Abstract: An Fe--Ni alloy cold-rolled sheet excellent in cleanliness and etching pierceability prepared as specified in the claims, which consists essentially of: 30 to 45 wt. % nickel, 0.1 to 1 wt. % manganese, 0.003 to 0.03 wt. % aluminum and the balance being iron and incidental impurities comprising up to 0.4 wt. % silicon, up to 0.1 wt. % chromium, up to 0.005 wt. % carbon, up to 0.005 wt. % nitrogen, up to 0.005 wt. % sulfur, up to 0.010 wt. % phosphorus, up to 0.002 wt. % oxygen, and up to 0.002 wt. % as converted into oxygen for non-metallic inclusions. The non-metallic inclusions contain at least CaO, Al.sub.2 O.sub.3 and MgO, and the composition thereof is in a region of a melting point of at least 1,600.degree. C., which region is defined by the liquidus curve of 1,600.degree. C. in the CaO--Al.sub.2 O.sub.3 --MgO ternary phase diagram. The non-metallic inclusions have a particle size of up to 6 .mu.m.

Abstract: A method for manufacturing an Fe-Ni alloy cold-rolled sheet excellent in cleanliness and etching pierceability, comprising: preparing an Fe-Ni molten alloy, containing 30 to 45 wt. % nickel, and subjected to dephosphorization and decarburization; adding aluminum and flux to the Fe-Ni molten alloy in a ladle made of an MgO-CaO refractory containing 20 to 45 wt. %; strongly stirring the Fe-Ni molten alloy which contains the added aluminum and flux in the ladle to produce a CaO-Al.sub.2 O.sub.3 -MgO slag so as to react the Fe-Ni molten alloy with the CaO-Al.sub.2 O.sub.3 -MgO slag to deoxidize the Fe-Ni molten alloy while controlling a value of activity of SiO.sub.2 from 0.001 to 0.005 and a value of activity of Al.sub.2 O.sub.3 from 0.1 to 0.3 in the CaO-Al.sub.2 O.sub.3 -MgO slag, and the CaO-Al.sub.2 O.sub.3 -MgO slag having the following chemical composition: CaO and Al.sub.2 O.sub.3 : at least 57 wt. %, wherein the ratio of CaO/(CaO+Al.sub.2 O.sub.3) being at least 0.45, MgO: up to 25 wt. %, SiO.sub.

Abstract: A method for melting and reducing chrome ore, which comprises charging chrome ore and carbonaceous material, and blowing in oxygen gas under a pressure ranging from 1 to 600 Torr, while molten metal is being stirred by a stirring gas blown in. In this method, a reaction vessel capable of allowing top blowing and bottom blowing onto the molten metal and decreasing pressure within the vessel is employed. Chrome ore and carbonaceous material can be used in the form of lumps or powder. When powdered ore and material are used, they can be injected through a lance or a tuyere into the vessel.

Abstract: The gap between an insertion hole formed in a covering of a ladle and an electrode inserted through the insertion hole is sealed by sealing means. The sealing means has a cap seal longitudinally and slidably fitted over the electrode. A base seal is hermetically disposed between the cap seal and the covering in such a manner that a gap is provided between the electrode and the base seal. The base seal has a gas injection nozzle intended to discharge a gas toward the electrode and another gas injection nozzle intended to discharge the gas downwardly. The use of the base and cap seals enables securing the sealing functions thereof despite any movement of the electrode, thus preventing the pickup of [N] as well as the reoxidation of molten steel. When a gas seal is effected by the formation of a flow of gas rotating around the electrode about the axis thereof, the sealing performance can be more enhanced.

Abstract: Three electrodes are dipped into slag on molten steel in a ladle. The electrodes are connected to a three-phase AC voltage. An arc is formed between each electrode and molten steel upon energizing the electrodes. The molten steel is heated by arc heat. Each electrode has a gas flow path extending longitudinally along its center. The gas flow path is open at the lower end of each electrode to constitute a gas injection port. Ar gas is injected from the gas injection port through the gas flow path. Nitrogen is removed from the arc region between the electrodes and the molten steel and its peripheral region to prevent the nitrogen pickup phenomenon of molten steel. If a powder mixture of chromium ore and carbon is added to the Ar gas, chromium ore is reduced by carbon with arc heat to add reaction product of chromium to the molten steel. If a flux powder is added to the Ar gas, the flux is melted and slagged by the arc heat.

Abstract: The object is to introduce a bottom-blown gas into a molten metal refining furnace so as to minimize the rate of blowing gas flow and increase the control range of the rate of blowing gas flow. There are included a refractory (1) having a plurality of holes (2) having an inner diameter of from 0.5 to 3.0 mm.phi. formed through said refractory and extending its working surface to its back, a metal cover (3) enclosing at least a part of the sides of the refractory (1) and a pressure box (4) formed in the bottom of the refractory (1) so as to communicate with the holes (2) and define a gas reservoir space. The molten metal is prevented from entering the holes (2) when the blowing gas pressure and the rate of blowing gas flow are decreased.

Abstract: A gas blowing nozzle is produced by molding a non-porous substance into a molding frame under pressure and at the same time positioning a plurality of gas passageways forming members at predetermined spaces and distances from each other. The passageway holes have cross sectional shapes as desired, so that the gas blowing may be accurately controlled to perform refining of molten metal.

Abstract: A sub-lance assembly for sampling and temperature-measuring of molten metal during refining in a top-blowing oxygen converter, which comprises: a sub-lance having a concentric three-pipe structure comprising from inside to outside an air supply pipe, a water discharge pipe and a water supply pipe; a water supply outer cylinder having a water supply branch pipe, rotatably engaging with the upper end portion of said water supply pipe; a water discharge outer cylinder having a water discharge branch pipe, rotatably engaging with the upper end portion of said water discharge pipe; said water supply branch pipe and said water discharge branch pipe being integrally connected together by a fixing plate; a drive mechanism fitted onto the outer surface of said water supply outer cylinder or said water discharge outer cylinder, for rotating said sub-lance around the axial line thereof; and a sub-lance rotation angle detector at the tip of the axis of rotation of said drive mechanism, for detecting the angle of rotation