US2063603A

US2063603A - Annealing box

Info

Publication number: US2063603A
Application number: US40602A
Authority: US
Inventors: Percy E Hunter; Kenneth J Deahl
Original assignee: Hunter Co Inc
Current assignee: Hunter Co Inc
Priority date: 1935-09-14
Filing date: 1935-09-14
Publication date: 1936-12-08
Anticipated expiration: 1953-12-08

Description

Dec. 8, 1936.

P. E. HUNTER ET AL ANNEAL ING BOX Filed Sept. 14, 1935 2 Sheets-Sheet l Dec. 8, 193%. P. E. HUNTER ET AL 2,063,603

ANNEALING BOX Filed Sept. 14, 1935 2 Sheets-Sheet 2 l S IniTia) Lenglh of 778 Q SYressed 77'e and Chord lengih et Choral Lengih Patented Dec. 8, 1936 ANNEALING BOX Percy E. Hunter and Kenneth J. Deahl, Pittsburgh, Pa.; said Deahl assignor to said Hunter Application September 14, 1935, Serial No. 40,602

Claims. (Cl. 263-49) Our invention relates to annealing boxes adapted to be employed in the heat-treatment of metals.

Annealing boxes employed in the art are usual- 5 ly the cast metal type or the sheet metal plate type, composed of plates joined at their edges to form a unitary box structure. The boxes are, of course, subjected to high temperature conditions with alternate periods of heating and cool- ],0 ing. One of the main difficulties with such boxes is that the tops sag and the sides bulge or otherwise become so distorted to such an extent that they will no longer accommodate a desired charge of material to be treated or be capable of being placed in the furnaces. They are, therefore, useless for their intended purpose and must be scrapped after a limited number of heats.

Various devices and artifices have been employed to reduce distortion and maintain the 9 shape of the boxes. For example, internal supporting framework has been used to support the walls and tops of the boxes, but the framework is so massive and heavy as to materially reduce the charge capacity of the boxes while increasing the oxidizing volume of air in the boxes. Also, intricate forms of reinforcing and strengthening provisions have been utilized in attempting to increase the life of the boxes, but materially add to the cost of the boxes.

One of the principal objects of our invention is to provide means for restoring an. annealing box to approximately its original shape during the cooling period thereof.

Another object of our invention is to provide means disposed interiorly of the box and of such form as not to reduce the charge capacity of the box while maintaining the clearance of air space at a minimum, and operative to support the top and sides of the box during a heating 4 cycle or period thereby preventing excessive distortion and effective to restore the box to its initial shape during the cooling period.

A further object of our invention is to provide means of generally simplified and improved form for regulating the shape of the box to increase I on the line IIII of Fig. 1; Fig. 3 is a fragmentary sectional plan view of the box; Fig. 4 is a View, on an enlarged scale, taken on the line IVIV of Fig. 3; Fig. 5 is a cross-sectional view of the top portion of a modified form of box; Fig. 5 6 is a diagrammatic view illustrating the manner of setting up counteracting distorting stresses in the top portion of the box; Fig. 7 is a view similar to Fig. 5, but showing another modification; Fig. 8 is a modification showing a flat 10 top annealing box; Fig. 9 shows still another modification, and Fig. 10 is a view taken on the line XX of Fig. 9.

Referring first to Figs. 1 to l, the box is shown as provided with an arched roof or top and may 15 be suitably formed of cast metal or formed of plates welded together at their abutting edges to produce a unitary box structure. We have shown the box formed with reinforcing grooves or channels up the sides and across the top of the box that are in' efiect continuous, and permit of longitudinal expansion and contraction.

Disposed interiorly of the box and extending transversely thereof is a series of tie rods or bars I0, each bar having its end secured to the adjacent side wall I I of the box, as by means of plates I2 welded to the bar I0 and the side of the box II, respectively. The tie bars are arranged in pairs and spaced apart in directions longitudinally of the box. Each pair of tie bars are arranged at opposite sides of the grooves formed in the walls of the box and preferably are connected to the sides of the box at the points of juncture between the sides and the top of the box. Thus, the charge capacity of the box is not reduced.

