Patent ID: 6074493
Filing Date: 2000-06-13
Classification: C21D,C23C

Abstract:
A method of continuously carburizing a metal strip comprising the steps of:(a) preheating the metal strip;(b) heating the metal strip in a heating zone following step (a), to a temperature of 700.about.950.degree. C.;(c) maintaining the metal strip heated in step (b) at the temperature of 700.about.950.degree. C. in a uniform heating zone to form a congregated structure having a (1,1,1) organization;(d) carburizing the metal strip in a carburizing heating zone at a furnace temperature of 700.about.950.degree. C., in an atmosphere having a carbon monoxide concentration of 0%<CO.ltoreq.22% and hydrogen concentration of 0%.ltoreq.H.sub.2 .ltoreq.30%;(e) rapidly cooling the metal strip in a first cooling zone to a temperature of 500.about.400.degree. C. at a cooling speed of approximately 5.degree. C./sec or higher; and(f) cooling the metal strip in a second cooling zone to a temperature of 250.about.200.degree. C.