摘要:
A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances and machine structures and of constructing buildings, and a manufacturing method thereof are provided.The steel sheet is a hot-rolled steel sheet of carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D (μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by the formulas (1) and (2) given below and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal grain diameter D (μm) satisfy the relation defined by the formula (3) given below: 1.2≦D≦7 formula (1) D≦2.7+5000/(5+350·C+40·Mn)2 formula (2) D·X≦0.1 formula (3) wherein C and Mn represent the contents (in % by mass) of the respective elements in the steel.
摘要:
A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances and machine structures and of constructing buildings, and a manufacturing method thereof are provided. The steel sheet is a hot-rolled steel sheet of carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D (μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by the formulas (1) and (2) given below and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal grain diameter D (μm) satisfy the relation defined by the formula (3) given below: 1.2≦D≦7 formula (1) D≦2.7+5000/(5+350.C+40.Mn)2 formula (2) D·X≦0.1 formula (3) wherein C and Mn represent the contents (in % by mass) of the respective elements in the steel.
摘要:
A cold-rolled steel sheet of carbon steel or low-alloy steel comprising C: 0.01 to 0.25% by mass with a ferrite main phase is has an average ferrite crystal grain diameter D (μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfying formulas (5,6) and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and D (μm) satisfying formula (3): 1.2≦D≦9.3 (5) D≦5.0−2.0·Cr+5000/(5+350·C+40·Mn)2 (6) D·X≦0.1 (3) and, at said ¼ inch depth, the area percentage of ferrite crystal grains the crystal grain diameter d (μm) of which satisfying formula (4) is at least 80%: D/3≦d≦3D (4) wherein C, Cr and Mn represent mass % of the respective elements in the steel.
摘要:
A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances and machine structures and of constructing buildings, and a manufacturing method thereof are provided.The steel sheet is a hot-rolled steel sheet of carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D (μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by the formulas (1) and (2) given below and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal grain diameter D (μm) satisfy the relation defined by the formula (3) given below: 1.2≦D≦7 formula (1) D≦2.7+5000/(5+350·C+40·Mn)2 formula (2) D·X≦0.1 formula (3) wherein C and Mn represent the contents (in % by mass) of the respective elements in the steel.
摘要:
A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances and machine structures and of constructing buildings, and a manufacturing method thereof are provided. The steel sheet is a hot-rolled steel sheet of carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D (μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by the formulas (1) and (2) given below and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal diameter D (μm) satisfy the relation defined by the formula (3) given below: 1.2≦D≦7 formula (1) D≦2.7+5000/(5+350·C+40·Mn)2 formula (2) D·X≦0.1 formula (3) wherein C and Mn represent the contents (in % by mass) of the respective elements in the steel.
摘要:
A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances, machine structures, and of constructing buildings, and a manufacturing method thereof is provided. The steel sheet is a hot-rolled steel sheet of a carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D(μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by formulas (1) and (2) given below and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal grain diameter D(μm) satisfy the relation defined by the formula (3) given below: 1.2≦D≦7 formula (1) D≦2.7+5000/(5+350·C+40·Mn)2 formula (2) D·X≦0.1 formula (3) wherein C and Mn represent the content (in % by mass) of the respective elements in the steel.
摘要:
A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances and machine structures and of constructing buildings, and a manufacturing method thereof. are provided.The steel sheet is a hot-rolled steel sheet of carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D (μm) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by the formulas (1) and (2) given below and the increase rate X (μm/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal grain diameter D (μm) satisfy the relation defined by the formula (3) given below: 1.2≦D≦7 formula (1) D≦2.7+5000/(5+350·C+40·Mn)2 formula (2) D·X≦0.1 formula (3) wherein C and Mn represent the contents (in % by mass) of the respective elements in the steel.
摘要:
A method for producing a high-tensile cold-rolled steel sheet includes subjecting a slab having a composition containing C: more than 0.020% and less than 0.30%, Si: more than 0.10% and 3.00% or less, and Mn: more than 1.00% and 3.50% or less to hot rolling wherein the roll draft of the final one pass is higher than 15%, and rolling is finished in the temperature region of Ar3 point or higher, optionally annealing wherein the hot-rolled steel sheet is heated to 300° C. or higher after being cooled to 780° C. or lower, coiling higher than 400° C. or lower than 400° C., cold rolling the hot-rolled steel sheet or the annealed steel sheet, and annealing wherein the cold-rolled steel sheet is soaked in the temperature region of (Ac3 point−40° C.) or higher, cooling to 500° C. or lower and 300° C. or higher, and holding in that temperature region for 30 seconds or longer.
摘要:
A hot-dip galvanized cold-rolled steel sheet has a tensile strength of 750 MPa or higher, a composition consisting, in mass percent, C: more than 0.10% and less than 0.25%, Si: more than 0.50% and less than 2.0%, Mn: more than 1.50% and 3.0% or less, and optionally containing one or more types of Ti, Nb, V, Cr, Mo, B, Ca, Mg, REM, and Bi, P: less than 0.050%, S: 0.010% or less, sol. Al: 0.50% or less, and N: 0.010% or less, and a main phase as a low-temperature transformation product and a second phase as retained austenite. The retained austenite volume fraction is more than 4.0% and less than 25.0% of the whole structure, and has an average grain size of less than 0.80 μm. A number density of retained austenite grains having a grain size of 1.2 μm or more is 3.0×10−2/μm2 or less.
摘要:
A method for producing a high-tensile cold-rolled steel sheet includes subjecting a slab having a composition containing C: more than 0.020% and less than 0.30%, Si: more than 0.10% and 3.00% or less, and Mn: more than 1.00% and 3.50% or less to hot rolling wherein the roll draft of the final one pass is higher than 15%, and rolling is finished in the temperature region of Ar3 point or higher, optionally annealing wherein the hot-rolled steel sheet is heated to 300° C. or higher after being cooled to 780° C. or lower, coiling higher than 400° C. or lower than 400° C., cold rolling the hot-rolled steel sheet or the annealed steel sheet, and annealing wherein the cold-rolled steel sheet is soaked in the temperature region of (Ac3 point−40° C.) or higher, cooling to 500° C. or lower and 300° C. or higher, and holding in that temperature region for 30 seconds or longer.