Intermediate the ends of each tie bar Ill, an upright strut member I3 is provided, the lower end of the strut I3 being Welded to the tie bar. A connecting bar I4 extends between the struts I3 01 each pair of tie bars Ill and is secured at its ends to the upper ends of the struts I3, preferably by welding. The ends of the connecting bar I4 extend through the adjacent strut I3 and slidably engage in U-shaped cup members I5 that are welded to and depend from the top I6 of the box. The connecting bar I4 and the struts I3 engage the top of the box to support the same but are not connected thereto, and, therefore, do not add to the weight of the roof.

The tie bars I0 may be initially placed under stress, so as to operate as tension members to restrain the side walls against bulging due to the weight of the top and loss of strength at elevated temperatures and to support the roof through 55 the struts l3 against sagging. Since the tie rods and strut members are disposed interiorly of the box they will not increase in temperature as rapidly as the box metal. Under increase in temperature, the. box being restrained by the tie rods ID, the top thereof will expand upwardly, expansion of the ties and struts lagging expansion of the box. Under elevated temperature, the top may move downwardly into engagement with the struts and their connecting bars, the bars being bent downwardly slightly, in tension, to a point to effect stability of the box. During cooling, contraction of the box leads the contraction of the bars ill, but due to the lever advantage of the tie bars over the top [6, when normal temperature is reached the box is returned to substantially original shape.

The tie bars In, the struts I3, and the connecting bars M are in effect a truss structure for supporting and maintaining the shape of the box during the heating and cooling periods. The tie bars and struts are preferably composed of metal having a higher tensile strength and expansion and contraction rate than that of the material of the box. That is, we prefer to employ in the supporting structure and in the box any two metals of diiferent heat expansion, or metals having different coefficients of expansion.

For example, a metal such as mild steel, having a given rate of expansion may be employed in the box structure While another metal, such as alloy steel, having a higher rate of expansion may be employed in the supporting structure. Or two alloy steels of different coefficients of expansion may be employed.

Initial stressing of the tie bars may be effected in one manner by making the. length of the tie bars equal to the chord distance of the top I6, heating the box to a temperature sufliciently high to produce loss of strength in the top and plastic slumping thereof to tension the tie bars, the temperature being suificiently low as not to produce loss of strength in the ties. Or, as shown graphically in Fig. 6, the length of the ties A initially is made less than the free chord length B of the top of the box. The chord length is then shortened by pressure applied externally to the sides of the box and the ends of the ties welded to the box. Removal of such pressure produces the desired stress in the ties, the box assuming the position indicated by the broken line C.

During the heating up period, expansion of the box leads the expansion of the supporting structure, the top I6 expanding upwardly. Since the ties I have a higher expansion rate per unit temperature rise than the box, they elongate to prevent development of too great stress therein and, at some temperature, the expansion of the ties will approximately equal the expansion of the top plus the initial deformity of the top. Until reaching such temperature, the ties will constantly be maintained in tension.

We prefer that such temperature be the upper temperature to which the box will be heated and be approximately 1570F. To this end, mild steel with a coefficient of expansion of .000006" per degree F. may be used to form the box. Alloy steel having an expansion coefiicient in the range between 1.16 and 1.84 times that of mild steel may be employed for the supporting structure.

For a box 42 inches in width, maximum temperature 1570 F., and normal room temperature of 70 F., the total expansion of the box composed of mild steel would be .378 inch. Total expansion of the ties composed of alloy steel having an expansion coefiicient of 1.25 times that of mild steel would be .473 inch. However, to maintain the ties under tension, they are initially shortened to a degree such as tension therein will not disappear until maximum temperature is reached and, thus, the amount of shortening is made equal to the difference in total expansion at maximum temperature, or .095 inch. The length A of the ties is, therefore, initially 41.905 inches.

At maximum annealing temperature, any tendency of the top to collapse, creep or sag tensions the tie. bars Ill to the point of stability, and they support the top and prevent excessive bulging of the sides.

During the cooling period, the greater rate of contraction ofthe tie bars develops the initial tension of the ties when the point of normal temperature is reached, thereby drawing in the sides and forcing the top upwardly to its original position if there has been any excessive deformation thereof.

Not only are the tie bars and their strut members of alloy steel able to restore the. box to substantially its initial shape, but are extremely efiective to support the box against excessive deformation at high temperatures because of their relatively greater strength at annealing temperature than that strength possessed by the metals forming the box.

