US3693955A

US3693955A - Component annealing base

Info

Publication number: US3693955A
Application number: US124090A
Authority: US
Inventors: Herbert Wald; Harold K Young; William O Blanch
Original assignee: Bethlehem Steel Corp
Current assignee: Bethlehem Steel Corp
Priority date: 1971-03-15
Filing date: 1971-03-15
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: FR2130301B1; DE2211978A1; FR2130301A1; CA983708A; NL7203362A; GB1374514A; BE780620A; IT952226B

Abstract

Apparatus for supporting a charge in a high temperature annealing furnace which comprises a plurality of components arranged in combination for easy replacement of any component or the entire assembly. The apparatus includes a refractory tray which is sealed from the gaseous atmosphere of the heating chamber by a unique arrangement of the component parts of the base assembly including separable top and bottom plates and a compartmented seal trough.

Description

United States Patent Wald et al.

1451 Sept. 26, 1972 COMPONENT ANNEALING BASE [72] Inventors: Herbert Wald; Harold K. Young; William O. Blanch, all of Baltimore, Md.

[52] US. Cl ...266/5 B, 263/47 R [51] Int. Cl. ..C2ld H06 [58] Field of Search ...266/5 B, 5 S; 263/42, 43, 47 A 2,834,590 5/l958 Pugh ..266/5 B 3,081,074 3/1963 Blackman ..263/47 A 3,179,394 4/1965 Sims ..266/5 B X Primary Examiner-Robert D. Baldwin Assistant ExaminerJohn S. Brown Attorney-Joseph J. OKeefe 5 7] ABSTRACT Apparatus for supporting a charge in a high temperature annealing furnace which comprises a plurality of components arranged in combination for easy replacement of any component or the entire assembly. The apparatus includes a refractory tray which is sealed from the gaseous atmosphere of the heating chamber by a unique arrangement of the component parts of the base assembly including separable top and bottom [56] References Cited UNITED STATES PATENTS l d l h ates an a Com artmented sea trou 2,283,982 5/1942 Germany ..266/5 B p p g 2,284,014 5/1942 Peck ..266/5 B 10 Claims, 3 Drawing Figures COMPONENT ANNEALING BASE BACKGROUND OF THE INVENTION This invention relates generally to heating or annealing furnaces and more particularly to an improved base for supporting articles during a heating cycle therein.

Conventional annealing equipment for processing steel consists of annealing bases on which to place a charge, furnaces to apply the heat, and, generally, inner covers which fit over the charge in-the furnace and contain a protective atmosphere that prevents oxidation of the steel. The base consists of a shallow refractorylined steel or cast iron tray with means to seal the open down-end of the inner cover comprising a trough around the periphery of the base containing a sealing material. The base also includes a sheath which surrounds the refractory pedestal and a top plate. The several parts of the base are welded together to form a rigid unitary structure.

Annealing furnaces for high temperature open or tight coil annealing of products such as chromized sheet and silicon diffused electrical sheet operating at temperatures of l,600-l,800 F. present difficulties in operation due to the high temperatures. Conventional furnace designs as noted above make extensive use of weldments, particularly in the fabrication of the base assemblies. The high temperatures incident to the annealing cycles of the products described above create destructive strains in the welded parts due to expansion and contraction of the parts. The unitary construction of the base is therefore subject to early failure. In addition the essential seals between the base and the furnace and heating chambers are conventionally vulnerable to. the direct high temperature radiation which results in a loss of expensive seal material such as the liquid metal seals, e.g., lead, woods metal, etc.

The circulating gaseous annealing atmosphere of the heating chamber during at least a portion of the chromizing cycle contains chlorine which is corrosive and therefore damaging to the furnace base. Although means is provided in prior art bases to protect the base from the corrosive effects of this atmosphere, frequent replacement of the base is necessary. The unitary construction of the prior art bases including base sheath,

refractory pedestal, and top plate requires replacement of the entire base assembly, which is expensive and time consuming.

It is an object of this invention, therefore, to provide a relatively inexpensive base assembly in an annealing furnace that is readily replaceable as a unit or as separate components.

