An improved method of manufacturing a powder metal material by water, gas, plasma, or rotating disk atomization is provided. The method includes adding at least one additive to a melted metal material before or during the atomization process. The at least one additive forms a protective gas atmosphere surrounding the melted metal material which is at least three times greater than the volume of melt to be treated. The protective atmosphere prevents introduction or re-introduction of contaminants, such as sulfur (S) and oxygen (O.sub.2), into the material. The atomized particles produced include at least one of the following advantages: median circularity of at least 0.60, median roundness of at least 0.60, less internal pores, less internal oxides, and an increased sphericity of the microstructural phases and/or constituents.

A process for manufacturing an iron-based alloy comprising forming targeted fine oxide and/or carbide dispersoids in a melt, and sequentially precipitating transition-metal nitrides on the dispersoids for heterogeneous nucleation of equiaxed grains. An iron-based cast alloy having a highly equiaxed fine grain structure.

[Summary]

[Assignment] A precipitation hardening martensitic stainless steel having superior strength and improved welding properties.

[Solution] In mass %, C: 0.030 to 0.065%, Si: 1.0 to 2.0%, Mn: 0.51 to 1.50%, P: not more than 0.04%, S: not more than 0.0020%, Ni: 4.0 to 10.0%, Cr: 11.0 to 18.0%, Mo: 0.1 to 1.50%, Cu: 0.30 to 6.0%, Al: 0.005 to 0.2%, Sn: 0.003 to 0.030%, N: 0.001 to 0.015%, Ti: 0.15 to 0.45%, Nb: 0.15 to 0.55%, Ca: not more than 0.0025%, Mg: 0.0001 to 0.0150%, O: not more than 0.01% and Fe and inevitable impurities as a remainder, and satisfying the following formula (1). and cal. (vol. %) defined by the formula (2) is in a range of 1.0 to 9.0.

Sn+0.009Cu0.06(1)

cal. (vol. %)=4.3(1.3Si+Cr+Mo+2.2Al+Ti+Nb)3.9(30C+30N+Ni+0.8Mn+0.3Cu)31.5(2)

A wire for out-of-furnace treatment of metallurgical melts comprises a metallic sheath which encloses a core comprising at least one element selected from the group consisting of Ca, Ba, Sr, Mg, Si and Al, wherein at least one layer of a composite coating is applied to an inner and/or outer surface of said sheath, which coating consists of a lacquer paint material and contains high-melting ultrafine particles selected from compounds of metal carbides and/or nitrides and/or carbonitrides and/or silicides and/or borides. The composite coating comprises a protector material, for which ferroalloys and/or flux agents are used. The metals contained in the high-melting compounds are titanium and/or tungsten and/or silicon and/or magnesium and/or niobium and/or vanadium. Said coating is applied evenly onto the surface of the sheath.

A method for preparing low-cost clean steel includes steps of: preliminarily desulfurizing iron melt: preliminarily desulfurizing in an iron melt channel during blast furnace tapping and during iron folding in an iron folding room, adding a desulfurizing ball into the iron melt during the blast furnace tapping or the iron folding; dephosphorizing and controlling sulfur: dephosphorizing and controlling sulfur during converter steelmaking, in such a manner that P0.014% and S0.004% during tapping; rapidly dephosphorizing by slag-forming: rapidly dephosphorizing by slag-forming during converter tapping, at a converter end point, controlling a C content at 0.020.10%, adding a dephosphorizing ball through an alloy chute during the converter tapping, blowing argon and stirring at the same time; purifying steel melt during RH refining: adding a purifying ball at a late stage of the RH refining when a vacuum degree is at 66.7500 Pa; and continuously casting with whole-process protection.

An impeller for stirring a melt pool includes: an impeller body extending in the length direction; a blowing nozzle which is provided in such a way as to pass through one part at the bottom end of the impeller body; and a blade provided on the upper part of the impeller body. As a result, when the impeller is used, a stirring flow produced due to the blade and a stirring flow due to substances blown into the melt-pool via the blowing nozzle correspond to each other, and the two flows are combined such that the overall stirring force is improved. Consequently, it is possible to improve the efficiency of stirring by the impeller as compared with hitherto, and, as a result, refining efficiency in the refining step is improved as the rate of reaction between the melt-pool and additives is increased.

The present invention provides a high-strength steel sheet including: C: 0.03 to 0.25 mass %, Si: 0.1 to 2.0 mass %, Mn: 0.5 to 3.0 mass %, P: not more than 0.05 mass %, T.O: not more than 0.0050 mass %, S: 0.0001 to 0.01 mass %, N: 0.0005 to 0.01 mass %, acid-soluble Al: more than 0.01 mass %, Ca: 0.0005 to 0.0050 mass %, and a total of at least one element of Ce, La, Nd, and Pr: 0.001 to 0.01 mass %, with a balance including iron and inevitable impurities, in which the steel sheet contains a chemical component on a basis of mass that satisfies 0.7<100([Ce]+[La]+[Nd]+[Pr])/[acid-soluble Al]70 and 0.2([Ce]+[La]+[Nd]+[Pr])/[S]10, the steel sheet contains compound inclusion including a first inclusion phase containing at least one element of Ce, La, Nd, and Pr, containing Ca, and containing at least one element of O and S, and a second inclusion phase having a component different from that of the first inclusion phase and containing at least one element of Mn, Si, and Al, the compound inclusion forms a spherical compound inclusion having an equivalent circle diameter in the range of 0.5 m to 5 m, and a ratio of the number of the spherical compound inclusion relative to the number of all inclusions having the equivalent circle diameter in the range of 0.5 m to 5 m is 30% or more.

Provided are a hot-rolled, low-temperature-resistant, H-shaped steel with a grade of 420 MPa and a preparation method therefor. The H-shaped steel comprises the following chemical components in percentages by weight: C: 0.08-0.10%, Si0.2%, Mn: 1.25-1.45%, V: 0.03-0.045%, Ti: 0.015-0.025%, Cr: 0.15-0.30%, Als: 0.02-0.04%, N: 0.007-0.01%, P0.008%, S0.005%, O0.004%, and the balance being Fe and inevitable impurities. In the preparation method, the characteristic of the flange of the small-specification H-shaped steel being thin in rectangular blank rolling is combined, the design of a low content of C suitable for normalizing rolling being in cooperation with a V micro-alloyed component is used, an appropriate amount of Cr is added to control the cooling rate, and the situation whereby the low-temperature impact toughness of steel deteriorates due to the occurrence of abnormal structures such as widmanstatten is avoided, thus a stably controlled, high-strength and high-toughness, hot-rolled, H-shaped steel with a grade of 420 MPa or more is obtained on a hot-rolled H-shaped steel rolling mill.

A secondary material for steel refining is to be supplied to a molten iron together with a lime so as to promote a desulfurization reaction in the molten iron. The secondary material for steel refining contains aluminum nitride in an amount of 20 wt % or more in terms of weight percentage.

A method capable of efficiently producing grained iron with a low P concentration includes a first step of melting reduced iron to obtain primary molten iron, a second step of separating the primary molten iron from slag, a third step of subjecting the primary molten iron separated from the slag to dephosphorization to obtain secondary molten iron, and a fourth step of solidifying the secondary molten iron into a grained form to obtain grained iron, in which in the third step, the dephosphorization is performed by supplying an oxygen source and a CaO source to the primary molten iron, and a temperature of the secondary molten iron at the end of the dephosphorization is set to a temperature of the primary molten iron at the start of the dephosphorization or lower.