Abstract: The present invention provides an ultrahigh hole expansion steel and a method for manufacturing therefor. The steel comprises the following components in percentage by mass: C: 0.03-0.09%; Si?0.2%; Mn: 0.5-2.0%; P?0.02%; S?0.003%; Al: 0.2-1.2%; N?0.004%; Ti: 0.05-0.20%; Mo: 0.05-0.5%; Mg?0.005%; O?0.003%; B?0.001%; and the balance being Fe and inevitable impurities. wherein C, Mn, Mo and B in the steel satisfy the following formula: 0.25?2×C+Mn/3+Mo+150×B?1.5; wherein each chemical element in the formula represent the numerical value before the percentage sign of the percentage by mass of corresponding chemical elements. The steel according to the present invention has excellent matching of strength, plasticity and hole expansion performance, and can be applied in passenger vehicle chassis parts that require high strength and thickness reduction, such as a control arm and a subframe.

Abstract: The present invention provides a steel and a method for manufacturing therefor. The steel comprises the following components in the percentage by mass: C: 0.01-0.10%; Si: ?0.2%; Mn: 0.5-2.0%; P: ?0.02%; S: ?0.003%; Al: 0.01-0.08%; N: ?0.004%; V: 0.10-0.50%; O: ?0.003%; and the balance of Fe and inevitable impurities. The steel of the present invention can be applied in passenger vehicle chassis parts needing high strength and thickness reduction such as a control arm and a subframe.

Abstract: Provided in the present invention are a high-plasticity steel and a manufacturing method therefor. The steel comprises the following components in percentage by mass: C: 0.10-0.35%, Si: 0.8-2.0%, Mn: 1.0-3.0%, P: ?0.02%, S ?0.005%, Al: 0.1-2.0%, N: ?0.005%, with the balance being Fe and other inevitable impurities. The steel of the present invention can achieve good matching among a low yield strength, a low yield ratio, a high tensile strength and an ultrahigh elongation rate, and can be widely applied to components with complex shape requirements, or other parts that require thinning while maintaining high strength, such as those in commercial or passenger vehicles.

Abstract: Steel for coiled tubing with a low yield ratio and ultra-high strength and a preparation method thereof, wherein the chemical composition of the steel in mass percentage is: C: 0.05-0.16%, Si: 0.1-0.9%, Mn: 1.25-2.5%, P?0.015%, S?0.005%, Cr: 0.51-1.30%, Nb: 0.005-0.019%, V: 0.010-0.079%, Ti: 0.01-0.03%, Mo: 0.10-0.55%, Cu: 0.31-0.60%, Ni: 0.31-0.60%, Ca: 0.0010-0.0040%, Al: 0.01-0.05%, N?0.008%, and the rest being Fe and inevitable impurity elements. The chemical composition combines the technologies of low temperature finishing rolling and low temperature coiling to obtain an MA constituent+bainite+ferrite multiphase structure. The steel has a low yield ratio and ultra-high strength with the following specific properties: yield strength?620 MPa, tensile strength?750 MPa, elongation?11%, and yield ratio?0.83, and is suitable for manufacturing coiled tubing with ultra-high strength having a grade of 110 ksi or higher.

Abstract: Steel for coiled tubing with a low yield ratio and ultra-high strength and a preparation method thereof, wherein the chemical composition of the steel in mass percentage is: C: 0.05-0.16%, Si: 0.1-0.9%, Mn: 1.25-2.5%, P?0.015%, S?0.005%, Cr: 0.51-1.30%, Nb: 0.005-0.019%, V: 0.010-0.079%, Ti: 0.01-0.03%, Mo: 0.10-0.55%, Cu: 0.31-0.60%, Ni: 0.31-0.60%, Ca: 0.0010-0.0040%, Al: 0.01-0.05%, N?0.008%, and the rest being Fe and inevitable impurity elements. The chemical composition combines the technologies of low temperature finishing rolling and low temperature coiling to obtain an MA constituent+bainite+ferrite multiphase structure. The steel has a low yield ratio and ultra-high strength with the following specific properties: yield strength?620 MPa, tensile strength?750 MPa, elongation?11%, and yield ratio?0.83, and is suitable for manufacturing coiled tubing with ultra-high strength having a grade of 110 ksi or higher.

Abstract: The present invention relates to a method for producing hot rolled strip steel, especially the producing method of hot rolled strip steel with multiple target thicknesses in the longitudinal direction. It is a method to produce the strip steel with different target thicknesses in the longitudinal direction by using a hot continuous rolling mill. In this method, the first equal-thickness section of the strip steel is controlled with the conventional thickness control strategy, while other equal-thickness sections and the transition section between equal-thickness sections are controlled with the variable-thickness control strategy.

Abstract: The present invention relates to a method for producing hot rolled strip steel, especially the producing method of hot rolled strip steel with multiple target thicknesses in the longitudinal direction. It is a method to produce the strip steel with different target thicknesses in the longitudinal direction by using a hot continuous rolling mill. In this method, the first equal-thickness section of the strip steel is controlled with the conventional thickness control strategy, while other equal-thickness sections and the transition section between equal-thickness sections are controlled with the variable-thickness control strategy.