Pressure Piping Steel Pipe And Steel Pipe Material

Abstract: Provided is a pressure piping steel pipe subjected to autofrettage, wherein the average hardness of an outer surface layer region is at least 1.20 times greater than the average hardness of an inner surface layer region, and, in the case in which it is assumed, regarding the steel pipe, that the outer diameter is D, the inner diameter is d, the actual measured value of the residual stress at the outer surface is so1, the actual measured value of the residual stress at the outer surface after being halved is so2, and the actual measured value of the residual stress at the inner surface after being halved is si2, the estimated value si1 of the residual stress at the inner surface of the steel pipe, determined from [si1=(-si2)/(A×(t/T)2-1)], [t/T=((so2-so1)/(A×(so2-so1)-C×si2))1/2], [A=3.9829×exp(0.1071×(D/d)2)], and [C=-3.3966×exp(0.0452×(D/d)2)], is equal to or less than -150 MPa.

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