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 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 manufacturing a hot-rolled sheet is provided, wherein the method attains grain refinement of the steel sheet containing C, Si, and Mn, wherein the grain size thereof is set to particularly below average of 2 μm, which has ferrite grain with equiaxed morphology, which has high formability in forming, and the ferrite grain-size deviation in the thickness direction is uniformed down to the level not higher than a predetermined amount whereby uniform formability in forming is high. The method includes a first rolling for rolling the sheet such that the total rolling reduction is 80% or more or the average grain size is 30 μm or less in a form of single phase of austenite, a second rolling of a single-pass, a third rolling being conducted thereafter, and a following cooling.
摘要:
The present invention provides a method for manufacturing the hot-rolled sheet, which includes: a step A including a first rolling in which a steel sheet containing 0.04-0.20% C, 0.01-2.0% Si, 0.5-3.0% Mn by mass, and the reminder being Fe and inevitable impurities, is rolled by successive multi-pass rolling at a total rolling reduction of 80% or more while keeping the steel sheet at temperatures not lower than the para-equilibrium transformation temperature Ae3; a step B including a second rolling in which a single-pass rolling is carried out at a rolling reduction of 30-55% when an entry side temperature is not lower than the para-equilibrium transformation temperature Ae3; a step C including a third rolling in which a single-pass rolling is carried out at a rolling reduction of 35-70% when an entry side temperature is set within a predetermined range; and a step D in which within 0.2 seconds after the third rolling, the rolled sheet is cooled at a cooling rate of 600 degree C./sec or higher to a temperature not higher than {(the para-equilibrium transformation temperature Ae3)−130 degree C.}, in the step C, the third rolling being carried out: within 0.6 seconds after the second rolling when the predetermined temperature range is {(the para-equilibrium transformation temperature Ae3)−60 degree C.} or more and below {(the para-equilibrium transformation temperature Ae3)−30 degree C.}; within 0.5 seconds after the second rolling when the predetermined temperature range is {(the para-equilibrium transformation temperature Ae3)−30 degree C.} or more and below {(the para-equilibrium transformation temperature Ae3)−5 degree C.}; and within 0.3 seconds after the second rolling when the predetermined temperature range is {(the para-equilibrium transformation temperature Ae3)−5 degree C.} or more and below {(the para-equilibrium transformation temperature Ae3)+20 degree C.}.
摘要:
A method for manufacturing a hot-rolled sheet attains grain refinement of the steel sheet whose grain size is extremely fine. In particular, a ferrite grain size of less than average 2 μm is obtained, which is not laminar but has ferrite grains with equiaxed morphology and exhibits high formability in forming. The method comprises the steps of rolling and cooling, wherein the rolling reductions, cooling steps, and temperature are closely regulated. A hot rolled sheet made from the method of manufacturing has a controlled ferrite grain in different regions of sheet thickness.