Steel for rotor shafts of electric machines and method and product thereof
AssigneeHitachi, Ltd.
InventorsMasao Siga, Mitso Kuriyama, Takanobu Mori, Yutaka Fukui, Tatsuro Ishizuka
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Abstract
New low-alloy steel compositions and rotor shafts for electric machines made from them are described. High nickel and chromium contents ensure high strength and toughness, while other components, notably silicon and other impurities, are kept low with the result that magnetic properties remain good. One aspect provides a steel with the following proportions by weight: C 0.15 to 0.3% Si <0.1% Mn <1% Ni 3 to 5% Cr >2%, <3.5% (Mo+W) 0.1 to 1.0%, W being optional V 0.03 to 0.35%, and the remainder substantially Fe. Other aspects are also described.
Claims21
A steel suitable for use in an electric machine rotor shaft, supported to rotate, and having a coupling portion for transmitting power and a slot-forming portion having slots formed therein in which coils are embedded in an axial direction, said steel consisting essentially of the following composition, by weight:
- C 0.15 to 0.3%
- Si less than 0.1%
- Mn less than 1%,
- Ni 3 to 5%,
- Cr from more than 2 to 3.5%
- Mo 0.1% to 1.0%,
- V 0.03 to 0.35%,
- and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1, said steel having a tensile strength at room temperature of at least 93 kg/mm.sup.2, a 50% fracture appearance transition temperature (FATT) below 0.degree. C., 0.02% yield strength of at least 74 kg/mm.sup.2, and magnetic field strength at 21 kG less than 990 AT/cm.
A rotor shaft of an electric machine, supported to rotate, and having a coupling portion for transmitting power and a slot-forming portion having slots formed therein in which coils are embedded in an axial direction, said rotor shaft being made of a steel consisting essentially of the following composition, by weight:
- C 0.15 to 0.3%,
- Si less than 0.1%,
- Mn less than 1%,
- Ni 3 to 5%,
- Cr from more than 2 to 3.5%,
- Mo 0.1 to 1.0%,
- V 0.03 to 0.35%
- and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1.
A steel for use in an electric machine rotor shaft, having the following composition by weight:
- C 0.15 to 0.3%,
- Si less than 0.3%,
- Mn less than 1%,
- Ni 3 to 5%,
- Cr from more than 2 to 3.5%,
- Mo 0.1 to 0.6%,
- V 0.03 to 0.35%,
- Al less than 0.006%,
- P+S+Sn+Sb+As total in an amount less than 0.03%
- and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1.
A low-alloy, high strength, high toughness steel for making an electric machine rotor shaft, having the composition by weight:
- C 0.15 to 0.3%,
- Si less than 0.1%,
- Mn less than 0.5%,
- Ni 3.25 to 4.5%,
- Cr 2.05 to 3.5%,
- Mo 0.25 to 0.6%,
- V 0.05 to 0.2%,
- Al less than 0.006%,
- and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1.
A rotor shaft for an electric machine, made from a Ni-Cr-Mo-V alloy steel comprising by weight,
- C 0.15 to 0.3%,
- Si less than 0.3%,
- Mn less than 1%,
- Ni 3 to 5%,
- Cr from more than 2 to 3.5%,
- Mo 0.1 to 0.6%,
- V 0.03 to 0.35%,
- Al less than 0.006%,
- P+S+Sn+Sb+As total in an amount less than 0.03%
- and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1, and having a tensile strength at room temperature of at least 93 kg/mm.sup.2, a 50% fracture appearance transition temperature (FATT) below 0.degree. C., 0.02% yield strength of at least 74 kg/mm.sup.2, and magnetic field strength at 21 kG less than 990 At/cm.
A rotor shaft of an electric machine, supported to rotate and having a coupling portion for transmitting power and a slot-forming portion having slots formed therein for receiving therein and supporting a coil in an axial direction, said rotor shaft being made from an alloy steel comprising 0.15 to 0.3 wt % C, less than 0.1 wt % Si, less than 1 wt % Mn, 3 to 5 wt % Ni, from more than 2 to 3.5 wt % Cr, 0.1 to 1.0 wt % Mo, 0.03 to 0.35 wt % V, and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1, and subjected to heat treatment comprising the steps of quenching at a room temperature from 800.degree. C. to 900.degree. C. and tempering at a temperature from 525.degree. C. to 650.degree. C. for at least 10 hours.
A rotor shaft of an electric machine, supported to rotate, having a coupling portion for transmitting power and a slot-forming portion forming therein a plurality of axial slots in which coils are embedded in an axial direction, made from an alloy steel comprising 0.15 to 0.3 wt % C, less than 0.3 wt % Si, less than 1 wt % Mn, 3 to 5 wt % Ni, from more than 2 to 3.5 wt % Cr, 0.1 to 0.6 wt % Mo, 0.03 to 0.35 wt % V, less than 0.01 wt % Al, less than 0.03 wt % total P+S+Sn+Sb+As and the remainder substantially Fe, a ratio of Ni:Cr being less than 2.1 and subjected to heat treatment comprising the steps of quenching at a room temperature from 800.degree. C. to 900.degree. C. and tempering at a temperature from 525.degree. C. to 650.degree. C. for at least 10 hours.
Dependencies are inferred from the claim text.