Referring now to Fig. 5, the box 20 is provided with an arched roof not continuously curved as in the roof l6, and may be of greater span. Tie bars 2 I, similar to the tie bars ID, are secured at their ends to the points of juncture between the roof and the sides of the box. A medially-disposed triangular supporting member 22 is welded to each tie bar and engages the roof and affords vertical and diagonal support therefor. The tie bars 2| and their members 22 are composed 01' metal having a higher tensile strength and higher expansive coefficient than the metal of the box. In this construction, also, the tie bars may be ini-- tially stressed and tension maintained therein during an annealing cycle or operation.

In Fig. '7, for boxes of great width or for additionally supporting the roof thereof against collapsing, we provide an internally-disposed roof truss composed of chord tie bars 25, an intermediate vertical strut 26, a top compression member 21 and diagonal brace bars 28. All of the various bars are. composed preferably of alloy steel and are welded together to form a unitary truss, and the only point of rigid connection between the truss and the box being at the ends of the tie bars, such ends being welded to the box at points of juncture between the top and sides.

The compression member 21 engages the roof only at points spaced longitudinally of the truss, whereby transfer of heat from the top to the truss member by conduction is reduced to a minimum and prevents heating of the truss too rapidly.

The top is free to expand upwardly away from the member 21, and any sagging of the roof at annealing temperatures will be arrested by the truss, thereby preventing excessive deformation of the box.

Not only may light gauge sheet metal be employed to form the boxes to lower the cost thereof, but they will be maintained against excessive deformation and efiectively reinforced by the alloy steel supporting structure operative to restore the boxes to their proper working condition.

Various features of the invention are capable of use also with annealing boxes having flat tops,

as shown for example in Fig. 8. In this structure, the box top is supported from sagging by a tie bar 3| and a strut 32, the tie bar 3| being preferably of a metal which has a different coefficient of expansion than the metal of the box. The strut 32 will prevent the roof expanding in a downward direction, when subjected to heat, and will, of course, prevent sagging.

In Figs. 9 and 10, we show a beam-like truss of alloy steel for supporting the top against excessive sagging, and comprises an angle member 34 disposed beneath the top 35. The flange 36 of the angle member is welded at its ends to the sides of the box adjacent to the points of juncture with the top and serves as a tie member.

The web portion of the member 34 has its upper edge 31 cut away to conform with the contour of the top and is disposed in spaced relation thereto. Seating blocks 38 are preferably welded to opposite sides of the web portion of the member 34 in position tosupportingly engage the top 35. The spaced relation of the top and the upper edge 31 of the truss member 34 prevents too rapid heating of the truss member while the oppositely-arranged blocks 38 maintain the truss perpendicular to the top wall of the box.

We claim as our invention:-

1. An annealing box having sides, ends and a roof formed of metal, a tie bar within the box and having its ends welded to opposite sides of the box adjacent to the points of juncture thereof with the roof, an upwardly-extending strut carried by said tie bar intermediate its ends in position to supportingly engage the roof, and means depending from the roof and slidably engaging the upper end of said strut, for maintaining said strut against lateral shifting movement.

2. An annealing box having sides, ends and a roof formed of metal, a pair of tie bars arranged in side-by-side relation with the box and having their ends welded to opposite sides of the box adjacent to the points of juncture thereof with the roof, a strut carried by each tie bar intermediate its ends, in position to supportingly engage the roof, a connecting bar joining the said struts, and means depending from the roof and slidably engaging the upper end of said strut, for maintaining said struts against lateral shifting movement.

3. An annealing box of sheet metal having sides and a convex top, the top being of such thinness that it is not self-sustaining at annealing temperatures, and a self -contained truss having only abutting engagement with the underside of the top and secured at its ends to the box, at the lines of juncture between the top and said sides.

4. An annealing box having a top formed of sheet metal and sides joined thereto, a tie bar disposed interiorly of the box and having its ends secured to opposite sides of the box, adjacent to the lines of juncture between the sides and the top, and a strut carried by said tie bar intermediate its ends, in position to supportingly engage the top, the said strut having only abutting engagement with said top.

5. An annealing box having a top formed of sheet metal and sides joined thereto, a tie bar disposed interiorly of the box and having its ends secured to opposite sides of the box, adjacent to the lines of juncture between the sides and the top, and a plurality of struts carried by said tie bar, in position to supportingly engage the top at points to each side of the longitudinal center line of the top, the said struts having only abutting engagement with the said top.

PERCY E. HUNTER. KENNETH J. DEAHL.