US4404047A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the improved heat treatment of steels using direct electrical resistance heating
Assignee: Lasalle Steel Co
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Filing: 1980-12-10
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Granted: 1983-09-13
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Expires: 2000-12-10
Abstract
Abstract A process for the energy efficient heat treatment of steels wherein a steel workpiece is rapidly heated to a temperature above the A 3 temperature of the steel to convert the steel to austenite, the workpiece is then rapidly quenched in a liquid quench medium to convert the austenite to a predominantly martensitic microstructure, and the steel is then tempered by rapid heating while the workpiece is under tension, the tempering serving to convert the steel to a tempered martensitic form. The present invention virtually eliminates the problem of quench cracking and minimizes quench distortion as well as providing a finished product with improved uniformity, improved surface quality, and improved mechanical properties.
Inventors
- 👤 Gerald W. Wilks
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 19:51
CPC Classifications
C; C21; C21D; C21D1/00; C21D1/18; C21D9/00; C21D9/52
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
168 words
A method for heat-treating a steel workpiece which substantially eliminates quench cracking and quench distortion, which method comprises (a) affixing suitable electrical contacts to opposite ends of a single steel workpiece of finite length and uniform cross section that is susceptible to quench cracking and quench distortion when austenitized in a conventional furnace and severely quenched, (b) rapidly electrically heating the entire workpiece to an austenitizing temperature above the A 3 temperature for said steel such that the heating time required between the A 1 and the austenitizing temperature is less than 100 seconds, (c) immediately quenching the entire austenitized workpiece in a liquid quenching medium having a severity of quench factor equal to or greater than that of unagitated water to form a predominantly martensitic microstructure, and (d) tempering said hardened workpiece by rapidly electrically heating the entire workpiece to a temperature below the A 1 temperature for said steel while maintaining said workpiece in tension at a load level below the yield strength of the steel.
Claim 2
Independent Claim
168 words
A method for heat-treating a steel workpiece which substantially eliminates quench cracking and quench distortion, which method comprises (a) affixing suitable electrical contacts to opposite ends of a single steel workpiece of finite length and uniform cross section that is susceptible to quench cracking and quench distortion when austenitized in a conventional furnace and severely quenched, (b) rapidly electrically heating the entire workpiece to an austenitizing temperature above the A 3 temperature for said steel such that the heating time required between the A 1 and the austenitizing temperature is less than 100 seconds, (c) immediately quenching the entire austenitized workpiece in a liquid quenching medium having a severity of quench factor equal to or greater than that of unagitated water to form a predominantly martensitic microstructure, and (d) tempering said hardened workpiece by rapidly electrically heating the entire workpiece to a temperature below the A 1 temperature for said steel while maintaining said workpiece in tension at a load level below the yield strength of the steel.
Claim 3
Dependent Claim
20 words
A method in accordance with claim 1 wherein the total heating time is between about 5 and about 100 seconds.
Claim 4
Dependent Claim
25 words
A method in accordance with claim 1 wherein the heating time between the A 1 and the austenitizing temperature is less than about 40 seconds.
Claim 5
Dependent Claim
26 words
A process as defined in claim 1 wherein the steel is rapidly heated to a temperature above the A 3 temperature by direct electric resistance heating.
Claim 6
Dependent Claim
19 words
A process as defined in claim 4 wherein the steel is heated in tempering by direct electric resistance heating.
Claim 7
Dependent Claim
22 words
A process as defined in claim 5 wherein the workpiece is in the form of a steel having a repeating cross section.
Claim 8
Dependent Claim
21 words
A process as defined in claim 5 wherein the workpiece is quenched under conditions providing a severity-of-quench coefficient greater than 1.2.
References Cited (Backward Citations)
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US3699797A
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US3847002A
Cited
US3929524A
Cited
US4252578A
Cited
SU679634A1
Cited
SU763477A1
Cited
US4321098A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-09-12 | 1987-03-14 | 1987-09-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-09-12 | 1991-03-14 | 1991-09-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-09-12 | 1995-03-14 | 1995-09-13 | $7700.00 | Window Closed / Lapsed |