Iron-based powder composition having good dimensional stability after sintering

Claim 1

A compacted and sintered iron-based powder composition which in addition to iron consists essentially of 0.5-4.5% by weight Ni 0.65-2.25% by weight Mo 0.35-0.65% by weight C, less than about 2% by weight of impurities and optionally lubricant, wherein the powder is sintered at a temperature not greater than 1140° C. and a variation of dimensional change no greater than 0.07%, irrespective of density variations within the range of 6.8-7.2 g/cm 3 in the green body, is obtained during sintering.

Claim 10

A method of producing a high-strength compacted and low-temperature sintered body comprising the steps of: a1) preparing an iron powder and diffusion-alloying Ni and/or Mo to the iron powder or mixing metal particles of Ni and/or Mo to the iron powder, or a2) preparing a melt or iron and molybdenum, water-atomizing the melt to a powder and diffusion-alloying Ni to the resulting powder or mixing metal particles of Ni with the powder, b) adding carbon to the powder obtained, the amount of the included components being so selected that the resulting powder composition in addition to iron essentially consists of about 0.5-4.5% by weight Ni 0.65-2.25% by weight Mo 0.35-0.65% by weight C, less than 2% by weight, preferably less than about 1% by weight, of impurities and optionally lubricant, c) compacting the powder composition for obtaining a green body, and d) sintering the green body at a temperature below 1150° C.

Claim 11

A method of producing a high-strength compacted and low-temperature sintered body comprising the steps of: a1) preparing an iron powder and diffusion-alloying Ni and/or Mo to the iron powder or mixing metal particles of Ni and/or Mo to the iron powder, or a2) preparing a melt or iron and molybdenum, water-atomizing the melt to a powder and diffusion-alloying Ni to the resulting powder or mixing metal particles of Ni with the powder, b) adding carbon to the powder obtained, the amount of the included components being so selected that the resulting powder composition in addition to iron essentially consists of about 0.5-4.5% by weight Ni 0.65-2.25% by weight Mo 0.35-0.65% by weight C, less than 2% by weight, preferably less than about 1% by weight, of impurities and optionally lubricant, c) compacting the powder composition for obtaining a green body, and d) sintering the green body at a temperature below 1150° C.

Claim 12

A method of producing a high-strength compacted and sintered body comprising the steps of a1) preparing an iron powder provided that the powder composition does not consist of, by weight 4% Ni, 1% Mo, 0.5% C, with the balance being Fe, and diffusion-alloying Ni and/or Mo to the iron powder or mixing metal particles of Ni and/or Mo to the iron powder, or a2) preparing a melt of iron and molybdenum, water-atomizing the melt to a powder and diffusion-alloying Ni to the resulting powder or mixing metal particles of Ni with the powder, b) adding carbon to the powder obtained, the amount of the included components being so selected that the resulting powder composition in addition to iron essentially consists of about

Claim 13

A method of producing a high-strength compacted and sintered body comprising the steps of a1) preparing an iron powder provided that the powder composition does not consist of, by weight 4% Ni, 1% Mo, 0.5% C, with the balance being Fe, and diffusion-alloying Ni and/or Mo to the iron powder or mixing metal particles of Ni and/or Mo to the iron powder, or a2) preparing a melt of iron and molybdenum, water-atomizing the melt to a powder and diffusion-alloying Ni to the resulting powder or mixing metal particles of Ni with the powder, b) adding carbon to the powder obtained, the amount of the included components being so selected that the resulting powder composition in addition to iron essentially consists of about

Claim 16

A method of producing a high-strength sintered body without subsequently heat treating the sintered body according to U.S. Pat. No. 4,954,171 or EP 334,968 comprising the steps of a1) preparing an iron powder, provided that the powder composition does not consist of by weight, 4% Ni, 1% Mo, 0.5% C, with the balance being Fe and diffusion-alloying alloying Ni and/or Mo to the iron powder or mixing powder, or a2) preparing a melt of iron and molybdenum, water-atomizing the melt to a powder and diffusion-alloying Ni to the resulting powder or mixing metal particles of Ni with the powder, b) adding carbon to the powder obtained, the amount of the included components being so selected that the resulting powder composition in addition to iron essentially consists of about 0.5-4.5% by weight Ni 0.65-2.25% by weight Mo 0.35-0.65% by weight C, less than 2% by weight of impurities and optionally lubricant, c) compacting the powder composition for obtaining a green body, and d) sintering the green body at a temperature below 1150° C. whereby the sintering gives a variation in the dimensional change no greater than 0.07%, irrespective of density variations within the range of 6.8-7.2 g/cm 3 in the green body.

Claim 17

A method of producing a high-strength sintered body without subsequently heat treating the sintered body according to U.S. Pat. No. 4,954,171 or EP 334,968 comprising the steps of a1) preparing an iron powder, provided that the powder composition does not consist of by weight, 4% Ni, 1% Mo, 0.5% C, with the balance being Fe and diffusion-alloying alloying Ni and/or Mo to the iron powder or mixing powder, or a2) preparing a melt of iron and molybdenum, water-atomizing the melt to a powder and diffusion-alloying Ni to the resulting powder or mixing metal particles of Ni with the powder, b) adding carbon to the powder obtained, the amount of the included components being so selected that the resulting powder composition in addition to iron essentially consists of about 0.5-4.5% by weight Ni 0.65-2.25% by weight Mo 0.35-0.65% by weight C, less than 2% by weight of impurities and optionally lubricant, c) compacting the powder composition for obtaining a green body, and d) sintering the green body at a temperature below 1150° C. whereby the sintering gives a variation in the dimensional change no greater than 0.07%, irrespective of density variations within the range of 6.8-7.2 g/cm 3 in the green body.