Sintered materials and method thereof

• US 5,188,659 A
• Filed: 08/15/1990
• Issued: 02/23/1993
• Est. Priority Date: 09/20/1989
• Status: Expired due to Term

• Current Assignee: Brico Engineering Limited (Apollo Global Management, Inc.)
• Original Assignee: Brico Engineering Limited (Apollo Global Management, Inc.)
• Inventors: Purnell, Charles G.
• Primary Examiner(s): Yee, Deborah
• Application Number:
  US07/567,766
• Time in Patent Office: 923 Days
• Field of Search: 419/2, 419/6, 419/10, 75/246, 420/111, 148/334
• US Class Current: 75/246
• CPC Class Codes: B22F 2202/03 Treatment under cryogenic or supercritical conditions
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: C22C 33/0207 Using a mixture of prealloyed powders or a master alloy mixtures of metal powder in general B22F1/09
• CPC Class Codes: C22C 33/0264 the maximum content of each alloying element not exceeding 5%

Abstract

Sintered materials and a method are described for the production of ferrous articles, particularly valve seat inserts. The materials are based on A1S1 H11, H12 and H13 materials plus diluent material.

Claims

1. A sintered ferrous material, the material having a composition expressed in weight % lying within the ranges:

C 0.7-1.3/Si 0.3-1.3/Cr 1.9-5.3/Mo 0.5-1.8/V 0.1-1.5/Mn 0.6max/Fe balance apart from incidental impurities, and having a microstructure comprising a tempered martensitic matrix containing fine spheroidal alloy carbides.

2. A material according to claim 1 also having from 1 to 6 wt % of copper.

3. A material according to claim 1 also having up to 1.0 wt % of sulphur.

4. A material according to claim 1 also having up to 5 wt % of metallic sulphide.

5. A method of making a valve seat insert, the method comprising the steps of mixing a hot working tool steel powder of composition C 0.3-0.7/Si 0.8-1.20/Cr 4.5-5.5/Mo 1.2-1.8/V 0.3-1.5/Mn 0.1-0.6/Fe balance with graphite powder and up to 60 wt % of iron or low-alloy iron powder to give a composition according to claim 1, pressing a valve seat insert and sintering the green pressing.

6. A method according to claim 5 further including the step of mixing in from 1 to 6 wt. % of copper.

7. A method according to claim 5 further including the step of mixing in up to 1.0 wt. % of sulphur.

8. A method according to claim 5 further including the step of mixing in up to 5 wt. % of metallic sulphide.

9. A method according to claim 5 further including the step of infiltrating the valve seat insert with a copper based material.

10. A method according to claim 5 further including the step of giving the valve seat insert a cryogenic treatment.

11. A valve seat insert having a composition according to claim 1.

12. A valve seat insert when made by the method of claim 5.

13. A sintered ferrous material according to claim 1 having an as-pressed density of 85% of theoretical density or greater.