GB2066439A - Furnace Work Piece Support Beams - Google Patents

Abstract

The invention relates to furnaces and in particular solid hearth walking beam furnaces and support beams thereof. The support beam (2 or 3) has a billet support surface (11) raised above an upper refractory layer (19) and extending longitudinally along the beams. The support surface (11), along most of its length, is narrower than the beams to achieve as even and rapid a heat input to the billet as possible and has along part of its length a meander or zig-zag, such that the area of contact on the underside of the billet is changed each time a walking beam stroke is effected. On the lateral side of the support surface (11) are surfaces extending at an angle to the upper refractory layer (19), the angles varying along the length of the support surface (11) by virtue of the meander of the latter. Scale (14) shedded from the billet during operation of the furnaces is caused to move along the angled surfaces into specific areas where arrangements can be made to collect and dispose of the scale. <IMAGE>

Description

SPECIFICATION Furnace Work Piece Support Means This invention relates to metal processing and in particular to furnaces and support beams thereof used in the heating of billets, slabs and the like, of ferrous or non-ferrous metal.

According to the present invention there is provided a support beam for use in a furnace through which a billet or the like is arranged to be moved, said beam having a refractory layer formed along its longitudinal axis and a support surface for a billet defined on the refractory layer, at least part of the support surface being defined by a plateau, lateral surfaces of which extend upwardly relative to the refractory layer at angles varying along the length of said part of the support surface.

The present invention also provides a furnace comprising a plurality of support beams as described in the preceding paragraph so arranged as to have their longitudinal axes parallel to one another, some of the beams being movable simultaneously relative to the other beams so as to move a billet through the surface. Scale and the like which is deposited on the surfaces of the moving beams and is displaced during forward motion of the walking beams, and scale and the like which is deposited on the fixed beams and which is displaced during return movement of the walking beams, collects at those areas of the lateral surfaces having the greatest angle, enlarged clearance being provided between the fixed and moving beams in the region of such areas in order to facilitate gravitational discharge of scale and the like from the furnace.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figs. 1 and 2 are respectively an end view and a plan view of a known refractory floor for a walking beam furnace shown schematically; Fig. 3 shows schematically typical support beam cross-sections of known refractory floors; Fig. 4 is a plan view of a furnace floor utilising support beams according to the invention; Figs. 5 and 6 show diagrammatically different arrangements of support beams; Fig. 7 is an enlarged diagrammatic plan view of an area between adjacent support beams; and Fig. 8 is a cross-section of a beam according to the invention.

With reference to Figs. 1 and 2 of the drawings, in order to progress billets 1 through a known walking beam furnace in the direction of arrow 5, moving or walking beams 2 are raised in the direction of arrow 4 until the billets 1 are lifted clear of fixed beams 3, and the walking beams 2are then moved horizontally in the direction of arrows 5 and lowered, thus replacing the billets 1 on the fixed beams 3. Each billet will have advanced one increment, one having probably been discharged from the furnace and another having probably entered the furnace.

Fig. 4 shows a walking beam furnace floor 6 comprising three fixed beams 3 and two walking beams 2. Each beam comprises a bulk of refractory material and has a raised support surface 11 for the billets. The surface 11 extends along the longitudinal dimension of the beam in the form of a meander or zig-zag and along the major part of its length has a transverse dimension considerably smaller than that of the beam. At an inlet end 9, each surface 11 is located centrally of its beam in order to minimise twisting moments on the beams when the first of a succession of billets is fed into the initially empty furnace. At the other or exit end 10, the support surface 11 widens to an area 8 which extends the full width of each beam.This is due to the fact that in the soaking zone, the refractory and metal are hotter and more liable to damage from high load carrying stresses than is the case in other zones of the furnace.

Due to the meander of the support surface 11, the areas of contact on the underside of each billet are changed each time a walking beam feed stroke is effected. The angle of the meander relative to the beam axis is preferably optimised in relation to the support surface width and the commonest feed stroke for the furnace such that the previous billet contact area is totally exposed to heating gases at the completion of the associated forward feed. The support surfaces 11 may be rectilinear or of any other suitable form, for example sinusoidal or arcuate in plan view, provided that satisfactory variation of the billet contact areas is achieved.

Under some circumstances it may be advisable to choose the pitch of the meander in relation to the walking beam stroke, although the phasing of these two pitches will not normally be critical as the advance stroke will be very short in relation to the meander pitch.

As shown in Fig. 4 the meander of the support surfaces of adjacent beams may be in phase.

Alternatively as shown in Fig. 5 the meanders of the support surfaces of adjacent beams may be of opposite phase, or as shown in Fig. 6 may be 900 out of phase. Slots 12 or 13 (Fig. 4) may be formed in the support surfaces 11 so as to improve gas circulation around the underside of the billets.

