Nickel-chromium alloys iron-chromium aluminum alloys have different metallographic structures, their high-temperature characteristics are different. How to grasp the hot workability of the alloy is an important part in the blanking hot rolling production.
Hot workability of iron-chromium aluminum alloy:
The iron-chromium aluminum alloy has a ferrite structure at high temperature, the carbides, nitrides, other precipitates existing in the alloy at room temperature will partially dissolve. The iron-chromium aluminum alloy exhibits the following hot working characteristics. These characteristics should be paid attention to when formulating hot processing technology.
1) The ferrite grains start to grow 720 to 780 ° C, grow rapidly at 900 ° C, grow sharply above 1000 ° C. The roughened ferritic iron alloy's hot workability significantly decreases. For this reason, when formulating the iron-chromium-aluminum alloy heating process, we must strive to shorten the residence time in the high temperature area, especially the residence time above 1000 ℃ should be shorter.
2) The carbides, nitrides other precipitates present in the ferrite alloy are precipitated during high temperature cooling, which will reduce the cold workability of the alloy. For this reason, the alloy should be rapidly cooled after high temperature blanking hot rolling to reduce the amount of precipitation of compounds precipitated phases improve the cold workability of hot rolled products.
3) The thermal conductivity of the ferrite alloy is relatively good, the thermal conductivity is 1.5 times that of the austenitic alloy. Therefore, when heating up, the iron-chromium aluminum alloy can be heated at a faster speed to shorten the heating time.
4) The linear expansion coefficient of ferrite alloy is about 60% smaller than that of austenitic alloy. The ability to withstand the thermal stress caused by rapid cooling rapid heat is weak. Therefore, it is required that the temperature of the steel ingot billet during heating should be too high, so that the internal stress caused by the excessive temperature difference will cause the alloy to crack.
In summary, the above high-temperature properties of iron-chromium aluminum alloys should be considered emphasized when formulating the blanking hot rolling processes.
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