- In high-speed steel, chromium is not only partially present in M6C carbides, but also can form M23C6 carbides.
- However, if the chromium content is too high.
- Excessive chromium will be involved.
- It forms carbides during the tempering process.
- These carbides with chromium are easy to precipitate at low temperatures.
- This lowers the thermal stability of high-speed steel.
- High chromium content increases the non-uniformity of carbides.
- Adding 3% to 4% chromium can increase the hardness by about 3 degrees.
- Chromium can also significantly reduce the oxidation of high speed steel.
- However, if the content of chromium is too high.
- Excessive chromium will be involved in the formation of carbides precipitated during the tempering process.
- These chromium-containing carbides are easy to precipitate at low temperatures.
- This reduces the thermal stability of high-speed steel.
- High chromium content will increase the non-uniformity of carbides.
The function and suitable content analysis
- Because chromium increases the number of M7C3 carbides in the high speed steel roll, the amount of MC carbides is reduced. The hardness of M7C3 carbides is lower than that of MC carbides, which is unfavorable to wear resistance.
- However, for rolls with low chromium content, the surface of the roll is easy to become rough. This is due to the faster wear of the substrate and the adhesion of the rolled material to the roll surface. As a result, the rolling friction coefficient and rolling force increase.
- By increasing the chromium content, the roll contains a certain amount of M7C3 carbides. This is helpful to enhance the roughness resistance of the roll surface 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 appropriate content of chromium in high-speed steel bars is 4.0%-7.0%.
Discussion on work roll in continuous cold rolling
- Continuous cold rolling requires higher roll performance.
- Especially when the mill is fully integrated with the pickling line and/or the continuous annealing line.
- In order to achieve high productivity.
- The working roll needs to have superior performance.
- Especially the ability to maintain the appropriate roughness during the rolling process.
- Therefore, the deterioration of work roll surface is one of the problems.
- It needs to be paid attention to in cold rolling.
- The roll must have the ability to wear and maintain roughness.
- Low roughness levels are critical.
- They ensure the friction required for rolling.
