US3847682A
Expired / Lapsed
US
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Method of strengthening low carbon steel and product thereof
Assignee: Armco Inc
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Filing: 1972-11-14
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Granted: 1974-11-12
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Expires: 1992-11-14
Abstract
Abstract Deep drawing steel is strengthened by alloy-nitrogen precipitation strengthening to a minimum average yield strength of 50 ksi. A deoxidized, low carbon steel sheet stock or article formed therefrom, containing from about 0.02 percent to 0.2 percent titanium in solution, from about 0.025 percent to 0.3 percent columbium in solution, from about 0.025 percent to about 0.3 percent zirconium in solution, alone or in admixture, is heat treated at 1,100* - 1,350*F in an atmosphere containing ammonia in an amount insufficient, at the temperature and time involved, to permit formation of iron nitride.
Inventors
- 👤 R Hook
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 05:09
CPC Classifications
C; C21; C21D; C21D8/00; C21D8/02; C21D8/04; C21D8/0447; C21D8/0457; C21D3/00; C21D3/02; C21D3/08; C21D8/0473
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
205 words
A METHOD OF INCREASING THE YIELD STRENGTH OF A LOW CARBON STEEL SHEET STOCK, WHICH COMPRISES: PROVIDING A DEEP DRAWING QUALITY STEEL CONTAINING FROM ABOUT 0.002 PERCENT TO ABOUT 0.015 PERCENT CARBON, UP TO ABOUT 0.012 PERCENT NITROGEN, UP TO ABOUT 0.08 PERCENT ALLUMINUM, AND A NITRIDE-FORMING ELEMENT CHOSEN FROM THE GROUP CONSISTING OF TITANIUM, COLUMBIUM, ZIRCONIUM, AND MIXTURES THEREOF, IN AMOUNTS SUCH THAT TITANIUM IN SOLUTION IS FROM ABOUT 0.02 TO ABOUT 0.2 PERCENT, COLUMBIUM IN SOLUTION IS FROM ABOUT 0.025 PERCENT TO ABOUT 0.3 PERCENT, AND ZIRCONIUM IN SOLUTION IS FROM ABOUT 0.025 PERCENT TO ABOUT 0.3 PERCENT, ALL PERCENTAGES BEING BY WEIGHT; REDUCING SAID STEEL TO FINAL THICKNESS; AND HEATING THE RESULTING SHEET STOCK IN AN ATMOSPHERE COMPRISING AMMONIA AND HYDROGEN AT A TEMPERATURE BETWEEN 1,100* AND 1,350*F FOR A PERIOD OF TIME SUFFICIENT TO CAUSE REACTION OF SAID NITRIDE-FORMING ELEMENT WITH THE NITROGEN OF SAID AMMONIA TO FORM SMALL, UNIFORMLY DISPERSED NITRIDES, WHEREBY TO INCREASE THE AVERAGE YIELD STRENGTH OF SAID SHEET STOCK TO A MINIMUM OF 60 KSI, THE CONCENTRATION OF AMMONIA IN SAID ATMOSPHERES RANGING BETWEEN ABOUT 2 PERCENT AND 10 PERCENT BY VOLUME AND BEING INSUFFICIENT, AT THE TEMPERATURE AND TIME INVOLVED, TO PERMIT FORMATION OF IRON NITRIDE.
Claim 2
Independent Claim
205 words
A METHOD OF INCREASING THE YIELD STRENGTH OF A LOW CARBON STEEL SHEET STOCK, WHICH COMPRISES: PROVIDING A DEEP DRAWING QUALITY STEEL CONTAINING FROM ABOUT 0.002 PERCENT TO ABOUT 0.015 PERCENT CARBON, UP TO ABOUT 0.012 PERCENT NITROGEN, UP TO ABOUT 0.08 PERCENT ALLUMINUM, AND A NITRIDE-FORMING ELEMENT CHOSEN FROM THE GROUP CONSISTING OF TITANIUM, COLUMBIUM, ZIRCONIUM, AND MIXTURES THEREOF, IN AMOUNTS SUCH THAT TITANIUM IN SOLUTION IS FROM ABOUT 0.02 TO ABOUT 0.2 PERCENT, COLUMBIUM IN SOLUTION IS FROM ABOUT 0.025 PERCENT TO ABOUT 0.3 PERCENT, AND ZIRCONIUM IN SOLUTION IS FROM ABOUT 0.025 PERCENT TO ABOUT 0.3 PERCENT, ALL PERCENTAGES BEING BY WEIGHT; REDUCING SAID STEEL TO FINAL THICKNESS; AND HEATING THE RESULTING SHEET STOCK IN AN ATMOSPHERE COMPRISING AMMONIA AND HYDROGEN AT A TEMPERATURE BETWEEN 1,100* AND 1,350*F FOR A PERIOD OF TIME SUFFICIENT TO CAUSE REACTION OF SAID NITRIDE-FORMING ELEMENT WITH THE NITROGEN OF SAID AMMONIA TO FORM SMALL, UNIFORMLY DISPERSED NITRIDES, WHEREBY TO INCREASE THE AVERAGE YIELD STRENGTH OF SAID SHEET STOCK TO A MINIMUM OF 60 KSI, THE CONCENTRATION OF AMMONIA IN SAID ATMOSPHERES RANGING BETWEEN ABOUT 2 PERCENT AND 10 PERCENT BY VOLUME AND BEING INSUFFICIENT, AT THE TEMPERATURE AND TIME INVOLVED, TO PERMIT FORMATION OF IRON NITRIDE.