It is a further object of this invention to provide apparatus which protects the refractory pedestal from the corrosive effect of the annealing atmosphere.

It is still a further object of this invention to provide apparatus which seals the annealing atmosphere within the heating chamber.

It is an additional object of the instant invention to provide apparatus which minimizes the effect of direct high temperature radiation on the seal material.

SUMMARY OF THE INVENTION The instant invention accomplishes these objects by providing apparatus which is adapted to be fabricated in component parts with a minimum of welding and includes a unique arrangement of seal means. The

downwardly extending flanges provided on the one piece bottom and top plates which extend into a seal channel filled with a liquid metal seal material provides positive seal means for the separate refractory tray enclosed between the plates. The parts of the base are readily separately removable from the base. The seal troughs are positioned to eliminate direct high temperature radiation effect on the sealing material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view through an annealing furnace employing apparatus constructed in accordance with the instant invention;

FIG. 2 is an enlarged sectional view of the outer portion of the base assembly of FIG. 1, and

FIG. 3 is an enlarged sectional view of an alternate arrangement for the seal means at the fan shaft opening of the base assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the FIGURES, and more particularly to FIG. 1, a preferred embodiment of the apparatus of the instant invention is seen incorporated in a bell-type furnace 10. The furnace 10 is seen to comprise generally an outer annealing furnace cover 11, removable inner cover 12, base assembly 13, outer peripheral seal trough 14 which extends around the peripherty of the base 13, and supporting structure 15. The furnace cover 11 is of conventional form including a refractory lining and provided with suitable heating means. The inner cover 12, the base assembly 13 and trough 14 rest on support structure 15 in a manner to be described in detail to form heating chamber 16 through which a gaseous atmosphere is circulated. The inner cover 12 is provided with a peripheral skirt 12', welded to the cover near its lower end, which extends outwardly from the cover and downwardly therefrom. The charge C to be annealed is shown to be of a coil of strip resting on coil support 17 and plenum chamber 18. The annealing atmosphere inside the heating chamber 16 is circulated by means of the fan 19.

The supporting structure 15 is fabricated from standard structural sections welded together and bolted to columns 20. The outer peripheral seal trough 14 is removably resting on the supporting structure 15. The base assembly 13, the design of which will presently be discussed in detail, is removably supported on structure 15 with portions extending into seal trough 14.

Base assembly 13 comprises ,bottom plate 21, refractory tray 22 and top plate 23. The bottom plate 21 and top plate 23 comprise one-piece flanged plates produced on a modern flange mill and having flanges 24 and 25 respectively which extend downwardly into seal trough 14. Bottom plate 21 is provided with a plurality of bolts 26 welded thereto and extending downwardly therefrom for rigid attachment of the fan drive housing for gas circulating fan 19. The bottom plate 21 is further provided with an upwardly extending flange 27 welded to, plate 21 and plate 43 with shaft collar 42 welded thereto, the combination thus forming a central fan shaft opening 28 in base 13.

The refractory tray 22 is fabricated from 1% inch steel plate or a lightweight flanged plate as a support and form which is filled with castable refractory 29. The

castable refractory provides the necessary insulation between the top and

bottom plates

23 and 21 and acts as a load bearing spacer between the plates. Steel pads 30 are welded to the inside of the steel form of refractory tray 22 before the castable refractory is applied. The pads 30 are provided with tapped holes drilled therein and pipe sleeves 31 welded thereto and extending upwardly to the top surface of the tray 22 to accommodate eye bolts (not shown) for lifting. Pipe sleeves 32 are also provided in the tray 22 extending through the bottom providing access to a network of connecting channels 33 formed by inverted 2 inch angles cast in the top of the castable refractory material whereby a protective atmosphere, e.g. 4% NH gas, can be introduced into the sheath chamber 34 at slightly higher pressure than the gaseous annealing atmosphere through sheath gas inlet 35 and exhausted through sheath gas outlet 36.

