Abstract: This invention describes a method to promote the decarburization reaction of the molten steel in a vacuum refining furnace by adding manganese ore into the molten steel.The added manganese ore melts and release oxygen into the steel bath with the additional dissolved oxygen content effectively promoting the decarburization reaction of carbon steel, even below the 50 ppm level of ultra-low carbon content. The addition of the manganese ore increases the oxygen content of molten steel and enables the vacuum degassification treatment to have an effect similar to that of gaseous oxygen blowing without the excessive refractory erosion of the vacuum chamber lining. In this manner, baths having relatively high carbon contents and/or low dissolved oxygen contents can be effectively decarburized to ultra low carbon levels. This invention and the addition technique are not limited in application to RH vacuum-degassing equipment.

Abstract: A high strength vacuum melted ferrous alloy having enhanced fracture toughness comprising not more than about 0.01% by weight sulfur, not more than about 0.1% manganese, and titanium in an amount in atomic percent of not less than about twice the atomic percentage of sulfur present in the alloy. Other detailed limits of titanium, zirconium, and niobium are also disclosed.

Abstract: 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.

Abstract: A multi-chamber vacuum installation includes a charge-changing chamber (5) and a plurality of processing chambers (1, 2, 3, 4) located within the charge-changing chamber. One of the processing chambers (4) also serves as an air lock chamber. The air lock chamber (4) is formed of two parts, and inner part (4a) and an outer part (4b). The inner part is secured to the inside and the outer part is secured to the outside of the charge-changing chamber.

Abstract: A process of production of high cleanness extra low carbon steel includes steps of producing low carbon rimmed steel by means of a refining furnace, supplying a deoxidization agent to a slag in a laddle for adjusting iron concentration in slag at lower than or equal to 5%, subsequently performing vacuum degassing process with blowing oxygen to lower carbon content in the steel lower than or equal to 0.006%.

Abstract: The disclosed method is a method of manufacturing clean steel comprising refining molten steel by adding additives of from not more than 0.5% to more than 0.001% by weight of molten steel to the molten steel bath, in vacuo or a non-oxidizing atmosphere within a melting furnace or vessel made of or lined with a basic refractory material consisting essentially of 7-90 wt % of CaO and 90-7 wt % of MgO, which total content being 70% to 99.9%, and optionally included a basic refractory material consisting of 30-0.1 wt % of at least one element selected from the group consisting of Al.sub.2 O.sub.3, CrO, ZrO.sub.2.SiO.sub.2, ZrO.sub.2, ZrC and C as selected components, and obtaining clean steel containing less than 30 ppm of oxygen, less than 30 ppm of sulfur, less than 150 ppm of nitrogen, 5 to 0.1 ppm of Mg and 25 to 0.1 ppm of Ca. Said additives comprises Al and at least one optional element selected from Ti, Nb, Ta, B and alkali earth metal. 5% of a solvent can be included to said additives.