Metallurgical apparatus – Process
Patent
1996-04-08
1997-12-23
Kastler, Scott
Metallurgical apparatus
Process
266139, 266144, F27D 702, B22D 1110
Patent
active
057004200
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a non-oxidizing heating method and apparatus, and in particular, to a non-oxidizing heating technique using a non-oxidizing gas effective in furnaces of various types in a steel manufacturing and continuous casting field such as ladles, tundishes, and the like, and in furnaces of various types in a heating and heat treatment field for heating metallic (including non-ferrous metals) materials.
BACKGROUND ART
In the prior art, as methods of heating metallic materials such as a steel material and the like in a non-oxidizing state in a heating surface, the following methods are known including; (1) a radiant tube heating method ("Recent Practical Combustion Technique" (1983), p31, edited by Japanese Iron and Steel Association), (2) a direct flame reducing heating method (the 88th Nishiyama Memorial Technical lecture, (1983), p75), and (3) a two-layer atmospheric combustion method (Nippon Koh Kan Technical Bulletin, No.120 (1988), p24).
In the method of the present invention, the inside of a radiant tube disposed in a heating furnace is heated by combustion by a burner, and a steel material is heated by utilizing heat radiated from an outer surface of the tube. Accordingly, since an atmosphere within the furnace in contact with the steel material can be set at will, the atmosphere within the furnace can be easily made to be a non-oxidizing state.
Further to the invention, a reducing flame formed in an outer flame portion of a burner flame is made to directly collide with the steel material thereby to heat under a reducing atmosphere.
Finally, the steel material is wrapped in a non-oxidizing atmosphere produced by incomplete combustion, and at the same time, secondary combustion is caused in an unburned region existing in an outer portion of the non-oxidizing atmosphere so that the heating is performed by two-layer atmospheric adjustment.
The above-mentioned methods relate to the steel material, however, each of the above-mentioned methods is adopted in heating non-ferrous metals such as Al, Cu, and the like.
However, in the above-mentioned prior art non-oxidizing heating techniques for metallic materials, the following various problems are involved.
(1) Radiant Tube Heating
This method is excellent in the point that a combustion gas having an oxidizing property containing H.sub.2 O produced by combustion and residual O.sub.2 at the time of combustion can be completely isolated from the atmosphere in the furnace. However, 1) when a furnace temperature is at a high temperature equal to 1200.degree. C. or higher, there is no tube which is effective to endure this temperature, and 2) there is a limitation to a combustion capacity (heating capability of the furnace) of a burner to achieve combustion in a narrow space within the tube. For this reason, except for a heat treatment furnace, the radiant tube method has not been used in the prior art for a heating furnace for rolling a steel material in which the furnace temperature exceeds 1200.degree. C.
(2) Direct Flame Reducing Heating
In this method, since it is necessary to form a reducing atmosphere in the vicinity of the steel material, 1) there are limitations in operation such as a surface temperature (900.degree. C. or lower), combustion conditions (load, air ratio, burner capacity), and the like, 2) there is a limitation in facility such as a distance between the steel material surface and the burner, and 3) thermal efficiency is not satisfactory, since only a part of combustion heat possessed by fuel is used. For these reasons, the direct flame reducing method has not been used for a heating furnace (heating furnaces for hot rolling, thick plate and strip steel, etc.) for rolling a steel material.
(3) Two-Layer Atmospheric Combustion
In this method, 1) since two-layer atmosphere is formed, there is a limitation in disposing a burner within a furnace (for example, it is difficult to use a roof burner and a side burner jointly), and in the case of heating a steel material of a large size, there is a problem i
REFERENCES:
patent: 3738795 (1973-06-01), Heuer
patent: 4718643 (1988-01-01), Gitman
patent: 4818844 (1989-04-01), Ward
"4.2 Radiant Tube" on pp. 31-45 of Recent Progress of Combustion Technology in Iron and Steel Industry (Dec. 1990) edited by Japanese Iron and Steel Association.
"3.2 Direct Flame Heating Method" on pp. 89-94 of Heating Cooling Technique in Continuous Annealing in Progress in Continuous Annealing Technique of Strip (Dec. 1983) edited by the 88th Nishiyama Memorial Technical Lecture.
"Two-Layer Atmospheric Combustion Method" of Nippon Koh Kan Technical Bulletin No. 120 (Dec. 1988), pp. 24-30.
Hasunuma Junichi
Nakagawa Tsuguhiko
Osanai Hisashi
Yamaguchi Ryosuke
Yamamoto Takemi
Kastler Scott
Kawasaki Steel Corporation
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