' The seal trough 14 which extends around the outer periphery of the base 13, see FIG. 2, is constructed from rolled and formed angles with three compartmented channels upwardly open, viz., inner channel 37, intermediate channel 38 and outer channel 39, and a closed chamber or steam jacket 40. Inlet and outlet means are provided (not shown) in the steam jacket for the introduction of steam for reasons that will become apparent. The inner channel 37 is provided with a plurality of spacer bars 41, e.g. inch X 4 inch, to space the flange 25 of top plate 23 and flange 24 of bottom plate 21 above the bottom of the channel. The inner channel 37 is a reservoir for liquid metal seal material, as e.g. lead. The intermediate channel 38 is a support for the inner cover 12 which rests thereon and the outer channel 39 is a reservoir for liquid metal seal material, as e.g. woods metal. The intermediate channel 38 serves also as a service area for the protective atmosphere' of the annealing or heating chamber 16 having inlet and outlet means (not shown) for the protective atmosphere and thermocouples (not shown) requiring no flexible or liquid metal seals. The inner wall 44 of the inner channel 37 may extend upwardly to the bottom of the bottom plate 21 if desired. Inlet and outlet means 45 is provided to introduce a protective atmosphere into the chamber 46 thus formed.

In operation: the base 13 is assembled with the top plate 23 spaced above the bottom plate 21 and having the refractory tray 22 therebetween. The top plate 23 is welded to the top of the shaft collar 42 at the central fan shaft opening 28, thus forming a unit which is set down on the structural members of the supporting structure 15. Plenum chamber 18 and coil support 17 are placed on the top plate 23 of the base 13 and the fan drive housing is connected to the base by bolts 26. The downwardly extending flanges 24 and 25 of the bottom and top plates respectively extend into the inner channel 37 of the seal trough 14. A first body of liquid metal 47, as e.g. lead, having a level above the bottom edge of the flanges is introduced into channel 37. The lead seal 47 provides the means to seal the protective atmosphere in the heating chamber 16 from air atmosphere as well as an effective seal for the refractory tray from the gaseous atmosphere. The lead reaches a temperature of about 850 F. The top surface of top plate 23 is exposed to the protective atmosphere in the heating chamber 16. The bottom surface of the top plate 23 is exposed to the protective atmosphere within sheath chamber 34 as is the refractory tray 22 and the top surface of bottom plate 21.

A charge C, as e.g. a coil of strip, is placed on the coil support 17 and the inner cover 12 placed over the charge and the base. The lower end of the inner cover 12 rests in the intermediate channel 38 and the skirt 12' at the lower end of cover 12 extends into the outer channel 39 of the seal trough 14. A second body of liquid metal 48, as e.g. woods metal, is provided in the outer channel 39 having a level above the bottom edge of the skirt 12'. The woods metal seal 48 having a low melting temperature is located in the outer channel 39 of the seal trough 14 so that when the outercover ll of the furnace is lowered onto the supporting structure as seen in FIG. 1 the woods metal 48 is protected from direct .radiation and also from contamination by powder, salts and lead. Steam jacket 40 is provided ad- 0 jacent the outer channel 39 of the seal trough 14 with means for introducing steam for the purpose of maintaining the woods metal liquid to provide flexibility and freedom of movement of the inner cover skirt 12' during the annealing cycle and also to allow removal from and insertion of the cover into the woods metal seal 48.

Plugs 49 are provided in each of the liquid metal seals to facilitate removal of the liquid metal when necessary.

FIG. 3 shows an alternate embodiment for the arrangement of the base 13 at the central fan shaft opening 28 which provides an additional liquid metal seal adjacent thereto. An annular ring 50 spaced from shaft collar 42 is welded to plate 43 to form a reservoir 51 for a liquid metal seal material, as e.g. lead. Top plate 23' is provided with a downwardly extending inner flange 25. A plug 49 is provided as a drain for the liquid metal when removal thereof is desired.

