Abstract
The GA process for descaling hot rolled stainless steel is proposed, in which ammonium chloride vapor is introduced soon after annealing, reacting at high temperature with only the surface of the steel though use of the heat held in the steel, without damage to equipment composing materials.
Fundamental studies of the GA process were conducted to comfirm of its descaling effect, with the following results:
1. By comfirmig GA treatment with bending and brushing, it was possible to reduce descaling times for SUS 430 steel by acid cleaning using the ordinary HNO3-HF mixture to 10 seconds. In comparison with descaling times by bending only of 30∼50 seconds, this represented a time saving of 1/5∼1/3.
2. It was comfirmed that the hydrogen chloride and chlorine generated in GA treatment produced by the thermal decomposition of ammonium chloride and ferric chloride affected the scale, and changed the properties of the scale to acid soluble and mechanically frangible.
3. Problems still remain in terms of optimum GA process conditions for Austenite stainless steels snd systems for by-product recovery, but the process are judged to be practicable in principle.