Claim 3
Dependent Claim
81 words
The method of claim 1, wherein said steel initially consists essentially of from about 0.002 percent to about 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, from about 0.05 percent to about 0.6 percent manganese, from about 0.02 percent to about 0.2 percent titanium in solution, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 4
Dependent Claim
78 words
The method of claim 1, wherein said steel initially consists essentially of from 0.002 percent to about 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, from about 0.05 percent to about 0.6 percent manganese, from about 0.025 percent to about 0.3 percent columbium, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 5
Dependent Claim
79 words
The method of claim 1, wherein said steel initially consists essentially of from about 0.002 percent to about 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, from about 0.05 percent to about 0.6 percent manganese, from about 0.025 percent to about 0.3 percent zirconium, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 6
Dependent Claim
91 words
The method of claim 1, wherein said steel initially consists essentially of less than about 0.010 percent carbon, from about 0.05 percent to about 0.6 percent manganese, from about 0.02 percent to about 0.04 percent total aluminum, up to about 0.004 percent nitrogen, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, from about 0.08 percent to about 0.10 percent total titanium, from about 0.03 percent to about 0.06 percent total columbium, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 7
Dependent Claim
91 words
The method of claim 1, wherein said steel initially consists essentially of less than about 0.010 percent carbon, from about 0.05 percent to about 0.6 percent manganese, from about 0.02 percent to about 0.04 percent total aluminum, up to about 0.004 percent nitrogen, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, from about 0.08 percent to about 0.10 percent total titAnium, from about 0.03 percent to about 0.06 percent total zirconium, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 8
Dependent Claim
42 words
The method of claim 1, wherein said sheet stock is cold rolled to a thickness of from about 0.02 inch to 0.09 inch, and wherein said heating step increases the yield strength of said sheet stock to at least about 70 ksi.
Claim 9
Dependent Claim
21 words
The method of claim 1, wherein said atmosphere contains from 3 percent to 6 percent ammonia by volume, and remainder hydrogen.
Claim 10
Dependent Claim
39 words
The method of claim 1, wherein said atmosphere contains ammonia and hydrogen, and the balance an inert gas, with the ammonia to hydrogen ratio adjusted in such manner that the formation of iron nitride or iron-nitrogen austenite is avoided.
Claim 11
Dependent Claim
33 words
The method of claim 7, wherein said heating is conducted at 1,100* to 1,300*F for a period of time inversely proportional to the temperature and directly proportional to the square of the thickness.
Claim 12
Independent Claim
220 words
A method of increasing the yield strength of an article formed from a low carbon steel sheet stock of deep drawing quality, which comprises: providing a steel containing from about 0.002 percent to 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, and a nitride-forming element chosen from the group consisting of titanium, columbium, zirconium, and mixtures thereof, in amounts such that titanium in solution is from about 0.02 percent to 0.2 percent, columbium in solution is from about 0.025 percent to 0.3 percent, and zirconium in solution is from about 0.025 percent to 0.3 percent, all percentages being by weight; reducing said steel to final thickness; annealing to soften and impart excellent drawing quality properties; forming said article from said reduced and annealed steel; and strengthening said article in an atmopshere comprising ammonia and hydrogen at a temperature between 1,100* and 1,350*F for a period of time sufficient to cause reaction of said nitride-forming element with the nitrogen of said ammonia, whereby to increase the average yield strength of said article to a minimum of 50 ksi, the concentration of ammonia in said atmosphere being between about 2 percent and about 10 percent by volume and being insufficient, at the temperature and time involved, to permit formation of iron nitride or iron-nitrogen austenite.
