IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0083676
(2011-04-11)
|
등록번호 |
US-8308873
(2012-11-13)
|
발명자
/ 주소 |
- Chin, Herbert A.
- Ogden, William P.
|
출원인 / 주소 |
- United Technologies Corporation
|
대리인 / 주소 |
Carlson, Gaskey & Olds PC
|
인용정보 |
피인용 횟수 :
2 인용 특허 :
5 |
초록
▼
A method of processing steel includes carburizing a martensitic stainless steel work piece to produce a carburized case by utilizing in combination, (i) a composition of the martensitic stainless steel work piece, (ii) a preselected carbon concentration in the carburized case, and (iii) a preselecte
A method of processing steel includes carburizing a martensitic stainless steel work piece to produce a carburized case by utilizing in combination, (i) a composition of the martensitic stainless steel work piece, (ii) a preselected carbon concentration in the carburized case, and (iii) a preselected grain size of the martensitic stainless steel work piece such that the carburized case predominately forms carbides of composition M6C, M2C, M23C6 or combinations thereof. The martensitic stainless steel work piece is then heated to substantially solution the metal carbides. The work piece is then quenched at a cooling rate that is sufficient to avoid substantial precipitation of any carbides during cool down to the martensite start temperature, then given a low temperature temper. In so doing, the carburized case hardened martensitic stainless steel will have balanced mechanical, tribological and corrosion resistance properties for high performance bearing and gear components.
대표청구항
▼
1. A case-hardening method of processing martensitic stainless steel, the method comprising: carburizing a martensitic stainless steel work piece to produce a carburized case by utilizing in combination,(i) a prescribed composition range of the martensitic stainless steel work piece,(ii) a preselect
1. A case-hardening method of processing martensitic stainless steel, the method comprising: carburizing a martensitic stainless steel work piece to produce a carburized case by utilizing in combination,(i) a prescribed composition range of the martensitic stainless steel work piece,(ii) a preselected carbon concentration in the carburized case, and(iii) a preselected grain size of the martensitic stainless steel work piece, such that the carburized case predominantly forms carbides of compositions selected from a group consisting of M6C, M2C, M23C6 and combinations thereof, wherein M is a metal or metals and C is carbon;heating the martensitic stainless steel work piece to substantially solution the metal carbides; andimmediately quenching the martensitic stainless steel work piece at a cooling rate sufficient to avoid substantial precipitation of any carbides during cool down to the martensite start temperature. 2. The method as recited in claim 1, wherein the preselected grain size of the martensitic stainless steel work piece is ASTM grain size #5 or smaller. 3. The method as recited in claim 1, wherein the preselected carbon concentration in the carburized case is less than or equal to 1.75 wt. %. 4. The method as recited in claim 1, wherein the composition of the martensitic stainless steel work piece includes X wt. % chromium and Z wt. % molybdenum wherein X and Z are variables such that a ratio X/Z is between 1 and 18. 5. The method as recited in claim 4, wherein the ratio X/Z is between 3.0 and 4.7. 6. The method as recited in claim 4, wherein the composition further includes A1 wt. % nickel and A2 wt. % cobalt wherein A1 and A2 are variables such that a ratio A1/A2 is between 0.3 and 6.2. 7. The method as recited in claim 6, wherein the ratio A1/A2 is between 0.6 and 2.1. 8. The method as recited in claim 1, wherein, after the quenching, the stainless steel work piece includes less than 10 vol. % of any carbides. 9. The method as recited in claim 1, wherein the carburized case includes at least 8 wt. % chromium in solid solution. 10. The method as recited in claim 1, wherein the composition of the martensitic stainless steel work piece includes chromium, cobalt, molybdenum, nickel and optionally titanium that are in solid solution in the carburized case such that a ratio Cr/(Co+Mo+Ni+Ti), with regard to the amounts of the elements in wt. %, is between 1.1 and 1.5. 11. A method of processing steel, the method comprising: providing a martensitic stainless steel work piece with a composition that includes an amount X wt % of chromium and an amount Z wt % of molybdenum, wherein X and Z are variables, in a ratio X/Z that is between 1 and 18;thermo-mechanically processing the martensitic stainless steel work piece to produce and maintaining a grain size of ASTM#5 or smaller prior to carburization;carburizing the martensitic stainless steel work piece to form a carburized case that includes less than or equal to 1.75 wt % carbon and to predominantly form carbides of composition M6C, M2C, M23C6 or combinations thereof, where M is a metal or metals and C is carbon;heating the martensitic stainless steel work piece to a temperature above its austenization temperature to substantially solution the metal carbides; andimmediately quenching the martensitic stainless steel work piece at a cooling rate sufficient to avoid substantial precipitation of any carbides such that the carburized case includes at least 8 wt % chromium in solid solution. 12. The method as recited in claim 11, wherein the ratio X/Z is between 3.0 and 4.7. 13. The method as recited in claim 12, wherein the composition of the martensitic stainless steel work piece includes A1 wt. % cobalt and A2 wt. % nickel wherein A1 and A2 are variables such that a ratio A1/A2 is between 0.3 and 6.2. 14. The method as recited in claim 13, wherein the ratio A1/A2 is between 0.6 and 2.1. 15. The method as recited in claim 11, wherein the carburized case generally surrounds a core, and the core includes X1 wt. % chromium and the carburized case includes X2 wt. % chromium in solid solution such that a ratio X1/X2 is between 1 and 2.25.
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