Showing papers by "Nobuhiro Fujita published in 2003"
25 Jun 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, changes of microstructures and high temperature properties in high temperature aging were investigated using several Niobium added ferritic stainless steels, and it was found that the microstructure stability of Nb-Ti-Mo alloyed steels in high- temperature aging is superior to that of nb added steels.
Abstract: To improve the fuel economy and clean the exhaust gas of automobiles, the temperature of exhaust gas is getting higher and higher. Niobium added ferritic stainless steels are often being used in automotive exhaust systems, because of their excellent heat resistant properties, especially thermal fatigue resistance, which is very important for materials of exhaust manifold. However, coarse precipitates containing niobium, which cause degradation in high temperature strength and thermal fatigue resistance, are unavoidable during high temperature service. In this study, changes of microstructures and high temperature properties in high temperature aging were investigated using several Nb added ferritic stainless steels. It has been found that the microstructure stability of Nb–Ti–Mo alloyed steels in high temperature aging is superior to that of Nb added steels. The microstructure stability leads to less degradation in high temperature strength during high temperature aging and to longer thermal fatigue lives of Nb–Ti–Mo alloyed steels than in Nb added steels.
152 citations
Patent•
14 Oct 2003
TL;DR: In this article, the authors proposed a tensile strength of 800 MPa or higher for a high-strength steel sheet with a microstructure consisting of one or both of bainite and bainitic ferrite, the secondary phase consisting of austenite, and the balance being ferrite and/or martensite.
Abstract: PROBLEM TO BE SOLVED: To simultaneously improve hydrogen embrittlement resistance, weldability, hole-expandability, and ductility of a high-strength steel sheet having a tensile strength of 800 MPa or higher. SOLUTION: This steel sheet comprises, by mass%, 0.05-0.3% C, 0.01-3.0% Si, 0.01-4.0% Mn, 0.0001-0.020% P, 0.0001-0.020% S, 0.01-3.0% Al, 0.0001-0.01% N, and one or more elements of 0.001-5.5% Ni, 0.001-3.0% Cu, 0.001-5.0% Cr and 0.005-5% Mo, and the balance being iron with unavoidable impurities; has a microstructure comprising the main phase consisting of one or both of bainite and bainitic ferrite, the secondary phase consisting of austenite which occupies an area rate V γ of 3 to 30%, and the balance being ferrite and/or martensite; has a tensile strength TS of 800 MPa or higher; and satisfies the following expressions (1-1) and (1-2): 0≤0.8×{2Cu+20Mo+3Ni+Cr}-{0.1-3.5×10 7 ×(TS) -3.1 }-0.3V γ --- (1-1) and 0≤Si+Al+7.67C-1.78 --- (1-2). COPYRIGHT: (C)2005,JPO&NCIPI
42 citations
TL;DR: In this article, the free energy changes for the precipitation reactions from niobium-supersaturated ferrite have been obtained by using the solubility products of Fe 3 Nb 3 C and Fe 2 Nb, both of which are prominent precipitates in such steels.
Abstract: Precipitation behaviors in niobium alloyed ferritic stainless steels, which are widely used as heat resistant materials in automotive exhausts, were investigated. The solubility products of Fe 3 Nb 3 C and Fe 2 Nb, both of which are prominent precipitates in such steels, were experimentally obtained. The expressions of the solubility products with mass% are given by: Fe 3 Nb 3 C; log 10 {(Nb] 3 [C]}=-11 613/T+5.2178 Fe 2 Nb; log 10 [Nb]=-3 780.3/T+2.4646 These were verified with some published experimental data. An attempt was also made to get thermodynamic parameters using the solubility products. The free energy changes for the precipitation reactions from niobium-supersaturated ferrite have been obtained. The expressions with mole fractions in ferrite matrix, e.g. x αβ Nb, are given by: Fe 3 Nb 3 C (β); ΔG β =-222 509- RT{6.423+ln(x αβ Nb) 3 (x αβ c)} Fe 2 Nb (ω); ΔG ω = -72 334- RT{0.5469+ln N αω Nb}.
35 citations
Patent•
02 Jun 2003
TL;DR: In this article, a high strength steel sheet with excellent delayed fracture resistance is proposed, which contains, by mass, 0.05 to 0.3% C. The problem to be solved is to provide a high-strength steel sheet which has a tensile strength of ≥ 1,180 MPa.
