US4255188A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Free machining steel with bismuth and manganese sulfide
Assignee: Inland Steel Co
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Filing: 1979-08-29
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Granted: 1981-03-10
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Expires: 1999-08-29
Abstract
Abstract A free machining cast steel shape has in its microstructure, both bismuth-containing inclusions and manganese sulfide inclusions. The manganese sulfide inclusions act as microcrack initiators, and the bismuth-containing inclusions act as liquid metal embrittlers, propagating the microcracks. The mean size and spacing of the manganese-sulfide inclusions are controlled.
Inventors
- 👤 Lynda M. Riekels
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 10:16
CPC Classifications
C; C22; C22C; C22C38/00; C22C38/60; C22C38/002
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
113 words
In a free machining cast steel shape consisting essentially of, in wt.%, carbon--0.06-1.0 manganese--0.3-1.6 silicon--0.30 max. sulfur--0.03-0.50 phosphorous--0.12 max. bismuth--0.05-0.40 iron--essentially the balance said steel having, in its microstructure, manganese sulfide inclusions which act as microcrack initiators and bismuth-containing inclusions which act as liquid metal embrittlers, during a machining operation, the improvement wherein: said manganese sulfide inclusions have a mean size greater than 2 microns and less than 10 microns, to increase the number of manganese sulfide inclusions which act as microcrack initiators, compared to a steel having the same amount of manganese sulfide in inclusions of larger size, thereby enhancing the opportunity for said bismuth-containing inclusions to act as liquid metal embrittlers.
Claim 2
Dependent Claim
113 words
In a free machining cast steel shape consisting essentially of, in wt.%, carbon--0.06-1.0 manganese--0.3-1.6 silicon--0.30 max. sulfur--0.03-0.50 phosphorous--0.12 max. bismuth--0.05-0.40 iron--essentially the balance said steel having, in its microstructure, manganese sulfide inclusions which act as microcrack initiators and bismuth-containing inclusions which act as liquid metal embrittlers, during a machining operation, the improvement wherein: said manganese sulfide inclusions have a mean size greater than 2 microns and less than 10 microns, to increase the number of manganese sulfide inclusions which act as microcrack initiators, compared to a steel having the same amount of manganese sulfide in inclusions of larger size, thereby enhancing the opportunity for said bismuth-containing inclusions to act as liquid metal embrittlers.
Claim 3
Dependent Claim
27 words
In a free machining cast steel shape as recited in claim 1 wherein the mean inter-particle spacing of said manganese sulfide inclusions is less than 100 microns.
Claim 4
Dependent Claim
27 words
In a free machining cast steel shape as recited in claim 2 wherein said steel contains at least 0.37 wt.% sulfur and more than 0.63 wt.% manganese.
Claim 5
Dependent Claim
26 words
In a free machining cast steel shape as recited in claim 1 wherein: said manganese sulfide inclusions have a mean size no greater than eight microns.
Claim 6
Dependent Claim
26 words
In a free machining steel as recited in claim 1 wherein said steel further comprises up to 0.30 wt.% lead and up to 0.6 wt.% tellurium.
Claim 7
Dependent Claim
18 words
In a free machining cast steel shape as recited in claim 1 wherein said shape is an ingot.
Claim 8
Dependent Claim
35 words
In a free machining steel as recited in claim 1 wherein the total amount of ingredients which lower the wetting ability of bismuth, (copper, nickel, tin) is less than the bismuth content of said steel.
Claim 9
Dependent Claim
18 words
In a free machining steel as recited in claim 7 wherein said steel further comprises 0.015-0.06 wt.% tellurium.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-09 | 1984-09-08 | 1985-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-09 | 1988-09-08 | 1989-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-09 | 1992-09-08 | 1993-03-10 | $7700.00 | Window Closed / Lapsed |