摘要:
A method for suppressing shock and storage cracking when manufacturing seamless steel pipes comprises hot piercing and hot rolling a billet consisting of, by mass percent controlled amounts of C, Si, Mn, Cr, Mo, Ti, and Al, with the balance being Fe and impurities of Ni, P, S, N, and O also in controlled amounts. Further heat treatment is performed, wherein a hot rolled steel pipe is direct quenched from a temperature of not lower than the Ar3 transformation point and the pipe is then subjected to heat treatment at a temperature of not lower than 450° C. and not higher than the Ac1 transformation point in heat treatment equipment for performing direct quenching. The steel pipe subjected to the heat treatment is reheated, quenched from a temperature of not lower than the Ac3 transformation point, and tempered at a temperature of not higher than the Ac1 transformation point.
摘要:
There is provided a method for manufacturing a seamless steel pipe for line pipe, capable of improving the toughness of the seamless steel pipe for line pipe. A round billet having a chemical composition, by mass percent, of C: 0.02 to 0.15%, Si: at most 0.5%, and Mn: 0.5 to 2.5%, the balance being Fe and impurities, is heated. The heated round billet is piercing-rolled to produce a hollow shell. The hollow shell is elongated and rolled and sized to produce a seamless steel pipe. The seamless steel pipe is water cooled, and the water cooling is stopped when the temperature of the seamless steel pipe reaches at most 450° C. The water-cooled seamless steel pipe is quenched, and the quenched seamless steel pipe is tempered.
摘要:
A seamless steel pipe for line pipe having a high strength and good toughness and corrosion resistance even though having a thick wall has a chemical composition comprising, in mass percent, C: 0.02-0.08%, Si: at most 0.5%, Mn: 1.5-3.0%, Al: 0.001-0.10%, Mo: greater than 0.4% to 1.2%, N: 0.002-0.015%, Ca: 0.0002-0.007%, and a remainder of Fe and impurities, wherein the contents of the impurities are at most 0.03% for P, at most 0.005% for S, at most 0.005% for O and less than 0.0005% for B and wherein the value of Pcm calculated by the following Equation (1) is at least 0.185 and at most 0.250. The steel pipe has a microstructure which primarily comprises bainite and which has a length of cementite of at most 20 micrometers: Pcm=[C]+[Si]/30+([Mn]+[Cr]+[Cu])/20+[Mo]/15+[V]/10+5[B] (1) wherein [C], [Si], [Mn], [Cr], [Cu], [Mo], [V] and [B] are numbers respectively indicating the content in mass percent of C, Si, Mn, Cr, Cu, Mo, V and B.
摘要:
A steel pipe for an airbag inflator having a high strength of at least 900 MPa and preferably at least 1000 MPa in tensile strength along with a high toughness and exhibiting good resistance to bursting such that it has no propagation of cracks in a burst test at −40° C. or below is manufactured by quenching a pipe of a steel comprising, in mass %, C: 0.05-0.20 %, Si: 0.1-1.0 %, P: at most 0.025 %, S: at most 0.010 %, Cr: 0.05-1.45 %, Al: at most 0.10 %, and one or both of Ti and Mn satisfying Ti≦0.02% and 0.4%≦Mn+40Ti≦1.2% from a temperature of at least the Ac1 transformation point of the steel, tempering the pipe at a temperature lower than the Ac1 transformation point, applying cold working to it with a reduction of area of at most 65%, and subjecting it to stress relief annealing at a temperature lower than the Ac1 transformation point. The ratio L/T of the X-ray integrated intensity ratio of the {110} plane measured for the cross section perpendicular to the axial direction L of the steel pipe to that measured for the cross section perpendicular to the circumferential direction T is at most 50.
摘要:
A seamless steel pipe for line pipe having a high strength and good toughness and corrosion resistance even though having a thick wall has a chemical composition comprising, in mass percent, C: 0.02-0.08%, Si: at most 0.5%, Mn: 1.5-3.0%, Al: 0.001-0.10%, Mo: greater than 0.4% to 1.2%, N: 0.002-0.015%, Ca: 0.0002-0.007%, and a remainder of Fe and impurities, wherein the contents of the impurities are at most 0.03% for P, at most 0.005% for S, at most 0.005% for O and less than 0.0005% for B and wherein the value of Pcm calculated by the following Equation (1) is at least 0.185 and at most 0.250. The steel pipe has a microstructure which primarily comprises bainite and which has a length of cementite of at most 20 micrometers: Pcm=[C]+[Si]/30+([Mn]+[Cr]+[Cu])/20+[Mo]/15+[V]/10+5[B] (1) wherein [C], [Si], [Mn], [Cr], [Cu], [Mo], [V] and [B] are numbers respectively indicating the content in mass percent of C, Si, Mn, Cr, Cu, Mo, V and B.