Claim 13
Independent Claim
220 words
A method of increasing the yield strength of an article formed from a low carbon steel sheet stock of deep drawing quality, which comprises: providing a steel containing from about 0.002 percent to 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, and a nitride-forming element chosen from the group consisting of titanium, columbium, zirconium, and mixtures thereof, in amounts such that titanium in solution is from about 0.02 percent to 0.2 percent, columbium in solution is from about 0.025 percent to 0.3 percent, and zirconium in solution is from about 0.025 percent to 0.3 percent, all percentages being by weight; reducing said steel to final thickness; annealing to soften and impart excellent drawing quality properties; forming said article from said reduced and annealed steel; and strengthening said article in an atmopshere comprising ammonia and hydrogen at a temperature between 1,100* and 1,350*F for a period of time sufficient to cause reaction of said nitride-forming element with the nitrogen of said ammonia, whereby to increase the average yield strength of said article to a minimum of 50 ksi, the concentration of ammonia in said atmosphere being between about 2 percent and about 10 percent by volume and being insufficient, at the temperature and time involved, to permit formation of iron nitride or iron-nitrogen austenite.
Claim 14
Dependent Claim
81 words
The method of claim 11, wherein said steel initially consists essentially of from about 0.002 percent to about 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, from about 0.05 percent to about 0.6 percent manganese, from about 0.02 percent to about 0.2 percent titanium in solution, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, and remainder iron except for incidental impurities, and percentages being by weight.
Claim 15
Dependent Claim
81 words
The method of claim 11, wherein said steel initially consists essentially of from about 0.002 percent to about 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, from about 0.05 percent to about 0.6 percent manganese, from about 0.025 percent to about 0.3 percent columbium in solution, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, and remainder iron except for incidental impurities, and percentages being by weight.
Claim 16
Dependent Claim
81 words
The method of claim 11, wherein said steel initially consists essentially of from about 0.002 percent to about 0.015 percent carbon, up to about 0.012 percent nitrogen, up to about 0.08 percent aluminum, from about 0.05 percent to about 0.6 percent managense, from about 0.025 percent to about 0.3 percent zirconium in solution, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, and remainder iron except for incidental impurities, and percentages being by weight.
Claim 17
Dependent Claim
91 words
The method of claim 11, wherein said steel initially consists essentially of less than about 0.010 percent carbon, from about 0.05 percent to about 0.6 percent manganese, from about 0.02 percent to about 0.04 percent total aluminum, up to about 0.004 percent nitrogen, up to about 0.035 percent sulfur, up to about 0.01 percent oxygen, residual silicon and phosphorus, from about 0.08 percent to about 0.10 percent total titanium, from about 0.03 percent to about 0.06 percent total columbium, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 18
Dependent Claim
90 words
The method of claim 11, wherein said steel initially consists essentially of less than about 0.010 percent carbon, from about 0.05 percent to about 0.6 percent manganese, from about 0.02 percent to about 0.04 percent total aluminum, up to about 0.004 percent nitrogen, up to about 0.035 percent sulfur, up to 0.01 percent oxygen, residual silicon and phosphorus, from about 0.08 percent to about 0.10 percent total titanium, from about 0.03 percent to about 0.06 percent total zirconium, and remainder iron except for incidental impurities, all percentages being by weight.
Claim 19
Dependent Claim
21 words
The method of claim 11, wherein said atmosphere contains from 3 percent to 6 percent ammonia by volume, and remainder hydrogen.
Claim 20
Dependent Claim
39 words
The method of claim 11, wherein said atmosphere contains ammonia and hydrogen, and the balance an inert gas, with the ammonia to hydrogen ratio adjusted in such manner that the formation of iron nitride or iron-nitrogen austenite is avoided.
Claim 21
Dependent Claim
33 words
The method of claim 11, wherein said heating is conducted at 1,100* to 1,300*F for a period of time inversely proportional to the temperature, and directly proportional to the square of the thickness.
Claim 22
Dependent Claim
11 words
The method of claim 11, wherein said article is deep drawn.
Claim 23
Dependent Claim
45 words
The method of claim 1, including as a final step denitriding said sheet stock in a hydrogen atmosphere at a temperature between about 1,100* and 1,350*F for a period of time sufficient to decrease the ductile to brittle transition temperature to at least about -60*F.
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) | 1977-11-11 | 1978-05-13 | 1978-11-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-11 | 1982-05-13 | 1982-11-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-11 | 1986-05-13 | 1986-11-12 | $7700.00 | Window Closed / Lapsed |