Abstract: PROBLEM TO BE SOLVED: To provide a high strength steel sheet which has a tensile strength of ≥1,180 MPa and has excellent delayed fracture resistance, and to provide its production method. SOLUTION: The high strength steel sheet having excellent delayed fracture resistance contains, by mass, 0.05 to 0.3% C, COPYRIGHT: (C)2005,JPO&NCIPI
33 citations
Patent•
15 Oct 2003
TL;DR: In this article, a high strength low specific gravity steel plate characterized by 10,000 MPa ·% or more is presented, and a method for producing the same is proposed. But the method is not suitable for high strength steel plate.
Abstract: PROBLEM TO BE SOLVED: To provide a high strength low specific gravity steel plate and a method for producing the same. SOLUTION By mass%, C: more than 0.01 to 5%, Si: 3.0% or less, Mn: 0.01 to 30.0%, P: 0.1% or less, S: 0.01 %: Al: 3.0 to 10.0%, N: 0.001 to 0.05%, the balance being Fe and inevitable impurities, specific gravity <7.20, tensile strength: TS (MPa) Elongation at break: El (%) product value: TS × El is a high strength low specific gravity steel plate characterized by 10000 MPa ·% or more. [Selection figure] None
29 citations
Patent•
28 Apr 2003
TL;DR: In this article, a high strength galvanized steel sheet having excellent hydrogen embrittlement resistance, weldability and hole expansibility has a composition comprising, by mass, ≤0.25% C, ≤2.0% P, ≤ 0.05% S, ≤3.5% Nb, and the balance iron with inevitable impurities, has a structure comprising bainite and/or martensite of ≥70% in total by area and 0.
Abstract: PROBLEM TO BE SOLVED: To provide a high strength galvanized steel sheet in which the weldability and hole expansibility of a high strength steel sheet having a tensile strength of ≥900 MPa are simultaneously improved, and to provide its production method. SOLUTION: The high strength galvanized steel sheet having excellent hydrogen embrittlement resistance, weldability and hole expansibility has a composition comprising, by mass, ≤0.25% C, ≤2.0% Si, ≤4.0% Mn, ≤0.05% P, ≤0.05% S, ≤3.0% Al and ≤0.01% N, and comprising one or more kinds of metals selected from ≤5.5% Ni, ≤3.0% Cu, ≤5.0% Cr, ≤5% Mo and ≤1.0% Nb, and the balance iron with inevitable impurities, has a structure comprising bainite and/or martensite of ≥70% in total by area and 0, inequality (1-2): 0≤0.8×{2Cu+20Mo+3Ni+Cr}-{0.1-3.5×10 7× (TS) -3.1 }-0.3Vγ, and inequality (1-3): 0>Si+Al+2-(Mn+Ni+1.5Mo). COPYRIGHT: (C)2005,JPO&NCIPI
21 citations
Patent•
28 Feb 2003
TL;DR: In this paper, a high strength steel sheet with excellent stretch-flange formability is composed of steel having a composition consisting of, by mass, 002 to 03% C, 001 to 25% Si, 00 1 to 35% Mn, 0001 to 1 2% P, 0000 1 to 00 1% S, and a product of tensile strength TS(MPa) and bore expandability λ(%) is made to ≥30,000 MPa.
Abstract: PROBLEM TO BE SOLVED: To provide a steel sheet having ≥440 MPa tensile strength and excellent stretch-flange formability, and its manufacturing method SOLUTION: The high strength steel sheet with excellent stretch-flange formability is composed of steel having a composition consisting of, by mass, 002 to 03% C, 0001 to 25% Si, 001 to 35% Mn, 0001 to 012% P, 00001 to 001% S, 2 Further, in the steel sheet, tensile strength TS is made to ≥440 MPa and a product of tensile strength TS(MPa) and bore expandability λ(%) is made to ≥30,000(MPa%) COPYRIGHT: (C)2004,JPO&NCIPI
20 citations
Patent•
14 Oct 2003
TL;DR: In this paper, a high-strength and low-specific-gravity steel sheet has a composition consisting of, by mass, > 0.01 to 5.0% C, ≤ 3.0%, 0.02% P, ≤ 0.05% N and the balance Fe with inevitable impurities and has ≤6.5 specific gravity.
