摘要:
A base material portion of an electric resistance welded steel pipe has a composition including C at 0.25 to 0.55%, Si at 0.01 to 1.0%, Mn at 0.2 to 3.0%, Al at not more than 0.1% and N at 0.0010 to 0.0100%, with the balance being represented by Fe and inevitable impurities, and the weld defect area, which is a projected area of a weld defect in an electric resistance weld zone, is less than 40000 μm2.
摘要:
A raw steel tube has a composition containing, by mass, 0.25% to 0.60% carbon, 0.01% to 2.0% silicon, 0.2% to 3.0% manganese, 0.001% to 0.1% aluminum, 0.001% to 0.05% phosphorus, 0.02% or less sulfur, 0.0010% to 0.0100% nitrogen, 0.0003% to 0.0050% boron, and 0.0001% to 0.0050% calcium, the balance being iron and incidental impurities. The raw steel tube is heated to and soaked at an Ac3 transformation point or higher and is then subjected to stretch-reducing rolling at a finishing temperature of rolling of 900° C. to (Ac1 transformation point) with a cumulative reduction in diameter of 30% to 70% within the temperature range of 900° C. or lower.
摘要:
A stainless steel tube having excellent formability for secondary operation comprises: a chemical composition including not more than 0.20 mass % of C; not more than 1.5 mass % of Si; not more than 2.0 mass % of Mn; 10-18 mass % of Cr; not more than 0.03 mass % of N; or further at least one type of element selected from the group of: not more than 0.6 mass % of Cu; not more than 0.6 mass % of Ni; not more than 2.5 mass % of Mo; not more than 1.0 mass % of Nb; not more than 1.0 mass % of Ti; and not more than 1.0 mass % of V; Fe as the remainder and the inevitable impurities; and a structure constituted of ferrite or ferrite and martensite, wherein the TE value defined by the following formula exceeds 25,000 Mpa·%, TE=TS×(El+21.9) TS represents the tensile strength in the tube axial direction, and El represents the elongation in such direction.
摘要:
A welded steel pipe is formed by heating or soaking an untreated welded steel pipe having a steel composition containing, on the basis of mass percent: about 0.03% to about 0.2% C, about 2.0% or less of Si, not less than about 1.0% to about 1.5% Mn, about 0.1% or less of P, about 0.01% or less of S, about 1.0% or less of Cr, about 0.1% or less of Al, about 0.1% or less of Nb, about 0.1% or less of Ti, about 0.1% or less of V, and about 0.01% or less of N; and by reduction-rolling the treated steel pipe at a cumulative reduction rate of at least about 35% and a final rolling temperature of about 500° C. to about 900° C. The welded steel pipe exhibits excellent hydroformability, i.e., has a tensile strength of at least about 590 MPa and an n×r product of at least about 0.22. The treated steel pipe is preferably reduction-rolled at a cumulative reduction rate of at least about 20% below the Ar3 transformation point.
摘要:
The invention provides a high-carbon steel pipe having superior cold workability and induction hardenability, and a method of producing the steel pipe. The method comprises the steps of heating or soaking a base steel pipe having a composition containing C: 0.3 to 0.8%, Si: not more than 2%, and Mn: not more than 3%, and then carrying out reducing rolling on the base steel pipe at least in the temperature range of (Ac1, transformation point −50° C.) to Ac1, transformation point with an accumulated reduction in diameter of not less than 30%. A structure in which the grain size of cementite is not greater than 1.0 &mgr;m is obtained, thus resulting in improved cold workability and induction hardenability.
摘要:
A welded steel pipe is formed by heating or soaking an untreated welded steel pipe having a steel composition comprising, on the basis of mass percent: about 0.05% to about 0.3% C; about 2.0% or less of Si; more than about 1.5% to about 5.0% Mn; about 0.1% or less of P; about 0.01% or less of S; about 0.1% or less of Cr; about 0.1% or less of Al; about 0.1% or less of Nb; about 0.3% or less of Ti; and about 0.01% or less of N; and by diameter-reduction-rolling the treated steel pipe at a accumulated diameter reduction rate of at least about 35% and a finish rolling temperature of about 500° C. to about 900° C. The welded steel pipe exhibits excellent hydroformability, i.e., has a tensile strength of about 780 MPa or more and a n×r product of at least about 0.15. The treated steel pipe is preferably diameter-reduction-rolled at a accumulated diameter reduction rate of at least about 20% below the Ar3 transformation point.
摘要:
A steel pipe is produced by a method including performing diameter-reducing rolling on a steel pipe in a temperature range of from 600° C. to Ac3 with a reduction in diameter of not less than 30%, preferably after heating the steel pipe to temperatures of not lower than Ac1, the steel pipe being produced by seam-welding strip steel, or a method further including the step of performing heat treatment of holding the rolled steel pipe in a temperature range of from 600° C. to 900° C. for a time of 1 second or longer during cooling subsequent to the diameter-reducing rolling or by reheating the rolled steel pipe after the cooling.
摘要:
A welded steel pipe is formed by heating or soaking an untreated welded steel pipe having a steel composition containing, on the basis of mass percent: about 0.05% to about 0.2% C; about 0.2% or less of Si; about 1.5% or less of Mn; about 0.1% or less of P; about 0.01% or less of S; about 0.1% or less of Al; and about 0.01% or less of N; and by reduction-rolling the treated steel pipe at a cumulative reduction rate of at least about 35% and a final rolling temperature of about 500° C. to about 900° C. The welded steel pipe exhibits excellent hydroformability, i.e., has a tensile strength of at least about 400 MPa and an n×r product of at least about 0.22. The treated steel pipe is preferably reduction-rolled at a cumulative reduction rate of at least about 20% below the Ar3 transformation point. The welded steel pipe is suitable for forming structural components.
摘要:
A steel tube having a composition which contains: 0.05 to 0.30% of C; 1.8 to 4.0% of Mn; Si; and Al is subjected to a diameter-reducing rolling process in which the total diameter-reduction rate is no less than 20% and the temperature at which the diameter-reducing rolling process is finished is no higher than 800° C., whereby a structure constituted of martensite and/or bainite or further of ferrite is obtained as a transformation product from the deformed γ. As a result, a steel tube having tensile strength of 1000 MPa or more and excellent three-point-bending property can be obtained. The composition of the steel tube of the present invention may further include at least one type of element selected from the group consisting of Cu, Ni, Cr and Mo, or at least one type of element selected from the group consisting of Nb, V, Ti and B, or at least of one type selected from the group consisting of REM and Ca.
摘要:
An impeder, for manufacturing a welded pipe, including an insulating case 4 containing laminations 10 having coated steel sheets 8 formed by providing an insulating coating on untreated steel sheets having a thickness of 0.3 mm or less and an insulating case 8 containing the laminations, wherein the steel sheets contain 1.5-20% of Cr, 2.5-10% of Si, and 100 ppm or less of C and N in total, or further contain one or more of Al, Mn, and P, where the content of Al is 5% or less and the content of each of Mn and P is 1% or less, the remainder being Fe and unavoidable impurities; and preferably have a resistivity of 60 μΩ·cm or more.