US4497670A — Rotor shaft and manufacturing method thereof

Claim 1

Independent Claim 135 words

A rotor shaft having at least one journal portion adapted to be supported by a bearing means, comprising a plurality of segments joined to each other by welding to form a cylindrical sleeve, said sleeve being mounted on said journal portion by a shrink-fit, each of said segments being made of an alloy steel of bainite structure comprising, by weight, 0.04 to 0.35% C, 0.2 to 2% Mn, 0.1 to 0.6% Si, 0.5 to less than 5% Ni, 0.5 to 3% Cr, 0.2 to 2%Mo, and the balance Fe, and having at least 50 kg/mm 2 yield strength at room temperature and a hot crack susceptibility (Lt) of less than 24, which is expressed by the following equation: Lt=70(C-Si/12-Mn/9+3P+4S+Ni/23+Cr/35+Mo/70), wherein each element symbol in the equation represents the content of the element in weight percent.

Claim 2

Dependent Claim 135 words

A rotor shaft having at least one journal portion adapted to be supported by a bearing means, comprising a plurality of segments joined to each other by welding to form a cylindrical sleeve, said sleeve being mounted on said journal portion by a shrink-fit, each of said segments being made of an alloy steel of bainite structure comprising, by weight, 0.04 to 0.35% C, 0.2 to 2% Mn, 0.1 to 0.6% Si, 0.5 to less than 5% Ni, 0.5 to 3% Cr, 0.2 to 2%Mo, and the balance Fe, and having at least 50 kg/mm 2 yield strength at room temperature and a hot crack susceptibility (Lt) of less than 24, which is expressed by the following equation: Lt=70(C-Si/12-Mn/9+3P+4S+Ni/23+Cr/35+Mo/70), wherein each element symbol in the equation represents the content of the element in weight percent.

Claim 3

Dependent Claim 19 words

The rotor shaft as defined in claim 1, wherein said alloy steel comprises, by weight, less than 0.5% V.

Claim 4

Dependent Claim 160 words

A turbine assembly for steam turbines comprising a rotor shaft; a plurality of moving blades arranged on the circumference of the rotor shaft; a journal portion of said rotor shaft adapted to be rotatably supported by a bearing; and a cylindrical sleeve secured on said journal portion, said sleeve comprising a plurality of segments secured together by welding of abutments axially extending between the segments and each of said segments being made of an alloy steel of bainite structure consisting essentially of 0.04 to 0.35% C, 0.2 to 2% Mn, 0.1 to 0.6% Si, 0.5 to 3% CR, 0.2 to 2% Mo, 0.5 to less than 5% Ni and the balance Fe, and having a yield strength of more than 50 kg/mm 2 at room temperature and a weld crack susceptibility (Lt) of less than 24 which is expressed by the following equation: Lt=70(C-Si/12-Mn/9+3P+4S+Ni/23+Cr/35+Mo/70), wherein each element symbol in said equation represents the content of the element in weight percent.

Claim 5

Dependent Claim 160 words

A turbine assembly for steam turbines comprising a rotor shaft; a plurality of moving blades arranged on the circumference of the rotor shaft; a journal portion of said rotor shaft adapted to be rotatably supported by a bearing; and a cylindrical sleeve secured on said journal portion, said sleeve comprising a plurality of segments secured together by welding of abutments axially extending between the segments and each of said segments being made of an alloy steel of bainite structure consisting essentially of 0.04 to 0.35% C, 0.2 to 2% Mn, 0.1 to 0.6% Si, 0.5 to 3% CR, 0.2 to 2% Mo, 0.5 to less than 5% Ni and the balance Fe, and having a yield strength of more than 50 kg/mm 2 at room temperature and a weld crack susceptibility (Lt) of less than 24 which is expressed by the following equation: Lt=70(C-Si/12-Mn/9+3P+4S+Ni/23+Cr/35+Mo/70), wherein each element symbol in said equation represents the content of the element in weight percent.

Claim 6

Dependent Claim 21 words

The assembly as defined in claim 3, wherein in said alloy steel, each of S and P is less than 0.03%.

Claim 7

Dependent Claim 26 words

The assembly as defined in claim 4, wherein said segments forming said sleeve are semicylindrical, said sleeve being fitted on said journal portion by a shrink-fit.

Claim 8

Dependent Claim 47 words

The assembly as defined in claim 5, further comprising a coupling integral with said rotor shaft at an end portion thereof, and said rotor shaft having a small diameter portion less in diameter than that of said journal portion located between said journal portion and said coupling.