Abstract: PROBLEM TO BE SOLVED: To provide a high-strength and low-specific-gravity steel sheet having excellent ductility and its manufacturing method. SOLUTION: The high-strength and low-specific-gravity steel sheet has a composition consisting of, by mass, >0.01 to 5.0% C, ≤3.0% Si, 0.01 to 30.0% Mn, ≤0.02% P, ≤0.01% S, >10 to 32.0% Al, 0.001 to 0.05% N and the balance Fe with inevitable impurities and has ≤6.5 specific gravity. In this steel sheet, the value of a product of tensile strength TS(MPa) and fracture elongation El(%), TS×El, is ≥8,500 MPa×%. COPYRIGHT: (C)2005,JPO&NCIPI
18 citations
Patent•
24 Jun 2003TL;DR: In this paper, a high strength steel plate with a chemical composition in mass %: C: 0.03 to 0.20 %, Si: 0,005 to 0,3 %, Mn: 1.0 to 3.5 %, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula (1): (0.0012×[objective value of TS]-0.29-[Si])/2.5-3×[Si] ····
Abstract: A high strength steel plate excellent in formability which has a chemical composition in mass %: C: 0.03 to 0.20 %, Si: 0.005 to 0.3 %, Mn: 1.0 to 3.1 %, P: 0.001 to 0.06 %, S: 0.001 to 0.01 %, N: 0.0005 to 0.01 %, Al: 0.2 to 1.2 %, Mo ≤ 0.5 %, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula (1): (0.0012×[objective value of TS]-0.29-[Si])/2.45 < Al < 1.5-3×[Si] ····(1) wherein [objective value of TS] represents a design strength value for the steel plate in an Mpa unit, and has a metal structure containing ferrite and martensite. The above high strength steel plate is also excellent in formability and the capability of being chemically treated and that of being hot-dip zinc plated.
17 citations
17 citations
Patent•
08 Dec 2003
TL;DR: In this paper, a high strength thin steel sheet having excellent hydrogen embitterment resistance is characterized in that: the steel sheet comprises, by mass, 0.01 to 3% in total of one kind or two or more kinds of Nb, V, Cr, Ti and Mo, and the balance Fe and inevitable impurities; the steel has a bainite or martensite structure as the phase of the maximum area rate.
Abstract: PROBLEM TO BE SOLVED: To provide a thin steel sheet in which hydrogen-related defects are prevented and has excellent delayed fracture resistance and to provide its manufacturing method. SOLUTION: The high strength thin steel sheet having excellent hydrogen embitterment resistance is characterized in that: the steel sheet comprises, by mass%, 0.01 to 0.30% C, ≤2.0% Si, 0.01 to 3% Mn, 0.1% P, 0.05% S, 0.005 to 4% Al, ≤0.01% N, 0.001 to 3% in total of one kind or two or more kinds of Nb, V, Cr, Ti and Mo, and the balance Fe and inevitable impurities; the steel has a bainite or martensite structure as the phase of the maximum area rate; the grains contain one or more kinds of oxides, sulfides, nitrides, compound crystallized products and compound precipitates of Nb, V, Cr, Ti, Mo and have 0.001 to 5.0 μm average particle size d and 100 to 1×10 13 particles/mm 2 density ρ, satisfying σ/d≤0.1, wherein σ is the standard deviation of the average particle size; and the steel has ≥980 MPa tensile strength. COPYRIGHT: (C)2005,JPO&NCIPI
Patent•
28 Jan 2003
TL;DR: In this article, a steel sheet with excellent resistance to hydrogen embrittlement has been proposed. But it is not shown how to construct a high strength steel sheet in which hydrogen-induced defects are prevented and excellent delayed fracture resistance is provided and its manufacturing method.
