Optimization of high
To improve the overall performance of high-speed steel and improved heat treatment process is a key technology.
In the quenching and tempering of high speed steels organization, residual carbide, which is a part of the secondary carbides and carbide at high temperatures does not dissolve. Their shape, size and distribution of the life of the tool has a great influence. Before hardening, reticular carbide, blocks, or chain distribution, the quenching uneven hardness, poor wear resistance, carbide accumulation place, brittleness. In order to increase its life, carbides become fine particle evenly distributed.
A. Control austenitizing concentric drill bits temperature.
Refined grains are not only improves the strength of the material can be the only way to improve the toughness of material. For high-speed steel and high carbon, high-alloy cold work tool steels can be appropriate to reduce the quenching temperature to reduce the tendency of brittle cracking. Because of the reduced quenching temperature, one can control the M6C, MC carbides dissolved in the matrix, the austenite average carbon content decreased, resulting Ms point rises, reducing the number of twins martensite after quenching, access to lath martensite-based quenching, thereby increasing the toughness of the steel; on the other hand, due to the quenching temperature decreases, the austenite grain size is refined, but also help to improve the toughness. The results showed that the austenitizing temperature of 1200 and 1180 %3, the grain size is 11.5; austenitizing temperature of 1160 %3, the grain size is 12, indicating that the appropriate temperature can reduce the quenching austenite grain has been refined. In addition, with austenitizing temperature decreases from 1200 %3 to 1160 %3, the hardness W6Mo5Cr4V2 speed steel decreased slightly, while the impact energy has increased, the impact energy absorption test values %Brom the 4.62J increased to 4.96J.
B. Hierarchical tempering process.
The purpose of high-speed steel and tempered by the precipitation of alloy carbides dispersion and transformation of retained austenite sufficient to obtain a stable organization. High-speed steel tempering process is to obtain a higher red hardness, wear resistance and strength and toughness of the key. Recommended literature abroad tempering process generally tend to use twice tempering method. Grade tempered by some domestic factories also be used instead of the conventional three tempering process. W6Mo5Cr4V2 use of high-speed steel grade tempering process, an increase of processing 350 %3 tempering at high temperatures, (350 %3 1 h + 560 %3 1 h), the results achieved compared to conventional tempering better strength and toughness. The results show that under the same austenitizing temperature, W6Mo5Cr4V26 high-speed steel grade tempered abrasion resistance and red hardness better than conventional tempering. Metallurgical testing showed that after W6Mo5Cr4V2 high-speed steel grade tempered with more uniform distribution of carburizing physical point, and more diffuse along the twin boundary carbide precipitation. Tempering allows W6Mo5Cr4V2 grade than conventional high-speed steel and tempered with a better performance. This is because, tempering increases fractionated 350 %3, so that high-speed steel to the precipitation of cementite uniformly dispersed physical point, can promote subsequent tempering M2C precipitation alloy carbides. It is these dispersion, fine carbide distribution makes high-speed steel grade tempered secondary hardening effect is more significant, which has a higher hardness, red hardness and better wear resistance than conventional high-speed steel and tempered. Meanwhile, the crack initiation and propagation along the twin boundary is more difficult, but also help to improve toughness. Performance test comparison are as follows: Hardness: Classification tempered sample is 64.6 HRC, conventional tempering sample is 63.8 HRChttp://thomaschap.blogtez.com/post25.php
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