The present application provides a hot-work die steel and a preparation method thereof wherein the chemical constituents of the hot-work die steel in mass percentage are as follows: C: 0.20-0.32 wt %, Si: ≤0.5 wt %, Mn: ≤0.5 wt %, Cr: 1.5-2.8 wt %, Mo: 1.5-2.5 wt %, W: 0.5-1.2 wt %, Ni: 0.5-1.6 wt %, V: 0.15-0.7 wt %, Nb: 0.01-0.1 wt %, and a balance of iron, wherein an alloying degree is 5-7%; a tensile strength of the hot-work die steel at 700° C. is 560-700 MPa; a value of hardness of the hot-work die steel at room temperature is 32-38 HRC after holding at 700° C. for 3-5 h; and the hot-work die steel has an elongation of 14% to 16% at room temperature, a percentage reduction of area of 48% to 65%, and an impact toughness of 52-63 J at room temperature. The hot-work die steel of the present application has an excellent thermal stability as well as a good plasticity and a toughness at room temperature.

A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 5% or less, and at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 95% to 100% by area percentage, and retained γ: 4% to 15% by volume percentage. Retained γ.sub.UB has a specified area percentage S.sub.γUB, retained γ.sub.LB has a specified distribution number N.sub.γLB, and at least one of (i) fresh martensite has a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains has a specified equivalent circular grain diameter and aspect ratio.

A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 5% or less, and at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 95% to 100%, and retained γ: 5% to 20%. Retained γ.sub.UB has a specified area percentage S.sub.γUB, retained γ.sub.LB has a specified distribution number N.sub.γLB, and at least one of (i) fresh martensite has a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains has a specified equivalent circular grain diameter and aspect ratio.

A non-magnetic austenitic stainless steel includes, in percent (%) by weight of the entire composition, C: 0.01 to 0.05%, Si: 1.5% or less, Mn: 0.5 to 3.5%, Cr: 17.0 to 22.0%, Ni: 9.0 to 14.0%, Mo: 1.0% or less, Cu: 0.2 to 2.5%, N: 0.05 to 0.25%, the remainder of iron (Fe) and other inevitable impurities, and satisfies following Formulas (1) and (2). (1) 0≤3*(Cr+Mo)+5*Si−65*(C+N)−2*(Ni+Mn)−27≤5 and (2) 660−500*(C+N)−10*Cr−30*(Ni+Si+Mo+Cu)≤0.

The present invention relates to a steel material for a pressure vessel, which is used in a hydrogen sulfide atmosphere, and, more specifically, to a steel material having excellent hydrogen induced cracking (HIC) resistance, and a manufacturing method therefor.

The present invention relates to a steel material for a pressure vessel, which is used in a hydrogen sulfide atmosphere, and, more specifically, to a steel material having excellent hydrogen induced cracking (HIC) resistance, and a manufacturing method therefor.

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.

A steel with high hardness and excellent toughness contains, in mass %, 0.40-1.00% C, 0.10-2.00% Si, 0.10-1.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-3.20% Cr, 0.010-0.10% Al, and 0.15-0.50% V, and further contains at least one or two of 2.50% or less Ni and 1.00% or less Mo, with an amount of (C+V) being 0.60% or more in mass %, with the balance consisting of Fe and unavoidable impurities. The steel has a microstructure which is a martensitic structure with finely dispersed Fe-based ε carbides, with its prior austenite grain size being 20 μm or less.

A steel with high hardness and excellent toughness contains, in mass %, 0.40-1.00% C, 0.10-2.00% Si, 0.10-1.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-3.20% Cr, 0.010-0.10% Al, and 0.15-0.50% V, and further contains at least one or two of 2.50% or less Ni and 1.00% or less Mo, with an amount of (C+V) being 0.60% or more in mass %, with the balance consisting of Fe and unavoidable impurities. The steel has a microstructure which is a martensitic structure with finely dispersed Fe-based ε carbides, with its prior austenite grain size being 20 μm or less.

The present disclosure provides cladding in which at least two layers of alloys are joined, the cladding having high wear resistance, high workability, and excellent strength at the joining interface of the alloys. The cladding is composed of two or more layers including a first alloy and a second alloy joined to the first alloy. The hardness of the second alloy of the cladding is greater than that of the first alloy, and the difference in hardness between the first alloy and the second alloy is at least HRC 44. When a shearing test based on JIS G 0601 is performed on the cladding, the breakage is on the first alloy side.