Abstract: PROBLEM TO BE SOLVED: To provide a steel sheet in which hydrogen-induced defects are prevented and excellent delayed fracture resistance is provided and its manufacturing method. SOLUTION: The high strength steel sheet with excellent resistance to hydrogen embrittlement has a composition consisting of, by mass, 0.05 to 0.3% C, 0.01 to 3.0% Si, 0.01 to 4.0% Mn, 0.0001 to 0.020% P, 0.0001 to 0.020% S, 0.01 to 3.0% Al, 0.0001 to 0.01% N, one or more among 0.001 to 5.5% Ni, 0.001 to 3.0% Cu, 0.001 to 5.0% Cr and 0.005 to 5% Mo and the balance iron with inevitable impurities and satisfying the inequality, 0≤0.8×{2Cu+20Mo+3Ni+Cr}-{0.1-3.5×10 7 ×(TS) -3.1 } (where TS is tensile strength (MPa)). COPYRIGHT: (C)2004,JPO&NCIPI
Patent•
12 Feb 2003
TL;DR: In this article, the authors proposed a high-strength and high-ductility steel plate having excellent ductility and suitably used for building materials, household electrical appliances, automobiles, and also to provide its manufacturing method.
Abstract: PROBLEM TO BE SOLVED: To provide a high-strength and high-ductility steel plate having excellent ductility and suitably used for building materials, household electrical appliances, automobiles, etc., and also to provide its manufacturing method. SOLUTION: The high-strength and high-ductility steel plate has a composition containing, by mass, 0.0001 to 0.3% C, 0.001 to 2.5% Si, 0.01 to 3% Mn, 0.0001 to 0.3% P, 0.0001 to 0.1% S, 0.0001 to 4% Al, 0.0001 to 0.3% N and 0.0001 to 0.1% O, also containing one or more kinds among 0.0005 to 0.3% Rem, 0.0005 to 0.3% Y, 0.0001 to 1% Ti, 0.0001 to 1% Zr, 0.0001 to 1% Hf and 0.0001 to 1% Ca within the range satisfying equations [(Ti/48+Zr/91+Hf/178+Ca/40)/(Rem/140+Y/89)=0 to 20] and [(O/16+S/32+N/14)/(Rem/140+Y/89)=0 to 10], and having the balance Fe with inevitable impurities. COPYRIGHT: (C)2004,JPO&NCIPI
Patent•
28 Oct 2003
TL;DR: In this article, a U-shaped test piece is provided with load stress by U-bending sheet steel with hydrogen and an anode is arranged in such a way as to lie within the 50% range or less of the average concentration of hydrogen.
Abstract: PROBLEM TO BE SOLVED: To provide a method for evaluating hydrogen embrittlement and its evaluation method capable of correctly and simply evaluating the characteristics of thin sheet steel in consideration of its environment of use and required characteristics SOLUTION: The system for evaluating the hydrogen embrittlement of thin sheet steel comprises: an electrolyte cell 1 for holding an electrolytic solution; a cathode 3 for charging a U-shaped test piece 2, provided with load stress by U-bending sheet steel, with hydrogen; an anode 4 in which a hydrogen concentration distribution is arranged in a U-bent part of the test piece in such a way as to lie within the 50% range or less of the average concentration of hydrogen; and a current generating means 5 COPYRIGHT: (C)2005,JPO&NCIPI
Patent•
27 May 2003TL;DR: A thin steel sheet which contains 7 vol % or less of retained austenite and 100 to 100,000 pieces per 1 square millimeter of crystallized products and/or precipitates having a particle diameter of 0.01 to 5.0 mum.
Abstract: A thin steel sheet which contains 7 vol % or less of retained austenite and 100 to 100,000 pieces per 1 square millimeter of crystallized products and/or precipitates having a particle diameter of 0.01 to 5.0 mum, and has a chemical composition in mass %: C: 0.05 to 0.3 %, Si: 3.0 % or less, Mn: 0.01 to 3.0 %, P: 0.02 % or less, S: 0.02 % or less, Al: 0.01 to 3.0 %, N: 0.01 % or less, Mg: 0.0002 to 0.01 %, and the balance: Fe and inevitable impurities.
Patent•
14 Oct 2003
TL;DR: In this article, the authors proposed a solution to simultaneously improve hydrogen embrittlement resistance, weldability, holeexpandability, and ductility of a high-strength steel sheet having a tensile strength of 800 MPa or higher.
