chromium inhigh speed steel rollWhat is the role in?

The chromium in high-speed steel is partially present in M6C type carbides and can also form M23C6 type carbides. M23C6 can be completely dissolved at a lower quenching temperature, so that the solid solution can reach carbon chromium saturation without affecting the grain size. Chromium can also promote the complete dissolution of M6C in austenite, thereby improving the hardenability and red hardness of high-speed steel. In addition, when high-speed steel is tempered at 450-525°C, a part of chromium precipitates from martensite, which promotes dispersion hardening; another part of chromium remains in solid solution a to prevent softening when heated to higher temperatures. Adding 3%-4% chromium can obtain three times slightly higher hardness. Chromium can also significantly reduce oxidation in high speed steels. However, if the chromium content is too high, the excess chromium will participate in the formation of carbides precipitated during tempering. Such chromium-containing carbides tend to precipitate at lower temperatures, reducing the thermal stability of high-speed steels. If the chromium content is too high, the unevenness of the carbides also increases.

Due to the increase of chromiumhigh speed steel rollThe amount of MC carbide is reduced, and the hardness of M7C3 carbide is lower than that of MC carbide, which is not good for wear resistance. However, for a roll having a low chromium content, the roll surface tends to become rough due to preferential wear of the base material and adhesion of the rolling material to the roll surface, which increases the rolling friction coefficient and the rolling force. By increasing the chromium content, the roll contains a certain amount of M7C3 type carbide, which is beneficial to improve the surface roughness of the roll and reduce the rolling force. The increase of chromium content is also beneficial to improve the thermal shock resistance of high-speed steel rolls. Therefore, the suitable content of chromium in high-speed steel bars is 4.0-7.0%.

Continuous cold rolling requires high performance of the rolls, especially when the rolling mill is fully integrated with the pickling line and/or continuous annealing line. High productivity requires higher performance of the work rolls, especially the ability to maintain appropriate roughness during the rolling process. Therefore, the deterioration of the work roll surface is one of the main problems to be considered in cold rolling. Rolls need to have wear resistance and the ability to maintain roughness, because a low level of roughness is essential to ensure the friction required for rolling.

In recent years, the output of cold rolling work rolls has been greatly improved, and rolling technology and roll materials have greatly promoted this. This is a process of continuous development. First, half.high speed steel rollfor hot rolling and then for cold rolling. High-speed steel rolls (HSS) are now being introduced into cold rolling. These high alloy casting materials will become an effective substitute for forged steel rolls.

Generally, in order to expand the use range of forged steel rolls, in many cases, the surface thereof needs to be chrome-plated. High-speed cast steel rolls have good wear resistance, so similar rolling effects can be achieved without chrome plating, and there is no additional cost and environmental impact. In addition to these characteristics, high-speed steel rolls also have many characteristics in the grinding process.