Daido Tokushuko Kabushiki Kaisha

Denso Corporation

Saburo Sugiura

Noboru Demukai

Tetsuo Okamoto

Kenji Kanada

Shizunori Hayakawa

Kiyohide Hayashi

Masanobu Ikeda

Kazumasa Hasegawa

Minao Ito

Kiyoichi Yamano

Masami Tanaka

Yoshio Inagaki

Senji Fujita

Shu Miyashita

Yoshitaka Nishizawa

Hiroya Nakata

Keiichi Mizuguchi

Atsushi Ishii

The high carbon stainless steel containing more than 0.5 mass % carbon and more than 8 mass % chromium, or the tool steel containing more than 0.5 mass % carbon and more than 0.5 mass % at least one of carbide producing metal elements including chromium, molybdenum, tungsten, vanadium, niobium and titanium is processed by cold-warm working such as forging at a temperature of less than 800 &deg; C. to make more than 10% plastic deformation to an extent that cracks and voids are formed in the crystallized first stage carbide and, further, processed by a Hot Isostatic Pressing treatment so that the cracks and voids may be cured.

Cold-warm working and heat treatment method of high carbon-high alloy group steel

Disclosed are an improved method of refining steel and an apparatus for practicing the method. The refining method comprises, basically, carrying out the refining, particularly, decarburization, while stirring molten steel in the refining furnace by injecting gas thereinto, while supplying heat with a burner installed at the top of the furnace to the molten steel. According to this method, it is possible to start at an initial carbon content of the moltend steel lower than that of known AOD process, and complete the refining in a curtailed period of time and with a decreased oxidation loss of Cr. Thus, damage of refractory materials of the furnace is reduced, and the amount of Si necessary for reducing Cr-oxides in the latter stage of the refining is also reduced. Oxygen for the decarburization is supplied usually in the form of gas, but can be supplied from a solid oxygen source. In an alternative of the present method, powdery metal oxide, which is reducable equally to or more easily than Cr-oxides, is shot into the furnace through the burner or injected into the molten steel through a tuyere or an immersed lance. Preferably, the burner is of a type of variable flame length. Use of the burner disclosed here makes it possible to lengthened the flame at the former stage of the refining so that not only heat but also oxygen may be supplied to the molten steel surface of promoting the decarburization, and to shorten the flame at the latter stage of the refining so that only heat may be supplied.

Method and apparatus for refining steel

A reactor for iron making having an upper gas blowing nozzle, a lower gas blowing nozzle, and an iron scrap charging inlet. A vertical shaft is installed directly above the inlet at the top part of the reactor. A mechanism is provided in the lower end of the vertical shaft for controlling charging of the iron scrap to the reactor. A by-pass tube is connected between the top part of the reactor and a gas inlet in the vertical shaft directly above the mechanism for controlling the charging of iron scrap and permits exit of high temperature exhaust gases from the reactor and introduces the exhaust gases to flow through the iron scrap in the vertical shaft to pre-heat the same. Structure is provided in the by-pass tube for introducing oxygen gas or air into the high temperature exhaust gases to react therewith and generate further heat. The structure can comprise a nozzle. The mechanism for controlling charging of iron scrap can include a damper positioned immediately above the inlet in the top part of the reactor which is movable to open and close the vertical shaft together with a stopper positioned above the damper and movable to open and close the vertical shaft. Certain amounts of iron scrap can thereby be charged to the reactor by sequential openings and closings of the damper and the stopper.

Reactor for iron making

An improvement to a scrap melting method employing an electric arc furnace, which comprises the step of heating the scrap by a powdered coal burner prior to the step of heating the scrap by the electric arc. The burning conditions are controlled so as to reduce the amount of oxidized Fe as well as the amount of NO.sub.x contained in the exhaust gases. In preferred embodiments, a pair of furnaces are employed to heat the scrap alternately by the powdered coal burner and by the electric arc.

Scrap melting method

An improved apparatus for reactor iron making has a furnace body to melt raw material, typically as scrap, a shaft to heat the raw material, and a raw material supply bucket, these three components being arranged vertically, with an exhaust gas combustion tower positioned close to the shaft. Raw material is supplied to the shaft with this apparatus by the bucket, and, after being heated by exhaust gas from the furnace body, the raw material is charged into the furnace body by the opening/closing operation of a shaft damper and a furnace body cover. Exhaust gas is introduced from the furnace body into the combination tower, air is supplied in stages, the temperature of the gas is gradually raised through combustion of CO, and the gas is used to heat the raw material in the shaft.

Apparatus for reactor iron making

A powdered coal burner used for directly heating an object to be heated, particularly iron scrap, in a heating vessel. The burner is composed of an oxygen nozzle, a powdered coal nozzle, an air nozzle, disposed concentrically from the center, and a cone which is provided at the end of the opening part of the oxygen nozzle in such a way as to disperse oxygen in a radial direction and burn powdered coal. The burner burns with shortened length of flame, and temperature of the flame is not excessively high.

Powdered coal burner

Method of reactor iron making without using electric power in the reactor. Iron scrap and a solid non-petroleum carbonaceous material, i.e., powdery coal or coke, are continuously charged from above into molten iron in the reactor with a space over the molten iron. The carbonaceous material is charged by injecting it with a stream of nitrogen or air. Oxygen gas is simultaneously blown into molten iron below its surface so as to stir it and oxidize the carbonaceous material mainly to CO and blown into the space over the iron to oxidize the CO to CO.sub.2. The amount of oxygen is increased as the amount of molten iron increases. The iron scrap melts from the heat generated by the oxidation. The high temperature exhaust gas is used to preheat scrap to be charged. When the amount of molten iron reaches a predetermined level, it is tapped off until a lower predetermined level is reached. The above steps are repeated. Twin reactor iron making can use the method. Only part of the CO produced in one reactor is oxidized and high temperature exhaust gas is passed to the other reactor while oxygen is added thereto to oxidize the remainder and generate more heat. The heat of the gases and the additional heat of oxidation preheats scrap and carbonaceous material in that reactor.

Reactor iron making

Refining method of molten metal which employs a refining apparatus provided with a tiltable refining vessel, a tuyere formed therein for blowing inert gas and/or flux or further sometimes additive alloy component(s), with the aid of inert gas into the molten metal, and a suitable number of electrodes for heating the molten metal and flux, for the purpose of performing a first refining process of carrying out the heating of the molten metal and the flux with the electrodes and a second refining process of tilting the vessel for blowing into the molten metal insert gas and others from the tuyere, whereby harmful or unnecessary metallic and/or non-metallic impure components can be removed for improving the quality of the article.

Process for refining a molten metal

Refining method of molten metal which employs a refining apparatus provided with a tiltable refining vessel, a tuyere formed therein for blowing inert gas and/or flux or further sometimes additive alloy component(s), with the aid of inert gas into the molten metal, and a suitable number of electrodes for heating the molten metal and flux, for the purpose of performing a first refining process of carrying out the heating of the molten metal and the flux with the electrodes and a second refining process of tilting the vessel for blowing into the molten metal inert gas and others from the tuyere, whereby harmful or unnecessary metallic and/or non-metallic impure components can be removed for improving the quality of the article.

Growing community of inventors

Nagoya, Japan

Saburo Sugiura