Changzhou Longfu Knitting Co., Ltd. , https://www.czcircularmachine.com
What should you pay attention to when using the extrusion die?
The extrusion die belongs to a molding die, which is a non-cutting precision plastic forming process with a heating temperature between room temperature and a complete internal crystallization temperature (200-850 ° C for steel materials). Extrusion parts have high strength, good rigidity, light weight, and precision and surface roughness are close to machining. When we use extrusion dies, we should pay attention to the following four major issues:
1, mold material
During the working cycle of the extrusion die, due to the high temperature, high pressure and alternating load, the die steel should have high strength, high hardness, toughness, wear resistance and good red hardness. specifically is:
1) When pressing at low temperature (200-400 ° C), 3Cr3Mo3W2V, W18Cr4V, W6Mo5Cr4V2, etc. are selected.
2) When pressing at medium temperature (400-500 ° C), 4Cr5MoSiV, 4Cr5W2SiV, 5CrNiMo, etc. are selected.
3) When pressing at high temperature (above 500 °C), 5Cr4Mo3SiMnVAl, 6Cr4Mo3Ni2WV, 3Cr3Mo3W2V, 9Cr6W3Mo2V2 are selected.
2, mold structure
When designing the mold structure, it should be considered that the mold structure is as favorable as possible to the metal flow, the force of each part of the mold is uniform, and the shape of the cross-section of the cavity should be fully considered. The working part should be connected smoothly, and the stress concentration source caused by sharp corners and narrow joints should be avoided as much as possible. To prevent cracking during heat treatment and extrusion.
3, surface strengthening and toughening treatment
Reasonable toughening treatment and surface strengthening treatment should be adopted to make the mold obtain good overall toughness and high surface hardness, wear resistance and anti-mucosal performance, and effectively improve the service life of the mold. For example, Cr4W2Mo2V warm extrusion die process: deformation residual heat normalizing treatment (960 ° C, heat preservation 1.5h) + isothermal spheroidizing annealing (900 ° C, heat preservation 5h) + high temperature quenching (1000-1050 ° C, oil quenching) + high temperature back Fire (560-580 ° C, 1.5 h) + SCN ternary co-infiltration process for strengthening and toughening treatment. Another example is 3Cr2W8V warm extrusion die: preheated by heating at 1100 °C for 2-3 min, then placed in 50% K2NO3 + 50% Na2NO3 salt bath, 390 °C for 0.5 h, air cooled to room temperature, austempering plus 560 °C × 2h tempered twice.
4, anti-friction and lubrication methods
In order to reduce the direct contact between the surface of the mold and the blank, the lubricant is applied to the surface of the mold or the blank to reduce the friction, and the thermal conductivity can also be improved. Dip coating before heating can also reduce oxidation and decarburization. Found in the production: boron oxide + graphite, boron oxide + molybdenum disulfide, graphite water or oil, graphite + molybdenum disulfide + oleic acid, silica sand + alumina + boric acid and other lubricants, can achieve good lubrication.