Metallurgical apparatus – Means treating a continuum of work – With heating means
Patent
1996-02-13
1997-12-02
Kastler, Scott
Metallurgical apparatus
Means treating a continuum of work
With heating means
432242, C21D 954
Patent
active
056932880
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a seal assembly having an improved sealability, which is used at an entrance and/or exit of a heat treatment furnace for annealing, stress relieving annealing or otherwise heat treating a metallic strip such as a stainless steel or high alloy strip with no formation of oxide films on the surface thereof, using a reducing, combustible atmospheric gas containing hydrogen gas as a furnace gas, thereby isolating the inside of the furnace from the outside air.
BACKGROUND TECHNIQUE
In a heat treatment furnace for annealing, stress relieving annealing or otherwise heat treating a metallic strip such as a stainless steel or high alloy strip while no oxide film is formed on the surface thereof, a combustible, reducing atmospheric gas such as a mixed gas consisting of 75% of hydrogen gas and 25% of nitrogen gas (hereinafter called simply the furnace gas) is fed into the furnace.
An assembly for isolating the inside of the furnace from the outside air is usually mounted on portions of the entrance and/or exit thereof through which the metallic strip is to be passed, thereby preventing mixing of the outside air with the furnace gas (hereinafter called sealing). A typical example of such a seal assembly is disclosed in Japanese Patent Publication No. 42(1967)-18893. As disclosed, this seal assembly is built up of elastic rotating rolls for holding therebetween a metallic strip continuously fed into the furnace, said rolls rotating at a speed substantially equal to the feed speed of the metallic strip, a flexible seal plate fixed at ends to the furnace body, and felt or other elastic pads for making seals between the seal plate and the elastic rotating rolls.
One example of a conventional heat treatment furnace for heat treating a metallic strip continuously fed thereinto using an atmospheric gas containing hydrogen gas as a furnace gas will now be explained generally with reference to a shaft type of a bright annealing furnace for annealing a stainless steel strip or other high alloy strip.
FIG. 15 is a schematic view of the general structure of a shaft type of bright annealing furance for a stainless steel strip, etc. A metallic strip S is guided by a bottom roll into the furnace through a seal assembly 13 located on the entrance side of of a furnace body 1, where it is heated to a predetermined temperature, then cooled and finally annealed as desired. The thus treated strip is then fed out of the furnace through a seal assembly 13 located on the exit side. Usually, a reducing, combustible furnace gas 12 containing hydrogen gas is continuously fed into the furnace while it is cooled and circulated through, so that the inside pressure of the furnace can be kept an about 10 to about 50 mmH.sub.2 O higher than the outside air. It is here to be noted that while the furnace is in operation, the furnace gas 12 leaks little by little through the seal assemblies 13 and 13 located at the entrance and exit of the furnace body 1, thereby preventing penetration of air (oxygen) into the furnace body 1 and so avoiding mixing of air with the furnace gas 12.
FIGS. 16 and 17 are enlarged front and side views of a conventional seal assembly located on the exit side of the furnace respectively. The conventional seal assembly, shown at 13, is of the structure wherein elastic pads 15 formed of felt or a felt equivalent are fixed on the surfaces of seal plates 14 secured on a furnace wall 2 by a bolt-and-nut combination, and elastic rotating rolls 16 with the surfaces made of elastic rubber are engaged with the metallic strip S and elastic pads 15 by the working force of a piston rod 11a driven by a cylinder, so that the inside of the furnace 1 can be isolated from the outside air.
Based on FIGS. 16 and 17, a brief account will here be given of a roll-driving mechanism 11 for pressedly engaging the elastic rotating rolls 16 with the elastic pads 15 fixed on the surfaces of the seal plates 14 secured on the furnace wall 2 and the metallic strip S. A lever 11b is pivotally fixed on a fixed
REFERENCES:
patent: 2367174 (1945-01-01), Renkin
patent: 3291468 (1966-12-01), Albertsen et al.
patent: 3306594 (1967-02-01), Bauer
Kastler Scott
Nisshin Steel Co. Ltd.
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