A high strength galvanized steel sheet having excellent surface qualities, plating adhesion, and formability is provided, wherein a galvanized layer is formed on a cold-rolled steel sheet comprising 0.1-0.3 wt % of C, 1-2.5 wt % of Si, 2.5-8 wt % of Mn, 0.001-0.5 wt % of sol. Al, at most 0.04 wt % of P, at most 0.015 wt % of S, at most 0.02 wt % of N (excluding 0 wt %), 0.1-0.7 wt % of Cr, at most 0.1 wt % of Mo, (48/14)*[N] to 0.1 wt % of Ti, 0.005-0.5 wt % of Ni, 0.01-0.07 wt % of Sb, at most 0.1 wt % of Nb, and at most 0.005 wt % of B, with the remainder being Fe and other inevitable impurities.

A high-strength galvanized steel sheet that includes a chemical composition containing, by mass %, C: 0.15% or more and 0.25% or less, Si: 0.50% or more and 2.5% or less, Mn: 2.3% or more and 4.0% or less, P: 0.100% or less, S: 0.02% or less, Al: 0.01% or more and 2.5% or less, and Fe and inevitable impurities. The steel sheet having a microstructure containing, by an area percentage basis, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 20% or less, and other phases: 10% or less (including 0%), the other phases containing a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%).

Provided are a high-strength steel sheet and a method for manufacturing the steel sheet. The high-strength steel sheet has a specified chemical composition with the balance being Fe and inevitable impurities, a microstructure including, in terms of area ratio, 25% or less of a ferrite phase, 75% or more of a bainite phase and/or a martensite phase, and 5% or less of cementite, in which, in a surface layer that is a region within 50 μm from the surface in the thickness direction, the area ratio of a ferrite phase is 5% to 20%, and a tensile strength is 1180 MPa or more.

This disclosure is related to high yield strength steel where yield strength can be increased without significantly affecting ultimate tensile strength (UTS) and in some cases, higher yield strength can be obtained without significant decrease in ultimate tensile strength and total elongation.

This disclosure is related to high yield strength steel where yield strength can be increased without significantly affecting ultimate tensile strength (UTS) and in some cases, higher yield strength can be obtained without significant decrease in ultimate tensile strength and total elongation.

A hot-rolled strip steel product having a chemical composition consisting of, in terms of weight percentages (wt. %): 0.025%-0.070% C, 0%-1.10% Si, 0.50%-2.0% Mn, <0.020% P, <0.050% S, <0.010% N, 0%-0.60% Cr, 0%-0.20% Ni, 0%-0.25% Cu, 0%-0.20% Mo, 0%-0.15% Al, 0%-0.050% Nb, 0.020%-0.20-% V, 0.020%-0.15% Ti, 0%-0.0010% B, remainder Fe and inevitable impurities, wherein the strip steel product has a microstructure comprising of, in terms of volume percentages (vol. %), ferrite ≥90%, wherein the ferrite structure comprises 10%-50% quasi-polygonal ferrite and a reminder of ferrite structure is polygonal ferrite and/or bainite: and wherein the steel strip product has an average ferrite grain size of <10 μm, an average hole expansion ratio of ≥50%, a yield strength (Rp0.2%) longitudinal to rolling direction of ≥660 MPa and a tensile strength of ≥760 MPa.

A hot-rolled strip steel product is described having a chemical composition consisting of, in terms of weight percentages (wt. %): 0.030%-0.10% C, 0%-1.10% Si, 0.50%-2.0% Mn, <0.020% P, <0.010% S,<0.010% N, 0%-0.60% Cr, 0%-0.20% Ni, 0%-0.25% Cu, 0%-0.30% Mo, 0%-0.15% Al, 0%-0.10% Nb, 0.10%-0.30% V, <0.020% Ti, 0%-0.0010% B, remainder being Fe and inevitable impurities, wherein the hot rolled strip steel product has a a microstructure comprising, in terms of volume percentages (vol. %), ferrite≥90, wherein the ferrite structure comprises bainite, at least 50% of polygonal ferrite and at most 10% quasi-polygonal ferrite, and wherein the steel strip product has an average hole expansion ratio≥50%, a yield strength (Rp0.2%) longitudinal to rolling direction of ≥660 MPa and a tensile strength≥760 MPa.

The invention relates to a process for producing an at least partly quenched and tempered sheet steel component, where the process comprises the following steps: providing a sheet steel, at least partly austenitizing the sheet steel at a temperature of at least Ac1, at least partly hardening the at least partly austenitized sheet steel to give an at least partly hardened sheet steel component, where the at least partly austenitized sheet steel is cooled to a temperature below Ms, at least partly annealing the at least partly hardened sheet steel component at a temperature of less than Ac1 for producing an at least partly quenched and tempered sheet steel component. A further subject of the invention is an at least partly quenched and tempered sheet steel component.

The invention relates to a process for producing an at least partly quenched and tempered sheet steel component, where the process comprises the following steps: providing a sheet steel, at least partly austenitizing the sheet steel at a temperature of at least Ac1, at least partly hardening the at least partly austenitized sheet steel to give an at least partly hardened sheet steel component, where the at least partly austenitized sheet steel is cooled to a temperature below Ms, at least partly annealing the at least partly hardened sheet steel component at a temperature of less than Ac1 for producing an at least partly quenched and tempered sheet steel component. A further subject of the invention is an at least partly quenched and tempered sheet steel component.

Disclosed in the present invention is a manufacturing method for a carbon steel and austenitic stainless-steel rolling clad plate, comprising the steps of: (1) obtaining a blank material of a carbon steel layer and a blank material of a stainless-steel layer; (2) assembling blank materials; (3) cladding and rolling; (4) cold rolling; (5) first annealing; and (6) second annealing. The carbon steel and austenitic stainless-steel rolling clad plate has two unique annealing processes, so that the clad plate has the performance advantages of the austenitic stainless-steel and the carbon steel. In addition, further disclosed in the present invention is a carbon steel and austenitic stainless-steel rolling clad plate manufactured by this method.