Processing methods edit broadcast
1, the steel plate cutting method is suitable for 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"), equal particle cutting and laser cutting.
2, cutting method: Through the relevant process test, master the general characteristics of various cutting methods and cutting thickness range of steel plate.
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 the cutting of wear-resistant steel thick plate!! With the increase of the thickness and hardness of the steel plate, the crack tendency of the cutting edge increases. In order to prevent the generation of steel plate cutting cracks, the following recommendations should be followed when cutting:
Cutting cracks: Steel plate cutting cracks are similar to hydrogen caused cracks during welding, if the steel plate cutting edge cracks, it will appear within 48 hours to several weeks. Therefore, the cutting crack is a delayed crack, and the greater the thickness and hardness of the steel plate, the greater the cutting crack.
Preheat cutting: The most effective way to prevent steel plate cutting cracks is to preheat before cutting. Before flame cutting, the steel plate is usually preheated, and the preheating temperature mainly depends on the quality grade and plate thickness of the steel plate, as shown in Table 2. The preheating method can be carried out by flame burner, electronic heating pad, or heating furnace. In order to determine the preheating effect of the steel plate, the required temperature should be tested on the surface of the hot spot.
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 plate preheating is not possible, local preheating can be used instead. The use of low speed cutting methods to prevent cutting cracks, its reliability is not as good as preheating. It is recommended to preheat the cutting belt with flame gun cavitation several times before cutting, and the preheating temperature is about 100°C. The maximum cutting speed depends on the grade and thickness of the steel plate.
Special note: The combination of preheating and low speed flame cutting methods can further reduce the incidence of cutting cracks.
Slow cooling requirements after cutting: regardless of whether the cutting is preheated or not, the slow cooling after cutting the steel plate will effectively reduce the risk of cutting cracks. If it is stacked with warm parts after cutting, it can also be covered with thermal insulation blankets, and slow cooling 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. Steel plate thickness through low temperature tempering treatment, can effectively eliminate cutting stress (low temperature tempering process; Holding time: 5min/mm)
For the method of heating after cutting, the heating method of burning gun, electronic heating blanket and mourning heat furnace is also used for heating after cutting.
4, reduce the measures of steel softening steel softening characteristics mainly depend on its chemical composition, microstructure and processing methods. For thermally cut parts, the smaller the part, the greater the risk of softening the whole part. If the steel plate temperature exceeds 200-250°C, the hardness of the steel plate will be reduced.
Cutting method: Steel plate When cutting small parts, the heat supplied by the welding torch and preheating will accumulate in the workpiece. The smaller the cutting size, 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 cold cutting, such as water jet cutting. If thermal cutting must be used, plasma or laser cutting should be selected. This is because the flame cutting provides more heat to the workpiece and therefore increases the temperature of the workpiece.
Underwater cutting method: An effective way to limit and reduce the extent of the softening zone, using water to cool the plate and the cutting surface during the cutting process. Therefore, the steel plate can be cut in water, or it can be cut by spraying water to the cutting surface. Plasma or flame cutting is available using the underwater cutting method. Underwater cutting has the following characteristics:
The cutting heat affected zone is small.
Prevent the hardness of the whole workpiece from decreasing;
Reduce cutting workpiece deformation;
The workpiece can be cooled directly after cutting.
5. Flame cutting
Wear-resistant steel can be cut using flame cutting, plasma arc cutting or laser cutting methods as long as the operation is correct and equipped with the right cutting tools.
Different manufacturers produce different types of cutting tools, you must pay attention to the requirements listed in the cutting table (nozzle selection, gas pressure, cutting method, speed, etc.).
The surface condition of the steel plate also has an obvious influence on the flame cutting condition and the quality of the cutting surface. If the quality of the cutting surface is very high, it is necessary to clean the oxide, rust, paint and other impurities above the cutting area of the workpiece.
