Date Published: 09/17/2007
Abstract:
Distortion has been cited as a primary problem for all heat treaters in many surveys of the industry, and remains a primary concern. Consequently, metallurgical and manufacturing engineers continue to face the challenge of minimizing part distortion through the prudent application of process controls during the various steps in the heat treatment process. Such process engineering requires foundational understanding of process variation relative to corresponding variation in part response. This study reports on the use of a simple coupon shape to assess sensitivity of a steel alloy during quenching in terms of its residual stress and distortion responses. Using a rectangular test bar that has a series of notches machined on one face, a series of carburization and quench hardening trials were conducted. Local distortion was measured along the length of the bar, as well as residual stress using both X-RAY diffraction and Barkhausen noise methods. The analyses were supplemented by use of heat treatment modeling to study the interaction of thermal and transformation strains on resulting distortion and residual stress in the coupons. The data were finally differentiated by the quenching process conditions. This permitted process sensitivity analyses linking local dimensional and measured residual stress changes to the method and consistency of the quench practice. The procedure demonstrates the utility of using a simple steel coupon in a standardized procedure for heat treatment process assessment.
Author: Andrew Freborg, Zhichao Li, and Lynn Ferguson
Tags: Distortion sensitivity and Process sensitivity
Process Used: Carburization, Austenitizing, Intensive quench, Oil quench, and Deep freeze
Other Topics: