Ferric pickling of silicon steel
View Patent ↗The pickling process designed for pickling electrical steel strip in a continuous fashion comprising immersing the strip in at least one pickling tub. The pickling tub contains a mixture of HCl, Fe 2+ , and Fe 3+ and a low concentration of HF. Upon exiting the final pickling tub, the strip may be brushed or scrubbed to loosen any residual scale to form a clean strip.
1. A process for pickling silicon-containing electrical steel comprising treating the silicon-containing electrical steel with a mixture comprising HCl, HF, Fe 3+ , and Fe 2+ , wherein the concentration of HF is less than 3 weight %; and wherein the concentration of Fe 3+ is not less than about 2 weight %.
2. The process of claim 1 , where the concentration of the Fe 3+ is from about 2 weight % to about 8 weight %.
3. The process of claim 1 , where the concentration of HCl is from about 6 weight % to about 15 weight %.
4. The process of claim 1 , where the concentration of HF is from 1 to 2 weight %.
5. The process of claim 1 , where the concentration of HF is about 1.5 weight %.
6. The process of claim 1 , where the concentration of Fe 2+ is less than about 6 weight %.
7. The process of claim 1 , where hydrogen peroxide is not sprayed onto the steel.
8. The process of claim 1 , where the steel is pickled in a continuous fashion.
9. The process of claim 1 , where the temperature of the mixture is not less than about 140° F.
10. The process of claim 1 , where the temperature of the mixture is not less than about 150° F.
11. The process of claim 1 , where the silicon-containing electrical steel comprises less than 2 weight % silicon.
12. The process of claim 1 , where the silicon-containing electrical steel comprises about 3 weight % silicon.
13. A pickling process for silicon-containing electrical steel comprising the steps of:
placing the silicon-containing electrical steel in a pickling tub kept at a temperature ranging from about 165° F. to about 180° F. containing a mixture comprising Fe 3+ , HF, and HCl; where the tub is agitated, the mixture is continuously or periodically fed with an oxidant, HF, and HCl.