Method and assembly for sealing up the entrance and exit of a he

Details Method and assembly for sealing up the entrance and exit of a he Method and assembly for sealing up the entrance and exit of a he

1996-01-19

1997-11-04

Kastler, Scott

Metallurgical apparatus

Process

266110, C21D 174

Patent

active

056836511

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a method for sealing up the entrance and exit of a heat-treating furnace operated in a reducing gas atmosphere including hydrogen gas, wherein metallic strips such as stainless steel strips are annealed or subjected to strain relieving annealing with no oxide coating formed on the surface thereof, and an assembly well suited for carrying out this method.


BACKGROUND TECHNIQUE

Metallic strips, for instance, stainless steel strips are subjected to bright annealing or strain relieving annealing in a heat-treating furnace wherein they are heat treated with no oxide coating formed on the surfaces thereof. Fed to this heat-treating furnace is an inflammable, reducing gas atmosphere including hydrogen gas such as a mixed gas consisting of 75% of hydrogen gas and 25% of nitrogen gas (which will hereinafter be simply called the furnace gas).
Seal assemblies (or seals) for shielding the furnace gas from the outside air are located at portions of the entrance and exit, through which the metallic strip that is to be treated and has been treated is passed, of a heat-treating furnace to which the furnace gas is fed (hereinafter may be called seals). Typical example of such seal assemblies is shown in Japanese Patent Publication No. 42-18893. The seal disclosed therein is made up of a pair of elastic rotating rolls with the metallic strip held therebetween, which rotate at a speed substantially equal to the speed of movement of the metallic strip, and a pad formed of felt for making a seal between a flexible seal sheet (which will hereinafter be called the elastic seal pad) fixed at one end to the furnace body and said elastic rotating rolls.
One example of a conventional heat-treating furnace using the furnace gas will now be explained with reference to a general shaft type of bright annealing furnace for stainless steel strips.
FIG. 8 illustrates the general structure of a bright annealing furnace for stainless steel strips. A metallic strip S consisting of a stainless steel strip is guided by a deflector roll and fed into a furnace body 1 through a seal assembly 2' located on the entrance side, wherein the strip is heated to a given temperature and then cooled. Upon leaving the furnace body, the strip is guided by a seal assembly 2' located on the exit side. Prevailing within the furnace body 1 is constantly an inflammable furnace gas containing hydrogen gas such as one mentioned as above, so that the furnace pressure is kept about 10 to 50 mm H.sub.2 O higher than the outside air pressure. In this arrangement, the furnace gas is allowed to leak little by little through the seal assemblies 2' and 2' located on the entrance and exit sides, thereby foreclosing the possibility that the air (oxygen) may enter the furnace body 1 and mixed with the furnace gas.
FIG. 9 is an enlarged front view of the conventional seal assembly located on the exit side, and FIG. 10 is an enlarged partial side view thereof. In this conventional seal assembly 2', elastic seal pad 5' formed of felt or a felt equivalent is fixed by an adhesive or a combined bolt and nut clamping means to the surface of a seal sheet 4' fixed at one end to a side plate 3a of a furnace wall 3 of the furnace body 1. This seal sheet 4' is formed of a thin stainless sheet having a thickness of about 0.5 mm and having some spring action. Then, a piston rod 8a is driven by a cylinder of a mechanism 8 for moving elastic rotating rolls 6' and 6' away from or toward each other, so that the elastic rotating roll 6' can be engaged with the metallic strip S and the elastic seal pad 5' to seal the interior of the furnace 1 against the outside air.
Here, the mechanism 8 for moving elastic rotating rolls 6' and 6' away from or toward each other so that the elastic rotating roll 6' can be engaged with the metallic strip S and the elastic seal pad 5' fixed to the surface of the seal sheet 4' fixed at one end to the side plate 3a of the furnace wall 3 of the furnace body 1 will briefly be explained with reference to FIGS. 9 and 10

REFERENCES:
patent: 890252 (1908-06-01), Thompson
patent: 890314 (1908-06-01), Thompson
patent: 3291468 (1966-12-01), Albertsen et al.

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