Daido Tokushuko Kabushiki Kaisha

Diado Tokushuko Kabushiki Kaisha

Daido Tokushuko Kabushiki Kaisha and Hitachi Zosen Corporation

Yoshio Inagaki

Kiyoshi Morii

Shuzo Kumura

Shyzunori Hayakawa

Tetsuo Okamoto

Saburo Sugiura

Motoshi Shinkai

Senji Fujita

Ichizo Taguchi

Shizunori Hayakawa

Hiroya Nakata

Takao Inoue

Akihiro Nagatani

Atsushi Ishii

Tatsuo Tagawa

Keiichi Mizuguchi

Masahide Tsuno

In the production of stainless steel it is aimed at to depress the highest temperature reaching during refining the molten steel with keeping the necessary tapping temperature so as to prolong the life of refractory materials of the refining furnace. After carrying out decarburization treatment under atmospheric pressure in a refining furnace by blowing an oxygen-containing gas into molten steel, further decarburization of the molten steel and reduction of chromium oxides is carried out under stirring by blowing a non-oxidizing gas under a reduced pressure, and then, reducing agent is charged into the furnace to reduce chromium oxides under keeping the reduced pressure. At the above atmospheric pressure operation total quantity of the oxygen gas blown is smaller than in a conventional process, while at the final stage of the reduced pressure operation an oxygen-containing gas is blown again in the quantity which is equivalent to the balance of the quantity of oxygen gas usually blown in the conventional process and the quantity of oxygen gas blown at the above atmospheric pressure operation so as to cause heat generation by oxidation reaction of chromium thereby increasing molten steel temperature to a necessary temperature with anticipation of subsequent temperature decrease.

Process for producing low-carbon chromium-containing steel

Disclosed are a method and an apparatus for vertical continuous casting. The vertical continuous casting includes drawing a strand formed in a watercooled mold vertically downward therefrom, positioning light reduction pinch rollers just prior to the solidification completing point of the strand, and applying a light reduction force to the strand sufficient to compensate for contraction caused by solidification of the strand. By this procedure the formation of central cavities is prevented and central segregation is lessened. The light reduction pinch rollers are arranged to be adjustably positioned up and down along the strand, in order to compensate for fluctuations in the location of the solidification completing point of the strand.

Vertical continuous casting method and casting apparatus

The continuous casting method uses a multistrand type continuous casting apparatus having a plurality of tundishes each provided with a plurality of nozzles for casting strands of at least two different alloys where at least one alloy is cast into two or more strands. The method transfers molten metal into the tundishes from separate ladles corresponding to each tundish, and one tundish feeds at least two water-cooled molds through the nozzles for continuous casting thereof. The number of strands cast for each of the different alloys is determined based on the time required for the preparation of each molten metal, an amount of charge and a casting speed of each molten metal, so as to improve the yield of expensive alloys and/or enhance the rate of operation of the apparatus.

Continuously and concurrently casting different alloys

Two tundish transport trucks move in alternate relation between a pouring position and a tundish preheating position. A swivel table is disposed at the forward end of a transport rail which extends laterally from the pouring station for guiding the tundish transport truck for movement thereon. Provided on the swivel table are a pair of swivel rails such that one of the rails is connected to the travel rail and the other is positioned in corresponding relation to a tundish preheating device. When the swivel table turns with the tundish transport trucks mounted on corresponding swivel rails, a preheated tundish is delivered to the pouring position and a used tundish is subjected to repair and preheating so as to be ready for a next tundish changing operation.

Tundish changing apparatus in a continuous casting installation

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

Growing community of inventors

Aichi, Japan

Yoshio Inagaki