Abstract: An inner peripheral edge of a toroidal glass substrate for a magnetic disk is subjected to mechanical polishing in such a manner that the surface roughness is no greater than 9 nm in terms of Rmax. Then, the inner peripheral edge is subjected to chemical polishing to remove at least 2 ?m of a surface layer. The inner peripheral edge has a non-conventional mirror-finished surface obtained by mechanical polishing. Thus, sufficient ring strength is obtained even when the chemical polishing depth is smaller than in the past. A polishing depth of less than 5 ?m is sufficient.

Abstract: An inner peripheral edge of a toroidal glass substrate for a magnetic disk is subjected to mechanical polishing in such a manner that the surface roughness is no greater than 9 nm in terms of Rmax. Then, the inner peripheral edge is subjected to chemical polishing to remove at least 2 ?m of a surface layer. The inner peripheral edge has a non-conventional mirror-finished surface obtained by mechanical polishing. Thus, sufficient ring strength is obtained even when the chemical polishing depth is smaller than in the past. A polishing depth of less than 5 ?m is sufficient.

Abstract: Iron carbide is produced by an apparatus comprising first fluidized bed reactor 4 and second fluidized bed reactor 5, wherein the charged grainy iron oxide is reduced and carburized by the high temperature and high pressure gas being introduced from the bottom of the reactor. Both fluidized bed reactors comprise chamber 23 for introducing gas into the reactor, distribution plate 27 having multiple gas-introducing nozzles 28, partition plate 26 partitioning the fluidized bed into plural division rooms, and gas supply inlet 25a, 25b arranged on chamber 23 for supplying gas to specific division room respectively. Each gas supply inlet is connected to gas supply line having a gas flow control valve for controlling gas pressure or gas flow rate.

Abstract: Provided is a method for producing iron carbide in which free carbon is generated with difficulty. When iron carbide is produced by reducing and carburizing iron-containing raw materials for iron making using a reaction gas mainly containing hydrogen and methane, steam or carbon dioxide is added into fluidized bed reactor (1) through line (7) in addition to the reaction gas supplied from line (2) into reactor (1) corresponding to a quantity of free carbon generated in reactor (1) which is obtained by means of dust meter (9). Consequently, the generation of the free carbon can be controlled.

Abstract: Iron carbide is produced by an apparatus comprising first fludized bed reactor 4 and second fluidized bed reactor 5, wherein the charged grainy iron oxide is reduced and carburized by the high temperature and high pressure gas being introduced from the bottom of the reactor. Both fluidized bed reactors comprise chamber 23 for introducing gas into the reactor, distribution plate 27 having multiple gas-introducing nozzles 28, partition plate 26 partitioning the fulidized bed into plural division rooms, and gas supply inlet 25a, 25b arranged on chamber 23 for supplying gas to specific division room respectively. Each gas supply inlet is connected to gas supply line having a gas flow control valve for controlling gas pressure or gas flow rate.

Abstract: Provided is a method for producing iron carbide in which free carbon is generated with difficulty. When iron carbide is produced by reducing and carburizing iron-containing raw materials for iron making using a reaction gas mainly containing hydrogen and methane, steam or carbon dioxide is added into fluidized bed reactor (1) through line (7) in addition to the reaction gas supplied from line (2) into reactor (1) corresponding to a quantity of free carbon generated in reactor (1) which is obtained by means of dust meter (9). Consequently, the generation of the free carbon can be controlled.

Abstract: Provided is a method for managing an operation of a producing process for obtaining an iron carbide product having a goal composition in a two-stages reaction process. A first-stage reaction process for partially reducing an iron-containing material for iron making is carried out, and a second-stage reaction process for performing further reduction and carburization is then carried out. A solid sample is taken at an outlet of a reactor for the first-stage reaction process to measure a reduction ratio of the solid sample. By regulating a parameter capable of changing a reduction ratio of the first-stage reaction process, an IC ratio obtained after the second-stage reaction process can be adjusted.

Abstract: Disclosed is a method for producing iron carbide, in which metallic carbide is difficult to be formed on the inside of heating tubes of a tube-shaped heater for heating reducing gas and carburizing gas to be supplied to a reactor. Carburizing gas which is supplied to reactor 1 is heated in tube-shaped heater 6 by combustion gas used for heating reducing gas and circulating gas, and then a mixture comprising carburizing gas, reducing gas and circulating gas is supplied to reactor 1. Iron-containing raw materials are reduced and carburized in reactor 1.

Abstract: Provided is a method for efficiently producing iron carbide depending on a particle size of an iron-containing material or the progress of reaction. In a fluidized bed reactor 7, a coarse iron ore is fluidized in blocks 8a to 8e, a fine iron ore is fluidized in blocks 9a to 9d, and a flow rate of a reaction gas supplied to the blocks for the fine iron ore is regulated by a flow regulating valve 11.

Abstract: An apparatus and method of producing iron carbide of predetermined quality is disclosed. The method of producing iron carbide (Fe.sub.3 C) comprises reducing and carburizing an iron-containing raw material containing iron oxides (e.g., hematite) or iron hydroxides as main components, wherein the raw material is partially reduced to a reduction ratio of 50 to 65% by a gas containing mainly hydrogen in a first stage of the reaction process, then the partially reduced raw material is further reduced and carburized with a gas containing mainly hydrogen and methane in a second stage of the reaction process to provide iron carbide.

Abstract: Powdered ore is fed into fluidized bed reactor 1 after preheating by hot blast in preheating furnace 2. Iron oxide particles are recovered from an exhaust gas of the preheating furnace 2 by dust catcher 3, and the iron oxide particles are reduced to iron in reducing furnace 4. The reduced iron particles are added into the flow path of fluidized bed reactor 1 to catalyze the reaction producing iron carbide.

Abstract: An apparatus and method of producing iron carbide of predetermined quality is disclosed. The method of producing iron carbide (Fe.sub.3 C) comprises reducing and carburizing an iron-containing raw material containing iron oxides (e.g., hematite) or iron hydroxides as main components, wherein the raw material is partially reduced to a reduction ratio of 50 to 65% by a gas containing mainly hydrogen in a first stage of the reaction process, then the partially reduced raw material is further reduced and carburized with a gas containing mainly hydrogen and methane in a second stage of the reaction process to provide iron carbide.

Abstract: The disclosure relates to a molten metal producing and refining method which does not damage the apparatus, realizes a stable and high second combustion rate, and is capable of effectively recovering heat generated by the second combustion. The method comprises introducing a metal-containing material, a carbonaceous material, a flux and O.sub.2 gas into a furnace. The carbon which dissolves into the metal bath in the furnace from the carbonaceous material is combusted with the O.sub.2 gas to generate heat and CO gas. The CO gas is subjected to the second combustion with the O.sub.2 gas to additionally generate heat, and the metal-containing material is melted and refined by both the generated heat and carbon. The method is characterized in that O.sub.2 gas or O.sub.2 -containing gas is blown into the furnace through large-diameter tuyeres installed near the bottom of the furnace and a part of the O.sub.

Abstract: In a rotary piston type engine comprising a rotor housing having exhaust port means, exhaust gas cleaning means comprising an auxiliary exhaust passage in the form of a cutout portion, and a secondary air port opening in a casing at the cutout portion. The cutout portion extends from the exhaust port means into a working chamber which is in the final part of expansion stroke.