Seamless steel pipe and inflator bottle for airbag
AssigneeNippon Steel Corporation
InventorsKosuke AOKI, Hirofumi NAKAMURA
Life of this patent
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Abstract
The seamless steel pipe has a chemical composition described in the specification, and the chemical composition satisfies [WT/(5C+Mo+Cr)≥1.00] in conjunction with a wall thickness WT (mm), and satisfies [GN−1.51×(Mn+85P−30Ca)≥8.50] in conjunction with a prior-γ grain size number GN. The seamless steel pipe has a tensile strength of 1000 MPa or more, an elongation after fracture is 8.0% or more, and a critical hydrogen concentration of 2.5 ppm or more.
Claims4
A seamless steel pipe having a chemical composition consisting of, in mass %:
- C:
- 0.05 to 0.20%,
- Si:
- 0.05 to 0.50%,
- Mn:
- 0.30 to 1.50%,
- P:
- 0.025% or less,
- S:
- 0.020% or less,
- Cu:
- 0.01 to 0.50%,
- Ni:
- 0.01 to 0.50%,
- Cr:
- 0.01 to 1.20%,
- Mo:
- 0.01 to 0.50%,
- Ti:
- 0.001 to 0.050%,
- Nb:
- 0.001 to 0.100%,
- Ca:
- 0.0005 to 0.0025%,
- Al:
- 0.080% or less,
- N:
- 0.0100% or less,
- V:
- 0 to 0.100%,
- B:
- 0 to 0.0050%,
- Mg:
- 0 to 0.0050%,
- REM:
- 0 to 0.0050%,
- Sn:
- 0 to 0.100%, and
- As:
- 0 to 0.010%,
- with the balance:
- Fe and impurities, wherein
- on a precondition that contents fall within respective ranges described above,
- the chemical composition satisfies Formula (i) shown below in conjunction with a wall thickness of the seamless steel pipe and
- the chemical composition further satisfies Formula (ii) shown below in conjunction with a prior-austenite grain size number of the seamless steel pipe, and wherein
- a tensile strength of the seamless steel pipe is 1000 MPa or more,
- an elongation after fracture of the seamless steel pipe is 8.0% or more, and
- a critical hydrogen concentration of the seamless steel pipe is 2.5 ppm or more:
- W
-
- T
- /
- (
- 5
-
- C
- +
- Mo
- +
- Cr
- )
- ≥
- 1.
- (
- i
- )
- GN
- -
- 1.51
- ×
- (
- Mn
- +
- 85
-
- P
- -
- 30
-
- Ca
- )
- ≥
- 8.5
- (
- ii
- )
- where symbols of elements in the formula mean contents (mass %) of the elements in the steel, and when an element is not contained, zero will be set to the corresponding symbol, and where WT means the wall thickness (mm) of the seamless steel pipe and GN means the prior-austenite grain size number of the seamless steel pipe.
An inflator bottle for an airbag including a cylindrical portion extending in one direction and a diameter-reduced portion formed on at least one end of the cylindrical portion in the one direction, wherein
- a chemical composition of the cylindrical portion consists of, in mass %:
- C:
- 0.05 to 0.20%,
- Si:
- 0.05 to 0.50%,
- Mn:
- 0.30 to 1.50%,
- P:
- 0.025% or less,
- S:
- 0.020% or less,
- Cu:
- 0.01 to 0.50%,
- Ni:
- 0.01 to 0.50%,
- Cr:
- 0.01 to 1.20%,
- Mo:
- 0.01 to 0.50%,
- Ti:
- 0.001 to 0.050%,
- Nb:
- 0.001 to 0.100%,
- Ca:
- 0.0005 to 0.0025%,
- Al:
- 0.080% or less,
- N:
- 0.0100% or less,
- V:
- 0 to 0.100%,
- B:
- 0 to 0.0050%,
- Mg:
- 0 to 0.0050%,
- REM:
- 0 to 0.0050%,
- Sn:
- 0 to 0.100%, and
- As:
- 0 to 0.010%,
- with the balance:
- Fe and impurities, wherein
- on a precondition that contents fall within respective ranges described above,
- the chemical composition of the cylindrical portion satisfies Formula (i) shown below in conjunction with a wall thickness of the cylindrical portion and
- the chemical composition of the cylindrical portion further satisfies Formula (ii) shown below in conjunction with a prior-austenite grain size number of the cylindrical portion, and wherein
- a tensile strength of the cylindrical portion is 1000 MPa or more,
- an elongation after fracture of the cylindrical portion is 8.0% or more, and
- a critical hydrogen concentration of the cylindrical portion is 2.5 ppm or more:
- W
-
- T
- /
- (
- 5
-
- C
- +
- Mo
- +
- Cr
- )
- ≥
- 1.
- (
- i
- )
- GN
- -
- 1.51
- ×
- (
- Mn
- +
- 85
-
- P
- -
- 30
-
- Ca
- )
- ≥
- 8.5
- (
- ii
- )
- where symbols of elements in the formula mean contents (mass %) of the elements in the steel of the cylindrical portion, and when an element is not contained, zero will be set to the corresponding symbol, and where WT means the wall thickness (mm) of the cylindrical portion and GN means the prior-austenite grain size number of the cylindrical portion.
Dependencies are inferred from the claim text.