Nano-composite martensitic steels
AssigneeMMFX Technologies Corporation
InventorsGrzegorz J. Kusinski, David Pollack, Gareth Thomas
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Abstract
Carbon steels of high performance are disclosed that contain dislocated lath structures in which laths of martensite alternate with thin films of austenite, but in which each grain of the dislocated lath structure is limited to a single microstructure variant by orienting all austenite thin films in the same direction. This is achieved by careful control of the grain size to less than ten microns. Further improvement in the performance of the steel is achieved by processing the steel in such a way that the formation of bainite, pearlite, and interphase precipitation is avoided.
Claims27
An alloy carbon steel having a martensite start temperature of at least about 300° C. and comprising martensite-austenite grains of 10 microns or less in diameter, each grain bounded by an austenite shell and having a microstructure containing laths of martensite alternating with thin films of austenite in a uniform orientation throughout said grain.
A process for manufacturing a high-strength, corrosion-resistant tough alloy carbon steel, said process comprising:
- (a) forming a carbon steel alloy composition having a martensite start temperature of at least about 300° C.;
- (b) heating said carbon steel alloy composition to a temperature sufficient to cause said alloy composition to assume a homogeneous austenite phase with all alloying elements in solution;
- (c) treating said homogeneous austenite phase while said austenite phase is above its austenite recrystallization temperature to achieve a grain size of about 10 microns or less;
- and
- (d) cooling said austenite phase through said martensite transition range to convert said austenite phase to a microstructure of fused grains, each grain having a diameter of about 10 microns or less and containing laths of martensite alternating with films of retained austenite in a uniform orientation throughout said grain.
Dependencies are inferred from the claim text.