Direct contact heating for hot forming die quenching

Abstract Most hot forming die quenching (HFDQ) lines use roller hearth furnaces to austenitize ultra high strength steel blanks. This paper describes an alternative heating technology in which Usibor ® 1500P blanks are austenitized by bringing them into contact with an electrically-heated monolith. In a laboratory-scale prototype, Usibor ® 1500P coupons austenitize in less than 30 s; subsequent material characterization confirms that a fully martensitic structure is formed, and that the hardness and yield strength are comparable to furnace-treated samples. Like many steels used in HFDQ, Usibor ® 1500P has a protective coating to prevent oxidation and decarburization of the coupons within the furnace. Preliminary tests found that the coating adheres to the monolith, which impedes coupon transfer. Five interchangeable striking surfaces were assessed to see if they were less prone to adhering to the molten Al–Si coating.