Iron-based sintered material and production method thereof

• US 20080233421A1
• Filed: 03/21/2008
• Published: 09/25/2008
• Est. Priority Date: 03/22/2007
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: KONDOH, Mikio, MATSUMOTO, Nobuhiko, ANDO, Kimihiko, MIYAKE, Toshitake, OMURA, Shinya, TANINO, Hitoshi
• Granted Patent: US 8,038,761 B2
• Time in Patent Office: Days
• US Class Current: 428/546
• CPC Class Codes: B22F 1/17 Metallic particles coated with metal
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/10 Sintering only
• CPC Class Codes: B22F 3/17 by forging
• CPC Class Codes: B22F 5/12 of wires of tubes B22F5/10
• CPC Class Codes: C22C 33/0264 the maximum content of each alloying element not exceeding 5%
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/12 containing tungsten, tantalum, molybdenum, vanadium, or niobium
• CPC Class Codes: C22C 38/16 containing copper
• CPC Class Codes: F16C 2202/08 Resilience, elasticity, super-elasticity
• CPC Class Codes: F16C 2220/20 by sintering pulverised material, e.g. powder metallurgy in general B22F
• CPC Class Codes: F16C 7/023 for piston engines, pumps or the like
• CPC Class Codes: Y10T 428/12014 having metal particles

Abstract

There is provided an iron-based sintered material resistant to the metal fatigue developing from the voids therein functioning as the initial points and improved in the strength and machinability thereof.

An iron-based sintered material, including a mixed structure of martensite, bainite, and pearlite and multiple voids formed in the mixed structure, wherein the ratio of martensite and bainite in the mixed structure is 70% or more; the ratio of martensite and/or bainite in the mixed structure forming the void surface is 90% or more; and the density of the iron-based sintered material is 7.4 g/cm³ or more.

Claims

1. An iron-based sintered material, comprising a mixed structure of martensite, bainite, and pearlite and multiple voids formed in the mixed structure, wherein

the ratio of martensite and bainite in said mixed structure is 70% or more;

the ratio of martensite and/or bainite in said mixed structure forming said void surface is 90% or more; and

the density of said iron-based sintered material is 7.4 g/cm³ or more.

2. The iron-based sintered material according to claim 1, wherein the Young'"'"'s modulus of-said iron-based sintered material is 160 GPa or more.

3. The iron-based sintered material according to claim 2, wherein said iron-based sintered material contains at least C:

0.4 to 1.0 mass %, Mo;

1.0 to 3.0 mass %, Cu;

1.0 to 4.0 mass %, Mn;

0.2 to 1.0 mass %, and S;

0.05 to 0.3 mass %.

4. The iron-based sintered material according to claim 3, wherein said iron-based sintered material further comprises P:

0.05 to 0.2 mass %.

5. The iron-based sintered material according to claim 3 or 4, wherein said iron-based sintered material is a material obtained by sintering an alloy powder of a Fe—

Mo—

Mn alloy having Mo diffused and deposited on the surface,

the total amount of Mo in said alloy and Mo diffused and deposited on said surface is in the range of 1 to 3 mass % with respect to the alloy powder, and

the amount of the Mo diffused and deposited on said surface is 0.1 mass % or more.

9. A connection rod, comprising the iron-based sintered material according to claims 1.

6. A method of producing an iron-based sintered material by sintering a powder, at least comprising:

a step of preparing a mixture of a powder containing at least, C;

0.4 to 1.0 mass %, Mo;

1.0 to 3.0 mass %, Cu;

1.0 to 4.0 mass %, Mn;

0.2 to 1.0 mass %, and S;

0.05 to 0.3 mass % and a lubricant as said powder and as said component of said iron-based sintered material;

a step of forming a composite compact by filling the mixture in a forging die and pressurizing said mixture under the condition of an applied pressure of 1000 to 1500 MPa by warm die-wall lubrication method;

a step of sintering the composite compact by heating said composite compact at a heating temperature in the range of 1110 to 1170°

C. for 10 to 30 minutes; and

a step of cooling the composite compact after sintering from the heating temperature to 550°

C. at a cooling speed in the range of 40 to 100°

C./minute.

7. The method of producing an iron-based sintered material according to claim 6, wherein P is added in an amount of P:

0.05 to 0.2 mass % as a component for the iron-based sintered material as said powder.

8. The method of producing an iron-based sintered material according to claim 6 or 7, wherein said powder used is an iron-based sintered material of Fe—

Mo—

Mn alloy having Mo diffuse-deposited on the surface, wherein the total amount of Mo in said alloy and Mo diffused and deposited on said surface is in the range of 1.0 to 3.0 mass % with respect to the alloy powder and the amount of the Mo diffused and deposited on said surface is 0.1 mass % or more.

10. A connection rod, comprising the iron-based sintered material prepared by the production method according to claims 6.