Disclosed are a low-cost ultra-high-strength multiphase steel plate/steel strip and its manufacturing method. Said steel plate/steel strip comprises the following components in percentage by weight: 0.03 to 0.07% of C, 0.1 to 0.5% of Si, 1.3 to 1.9% of Mn, less than or equal to 0.02% of P, less than or equal to 0.01% of S, 0.01 to 0.05% of Al, 0.2 to 0.5% of Cr, 0.07 to 0.14% of Ti, less than 0.03% of (Ni+Nb+Mo+V), and the balance being Fe and other inevitable impurities; and Mn+1.5Cr+5(Ti+Al+Cu)+10(Mo+Ni)+20(Nb+V)<3.0; Mn+2Cr+4Ti+4Nb+4V+4Mo—Si/3+2C≤3.0. The steel plate is mainly used for the manufacturing of automotive chassis and suspension system parts.

A high chromium and silicon-rich corrosion resistant steel is disclosed, which comprises, in weight percent: 22-30% Cr, 2-10% Si, and the balance Fe and incidental impurities, of which a content amount of Cr and Si is less than 37%. Experimental data reveal that, samples of the high chromium and silicon-rich corrosion resistant steel all have a pitting potential greater than 0.8 V and a hardness in a range between HV170 and HV500 in the as-homogenized condition. As a result, experimental data have proved that the high chromium and silicon-rich corrosion resistant steel of the present invention can replace conventional stainless steels having poor pitting resistance like type 304 and type 316 L, and then be adopted for the applications of components and/or structural parts requiring high corrosion resistance.

Disclosed herein is an electroslag welding wire containing, by mass % based on total mass of the wire: C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%; and Fe: 79% or more. The electroslag welding wire satisfies the following relationship (1): 0.150≤C+Si/30+Mn/20+Ni/60≤0.300 (1).

Disclosed herein is an electroslag welding wire containing, by mass % based on total mass of the wire: C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%; and Fe: 79% or more. The electroslag welding wire satisfies the following relationship (1): 0.150≤C+Si/30+Mn/20+Ni/60≤0.300 (1).

A high-strength hot-rolled steel sheet that has excellent punching workability and hole expandability, and a method for manufacturing the same. The hot-rolled steel sheet has a tensile strength of 980 MPa or more. The hot-rolled steel sheet has a chemical composition containing C, Si, Mn, P, S, Al, N, Ti, Cr, and B, and has a microstructure including a bainite phase having an area ratio of 85% or more as a main phase, and a martensite phase or martensite-austenite constituent having an area ratio of 15% or less as a second phase, the balance being a ferrite phase. The second phase has an average grain diameter of 3.0 μm or less, prior-austenite grains have an average aspect ratio of 1.3 or more and 5.0 or less, and recrystallized prior-austenite grains have an area ratio of 15% or less relative to non-recrystallized prior-austenite grains.

A high-strength hot-rolled steel sheet that has excellent punching workability and hole expandability, and a method for manufacturing the same. The hot-rolled steel sheet has a tensile strength of 980 MPa or more. The hot-rolled steel sheet has a chemical composition containing C, Si, Mn, P, S, Al, N, Ti, Cr, and B, and has a microstructure including a bainite phase having an area ratio of 85% or more as a main phase, and a martensite phase or martensite-austenite constituent having an area ratio of 15% or less as a second phase, the balance being a ferrite phase. The second phase has an average grain diameter of 3.0 μm or less, prior-austenite grains have an average aspect ratio of 1.3 or more and 5.0 or less, and recrystallized prior-austenite grains have an area ratio of 15% or less relative to non-recrystallized prior-austenite grains.

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.

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.

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.

A steel sheet includes a predetermined composition, in which a microstructure at a ¼ thickness position from a surface in a sheet thickness direction includes, by vol %, ferrite: 80% or more, martensite: 2% or less, and residual austenite: 2% or less, a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and in the microstructure of the steel sheet stretched by 10% at the ¼ thickness position from the surface in the sheet thickness direction, a number density of voids having a maximum diameter of 1.0 μm or more is 1.0×10.sup.9 pieces/m.sup.2 or less.