Heat Treatment Procedure Qualification for Steel Castings

Charles, Mariol ; Deskevich, Nicholas ; Varkey, Vipin ; Voigt, Robert ; Wollenburg, Angela

Pennsylvania State University

关键词: Mechanical Properties;    Alloys;    Foundries;    Austenite;    36 Materials Science;   

DOI  :  10.2172/840826
RP-ID  :  NONE
RP-ID  :  FC07-99ID13841
RP-ID  :  840826

美国|英语

来源: UNT Digital Library

【 摘 要 】

Heat treatment practices used by steel foundries have been carefully studied as part of comprehensive heat treatment procedure qualification development trials. These studies highlight the relationships between critical heat treatment process control parameters and heat treatment success. Foundry heat treatment trials to develop heat treatment procedure qualifications have shed light on the relationship between heat treatment theory and current practices. Furnace load time-temperature profiles in steel foundries exhibit significant differences depending on heat treatment equipment, furnace loading practice, and furnace maintenance. Time-temperature profiles of furnace control thermocouples can be very different from the time-temperature profiles observed at the center of casting loads in the furnace. Typical austenitization temperatures and holding times used by steel foundries far exceed what is required for transformation to austenite. Quenching and hardenability concepts were also investigated. Heat treatment procedure qualification (HTPQ) schema to demonstrate heat treatment success and to pre-qualify other alloys and section sizes requiring lesser hardenability have been developed. Tempering success is dependent on both tempering time and temperature. As such, furnace temperature uniformity and control of furnace loading during tempering is critical to obtain the desired mechanical properties. The ramp-up time in the furnace prior to the establishment of steady state heat treatment conditions contributes to the extent of heat treatment performed. This influence of ramp-up to temperature during tempering has been quantified.