With conventional beam cross-sections as shown in Fig. 3 the scale flakes off the billets during use and accumulates in the spaces between the support surfaces as indicated by 1 4.

This scale eventually rises to the underside of the billets and tends to be compacted by sequential billet lowering operations and also to be forced into the clearances between the fixed and walking beams. Also forward motion of the billets tends to push the scale towards the soaking or hot end of the furnace thus aggravating the problem still further.

With reference to Fig. 7 of the drawings, scale 14 is represented by a series of circles and arrow 5 indicates the feed direction of movement of the walking beam. In the following discussion the effect of up and down movement of the walking beam can be ignored since this movement is small when compared with forward movement.

Prior to forward feed of the walking beam, the scale 14 will be densely packed and it is likely that the piece of scale 1 4a will not move in response to movement of the walking beam. It is also likely that the piece of scale 1 4b will move with the walking beam. Thus when the walking beam 2 reaches the position shown in dotted lines the nine pieces of scale iliustrated will become spaced apart. Additional scale falling from the billet or being displaced from the billet support surfaces 11 will fill at least some of the spaces with the result that when the walking beam returns to its original position scale will be displaced in the direction of arrow 1 5.

The beam shown in Fig. 8 of the drawings is of conventional basic construction having a steel trough 23 filled successively with an insulating material 1 6 and different refractory mixes 17, 18, 19. Material 20 is provided above the upper refractory layer 1 9 and forms lateral surfaces which extend upwardly to a plateau defining the support surface 11. The lateral surfaces extend at angles relative to the layer 19, which angles vary along the length of the surface 11 by virtue of the direction in which the latter extends. The pitch of the upwardly extending inclined lateral surfaces is large when compared with the feed stroke of the walking beams. The material 20 thus extends across the full width of the beam and defines a supporting surface 11 of restricted width.This arrangement enhances the scale shedding characteristics of the fixed and walking beams, as scale landing on the surface 21 and moved along that surface in the manner described in relation to Fig. 7, moves along a slope of increasing angle and will eventually move down the slope at the area of greatest angle. Scale is thus caused to move into specific areas of the furnace and enlarged clearance is provided between the fixed and walking beams in the region of those areas while suitable under-grate collecting and disposal hoppers, chain conveyors and the like can also be incorporated at those areas.

It will be appreciated that the phasing of the meanders of the support surfaces is likely to affect the scale movement and it is considered that the 900 outer phase relationship shown in Fig. 6 will show the most pronounced tendency to discharge scale in a discrete area.

The refractories used in constructing the beams are preferably dense insulating refractories and may be either prefabricated or cast in situ, or a combination of these techniques may be used.

The support surfaces will normally be formed from a refractory selected for its high hot strength and low permeability and it will preferably have a non-wetting surface characteristic in relation to the metal being heated in the furnace.

Various modifications may be made without departing from the scope of the invention. For example although the invention has been described in relation to a walking beam steel slab heating furnace it will be evident that the invention can readily be applied to various types of furnace heating different materials.

In another aspect of the invention a support surface which may extend longitudinally of its beam may be defined by lateral surfaces extending at angles to the refractory layer of the beam, the angles varying by virtue of the design of the beam. In the manner previously described, the scale shedding characteristics of the fixed and walking beams can again be enhanced.

Claims (9)

Claims

1. A support beam for use in a furnace through which a billet or the like is arranged to be moved, said beam having a refractory layer formed along its longitudinal axis and a support surface for a billet defined on the refractory layer, at least part of the support surface being defined by a plateau, lateral surfaces of which extend upwardly relative to the refractory layer at angles varying along the length of said part of the support surface.

2. A beam according to claim 1, wherein the support surface is formed of a refractory material.

3. A beam according to claim 1 or 2, wherein said part of the support surface extends to one end of the beam whereat the support surface is located centrally of the beam and extends parallel to the beam axis, and at the other end of the beam the support surface extends over the transverse dimension thereof.

4. A beam according to any of claims 1 to 3, wherein gaps are formed in the support surface.

5. A beam according to any of the preceding claims, wherein the support surface is formed of a metallic tubular member arranged to have a coolant flow therethrough.

6. A furnace comprising a plurality of support beams according to any of the preceding claims, wherein the beams are arranged with their longitudinal axis parallel to one another, some of the beams being movable simultaneously relative to the other beams so as to move a billet through the furnace.

7. A furnace according to claim 6, wherein scale and the like which is deposited on the surfaces of the moving beams and is displaced during forward motion of the walking beams, and scale and the like which is deposited on the fixed beams and which is displaced during return movement of the walking beams, collects at those areas of the lateral surfaces having the greatest angle, enlarged clearance being provided between the fixed and moving beams in the region of such areas in order to facilitate gravitational discharge of scale and the like from the furnace.

8. A furnace according to claim 6 or 7, wherein the pitch of the angled lateral surfaces is large as compared with the feed stroke of the walking beams.

9. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.