Patent US3877281A successfully refreshed from Google Patents.
US3877281A
Expired / Lapsed
US
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Method for producing a high strength bolt
Assignee: Kobe Steel Ltd
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Filing: 1973-09-04
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Granted: 1975-04-15
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Expires: 1993-09-04
Abstract
Abstract A method for producing a high strength bolt from a carbon steel or a low alloy steel material, which comprises the steps of subjecting said material, in turn, to cold working at the reduction-of-area percentage of 10 percent and over rapid heating to a temperature range from 450* C to A1 transformation point, warm-forming to a bolt shape and air-cooling or cooling at a cooling rate higher than that of the air-cooling. The steel material adapted for use herein includes a steel having a pearlite structure or a tempered martensite structure, and particularly the steel having the latter structure presents excellent resistance to the delayed rupture phenomenon with an accompanied high tensile strength of over 100 kg/mm2, particularly, in the range from 130 to 140 kg/mm2 and over.
Inventors
- 👤 Kiyoshi Shimizu
- 👤 Toshihiro Minami
- 👤 Eiji Niina
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:24
CPC Classifications
C; C21; C21D; C21D8/00; C21D8/06
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
96 words
A METHOD FOR PRODUCING A HIGH STRENGTH BOLT FROM A CARBON STEEL OR A LOW ALLOY STEEL MATERIAL, COMPRISING THE STEPS OF: SUBJECTING SAID MATERIAL TO COLD WORKING AT A REDUCTION-OFAREA PERCENTAGE OF 10 PERCENT AND OVER; RAPIDLY HEATING SAID MATERIAL THUS WORKED TO A TEMPERATURE RANGE FROM 450*C TO THE A1 TRANSFORMATION POINT AND AT A RATE OF AT LEAST 50*C/MIN.; WARM-FORMING SAID MATERIAL TO A BOLT SHAPE; AND AIR COOLING SAID MATERIAL OR COOLING SAID MATERIAL AT A COOLING RATE HIGHER THAN THAT OF SAID AIR COOLING, SAID COOLING RARE BEING AT LEAST 50*C/MIN.
Claim 2
Independent Claim
96 words
A METHOD FOR PRODUCING A HIGH STRENGTH BOLT FROM A CARBON STEEL OR A LOW ALLOY STEEL MATERIAL, COMPRISING THE STEPS OF: SUBJECTING SAID MATERIAL TO COLD WORKING AT A REDUCTION-OFAREA PERCENTAGE OF 10 PERCENT AND OVER; RAPIDLY HEATING SAID MATERIAL THUS WORKED TO A TEMPERATURE RANGE FROM 450*C TO THE A1 TRANSFORMATION POINT AND AT A RATE OF AT LEAST 50*C/MIN.; WARM-FORMING SAID MATERIAL TO A BOLT SHAPE; AND AIR COOLING SAID MATERIAL OR COOLING SAID MATERIAL AT A COOLING RATE HIGHER THAN THAT OF SAID AIR COOLING, SAID COOLING RARE BEING AT LEAST 50*C/MIN.
Claim 3
Dependent Claim
111 words
A method as defined in claim 1, wherein a carbon steel or a low alloy steel material is subjected at least once to the strengthening treatment consisting of cold working at a reduction-of-area percentage of 10 percent and over, rapid heating to a temperature range from 250*C to the A1 transformation point, and rapid cooling, after which said material thus treated is subjected in turn to cold working at a reduction-of-area percentage of 10 percent and over, rapid heating to a temperature range from 450*C to the A1 transformation point; warm-forming to a bolt shape, and air cooling or cooling at a cooling rate higher than that of said air cooling.
Claim 4
Dependent Claim
48 words
A method as defined in claim 1, wherein the high strength bolt produced according to claim 1 is subjected in turn to reheating to a temperature range from 450*C to the A1 transformation point, air-cooling or cooling at a cooling rate higher than that of said air cooling.
Claim 5
Dependent Claim
25 words
A method as defined in claim 3, wherein the heating time for bolts at the reheating temperature during the reheating treatment is within 5 minutes.
Claim 6
Dependent Claim
34 words
A method as defined in claim 1, wherein said steel material is that which is hot-rolled or has been subjected to a normalizing treatment or annealing treatment after hot-rolling, thereby presenting a pearlite structure.
Claim 7
Dependent Claim
45 words
A method as defined in claim 1 wherein said steel material is that which has been subjected to hardening and tempering treatments after hot-rolling, thereby presenting a tempered martensite structure and wherein the reduction-of-area percentage for cold working used ranges from 10 to 40 percent.
Claim 8
Dependent Claim
74 words
A method as defined in claim 1, wherein said steel material is subjected at least once to a cycle of hot-rolling, rapid heating and hardening, thereby rendering finer the austenite crystal grain size to over No. 10 and inclusive according to ASTM grain size, after which said material is subjected to a tempering treatment, thereby presenting a tempered martensite structure, and wherein the reduction-of-area percentage of cold working ranges from 10 to 40 percent.
Claim 9
Dependent Claim
17 words
A method as defined in claim 1, wherein the content of carbon is 0.5 percent, or lower.
Claim 10
Dependent Claim
13 words
A method as defined in claim 1 wherein the cold working is wire-drawing.
Claim 11
Dependent Claim
25 words
A method as defined in claim 1, wherein the heating time for bolts at the heating temperature during the strengthening treatment is within 3 minutes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |