Divorced eutectoid transformation process and product of ultrahigh carbon steels
AssigneeThe Board of Trustees of the Leland Stanford Jr. University
InventorsOleg D. Sherby, Toshimasa Oyama, Jeffrey Wadsworth
Life of this patent
Estimating the term…
Abstract
An ultrahigh carbon steel consisting of a structure formed by divorced eutectoid transformation with or without accompanying deformation such that substantially no pearlite is formed, having a fine grained iron matrix stabilized by cementite in spheroidized form. A method for processing the steel including heat treatment and mechanical working to form spheroidized proeutectoid carbide particles then reheating the steel for a time such that the carbon is not uniformly distributed in the austentite so that upon cooling, with or without accompanying deformation, a divorced eutectoid transformation occurs leading to a structure of spheroidized cementite in a fine ferrite grain matrix.
Claims9
A method for processing ultrahigh carbon steel employing a divorced eutectoid transformation comprising the steps of:
- (a) heating an ultrahigh carbon steel with a carbon content from about 1.0% to 2.1% to a temperature in excess of the A.sub.cm transformation temperature, to form an austenite matrix in which substantially all of the carbon is dissolved;
- (b) cooling the steel treated in step (a) from the A.sub.cm temperture to about the A.sub.1 transformation temperature, and deforming the steel during at least part of the cooling step;
- (c) cooling the steel treated in step (b) to below the A.sub.1 transformation temperature to form pearlite and ferrite;
- (d) reheating the steel treated in step (c) to a soaking temperature approximately 50.degree. C. above the A.sub.1 temperature;
- (e) soaking the steel at a temperature above A.sub.1 treated in step (d) in the soaking temperature range for a sufficient time such that the major portion of the pearlite is dissolved into the austenite matrix in which the carbon is not uniformly distributed;
- and
- (f) cooling at a rate equivalent to air cooling a second time to below the A.sub.1 transformation temperature.
A method for processing ultrahigh carbon steel comprising the steps of:
- (a) heating an ultrahigh carbon steel with a carbon content from about 1.0% to 2.1%, containing substantially spheroidized pro-eutectoid carbides in a matrix of ferrite and cementite, to a soaking temperature approximately 50.degree. C. above the A.sub.1 temperature;
- (b) maintaining the steel treated in step (a) at a soaking temperature for a time sufficient such that the eutectoid carbides are dissolved into the austenite in which the carbon is not uniformly distributed;
- and
- (c) cooling at a rate equivalent to air cooling the steel of step (b) to below the A.sub.1 transformation temperature.
A method for processing ultrahigh carbon steel comprising the steps of:
- (a) heating an ultrahigh carbon steel with a carbon content from about 1.0% to 2.1%, containing substantially spheroidized pro-eutectoid carbides in a matrix of martensite, to approximately 50.degree. C. above the A.sub.1 temperature
- (b) maintaining the steel treated in step (a) at a soaking temperature for a time sufficient such that the eutectoid carbides are dissolved into the austenite in which the carbon is not uniformly destributed;
- and
- (c) cooling at a rate equivalent to air cooling the steel of step (b) to below the A.sub.1 transformation temperature.
Dependencies are inferred from the claim text.