Hot Workability of Heat Resistant Steel Alloys

Hot Workability of Heat Resistant Steel Alloys
Ni Cr alloy and Fe Cr Al alloy have different metallographic structures and high temperature characteristics. How to grasp the hot workability of alloy is an important link in the production of cogging and hot rolling.
Hot workability of Fe Cr Al alloy:
Fe Cr Al alloy has ferrite structure at high temperature, and carbides, nitrides and other precipitates existing at room temperature in the alloy will be partially dissolved. Fe Cr Al alloy shows the following hot working characteristics. These characteristics should be paid attention to when making hot working process.

1) Ferrite grains begin to grow at 720-780 ℃, rapidly grow at 900 ℃, and rapidly grow above 1000 ℃. The hot working plasticity of the coarsened ferritic ferroalloy decreases significantly. Therefore, the residence time in the high temperature zone should be shortened as much as possible when the heating process of Fe Cr Al alloy is formulated, especially when the temperature is above 1000 ℃.
2) Carbides, nitrides and other precipitates in ferritic alloys precipitate from the cooling process at high temperature, which will reduce the cold working plasticity of the alloy. Therefore, the alloy should be rapidly cooled after high temperature bloom and hot rolling to reduce the precipitation amount of compounds and precipitates and improve the cold working plasticity of hot rolled products.
3) The thermal conductivity of ferritic alloy is better, and the thermal conductivity is 1.5 times of that of austenitic alloy. Therefore, Fe Cr Al alloy can be heated at a faster speed to shorten the heating time.
4) The linear expansion coefficient of ferritic alloy is about 60% less than that of austenitic alloy. The ability to bear the thermal stress generated by quenching and heating is weak, so it is required that the temperature of ingots and billets should not be too high when they are heated, so as to prevent the internal stress caused by excessive temperature difference from causing cracks in the alloy.
To sum up, the above high temperature properties of Fe Cr Al alloy should be considered and paid attention to when developing the bloom and hot rolling process.