摘要:
(1) A steel pipe that is expanded radially in a state wherein it was inserted in a well such as an oil well, characterized in that the non-uniform wall thickness ratio E0 (%) before expanding satisfies the following expression {circle around (1)}. E0≦30/(1+0.018α) {circle around (1)} Wherein α is the pipe expansion ratio (%) calculated by the following expression {circle around (2)}. α=[(inner diameter of the pipe after expanding−inner diameter of the pipe before expanding)/inner diameter of the pipe before expanding]×100 {circle around (2)} (2) A steel pipe that should be expanded radially in a state wherein it is inserted in a well, such as an oil well, characterized in that the eccentric non-uniform wall thickness ratio is 10% or less.When the embedding-expanding method is performed with use of the steel pipe of (1) or (2), lowering of collapse strength of the expanded steel pipe is prevented and bending thereof can be decreased.
摘要:
(1) A steel pipe that is expanded radially in a state wherein it was inserted in a well such as an oil well, characterized in that the non-uniform wall thickness ratio E0 (%) before expanding satisfies the following expression {circle around (1)}. E0≦30 /(1+0.018α) {circle around (1)}Wherein α is the pipe expansion ratio (%) calculated by the following expression {circle around (2)}. α=[(inner diameter of the pipe after expanding−inner diameter of the pipe before expanding)/inner diameter of the pipe before expanding]×100 {circle around (2)}(2) A steel pipe that should be expanded radially in a state wherein it is inserted in a well, such as an oil well, characterized in that the eccentric non-uniform wall thickness ratio is 10% or less. When the embedding-expanding method is performed with use of the steel pipe of (1) or (2), lowering of collapse strength of the expanded steel pipe is prevented and bending thereof can be decreased.
摘要:
(1) A steel pipe that is expanded radially in a state wherein it was inserted in a well such as an oil well, characterized in that the non-uniform wall thickness ratio E0 (%) before expanding satisfies the following expression {circle around (1)}. E0≦30/(1+0.018α){circle around (1)} Wherein α is the pipe expansion ratio (%) calculated by the following expression {circle around (2)}. α=[(inner diameter of the pipe after expanding−inner diameter of the pipe before expanding)/inner diameter of the pipe before expanding]×100{circle around (2)} (2) A steel pipe that should be expanded radially in a state wherein it is inserted in a well, such as an oil well, characterized in that the eccentric non-uniform wall thickness ratio is 10% or less.When the embedding-expanding method is performed with use of the steel pipe of (1) or (2), lowering of collapse strength of the expanded steel pipe is prevented and bending thereof can be decreased.
摘要:
A steel pipe for an airbag inflator having a high strength of at least 900 MPa and preferably at least 1000 MPa in tensile strength along with a high toughness and exhibiting good resistance to bursting such that it has no propagation of cracks in a burst test at −40° C. or below is manufactured by quenching a pipe of a steel comprising, in mass %, C: 0.05-0.20 %, Si: 0.1-1.0 %, P: at most 0.025 %, S: at most 0.010 %, Cr: 0.05-1.45 %, Al: at most 0.10 %, and one or both of Ti and Mn satisfying Ti
摘要:
A high strength steel pipe for an airbag system has a steel composition comprising C: 0.05-0.20%, Si: 0.1-1.0%, P; at most 0.025%, S: at most 0.010%, Cr: 0.05-1.0%, Al: at most 0.10% at least one of Ti and Mn satisfying (1) Ti≦0.02% and (2) 0.4%≦Mn+40Ti≦1.2%, and a remainder of Fe. The composition may further include one or more of (i) at least one of Mo: 0.05-0.50%, Ni: 0.05-1.5%, V: 0.01-0.2%, and B: 0.0003-0.005%, (ii) at least one of Cu: 0.05-0.5% and Nb: 0.003-0.1%, and (iii) at least one of Ca: 0.0003-0.01%, Mg: 0.0003-0.01%, and REM: 0.0003-0.01%. The steel pipe can be manufactured by forming a pipe from the above-described steel composition to obtain prescribed dimensions, heating to at least the Ac1 transformation point and quenching, and then tempering at the Ac1 transformation point or below.