Abstract: PROBLEM TO BE SOLVED: To simultaneously improve hydrogen embrittlement resistance, weldability, hole-expandability, and ductility of a high-strength steel sheet having a tensile strength of 800 MPa or higher. SOLUTION: This steel sheet comprises, by mass%, specified amounts of C, Si, Mn, P, S, Al and N, specified amounts of one or more elements of Ni, Cu, Cr, Mo and Nb, and the balance being iron with unavoidable impurities; includes, by an area rate, 70% or more one or both of bainite and bainitic in total, and less than 3% retained austenite (V γ ); has a tensile strength (TS) of 800 MPa or higher; and satisfies the expressions (1-1) to (1-3): (3.0Nb+2.5Mo+1/10Si+Mn)-(2C 0.5 +2)>0 --- (1-1), 0≤0.8×a2Cu+20Mo+3Ni+Cr+V γ }-a0.1-3.5×10 7 ×(TS) -3.1 } --- (1-2), and 0>Si+Al+7.67C-1.78 --- (1-3). COPYRIGHT: (C)2005,JPO&NCIPI
Patent•
24 Jun 2003TL;DR: A high strength steel sheet excellent in formability which has a chemical composition in mass %: C: 0.03 to 0.20%, Si: 0,005 to 0,3, Mn: 1.0 to 3.1%, N: 0.,0005 to 0.,01, Al: 0 2 to 1.5%, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula.
Abstract: A high strength steel sheet excellent in formability which has a chemical composition in mass %: C: 0.03 to 0.20%, Si: 0.005 to 0.3%, Mn: 1.0 to 3.1%, P: 0.001 to 0.06%, S: 0.001 to 0.01%, N: 0.0005 to 0.01%, Al: 0.2 to 1.2%, Mo≦0.5%, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula (1): (0.0012×[objective value of TS]−0.29−[Si])/2.45
Patent•
10 Oct 2003
TL;DR: In this paper, an aluminum plated steel pipe has an Fe-Al coating layer on the surface of the steel pipe, wherein an Al concentration in a 1-3 μm deep surface region of the Fe-al coating layer is 3-35% by mass.
Abstract: PROBLEM TO BE SOLVED: To provide a steel pipe which controls formation of oxidized scale in diameter-reducing process at a high temperature, occurrence of plating failures at diameter-reducing process, adherence of the plated film to a diameter- reducing roll, and galling on the diameter-reducing roll by the steel pipe, and further has an adequate surface grade even after the provided steel pipe has been formed into a car component, and to provide a manufacturing method therefor and the car component using the steep pipe. SOLUTION: The aluminum plated steel pipe has an Fe-Al coating layer on the surface of the steel pipe, wherein an Al concentration in a 1-3 μm deep surface region of the Fe-Al coating layer is 3-35% by mass%, and the Al concentration in at least 1 μm thick region in the Fe-Al coating side from the interface between the Fe-Al coating layer and the iron matrix is 0.5-15% by mass%. The method for manufacturing the aluminized steel pipe is characterized by heating the steel pipe having the Al coating layer on its surface at a predetermined temperature for a fixed time, and forming it so as to have a 15% or more reduced diameter and a wall thickness changed in a ratio between minus 20% and plus 10%. COPYRIGHT: (C)2004,JPO
27 Oct 2003
TL;DR: A method of fatigue life prediction of spot welded joint under multi-axial loads has been developed by fatigue life estimation working groups in the committee on fatigue strength and structural reliability of JSAE as mentioned in this paper.
Abstract: A method of fatigue life prediction of spot welded joint under multi-axial loads has been developed by fatigue life estimation working groups in the committee on fatigue strength and structural reliability of JSAE This method is based on the concept of nominal structural stress proposed by Radaj and Rupp, and improved so that D value is not involved in stress calculation The result of fatigue life estimation of actual vehicle with nominal structural stress which was calculated through newly developed method had very good correlation with the result of multi-axial loads fatigue test carried out with test piece including high strength steel (A) For the covering abstract see ITRD E121867
Patent•
27 May 2003TL;DR: In this article, a steel sheet containing residual austenite of not more than 7 vol.%, crystallized and/or precipitated compounds with particle diameters of 0.01 to 5.0 µm of 100 to 100000 particle/mm 2 and C of C 0.05 to 0.3 mass was described.
