Roughly shaped material for induction hardened components and method for producing same

1. A material for induction hardened components comprising:

a steel as a base metal consisting of, as a chemical composition, by mass %,

C: 0.35% to 0.6%,

Si: 0.02% to 2.0%,

Mn: 0.35% to 1.5%,

Al: 0.001% to 0.5%,

Cr: 0.05% to 2.0%,

S: 0.0001% to 0.05%,

N: 0.003% to 0.0120%,

P: 0.03% or less,

O: 0.0050% or less,

B: 0% to 0.005%,

W: 0% to 0.5%,

Mo: 0% to 1.0%,

V: 0% to 1.0%,

Nb: 0% to 0.3%,

Ti: 0% to 0.2%,

Zr: 0% to 0.05%,

Sb: 0% to 0.1%,

Sn: 0% to 0.1%,

Cu: 0% to 2.0%,

Ni: 0% to 2.0%,

Ca: 0% to 0.01%,

Mg: 0% to 0.01%,

Te: 0% to 0.1%, and

the balance consisting of Fe and impurities,

further comprising an iron nitride layer at a surface, having a thickness of 0.1 μm to 50 μm in a depth direction;

wherein a volume fraction of a γ′ phase, which is a Fe nitride, in the iron nitride layer, is 80% or more.

2. The material for induction hardened components according to claim 1 , further comprising:

a magnetite coating film having a thickness of 0.1 μm to 5 μm on a surface of the iron nitride layer.

3. The material for induction hardened components according to claim 1 or 2 ,

wherein the steel as the base metal includes, as a chemical composition, by mass %, one or more of

B: 0.0003% to 0.005%,

W: 0.0025% to 0.5%,

Mo: 0.05% to 1.0%,

V: 0.05% to 1.0%,

Nb: 0.005% to 0.3%,

Ti: 0.005% to 0.2%,

Zr: 0.0005% to 0.05%,

Sb: 0.0005% to 0.1%,

Sn: 0.01% to 0.1%,

Cu: 0.01% to 2.0%,

Ni: 0.01% to 2.0%

Ca: 0.0005% to 0.01%,

Mg: 0.0005% to 0.01%, and

Te: 0.0005% to 0.1%.

4. An induction hardened component obtained by performing an induction hardening on the material according to claim 3 .

5. The induction hardened component according to claim 4 ,

wherein a number of pores having an equivalent circle diameter of 0.5 μm to 1 μm in a region at a maximum depth of 5 μm from a surface of the induction hardened component is less than 500 per mm 2 .

6. A method for producing an induction hardened component comprising:

performing an induction hardening on the material according to claim 3 .

7. A method for producing a material for induction hardened components comprising:

when a gas nitriding treatment is performed on a steel having a chemical composition of the steel as a base metal according to claim 3 ,

adjusting a composition of an atmosphere gas including NH 3 ; and

performing a gas nitriding at a temperature of 500° C. to 600° C. for 30 minutes or longer in the atmosphere gas not including CO 2 with a nitriding potential K N satisfying the following Expression a,

−1.4×( T− 773)/100+2.0≥ K N ≥−0.15×( T− 773)/100+0.3  (a),

here, K N =P NH3 /P H2 3/2 (P NH3 represents a partial pressure of NH 3 in the atmosphere gas, and P H2 represents a partial pressure of H 2 in the atmosphere gas), and T represents a gas nitriding treatment temperature (K).

8. The method for producing a material for induction hardened components according to claim 7 , further comprising:

performing a heat treatment under conditions of heating at 450° C. to 550° C. for 30 minutes to 60 minutes in a steam atmosphere after performing the gas nitriding.

9. A method for producing an induction hardened component,

wherein when an induction hardening is performed on the material obtained by the production method according to claim 8 , a heating time from a time when a surface temperature of the material reaches a temperature which is 50° C. lower than a hardening temperature to the induction hardening is set to be within 10 seconds, and the hardening temperature is 850° C. to 1000° C.

10. A method for producing an induction hardened component,

wherein when an induction hardening is performed on the material obtained by the production method according to claim 7 , a heating time from a time when a surface temperature of the material reaches a temperature which is 50° C. lower than a hardening temperature to the induction hardening is set to be within 10 seconds, and the hardening temperature is 850° C. to 1000° C.

11. An induction hardened component obtained by performing an induction hardening on the material according to claim 1 or 2 .

12. A method for producing an induction hardened component comprising:

performing an induction hardening on the material according to claim 1 or 2 .

13. The induction hardened component according to claim 11 ,

wherein a number of pores having an equivalent circle diameter of 0.5 μm to 1 μm in a region at a maximum depth of 5 μm from a surface of the induction hardened component is less than 500 per mm 2 .

14. A method for producing a material for induction hardened components comprising:

when a gas nitriding treatment is performed on a steel having a chemical composition of the steel as a base metal according to claim 1 ,

adjusting a composition of an atmosphere gas including NH 3 ; and

performing a gas nitriding at a temperature of 500° C. to 600° C. for 30 minutes or longer in the atmosphere gas not including CO 2 with a nitriding potential K N satisfying the following Expression a,

−1.4×( T− 773)/100+2.0≥ K N ≥−0.15×( T− 773)/100+0.3  (a),

here, K N =P NH3 /P H2 3/2 (P NH3 represents a partial pressure of NH 3 in the atmosphere gas, and P H2 represents a partial pressure of H 2 in the atmosphere gas), and T represents a gas nitriding treatment temperature (K).

15. The method for producing a material for induction hardened components according to claim 14 , further comprising:

performing a heat treatment under conditions of heating at 450° C. to 550° C. for 30 minutes to 60 minutes in a steam atmosphere after performing the gas nitriding.

16. A method for producing an induction hardened component,

wherein when an induction hardening is performed on the material obtained by the production method according to claim 14 or 15 , a heating time from a time when a surface temperature of the material reaches a temperature which is 50° C. lower than a hardening temperature to the induction hardening is set to be within 10 seconds, and the hardening temperature is 850° C. to 1000° C.