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 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-strength, high-toughness seamless steel pipe used for a line pipe contains 0.03 to 0.06% of C, 0.05 to 0.15% of Si, 1.6 to 2.0% of Mn, 0.010 to 0.10% of Al, 0.3 to 0.7% of Ni, 0.10 to 0.40% of Mo, 0.01 to 0.06% of V, 0.003 to 0.03% of Nb, 0.003 to 0.020% of Ti, and 0.0010 to 0.0100% of N, the relationships Mo+5V≧0.4% and 2Nb−V≦0% being satisfied, and the balance being Fe and incidental impurities. Consequently, it is possible to provide the high-strength, high-toughness seamless steel pipe used for a line pipe in which grade X80 strength and toughness are stably ensured, and the target strength can be easily attained regardless of the size.
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:
The present invention provides a seamless expandable oil country tubular goods, which has a superior pipe expansion property in a expanding process at an expand ratio of more than 30% although having a high strength such as a tensile strength (TS) of 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, whenever necessary, by inexpensive nonthermal-refining type heat treatment. In a particular product, 0.010% to less than 0.10% of C, 0.05% to 1% of Si, 0.5% to 4% of Mn, 0.03% or less of P, 0.015% or less of S, 0.01% to 0.06% of Al, 0.007% or less of N, and 0.005% or less of O are contained, and at least one of Nb, Mo, and Cr is contained in the range of 0.01% to 0.2% of Nb, 0.05% to 0.5% of Mo, and 0.05% to 1.5% of Cr, so that Mn+0.9×Cr+2.6×Mo≧2.0 and 4×C−0.3×Si+Mn+1.3×Cr+1.5×Mo≦4.5 are satisfied. The micro-structure of a steel pipe preferably contains ferrite at a volume fraction of 5% to 70%, and the balance is substantially composed of a low temperature-transforming phase. The manufacturing condition includes at least one of a: a rolling finish temperature of 800° C. or more in pipe forming, b: normalizing treatment after pipe forming, and c: holding of a steel pipe in a dual-phase region for five minutes or more after pipe forming, followed by air cooling.
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 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 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.