Nkk Corporation

Hidetoshi Matsuno

Yoshiteru Kikuchi

Atsushi Watanabe

Tadashi Inoue

Tomoyoshi Okita

Yoshihiko Kawai

Teruyuki Hasegawa

Toshio Ishii

Shuzo Fukuda

Shunichi Sugiyama

Toshio Takaoka

Tadahiko Nishi

Yutaka Okubo

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.

Fe-Ni alloy cold-rolled sheet excellent in cleanliness and etching

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.2 : up to 15 wt. %, and oxides of metals having an oxygen affinity lower than that of silicon: up to 3 wt. % in total; casting the deoxidized Fe-Ni molten alloy into an ingot; and blooming, hot-rolling and cold-rolling the ingot to manufacture an Fe-Ni alloy cold-rolled sheet containing non-metallic inclusions comprising a composition in a region of a melting point of at least 1,600.degree. C., which region is defined by a liquidus curve of 1,600.degree. C. in a CaO-Al.sub.2 O.sub.3 -MgO ternary phase diagram and having a particle size up to 6 .mu.m in a total amount of up to 0.002 wt. % as converted into oxygen.

Method for manufacturing an Fe-Ni cold-rolled sheet excellent in

Molten metal is put under pressure of up to 10 atmospheres in a covered ladle and a gas soluble in the metal is bubbled through the melt. Some gas goes into solution, while the remainder rises in bubbles and brings inclusions suspended in the molten metal up to the surface. Then the pressure is lowered, after which gas comes out of the solution in fine bubbles which also bring impurity inclusions up to the surface. In another method molten steel is refined at pressures not exceeding atmospheric pressure in a covered ladle equipped for evacuation and equipped for bubbling gas through the molten steel bath. Bubbling followed by pressure reduction can then be performed to form two stages of cleaning. Heat may be added for compensating the cooling effect of gas expansion. Instead of a closed ladle, an open ladle may be used, into which there can be dipped a chamber fitted for evacuation and having two large tubes at opposite sides of the chamber extending downwards to orifices that may be lowered into the molten metal in the ladle. The melt is then drawn up into the chamber by atmospheric pressure as the chamber is evacuated. Then bubbling may be performed in one connecting tube by injection of gas from the bottom of the ladle, or at a mid-level of the tube, to produce circulation of the molten metal up into the chamber and down through the other tube.

Method for cleaning molten metal and apparatus therefor

Method for manufacturing iron-boron-silicon alloy

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Tokyo, Japan

Hidetoshi Matsuno