Method for heat-treating work pieces made of temperature-resistant steels
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
C23C-008/02
C23C-008/26
C23C-008/24
출원번호
US-0432751
(2002-09-24)
우선권정보
DE-101 47 205(2001-09-25)
국제출원번호
PCT/DE02/003582
(2002-09-24)
§371/§102 date
20031022
(20031022)
국제공개번호
WO03/027349
(2003-04-03)
발명자
/ 주소
Lippmann,Nils
Lerche,Wolfgang
출원인 / 주소
Robert Bosch GmbH
대리인 / 주소
Kenyon &
인용정보
피인용 횟수 :
5인용 특허 :
6
초록▼
A method of producing a workpiece of a heat-resistant steel, such as hot forming tool steel, where the workpiece may be hardened and depassivated after mechanical machining and electrochemical treatment. The hardening including a reduction step, so that no depassivation need be performed by picklin
A method of producing a workpiece of a heat-resistant steel, such as hot forming tool steel, where the workpiece may be hardened and depassivated after mechanical machining and electrochemical treatment. The hardening including a reduction step, so that no depassivation need be performed by pickling, for example, before nitriding. The result of the hardening treatment is a favorable surface condition for stepwise nitriding.
대표청구항▼
What is claimed is: 1. A method for producing a workpiece from a heat-resistant steel, comprising the steps of: hardening the workpiece, including a reduction treatment to form a depassivated surface for stepwise nitriding, and convective heating of the workpiece under one of a nitrogen atmosphere
What is claimed is: 1. A method for producing a workpiece from a heat-resistant steel, comprising the steps of: hardening the workpiece, including a reduction treatment to form a depassivated surface for stepwise nitriding, and convective heating of the workpiece under one of a nitrogen atmosphere and in vacuo; nitriding the workpiece; replacing the one of the nitrogen atmosphere and the vacuum by a hydrogen atmosphere after reaching a predetermined heating temperature; and generating the hydrogen atmosphere in a pulsating operation over a pulse period of between about one and ten minutes. 2. The method as claimed in claim 1, wherein hydrogen is used as a reducing agent. 3. The method as claimed in claim 1, further comprising machining and electrochemically treating the workpiece before the hardening step. 4. The method as claimed in claim 1, further comprising cleaning the workpiece before the hardening step. 5. The method as claimed in claim 4, further comprising drying the workpiece after the cleaning. 6. The method as claimed in claim 1, further comprising cleaning the workpiece in an aqueous cleaning medium before the hardening step. 7. The method as claimed in claim 1, wherein the hardening step includes convective heating of the workpiece under a nitrogen atmosphere with a nitrogen pressure greater than 0.8 bar. 8. The method as claimed in claim 1, wherein the heat-resistant steel includes a hot forming tool steel and wherein the workpiece is heated at least to a hardening temperature of the hot forming tool steel. 9. The method as claimed in claim 1, wherein a hydrogen partial pressure is between about 1 and 100 mbar. 10. The method as claimed in claim 1, wherein a hydrogen flow rate is between about 100 and 2000 L/h. 11. The method as claimed in claim 1, wherein the hardening step is performed in one of a single-chamber and multichamber vacuum furnace. 12. The method as claimed in claim 1, further comprising quenching the workpiece after the hardening. 13. The method as claimed in claim 12, wherein the workpiece is quenched in the quenching step using nitrogen. 14. The method as claimed in claim 12, wherein the nitrogen has a pressure of between about 1 and 10 bar. 15. The method as claimed in claim 1, further comprising tempering after the hardening. 16. The method as recited in claim 15, wherein the tempering step includes heating the workpiece up to a temperature of about 650째 C. 17. The method as claimed in claim 15, further comprising heating the workpiece in a nitrogen atmosphere. 18. The method as recited in claim 15, further comprising heating the workpiece in a nitrogen-hydrogen atmosphere having a hydrogen content of up to about 5%. 19. The method as claimed in claim 15, wherein the tempering is performed in one of a vacuum furnace and an evacuable tempering furnace. 20. The method as claimed in claim 15, wherein the tempering is performed over a period of between about 1 and 4 hours. 21. The method as claimed in claim 1, further comprising in a first step heating the workpiece from room temperature up to a temperature of approximately 400째 C. 22. The method as claimed in claim 21, wherein the workpiece is heated in the heating step under an ammonia atmosphere. 23. The method as claimed in claim 1, wherein the workpiece is heated up in the heating step to a nitriding temperature. 24. The method as claimed in claim 1, wherein the nitriding of the workpiece includes the steps of: (a) nitriding under an atmosphere of ammonia and an oxidizing agent; (b) nitriding under an atmosphere of ammonia and a carbonaceous substance; and (c) nitriding under an atmosphere of one of ammonia and a gas additive. 25. The method as claimed in claim 24, wherein the carbonaceous substance includes one of about 1 to 10 vol % endogas and CO and CO2 in equal amounts. 26. The method as claimed in claim 24, wherein the oxidizing agent including one of about 0.5 to 10 vol % water vapor and up to 15% air. 27. The method as claimed in claim 1, further comprising cooling the workpiece under nitrogen after the nitriding. 28. The method as claimed in claim 1, further comprising hard machining the workpiece after cooling. 29. The method as claimed in claim 1, wherein the workpiece includes a direct-injection nozzle body. 30. The method as claimed in claim 1, wherein the heat-resistant steel includes hot forming tool steel.
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