摘要:
A martensitic stainless steel seamless tube for oil country tubular goods includes a yield strength of 95 ksi or more and low-temperature toughness in which a fracture transition temperature vTrs in a Charpy impact test is −40° C. or below, wherein the seamless tube has a composition comprising, by mass %, 0.020% or less C, 10 to 14% Cr, 3% or less Ni, 0.03 to 0.2% Nb, 0.05% or less N, and Fe and unavoidable impurities as a balance, and has a structure where a precipitated Nb quantity is 0.020% or more in terms of Nb.
摘要:
A heavy wall and high strength seamless steel pipe having high sour resistance is provided. In particular, a quenching and tempering treatment is conducted to adjust the yield strength to be higher than 450 MPa and adjust the Vickers hardness HV5 that can be measured at an outermost side or an innermost side of the pipe under a 5 kgf load (test load: 49 N) to be 250 HV5 or less.
摘要:
A seamless steel tube contains 0.15% to 0.50% C, 0.1% to 1.0% Si, 0.3% to 1.0% Mn, 0.015% or less P, 0.005% or less S, 0.01% to 0.1% Al, 0.01% or less N, 0.1% to 1.7% Cr, 0.4% to 1.1% Mo, 0.01% to 0.12% V, 0.01% to 0.08% Nb, and 0.0005% to 0.003% B or further contains 0.03% to 1.0% Cu on a mass basis and has a microstructure which has a composition containing 0.40% or more solute Mo and a tempered martensite phase that is a main phase and which contains prior-austenite grains with a grain size number of 8.5 or more and 0.06% by mass or more of a dispersed M2C-type precipitate with substantially a particulate shape.
摘要:
A seamless steel tube contains 0.15% to 0.50% C, 0.1% to 1.0% Si, 0.3% to 1.0% Mn, 0.015% or less P, 0.005% or less S, 0.01% to 0.1% Al, 0.01% or less N, 0.1% to 1.7% Cr, 0.4% to 1.1% Mo, 0.01% to 0.12% V, 0.01% to 0.08% Nb, and 0.0005% to 0.003% B or further contains 0.03% to 1.0% Cu on a mass basis and has a microstructure which has a composition containing 0.40% or more solute Mo and a tempered martensite phase that is a main phase and which contains prior-austenite grains with a grain size number of 8.5 or more and 0.06% by mass or more of a dispersed M2C-type precipitate with substantially a particulate shape.
摘要:
A method of producing a high-strength high-toughness martensitic stainless steel seamless pipe which includes heating a martensitic stainless steel raw material to an austenitic range and subjecting the raw material to piercing and elongating to form an original pipe. The original pipe is cooled to form a structure substantially composed of martensite in the original pipe. The original pipe is reheated to a temperature in the dual-phase range between the Ac1 transformation point and the Ac3 transformation point, and is subjected to finishing rolling at an initial rolling temperature T (° C.) between the Ac1 transformation point and the Ac3 transformation point. The original pipe is then cooled to form a processed pipe. The processed pipe is tempered at a temperature below the Ac1 transformation point. The reduction in area R in the finishing rolling step may be in the range of 10% to 90%, and the initial rolling temperature T and the reduction in area R may satisfy the relationship 800≦T−0.625R≦850.
摘要:
A martensitic steel for a line pipe having excellent corrosion resistance and weldability is disclosed. The martensitic steel contains about:0.02 wt % or less of C, 0.50 wt % or less of Si,0.2 to 3.0 wt % of Mn, 10 to 14 wt % of Cr,0.2 to 7.0 wt % of Ni, 0.2 to 5.0 wt % of Mo,0.1 wt % or less of Al, 0.07 wt % or less of N, andthe balance being Fe and incidental impurities; andthese elements satisfy substantially the following equations:(Cr %)+(Mo %)+0.1(N %)-3(C %).gtoreq.12.2,(Cr %)+3.5(Mo %)+10(N %)+0.2(Ni %)-20(C %).gtoreq.14.5, and150(C %)+100(N %)-(Ni %)-(Mn %).ltoreq.4.The martensitic steel may further contain at least one element selected from the group consisting ofabout 2.0 wt % or less of Cu, about 0.15 wt % or less of Ti, about 0.15 wt % or less of Zr, about 0.15 wt % or less of Ta andabout 0.006 wt % or less of Ca, andthese elements satisfy substantially the following equations:(Cr %)+(Mo %)+0.1(N %)+3(Cu %)-3(C %).gtoreq.12.2,(Cr %)+3.5(Mo %)+10(N %)+0.2(Ni %)-20(C %).gtoreq.14.5,150(C %)+100(N %)-(Ni %)-(Mn %).ltoreq.4.
摘要:
A high-Cr martensitic steel pipe having excellent pitting resistance and method for manufacturing the same, which involves forming a pipe of steel including C: about 0.03 wt % or less, Si: about 0.5 wt % or less, Mn: about 0.5-3.0 wt %, Cr: about 10.0-14.0 wt %, Ni: about 0.2-2.0 wt %, Cu: about 0.2-1.0 wt % and N: about 0.03 wt % or less with the balance being Fe and incidental impurities, and having a value X shown as defined in the following formula (1) of about 12.2 or more. The pipe is quenched after austenitizing it at a temperature substantially equal to an Ac.sub.3 point or higher, and the pipe is tempered in a temperature range from about 550.degree. C. or higher to a temperature lower than an Ac.sub.1 point.value X=(Cr %)+3(Cu %)-3(C %) (1)The high-Cr martensitic steel pipe made by this method exhibits excellent pitting resistance and general corrosion resistance even in an environment containing a carbonic acid gas, and further exhibits excellent weldability and toughness in the heat-affected zones.
摘要:
A martensitic stainless steel pipe having a heat-affected zone with high resistance to intergranular stress corrosion cracking is provided. In particular, the martensitic stainless steel pipe contains less than 0.0100% of C; less than 0.0100% of N; 10% to 14% of Cr; and 3% to 8% of Ni on a mass basis. Alternatively, the martensitic stainless steel pipe may further contain Si, Mn, P, S, and Al within an appropriate content range. The martensitic stainless steel pipe may further contain one or more selected from the group consisting of 4% or less of Cu, 4% or less of Co, 4% or less of Mo, and 4% or less of W and one or more selected from the group consisting of 0.15% or less of Ti, 0.10% or less of Nb, 0.10% or less of V, 0.10% or less of Zr, 0.20% or less of Hf, and 0.20% or less of Ta on a mass basis. The content Csol defined by the following equation is equal to less than 0.0050%: Csol=C−⅓×Cpre, wherein Cpre=12.0{Ti/47.9+½(Nb/92.9+Zr/91.2)+⅓(V/50.9+Hf/178.5+Ta/180.9)−N/14.0} or Cpre=0 when Cpre
摘要:
A high-Cr steel pipe for line pipes having further improved HAZ toughness and hot workability is provided by limiting the composition to: C: 0.02% or less, Si: 0.5% or less, Mn: 0.2 to 3.0%, Cr: 10.0 to 14.0%, Ni: more than 2.0 to 3.0%, N: 0.02% or less, preferably Nb: 0.3% or less, and the balance being Fe and incidental impurities.
摘要:
A seamless expandable oil country tubular article, which has a superior pipe expansion property in a expanding process at an expand ratio of more than about 30% although having a high strength such as a tensile strength (TS) of about 600 MPa or more, and a manufacturing method thereof, the seamless expandable oil country tubular goods being in an as-rolled state or being processed, optionally necessary, by inexpensive nonthermal-refining type heat treatment.