A converter blowing control method includes: calculating, by heat balance calculation and material balance calculation, an amount of oxygen supplied and an amount of a cooling material or a rising heat material charged to control a temperature and a component concentration of molten steel at end of blowing in a converter to target values; controlling the blowing in the converter based on the calculated amount of oxygen supplied and the calculated amount of a cooling material or a rising heat material charged; estimating a pre-blowing molten iron temperature that is a temperature of molten iron used as a raw material for blowing to be a target of the heat balance calculation, charged into the converter, and is in a state immediately before start of the blowing; and using the estimated pre-blowing molten iron temperature as a charged molten iron temperature in the heat balance calculation.

A converter blowing control method includes: calculating, by heat balance calculation and material balance calculation, an amount of oxygen supplied and an amount of a cooling material or a rising heat material charged to control a temperature and a component concentration of molten steel at end of blowing in a converter to target values; controlling the blowing in the converter based on the calculated amount of oxygen supplied and the calculated amount of a cooling material or a rising heat material charged; estimating a pre-blowing molten iron temperature that is a temperature of molten iron used as a raw material for blowing to be a target of the heat balance calculation, charged into the converter, and is in a state immediately before start of the blowing; and using the estimated pre-blowing molten iron temperature as a charged molten iron temperature in the heat balance calculation.

A method utilizing a humic acid substance for renovating and afforsesting slag is provided. A humic acid substance may be utilized for passivation, adsorption, reduction, chelation and immobilization of harmful heavy metal elements in slag, for example, Cr, As, Cd, Ni, Pb, Ba, Hg, Co, Se, Ag and Be, and aggregating the slag, thereby detoxifying the slag and producing artificial earth. The artificial earth may be used in combination with a carrier bacterial fertilizer to continuously produce the active humic acid substance, achieving an effect similar to the combination of blood transfusion and blood production, thereby forming a high-quality artificial soil.

A method utilizing a humic acid substance for renovating and afforsesting slag is provided. A humic acid substance may be utilized for passivation, adsorption, reduction, chelation and immobilization of harmful heavy metal elements in slag, for example, Cr, As, Cd, Ni, Pb, Ba, Hg, Co, Se, Ag and Be, and aggregating the slag, thereby detoxifying the slag and producing artificial earth. The artificial earth may be used in combination with a carrier bacterial fertilizer to continuously produce the active humic acid substance, achieving an effect similar to the combination of blood transfusion and blood production, thereby forming a high-quality artificial soil.

Provided is an FeNiCr alloy that has excellent surface characteristics and enables formation of a blackened coating having excellent blackening characteristics and peeling resistance. The FeNiCr alloy has a chemical composition containing, by mass %, C, Si, Mn, P, S, Cr, Ni, Mo, Co, Cu, N, Ti, Al, O, and H, the balance being Fe and inevitable impurities, and satisfying formulae (1) to (4): (1) T1=11[% N]+0.1; (2) T2=39[% N]1.0; (3) A1=7.5[% N]+0.1; (4) A2=42.5[% N]+1.0, where [% M] represents content (mass %) of element M in the alloy, and T1, T2, A1, and A2 satisfy relationships T1<[% Ti]<T2 and A1<[% A1]<A2.

A steel for machine structural use according to the present embodiment has a chemical composition which consists of, in mass %, C: 0.30 to 0.50%, Si: 0.01 to 0.80%, Mn: 0.20 to 2.00%, P: 0.030% or less, S: 0.010 to 0.100%, Pb: 0.010 to 0.100%, Al: 0.010 to 0.050%, N: 0.015% or less, O: 0.0005 to 0.0030% and Cr: more than 0.70% to 2.00%, with the balance being Fe and impurities, the chemical composition satisfying Formula (1). The total number of specific inclusions included in the steel which are any of MnS inclusions, Pb inclusions and composite inclusions containing MnS and Pb and which have an equivalent circular diameter of 5 m or more is 40 per mm.sup.2 or more.

Mn/S8.0(1)

Where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1).

An antiferromagnetic alloy consisting of: between 10.0 and 30.0 wt.-% manganese, between 4.0 and 10.0 wt.-% chromium, between 5.0 and 15.0 wt.-% nickel, between 0.1 and 2.0 wt.-% titanium, the remainder being iron and residual impurities, the alloy being free of beryllium.

Provided is a blocking material and a method for manufacturing alloy steel using the same. In maintaining a molten ferro alloy, used when manufacturing a manganese-containing alloy steel, at a temperature of at least a melting point of the ferro alloy, a blocking material layer is formed on the melt surface of the molten ferro alloy by using a blocking material which includes, with respect to the total of 100 wt %, 37-66 wt % of CaO and SiO.sub.2, 8-15 wt % of Al.sub.2O.sub.3, 6-18 wt % of MgO, and 20-30 wt % of MnO, wherein the ratio of CaO to SiO.sub.2 (CaO/SiO.sub.2) is in a range of 0.95-1.2. Thus, nitrogen in the air may be prevented from being mixed into the molten ferro alloy.

Provided is a blocking material and a method for manufacturing alloy steel using the same. In maintaining a molten ferro alloy, used when manufacturing a manganese-containing alloy steel, at a temperature of at least a melting point of the ferro alloy, a blocking material layer is formed on the melt surface of the molten ferro alloy by using a blocking material which includes, with respect to the total of 100 wt %, 37-66 wt % of CaO and SiO.sub.2, 8-15 wt % of Al.sub.2O.sub.3, 6-18 wt % of MgO, and 20-30 wt % of MnO, wherein the ratio of CaO to SiO.sub.2 (CaO/SiO.sub.2) is in a range of 0.95-1.2. Thus, nitrogen in the air may be prevented from being mixed into the molten ferro alloy.

The invention provides a maraging steel production method in which an oxide is added during an Mg oxide formation step, the production method including: the Mg oxide formation step in which Mg is added to molten steel and MgO is formed in the molten steel, during primary melting; a consumable electrode production step in which, after the Mg oxide formation step, the molten steel is solidified and a consumable electrode having residual MgO is obtained; and a vacuum arc re-melting step in which the consumable electrode is used and vacuum arc re-melting is performed.