In aluminum extrusion production, the maximum output is mainly determined by the extrusion speed, and the quality of aluminum profiles depends on the temperature at which the aluminum profiles are released. With the acceleration of the extrusion speed, the temperature of the aluminum profile will significantly increase. When the temperature exceeds a certain value, there will be a variety of problems in the structure and surface quality of the aluminum. Therefore, the choice of high temperature material for aluminum extrusion is important in the process.
How to choose high temperature material for aluminum extrusion？We can consider from the following aspects.
Hot work die steel must be able to withstand high mechanical and thermal stress during work to ensure that it does not develop at working temperature, obvious plastic deformation occurs, so the thermal yield strength and thermal hardness of steel are very important properties. When the temperature is below 500 ℃, the yield strength of 4Cr5 MoSin is slightly lower than that of 3Cr2W8V steel. When the temperature exceeds 500 ℃, the strength of 4Cr5 MoSin steel decreases rapidly, while the strength of 3Cr2W8V steel decreases rapidly above 600 ℃. So 4Cr5 MoSin steel meets the requirements in terms of thermal strength.
An important reason for the failure of the corner cracks of the extrusion die is the fracture toughness: the ability to generate and expand the grains, so the Kc of the hot work die steel is low. 3Cr2W8V steel is quenched at 1200 ℃, Cr5 MoSin steel is quenched at 1020 ℃. It is worth mentioning that the mold works at high temperature. Around 550 ℃, there is indeed a low Kc value in 3Cr2W8V steel, which is very unfavorable for the molds serving in this temperature zone.
Thermoplasticity reflects that hot work die steels are much better at resisting cracking at high temperatures than H21 steels, and they are all the same. At a high temperature of 550 ° C, the impact value AK of the 3Cr2W8V steel 3Cr2W8V steel at about 600 ° C also shows a trough, which is like its high temperature and trough, which indicates that the steel is hot brittle. This shows once again that the 3r2W8V steel is used as a frequent hot and cold cycle for hot work, so the limitation of the mold material for heat fatigue resistance.
When hot extrusion die is working, even careful comparison is made. The test method is as follows: the samples of two kinds of steel will also be subjected to severe mechanical vibration and thermal shock after quenching, so they are tempered to the same hardness (HRC47) after fire, and the material of the mold should have good impact toughness. The higher the grade, the easier the crack is to produce toughness.
In summary, H13 steel is better than 3Cr2W8v steel in terms of thermoplasticity, toughness, thermal fatigue resistance, thermal shock resistance, and high temperature oxidation resistance, except that it is slightly worse in thermal strength than 3Cr2W8V steel. In the working temperature range of aluminum alloy extrusion die, although the hot yield strength of H13 steel is lower than that of 3Cr2W8V steel, it can maintain a high level of strength and meet the strength required for mold work. In summary, 4Cr5 MoSiv steel is more suitable for hot extrusion die of aluminum alloy, which has been confirmed by many experiences at home and abroad.