Claim 9

Dependent Claim 45 words

The assembly as defined in claim 6, wherein said sleeve after being welded is subjected to stress relief treatment at a temperature more than 20° C. higher than that of heat treatment applied to said sleeve during tempering, and then shrink-fitted on said journal portion.

Claim 10

Dependent Claim 52 words

The assembly as defined in claim 7, wherein said sleeve consists essentially of 0.07 to 0.15% C, 0.1 to 0.6% Si, 0.2 to 2% Mn, 1 to 3.5% Ni, 0.7 to 1.8% CR, 0.3 to 1% Mo, 0.05 to 0.3 V, and balance Fe, and has a Lt of less than 22.

Claim 11

Dependent Claim 17 words

The assembly as defined in claim 8, wherein each of P and S is less than 0.01%.

Claim 12

Dependent Claim 70 words

The assembly as defined in claim 9, wherein said rotor shaft has a body portion that is an alloy steel having all martensite structure and consists essentially of, by weight, 0.1 to 0.3% Co, less than 0.6% Si, 0.4 to 1.5% Mn, less than 1.2% Ni, 8 to 13% Cr, 0.5 to 1.5% Mo, 0.05 to 0.3% V, 0.02 to 0.15% Nb, 0.04 to 0.1% N, and the balance Fe.

Claim 13

Dependent Claim 20 words

The assembly as defined in claim 3, wherein said alloy steel further includes less than 0.5% by weight of V.

Claim 14

Independent Claim 205 words

A method of manufacturing a rotor shaft, comprising: providing a rotor shaft body adapted for use in a steam turbine and having at least a journal portion and an adjacent small diameter portion; forming a cylindrical member for a sleeve made of an alloy steel of bainite structure comprising 0.04 to 0.35% C, 0.2 to 2% Mn, 0.1 to 0.6% Si, 0.5 to 3% Cr, 0.2 to 2% Mo, 0.5 to less than 5% Ni, and the balance Fe, and having a yield strength of more than 50 kg/mm 2 at room temperature and a hot crack susceptibility Lt of less than 24, the Lt being calculated according to the following equation: Lt=70(C-Si/12-Mn/9+3P+4S+Ni/23+Cr/30+Mo/70), wherein each element symbol in said equation represents the content of the element in weight percent; subjecting said member to heat treatment including hardening and tempering; dividing said member axially into a plurality of segments; forming a cylindrical sleeve by arranging said segments on said small diameter portion of said shaft and welding the segments to each other; subjecting said sleeve to stress relief treatment at a temperature higher than the temperature during said tempering treatment by at least 20° C.; and fitting said sleeve on said journal portion by a shrink-fit.

Claim 15

Independent Claim 205 words

A method of manufacturing a rotor shaft, comprising: providing a rotor shaft body adapted for use in a steam turbine and having at least a journal portion and an adjacent small diameter portion; forming a cylindrical member for a sleeve made of an alloy steel of bainite structure comprising 0.04 to 0.35% C, 0.2 to 2% Mn, 0.1 to 0.6% Si, 0.5 to 3% Cr, 0.2 to 2% Mo, 0.5 to less than 5% Ni, and the balance Fe, and having a yield strength of more than 50 kg/mm 2 at room temperature and a hot crack susceptibility Lt of less than 24, the Lt being calculated according to the following equation: Lt=70(C-Si/12-Mn/9+3P+4S+Ni/23+Cr/30+Mo/70), wherein each element symbol in said equation represents the content of the element in weight percent; subjecting said member to heat treatment including hardening and tempering; dividing said member axially into a plurality of segments; forming a cylindrical sleeve by arranging said segments on said small diameter portion of said shaft and welding the segments to each other; subjecting said sleeve to stress relief treatment at a temperature higher than the temperature during said tempering treatment by at least 20° C.; and fitting said sleeve on said journal portion by a shrink-fit.

Claim 16

Dependent Claim 32 words

The method as defined in claim 12, wherein P and S in said alloy steel are less than 0.03% by weight, said alloy steel further comprises, by weight, less than 0.5% V.

Claim 17

Dependent Claim 44 words

The assembly as defined in claim 7, wherein said alloy steel consists essentially of 0.07 to 0.15% C, 0.1 to 0.6% Si, 0.2 to 2% Mn, 0.5 to less than 5% Ni, 0.7 to 1.8% Cr, 0.3 to 1% Mo, and the balance Fe.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1988-02-05	1988-08-06	1989-02-05	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1992-02-05	1992-08-06	1993-02-05	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1996-02-05	1996-08-06	1997-02-05	$7700.00	Window Closed / Lapsed

Rotor shaft and manufacturing method thereof

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