Abstract: Steel sheets containing residual austenite of not more than 7 vol.%, crystallized and/or precipitated compounds with particle diameters of 0.01 to 5.0 µm of 100 to 100000 particle/mm 2 and C of 0.05 to 0.3 mass%, Si of not more than 3.0 mass%, Mn of 0.01 to 3.0 mass%, P of not more than 0.02 mass%, S of not more than 0.02 mass%, Al of 0.01 to 3.0 mass%, N of not more than 0.01 mass% and Mg of 0.0002 to 0.01 mass%, with the remainder comprising iron and unavoidable.impurities.
Patent•
10 Sep 2003
TL;DR: In this paper, a high-strength, high-ductility galvanized steel sheet superior in the shape freezability has a plated layer comprising, by mass% 0.001-0.5% Al, less than 20% Fe, and the balance Zn with unavoidable impurities.
Abstract: PROBLEM TO BE SOLVED: To provide a high-strength, high-ductility galvanized steel sheet superior in a shape freezability, and a manufacturing method therefor. SOLUTION: The high-strength, high-ductility galvanized steel sheet superior in the shape freezability has a plated layer comprising, by mass% 0.001-0.5% Al, 0.001-2% Mn, less than 20% Fe, and the balance Zn with unavoidable impurities, wherein a Si content X in the steel by percentage (by mass% hereafter), a Mn content Y in the steel, an Al content Z in the steel, an Al content A in the plated layer, and a Mn content B in the plated layer, satisfy the expression (1): 3-(X+Y/10+Z/3)-12.5×(A-B)≥0...(1); ferrite, or ferrite and bainite occupy 50-97% by volume fraction in total as a main phase; austenite occupies 3-50% by volume fraction in total as a second phase; and further the yield ratio is 0.7 or less. COPYRIGHT: (C)2003,JPO
Patent•
24 Jan 2003
TL;DR: In this article, a steel sheet consisting of, by mass, 0.001-1.2% C, 7-30% Al, as necessary, one or more kinds of Mn, Si, Nb, Ti, Ni, Mo and Cu of 0.0002-0.5% in total and the balance Fe with inevitable impurities is heated to ≤ 1,000°C.
Abstract: PROBLEM TO BE SOLVED: To provide a press method of a lightweight steel sheet excellent in impact property by which lightening of automotive parts or the like is possible. SOLUTION: In this press forming method of a lightweight steel sheet excellent in impact property, a steel sheet consisting of, by mass, 0.001-1.2% C, 7-30% Al, as necessary, one or more kinds of Mn, Si, Nb, Ti, Ni, Mo and Cu of 0.1-10% in total, furthermore, 0.0002-0.1% B, 0.1-10% Cr, one or two kinds of Zr and Ce of 0.01-0.5% in total and the balance Fe with inevitable impurities is heated to ≤ 1,000°C and the press working is performed at 600-1,000°C. COPYRIGHT: (C)2004,JPO&NCIPI
Patent•
09 Apr 2003
TL;DR: In this article, a high strength and high ductility galvanized steel sheet is obtained by providing the surface of a steel sheet having a composition containing C, Si, Mn, Al, Mo, P and S, and the balance Zn with inevitable impurities.
Abstract: PROBLEM TO BE SOLVED: To provide a high strength galvannealed steel sheet, and a galvanized steel sheet which have suppressed unplating and surface defects, and combinedly have corrosion resistance, particularly, that in the environment containing chlorine and high ductility, and to provide a production method for them. SOLUTION: This high strength and high ductility galvanized steel sheet is obtained by providing the surface of a steel sheet having a composition containing C, Si, Mn, Al, Mo, P and S, and the balance Fe with inevitable impurities with a plated layer having a composition containing, by mass, 0.001 to 4% Al and 5 to 20% Fe, and the balance Zn with inevitable impurities. Provided that the Al mass% in the plated layer is A, the Mo mass% in the plated layer is B, and the Mo mass% in the steel is C, the relation of 100>=(A/3+B/6)/(C/6)>=0.01 is satisfied. The steel has a composite microstructure containing a ferritic phase or a ferritic phase and a bainitic phase of 50 to 97% in a volume fraction as the main phases, and the balance either or both of a martensitic phase and a retained austenitic phase by 3 to 50% in a volume fraction.
