This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value that indicates periodicity of the microstructure is 10.7 or more, and an I value that indicates uniformity of the microstructure is less than 1.020, a standard deviation of a Mn concentration is 0.60 mass % or less, and a tensile strength is 980 MPa or more.

The present disclosure discloses a hot-forging die with the conformal meshy structured cavity surface layer and a preparation method thereof. A large-scale hot-forging die includes a die substrate, and a sandwiched layer, a transition layer and a reinforcement layer are formed on the die substrate in sequence. The reinforcement layer and the transition layer are separated into a plurality of small units by the grooves. All the grooves are interconnected and communicated to form a meshy structure. The transition layer grooves are filled with ordinary soft material; the reinforcement layer grooves are filled with high temperature resistant soft material. The reinforcement layer material and the high temperature resistant soft material of the present disclosure cooperate with each other to obtain a cavity surface layer with properties of both hard and soft, strong and tough, which can fully release the large tensile stress that may occur on the surface of the die cavity during the welding process and under the service conditions of the die, so as to avoid hot cracks during welding process and service process.

A rail includes a foot, a web, and a head. The web has a chemical composition containing C: 0.70 to 1.20 mass%, Si: 0.20 to 1.20 mass%, Mn: 0.20 to 1.50 mass%, P: 0.035 mass% or less, and Cr: 0.20 to 2.50 mass%, with the balance being Fe and incidental impurities. The area fraction of pearlite in the web is 95% or more, and the average size of pearlite blocks is 60 .Math.m or less.

A rail includes a foot, a web, and a head. The web has a chemical composition containing C: 0.70 to 1.20 mass%, Si: 0.20 to 1.20 mass%, Mn: 0.20 to 1.50 mass%, P: 0.035 mass% or less, and Cr: 0.20 to 2.50 mass%, with the balance being Fe and incidental impurities. The area fraction of pearlite in the web is 95% or more, and the average size of pearlite blocks is 60 .Math.m or less.

The invention relates to a turnout rail production technology, in particular to a deeply-hardened-surface turnout rail with high degree of undercooling and the preparation method thereof. The invention aims to solve the technical problem by providing a deeply-hardened-surface turnout rail with high degree of undercooling featured in even hardness distribution and a deeply hardened surface layer and the preparation method thereof. The method is described as follows: feeding molten iron for converter smelting.fwdarw.furnace rear argon blowing station.fwdarw.LF refining.fwdarw.RH vacuumization.fwdarw.casting steel blanks.fwdarw.slow cooling in the slow cooling pit.fwdarw.austenitic homogenization.fwdarw.rail rolling.fwdarw.heat treatment; in the converter smelting process, adding 0.2-0.3% Cr, 0.04-0.06 V and 0.75-0.80% C; the heat treatment process is divided into two cooling stages. The turnout rail prepared with the method described in the invention has a deeper deeply-hardened surface layer; the hardness is distributed more evenly, the anti-contact fatigue performance is higher and the resistance to wearing is ideal.

A 980 MPa-grade ultra-low-carbon martensite and retained austenite ultra-high hole expansion steel and a manufacturing method therefor. The hole expansion steel comprises the following chemical components in percentage by weight: C 0.03%-0.06%, Si 0.8%-2.0%, Mn 1.0%-2.0%, P≤0.02%, S≤0.003%, Al 0.02%-0.08%, N≤0.004%, Mo 0.1%-0.5%, Ti 0.01%-0.05%, and O≤0.0030%. The high hole expansion steel of the present invention has the yield strength ≥800 MPa, the tensile strength ≥980 MPa, the elongation rate (horizontal A50≥10%), the cold bending property (d≤4a, 180°), and the hole expansion ratio ≥80%, and can be applied to a chassis part of a passenger vehicle such as a control arm, an auxiliary frame and other parts that require high-strength thinning.

A 980 MPa-grade ultra-low-carbon martensite and retained austenite ultra-high hole expansion steel and a manufacturing method therefor. The hole expansion steel comprises the following chemical components in percentage by weight: C 0.03%-0.06%, Si 0.8%-2.0%, Mn 1.0%-2.0%, P≤0.02%, S≤0.003%, Al 0.02%-0.08%, N≤0.004%, Mo 0.1%-0.5%, Ti 0.01%-0.05%, and O≤0.0030%. The high hole expansion steel of the present invention has the yield strength ≥800 MPa, the tensile strength ≥980 MPa, the elongation rate (horizontal A50≥10%), the cold bending property (d≤4a, 180°), and the hole expansion ratio ≥80%, and can be applied to a chassis part of a passenger vehicle such as a control arm, an auxiliary frame and other parts that require high-strength thinning.

A preparation method of gradient high-silicon steel by molten salt electrolysis includes: weighing the inorganic fluoride salt and the inorganic silicon salt, mixing them uniformly and then drying; heating the electrolysis container over the melting point of the electrolyte, passing the inert gas through the electrolysis container, and connecting the electrode to the power supply to perform constant current electrolysis, after the electrolysis is finished, the cathode is taken out, washed and dried, placing the dried cathode in a constant temperature region of an annealing furnace; under a protective gas atmosphere, heating the cathode to the target temperature, and maintaining the temperature for a period of time; after the heat treatment, cooling the cathode to the room temperature, during which the cathode is always placed in the furnace.

A preparation method of gradient high-silicon steel by molten salt electrolysis includes: weighing the inorganic fluoride salt and the inorganic silicon salt, mixing them uniformly and then drying; heating the electrolysis container over the melting point of the electrolyte, passing the inert gas through the electrolysis container, and connecting the electrode to the power supply to perform constant current electrolysis, after the electrolysis is finished, the cathode is taken out, washed and dried, placing the dried cathode in a constant temperature region of an annealing furnace; under a protective gas atmosphere, heating the cathode to the target temperature, and maintaining the temperature for a period of time; after the heat treatment, cooling the cathode to the room temperature, during which the cathode is always placed in the furnace.

Provided are a gradient steel material having a surface layer with ferrite and an inner layer with ferrite+pearlite, and a manufacturing method, the weight percentages of the components are: C≤0.15%, Si≤1%, Mn≤1.5%, the balance of Fe and inevitable impurities, and the surface layer of the steel material is ferrite, the inner layer is ferrite+pearlite. The manufacturing method thereof includes: smelting, casting, rolling, heat treatment; wherein, in the heat treatment step, the steel material is heated above the austenitizing temperature Ac3, and hold at the temperature more than 3 min to ensure that the material is completely austenitized; subsequently, it is cooled to a temperature below Ar1 at a cooling rate lower than 0.5° C./s. The present steel material does not need to be obtained by means of the compound preparation of different materials, and is only processed and prepared by a single material, the process is short, the procedure is simple, and the cost is low.