The invention as hereinbefore described provides an annealing base constructed from component parts not rigidly attached to one another, employing minimal welding and providing liquid metal seals for flexibility and freedom of movement of the individual components. Strains caused by expansion and contraction normal to welded equipment and which cause cracks and weld failures in conventional bases are thus avoided. The component concept also makes possible the substitution of a plain carbon steel which is stabilized with additions such as titanium for high nickel alloys such as Inconel. The removal and replacing of the component base as described herein either as a unit or as individual components is quick, relatively inexpensive and comparatively easy.

We claim:

1. In an annealing furnace having a base and a removable cover thereon to form a heating chamber through which a gaseous atmosphere is circulated, said base comprising:

a. a supporting structure,

b. a trough extending around the periphery of said base,

c. a bottom plate having an outer peripheral flange extending downwardly into said through,

d. a top plate spaced above said bottom plate and having an outer peripheral flange extending downwardly into said trough,

e. a refractory tray between said bottom plate and said top plate, and

f. means to seal said refractory tray from said gaseous atmosphere.

2. Apparatus according to claim 1 wherein said trough comprises inner and outer channels with an intermediate channel therebetween.

3. Apparatus according to claim 2 wherein said intermediate channel supports said removable cover.

4. Apparatus according to claim 3 wherein said outer peripheral flanges extend into said inner channel of said trough.

5. Apparatus according to claim 4 wherein said removable cover comprises a peripheral skirt adjacent the bottom thereof extending downwardly into said outer channel of said trough.

6. Apparatus according to claim 5 including means to seal said gaseous atmosphere within said removable cover.

7. Apparatus according to claim 6 wherein said means to seal includes a first body of liquid metal within said inner channel having a level above the bottom edge of said flanges and a second body of liquid metal within said outer channel having a level above the bottom edge of said skirt.

8. Apparatus according to claim 7 wherein said first body of liquid metal is lead and said second body of liquid metal is woods metal.

9. In an annealing furnace having a base with a central fan shaft opening and a removable cover thereon to form a heating chamber through which a gaseous atmosphere is circulated, said base comprising:

a. a supporting structure,

b. an outer peripheral trough extending around the outer periphery of said base,

c. a bottom plate having an outer peripheral flange extending downwardly into said trough and an upwardly extending inner peripheral flange,

d. an inner peripheral trough extending around the inner periphery of said base adjacent said central fan shaft opening and said upwardly extending inner peripheral flange of said bottom plate,

. a top plate spaced above said bottom plate and having an outer peripheral flange extending downwardly into said outer peripheral trough and having an inner peripheral flange extending downwardly into said inner peripheral trough,

f. a refractory tray between said bottom plate and said top plate, and

g. means to seal said refractory tray from said gaseous atmosphere.

10. Apparatus according to claim 9 including means to seal said gaseous atmosphere within said removable cover.

Claims

1. In an annealing furnace having a base and a removable cover thereon to form a heating chamber through which a gaseous atmosphere is circulated, said base comprising: a. a supporting structure, b. a trough extending around the periphery of said base, c. a bottom plate having an outer peripheral flange extending downwardly into said through, d. a top plate spaced above said bottom plate and having an outer peripheral flange extending downwardly into said trough, e. a refractory tray between said bottom plate and said top plate, and f. means to seal said refractory tray from said gaseous atmosphere.

8. Apparatus according to claim 7 wherein said first body of liquid metal is lead and said second body of liquid metal is wood''s metal.

9. In an annealing furnace having a base with a central fan shaft opening and a removable cover thereon to form a heating chamber through which a gaseous atmosphere is circulated, said base comprising: a. a supporting structure, b. an outer peripheral trough extending around the outer periphery of said base, c. a bottom plate having an outer peripheral flange extending downwardly into said trough and an upwardly extending inner peripheral flange, d. an inner peripheral trough extending around the inner periphery of said base adjacent said centraL fan shaft opening and said upwardly extending inner peripheral flange of said bottom plate, e. a top plate spaced above said bottom plate and having an outer peripheral flange extending downwardly into said outer peripheral trough and having an inner peripheral flange extending downwardly into said inner peripheral trough, f. a refractory tray between said bottom plate and said top plate, and g. means to seal said refractory tray from said gaseous atmosphere.