the edge cutting (including the CNC cutting of the steel plate) after the steel plate is produced to reduce the probability of thermal cutting cracks.
Thermal cutting mainly includes flame cutting (including CNC), plasma cutting (including CNC), and laser cutting (including CNC). Among them, flame-cutting uses oxygen as the fuel and is the most widely used, but it has the disadvantage that it is easy to crack when cutting wear-resistant materials. This cutting crack is a delayed crack, which has the characteristics of being placed at room temperature for a period of time after cutting. But at the same time, the material cutting crack can be prevented by adjusting the material composition and optimizing the heat treatment and cutting process.
Cutting process improvement measures
1.Preheat the steel plate surface before cutting
This measure can not only reduce the cooling rate, improve the tissue of the cutting site but also facilitate the escape of hydrogen. The preheating temperature depends on the thickness and hardness level of the material. According to the thickness of the steel plate, formulate the preheating temperature range and formulate a suitable heating system. Use an electric heating furnace to heat the surface of the steel plate before the material is cut. During preheating, the entire surface of the steel plate is uniformly heated, and the preheating temperature cannot exceed the set temperature. Otherwise, the hardness of the material will decrease.
2. Set a lower cutting speed when cutting
If the steel plate surface cannot be preheated before cutting, this method can be used. The cutting speed in actual production is also related to the hardness level and thickness of the steel plate. In production practice, the appropriate cutting speed and cutting nozzle model are selected according to different material thicknesses. If the two processes of material preheating and low-speed cutting are used in practice, the possibility of cracks on the cutting surface can be further reduced.
3. Slow cooling or heat preservation in the furnace
Regardless of whether the cutting is warm or not, the slow cooling process of the material after the cutting will reduce the risk of cutting cracks. This requires that the workpieces that are still warm after the cutting are stacked together and covered with an insulating blanket to achieve slow cooling to room temperature. Regardless of whether the material can be heated by burning a gun, an electronic heating pad, or heating furnace, the holding temperature should follow the heating process regulations. Equipped with a suitable electric heating furnace, formulating a suitable insulation system, and using the heating furnace to heat the steel plate after cutting and slowly cool it to room temperature. The practice has proved that the effect is better.
4. Selection of other thermal cutting equipment
Under normal circumstances, according to the equipment capacity of thermal cutting equipment, it is not recommended to use flame cutting for steel plates with a thickness of less than 40 mm. Plasma cutting or laser cutting with faster cutting speed and fewer cutting heat affected zones is not recommended. Way to avoid delaying cracks. CNC plasma and laser cutting equipment have a faster cutting speed than flame cutting, and the maximum cutting speed can reach 10,000 mm/min when cutting medium and thick plate materials. However, the cutting thickness of this type of equipment is far inferior to flame cutting, especially since the thickness of laser blanking is smaller. Generally speaking, the greater the power of the cutter of the equipment, the greater the thickness and the faster the cutting speed, but the greater the equipment investment. CNC plasma and laser equipment for materials that require high precision and relatively thin specifications have become the first choice in the market. In order to solve the hot cutting cracks of the wear-resistant material steel plate, some processing units use waterjet equipment for cutting. This cutting method uses the high pressure generated by the high-pressure pump and uses a kind of sand called garnet as the medium to affect the edge of the material. Perform grinding and cutting. It has the characteristics of zero cutting heat-affected zone, reducing the hardness of the entire workpiece to zero, and cutting the workpiece without deformation. However, due to its relatively low processing efficiency, it has not been widely adopted in the field of steel plate material processing and is not recommended here.
By optimizing the thermal cutting process, selecting suitable cutting equipment and heating the plate before cutting the steel plate, setting low-speed cutting during cutting, and heating and slow cooling after cutting, cutting cracks can be effectively avoided or reduced.