The present invention relates to a steel for a mold including: on % by mass basis, 0.55% ≤ C ≤ 0.70%; 0.30% ≤ Si ≤ 0.60%; 0.55% ≤ Mn ≤ 1.2%; 5.7% ≤ Cr ≤ 6.9%; 1.2% ≤ Mo + W/2 ≤ 1.6%; 0.55% ≤ V ≤ 0.79%; and 0.005% ≤ N ≤ 0.1%, with the remainder being Fe and inevitable impurities including, Al ≤ 0.020%, Ni ≤ 0.20%, S ≤ 0.0015%, and Cu ≤ 0.10%, and satisfying P1 ≥ 24 and 4.9 ≤ P2 ≤ 7.3, P1 and P2 being a value obtained based on the following formula (1) and (2), respectively, P1 = 45 - 13.6[Si] - 7.0([Mo]+[W]/2) - 12.9[Ni] (1), P2 = 7.4[V] + 15.8[N] + 38.6[Al] (2) in which [M] represents a content of an element M in % by mass basis, and relates to a mold including the steel for a mold.

The present invention relates to a steel for a mold including: on % by mass basis, 0.55% ≤ C ≤ 0.70%; 0.30% ≤ Si ≤ 0.60%; 0.55% ≤ Mn ≤ 1.2%; 5.7% ≤ Cr ≤ 6.9%; 1.2% ≤ Mo + W/2 ≤ 1.6%; 0.55% ≤ V ≤ 0.79%; and 0.005% ≤ N ≤ 0.1%, with the remainder being Fe and inevitable impurities including, Al ≤ 0.020%, Ni ≤ 0.20%, S ≤ 0.0015%, and Cu ≤ 0.10%, and satisfying P1 ≥ 24 and 4.9 ≤ P2 ≤ 7.3, P1 and P2 being a value obtained based on the following formula (1) and (2), respectively, P1 = 45 - 13.6[Si] - 7.0([Mo]+[W]/2) - 12.9[Ni] (1), P2 = 7.4[V] + 15.8[N] + 38.6[Al] (2) in which [M] represents a content of an element M in % by mass basis, and relates to a mold including the steel for a mold.

A method for manufacturing a metal plate, the metal plate including a first surface and a second surface positioned on the opposite side of the first surface, may include a step of rolling a base metal having an iron alloy containing nickel to produce the metal plate. The metal plate may include particles containing as a main component an element other than iron and nickel. In a sample including the first surface and the second surface of the metal plate, the following conditions (1) and (2) regarding the particles may be satisfied: (1) The number of the particles having an equivalent circle diameter of 1 μm or more is 50 or more and 3000 or less per 1 mm.sup.3 in the sample, and (2) The number of the particles having an equivalent circle diameter of 3 μm or more is 50 or less per 1 mm.sup.3 in the sample.

A method for manufacturing a metal plate, the metal plate including a first surface and a second surface positioned on the opposite side of the first surface, may include a step of rolling a base metal having an iron alloy containing nickel to produce the metal plate. The metal plate may include particles containing as a main component an element other than iron and nickel. In a sample including the first surface and the second surface of the metal plate, the following conditions (1) and (2) regarding the particles may be satisfied: (1) The number of the particles having an equivalent circle diameter of 1 μm or more is 50 or more and 3000 or less per 1 mm.sup.3 in the sample, and (2) The number of the particles having an equivalent circle diameter of 3 μm or more is 50 or less per 1 mm.sup.3 in the sample.

A method for producing a silicon based alloy having between 45 and 95% by weight of Si; max 0.05% by weight of C; 0.01-10% by weight of Al; 0.01-0.3% by weight of Ca; max 0.10% by weight of Ti; 0.5-25% by weight of Mn; 0.005-0.07% by weight of P; 0.001-0.005% by weight of S; the balance being Fe and incidental impurities in the ordinary amount.

A method for producing a silicon based alloy having between 45 and 95% by weight of Si; max 0.05% by weight of C; 0.01-10% by weight of Al; 0.01-0.3% by weight of Ca; max 0.10% by weight of Ti; 0.5-25% by weight of Mn; 0.005-0.07% by weight of P; 0.001-0.005% by weight of S; the balance being Fe and incidental impurities in the ordinary amount.

The present disclosure relates, according to some embodiments to a method for steel production, the method comprising forming a hydrogen and a carbon from a natural gas using thermal plasma electrolysis; reducing iron ore fines with the H.sub.2 to form an iron briquette; melting the briquette iron from the furnace to form a melted iron and melted non-metallic slag; separating the non-metallic slag from the melted iron in the furnace; combining the carbon and the melted iron in a furnace to form a carbon black and iron mixture; and alloying the melted iron with the carbon black to form a steel.

The present disclosure relates, according to some embodiments to a method for steel production, the method comprising forming a hydrogen and a carbon from a natural gas using thermal plasma electrolysis; reducing iron ore fines with the H.sub.2 to form an iron briquette; melting the briquette iron from the furnace to form a melted iron and melted non-metallic slag; separating the non-metallic slag from the melted iron in the furnace; combining the carbon and the melted iron in a furnace to form a carbon black and iron mixture; and alloying the melted iron with the carbon black to form a steel.

A galvanized steel sheet includes: a steel sheet having a chemical composition satisfying an equivalent carbon content Ceq of 0.35% or more and less than 0.60%, and a specified steel microstructure; and a galvanized layer on a surface of the steel sheet. The retained austenite has a solute C content of 0.6% or more by mass, and retained austenite grains with an aspect ratio of less than 2.0 constitute 50% or more of all retained austenite grains. In 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction, an L cross section in a 0 to 50 μm region from a surface of the steel sheet on a compression side has a number density of voids of 1000/mm.sup.2 or less, and the galvanized steel sheet has a tensile strength of 590 MPa or more.

A galvanized steel sheet includes: a steel sheet having a chemical composition satisfying an equivalent carbon content Ceq of 0.35% or more and less than 0.60%, and a specified steel microstructure; and a galvanized layer on a surface of the steel sheet. The retained austenite has a solute C content of 0.6% or more by mass, and retained austenite grains with an aspect ratio of less than 2.0 constitute 50% or more of all retained austenite grains. In 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction, an L cross section in a 0 to 50 μm region from a surface of the steel sheet on a compression side has a number density of voids of 1000/mm.sup.2 or less, and the galvanized steel sheet has a tensile strength of 590 MPa or more.