The present disclosure provides a hot-press formed part comprising a plated steel sheet and an aluminum alloy plated layer formed on the plated steel sheet, wherein the aluminum alloy plated layer comprises: an alloying layer (I) formed on the plated steel sheet and containing, by weight %, 5-30% of Al; an alloying layer (II) formed on the alloying layer (I) and containing, by weight %, 30 to 60% of Al; an alloying layer (III) formed on the alloying layer (II) and containing, by weight %, 20-50% of Al and 5-20% of Si; and an alloying layer (IV) formed continuously or discontinuously on at least a part of the surface of the alloying layer (III), and containing 30-60% of Al, wherein the rate of the alloying layer (III) exposed on the outermost surface of the aluminum alloy plated layer is 10% or more.

The present disclosure relates to a steel for pressure vessels used in a hydrogen sulfide atmosphere, and relates to a steel material for pressure vessels having excellent resistance to hydrogen induced cracking (HIC) and a manufacturing method thereof.

This heat-resistant sintered material has, as an overall composition, a composition including, in terms of % by mass, Cr: 15% to 30%, Ni: 8% to 30%, Si: 2.0% to 6.0%, and C: 0.5% to 2.5% with a remainder being Fe and inevitable impurities, wherein the heat-resistant sintered material has a structure in which hard phases are dispersed in a matrix, the matrix includes Fe, Cr, Ni, and Si, the hard phase includes Fe, Cr, and C, and a porosity is 2.0% or less.

A grain-oriented electrical steel sheet having excellent iron loss property is produced from a steel slab containing, by mass %, C: 0.002-0.15%, Si: 2.5-6.0%, Mn: 0.01-0.80%, Al: 0.010-0.050% and N: 0.003-0.020%, when: a heating rate between 500-700° C. in decarburization annealing is not less than 80° C./s, a surface roughness Ra of a work roll in final cold rolling is 0.01-3.0 μm, a total content of alkaline earth metals to MgO in annealing separator is 0-5 mass %, an average length L in rolling direction of passed crystal grains is not more than 25 mm, a ratio of crystal grains having a length in rolling direction of not more than 5 mm is 40-90%, and an existence ratio of alkaline earth metal sulfides having a size corresponding to circle of not less than 0.5 μm in a cross section of forsterite film is not more than 0.2/μm per unit length in sheet width direction.

With a hot-rolled steel sheet for electrical steel sheet production having a scale layer on the surface, where the surface of the steel sheet has a lightness L* as defined in JIS Z 8781-4: 2013 satisfying 30≤L*≤50, and chromaticities a* and b* as defined in JIS Z 8781-4: 2013 satisfying −1≤a*≤2 and −5≤b*≤3 respectively, and with one end portion in the longitudinal direction of a coil as a reference, a color difference ΔE.sub.ab* as defined in JIS Z 8781-4: 2013 at the central portion and at the opposite end portion satisfies ΔE.sub.ab*≤8, it is possible to obtain a grain-oriented electrical steel sheet where the variation of properties in a product coil is small.

An ultra-high-strength hot-rolled steel plate and steel strip having good fatigue and reaming properties and a manufacturing method therefor. The weight percentages of the components of the steel plate and the steel strip are: C: 0.07-0.14%, Si: 0.1-0.4%, Mn: 1.55-2.00%, P≤0.015%, S≤0.004%, Al: 0.01-0.05%, N≤0.005%, Cr: 0.15-0.50%, V: 0.1-0.35%, Nb: 0.01%-0.06%, Mo: 0.15-0.50%, Ti≤0.02%, and the balance of Fe and unavoidable impurities. Such components need to meet: 1.0≤[(Cr/52)/(C/4)+(Nb/93+Ti/48+V/51+Mo/96)/(C/12)]≤1.6. The tensile strength of the ultrahigh-strength hot-rolled steel plate and steel strip is ≥780 MPa, the yield strength thereof is ≥660 MPa, the tensile fatigue limit (10 million cycles) FL thereof is ≥570 MPa, or the fatigue limit to tensile strength FL/Rm thereof is ≥0.72. The reaming rate meets: if an original hole is a punched hole, the reaming rate thereof is >85%; and if the original hole is a reamed hole, the reaming rate thereof is >120%.