TL;DR: In this article, the kinetics of simultaneous reactions of niobium precipitates in ferrite have been modelled, taking into account the multicomponent nature of the diffusion process whilst at the same time allowing for capillarity effects.
Abstract: Synopsis : Niobium is used as an important alloying element in the design of heat-resistant ferritic stainless steels for automotive exhaust systems. When in solid solution, the niobium improves both the high temperature strength and the resistance to thermal fatigue. However, it also forms several kinds of precipitates during service at elevated temperatures, making it important to understand the kinetics of its precipitation and coarsening. In the present work, the kinetics of simultaneous reactions of niobium precipitates in ferrite have been modelled, taking into account the multicomponent nature of the diffusion process whilst at the same time allowing for capillarity effects. The model can predict not only volume fraction changes but also particle size. The experimental results on Fe2Nb Laves phase and Fe3Nb3C carbide in a 19Cr-0.8Nb steel have been obtained and shown to be comparable to be the calculations with new simultaneous model.
Patent•
02 Oct 2003
TL;DR: In this paper, a method for manufacturing the aluminum plated steel pipe having the excellent workability, corrosion resistance and heat resistance comprises heating the steel pipe with the Al coating on the surface to 800 to 1,200°C and subjecting the pipe to working by which a diameter reduction of ≥15% and a board thickness change rate of -20 to +10% are attained.
Abstract: PROBLEM TO BE SOLVED: To provide a steel pipe which suppresses the formation of oxide scale in diameter reduction compression working at a high temperature and suppresses the occurrence of a plating defect during the diameter reduction working, the adhesion of the plating to diameter reduction rolls and the galling, etc., of the steel pipe to the diameter reduction rolls, a method for manufacturing the same and automotive parts using such steel pipe. SOLUTION: The aluminum plated steel pipe having the excellent workability, corrosion resistance and heat resistance is characterized in that the steel pipe has an Fe-Al coating on its surface and that the Al concentration of the Fe-Al coating is 5 to 70% by mass %. The method for manufacturing the aluminum plated steel pipe having the excellent workability, corrosion resistance and heat resistance comprises heating the steel pipe having the Al coating on the surface to 800 to 1,200°C and subjecting the steel pipe to working by which a diameter reduction of ≥15% and a board thickness change rate of -20 to +10% are attained. COPYRIGHT: (C)2004,JPO
Patent•
19 Jun 2003
TL;DR: In this article, the authors proposed a high-strength steel sheet which comprises, by mass, 0.03-0.5% or less Mo and the balance Fe with unavoidable impurities, while controlling Si, Mn and Al so as to satisfy the following expressions (A) and (B): (0.0012×[TS target value]-0.29]-Si/2.45
Abstract: PROBLEM TO BE SOLVED: To realize a high-strength steel sheet superior in formability, and a manufacturing method therefor on an industrial scale. SOLUTION: This steel sheet comprises, by mass%, 0.03-0.20% C, 0.005-0.3% Si, 1.0-3.1% Mn, 0.001-0.06% P, 0.001-0.01% S, 0.0005-0.01% N, 0.2-1.2% Al, 0.5% or less Mo and the balance Fe with unavoidable impurities, while controlling Si, Mn and Al so as to satisfy the following expressions (A) and (B): (A): (0.0012×[TS target value]-0.29-[Si])/2.45 COPYRIGHT: (C)2005,JPO&NCIPI
Patent•
24 Jun 2003TL;DR: A high strength steel sheet excellent in formability which has a chemical composition in mass %: C: 0.03 to 0.20%, Si: 0,005 to 0,3, Mn: 1.0 to 3.1%, N: 0.,0005 to 0.,01, Al: 0 2 to 1.5%, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula.
Abstract: A high strength steel sheet excellent in formability which has a chemical composition in mass %: C: 0.03 to 0.20%, Si: 0.005 to 0.3%, Mn: 1.0 to 3.1%, P: 0.001 to 0.06%, S: 0.001 to 0.01%, N: 0.0005 to 0.01%, Al: 0.2 to 1.2%, Mo≦0.5%, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula (1): (0.0012×[objective value of TS]−0.29−[Si])/2.45