Forging processing of the hottest magnesium alloy

2022-08-13
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The most suitable processing methods for magnesium alloys are extrusion, closed die forging and free forging in anvils. When processed by these methods, the tool wall forms a side pressing polyimide force on the metal, so that the tensile stress and strain are minimized

magnesium alloy and aluminum alloy have many similarities in all aspects of forging, for example, in forging design and die design, allowance, tolerance and die forging slope, the two are the same. Because the process plasticity of magnesium alloy is lower than that of aluminum alloy, some parameters are slightly different. For example, the web thickness of MB15 and mb7 alloy forgings is larger than that of aluminum alloy forgings under the same conditions

magnesium alloy has poor fluidity and is only suitable for single groove die forging. For some die forgings with complex shape and large size, free forging is generally used, and finally single groove die forging is carried out. The surface finish of the die cavity should be high, and the carefully polished surface is conducive to the flow of metal in the forging process, and can prevent the surface roughness, scratches and other defects of forgings from being trapped. Magnesium alloy has good thermal conductivity, which will cause cracks when encountering cold molds. Due to the large contact area and long contact time between the forging and the die during die forging, the die must be preheated to a temperature lower than that of the forging blank, and a thin layer of MoS2 (2 molybdenum sulfide) smooth grease must be coated regularly. The preheating temperature of the die is generally about 250 ~ 300 ℃. Because the contact surface between the ring rolling die and the workpiece is small and the contact time is short, the requirements for the preheating temperature of the die are not strict

all kinds of lubricants used for aluminum alloy die forging are suitable for magnesium alloys. Often paint or spray the cutting stress graphite with oil agent and no cross-section within this range on the hot mold. After the oil agent burns, there is a thin layer of graphite left on the mold. Water colloidal graphite can also be used to provide clean working conditions. Although it is inconvenient, sometimes the residual soot in the blowtorch flame can be directly used for lubrication. No matter what kind of lubricant is used, it should be applied evenly and the lubricant coating should be thin. If the graphite deposition on the forgings is very thick, pitting corrosion or electrochemical corrosion will easily occur during acid pickling

magnesium alloy forgings are usually cooled in air after forging. In foreign countries, magnesium alloys are quenched directly after forging to prevent further recrystallization and grain growth. For some age hardening alloys, quenching water prevents the hardening components from precipitating from the solid solution, so that they can precipitate in the subsequent aging treatment

in small batch production, magnesium alloy forgings are often cut by band saw in cold state. Magnesium alloy is prone to edge cutting cracks. When cutting burrs with edge cutting die, it is suitable to use bite type die to make the gap between male and female dies as small as possible or no gap, and the edge cutting temperature should be between 200 ~ 300 ℃

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