A production method for a high-strength steel sheet having a tensile strength TS of 780 MPa or more is provided. The production method comprises: heating a steel slab having a predetermined chemical composition; hotrolling the steel slab; coiling the hot-rolled sheet; subjecting the hot-rolled sheet to pickling treatment; holding the hot-rolled sheet in a pre-determined temperature range for predetermined time; cold rolling the hot-rolled sheet to obtain a cold-rolled sheet; subjecting the cold-rolled sheet to first annealing treatment; cooling the cold-rolled sheet at a pre-determined average cooling rate; cooling the cold-rolled sheet to room temperature; reheating the clod-rolled sheet to perform second annealing treatment; cooling the cold-rolled sheet at a first average cooling rate; cooling the cold-rolled sheet at a second average cooling rate; reheating the cold-rolled sheet to a predetermined reheating temperature range; and holding the cold-rolled sheet in the reheating temperature range.

A preferable aspect of the present invention provides a high-strength high-toughness hot-rolled steel sheet and a manufacturing method therefor, wherein the hot-rolled steel sheet contains, by weight, 0.07-0.13% C, 0.20-0.50% Si, 0.5-0.9% Mn, 0.03% or less P, 0.02% or less S, 0.005-0.03% Nb, 0.3-0.6% Cr, 0.005-0.03% Ti, 0.1-0.35% Cu, 0.05-0.3% Ni, 0.01-0.15% Mo, 0.007% or less N, 0.001-0.006% Ca, 0.01-0.05% Al, and the balance Fe and other unavoidable impurities, the alloy elements satisfying the following relational formulas [Relational formula 1] 1.6≤(Mo/96)/(P/31)≤6, [Relational formula 2] 1.6≤(Ca/S)≤3, and [Relational formula 3] 3.5≤(3*C/12+Mn/55)*100≤5; wherein a microstructure comprises, by area fraction, 85% or more of polygonal ferrite and 15% or less of pearlite, the crystal grain size of the polygonal ferrite being 10 μm or less; and wherein a variation in yield strength in a width direction is 35 MPa or lower.

A steel sheet has a composition comprising 0.060%≤C≤0.085%, 1.8%≤Mn≤2.0%, 0.4%≤Cr≤0.6%, 0.1%≤Si≤0.5%, 0.010%≤Nb≤0.025%, 3.42N≤Ti≤0.035%, 0≤Mo≤0.030%, 0.020%≤Al≤0.060%, 0.0012%≤B≤0.0030%, S≤0.005%, P≤0.050%, 0.002%≤N≤0.007% and optionally 0.0005%≤Ca≤0.005%, the remainder of the composition being iron and unavoidable impurities. The microstructure consists of 34% to 80% bainite, 10% to 16% martensite, and 10% to 50% of ferrite. The surface fraction of unrecrystallized ferrite, with respect to the whole structure, is of less than 30%. The martensite consists of self-tempered martensite and fresh martensite, the surface fraction of self-tempered martensite being comprised between 4% and 10%.

An alloy including an amorphous phase, and the alloy includes: an average Fe concentration in an entire alloy of 82.0 at. % or more and 88.0 at. % or less; an average Cu concentration in the entire alloy of 0.4 at. % or more and 1.0 at. % or less; an average P concentration in the entire alloy of 5.0 at. % or more and 9.0 at. % or less; an average B concentration in the entire alloy of 6.0 at. % or more and 10.0 at. % or less; an average Si concentration in the entire alloy of 0.4 at. % or more and 1.9 at. % or less; an average C concentration in the entire alloy of 0 at. % or more and 2.0 at. % or less; an average impurity concentration of an impurity other than Fe, Cu, P, B, Si, and C in the entire alloy of 0 at. % or more and 0.3 at. % or less; and a total of the average Fe concentration, the average Cu concentration, the average P concentration, the average B concentration, the average Si concentration, the average C concentration, and the average impurity concentration of 100.0 at. %.