METHOD FOR MANUFACTURING A COOLING PLATE FOR A METALLURGICAL FURNACE

Technical field

[0001] The present invention generally relates to a method for manufacturing a cooling plate for a metallurgical furnace.

Background Art

[0002] Such cooling plates for a metallurgical furnace, also called staves, are well known in the art. They are used to cover the inner wall of the outer shell of the metallurgical furnace, as e.g. a blast furnace or electric arc furnace, to provide: (1 ) a heat evacuating protection screen between the interior of the furnace and the outer furnace shell; and (2) an anchoring means for a refractory brick lining, a refractory guniting or a process generated accretion layer inside the furnace. Originally, the cooling plates have been cast iron plates with cooling pipes cast therein. As an alternative to cast iron staves, copper staves have been developed. Nowadays, most cooling plates for a metallurgical furnace are made of copper, a copper alloy or, more recently, of steel.

[0003] Different production methods have been proposed for copper stave coolers. Initially, an attempt was made to produce copper staves by casting in moulds, the internal coolant channels being formed by a sand core in the casting mould. However, this method has not proved to be effective in practice, because the cast copper plate bodies often have cavities and porosities, which have an extremely negative effect on the life of the plate bodies. The mould sand is difficult to remove from the channels and the channels are often not properly formed.

[0004] A cooling plate made from a forged or rolled copper slab is known from DE 2 907 511 C2. The coolant channels are blind boreholes introduced by deep drilling the rolled copper slab. The blind boreholes are sealed off by welding in plugs. Then, connecting bores are drilled from the rear side of the plate body into the blind boreholes. Thereafter, connection pipe-ends for the coolant feed or coolant return are inserted into these connecting bores and welded to the stave body. With these cooling plates, the above-mentioned disadvantages related to casting are avoided. In particular, cavities and porosities in the plate body are

virtually precluded. The above manufacturing method is however relatively expensive both in labour and material. Furthermore, due to considerable mechanical and thermal stress to which the stave cooler is exposed, the different welded connection joints are critical as regards fluid tightness. In addition, since the channels are integral with the stave body, there is only one level of separation between the coolant and the furnace interior, i.e. if the stave body cracks open, coolant will leak. A leakage of coolant fluid into the furnace however leads to a significant risk of explosion and should therefore be avoided at all cost.

Technical problem

[0005] It is an object of the present invention to provide an improved method for manufacturing a cooling plate for a metallurgical furnace, wherein the method does not display the aforementioned drawbacks. This object is achieved by a method as claimed in claim 1.

General Description of the Invention

[0006] A method for manufacturing a cooling plate for a metallurgical furnace in accordance with the present invention comprises the steps of providing a slab of metallic material, the slab having a front face, an opposite rear face and four side edges; and providing the slab with at least one cooling channel by drilling at least one blind borehole into the slab, wherein the blind borehole is drilled from a first edge towards an opposite second edge. In accordance with an important aspect of the present invention, the method comprises the further steps of deforming the slab in such a way that a first edge region of the slab is at least partially bent towards the rear face of the slab; and machining excess material from the front and rear faces of the slab to produce a cooling plate having a panel-like body wherein an opening to the cooling channel is located in the rear face.

[0007] By bending the slab towards the rear face and subsequently machining excess material from the front and rear faces of the slab, the opening to the cooling channel is located in the rear face. Compared to the prior art method, as e.g. described in DE 2 907 511 C2, it is no longer necessary to seal off the opening to the cooling channel in the first edge by welding in a plug. Nor is it necessary to drill a connecting bore between the rear face and the cooling channel

to access the cooling channel in the first edge region. The removal of these process steps reduces both labour and material costs.

[0008] More importantly, however, the absence of the plug provides a more reliant cooling plate. Indeed, as the cooling plate is exposed to considerable mechanical and thermal stress, in particular in the edge regions of the cooling plate, the plug has to be considered as a weak point. If the weld of the plug deteriorates, fluid tightness of the cooling channel can no longer be guaranteed and coolant could leak from the cooling channel into the furnace. Such leakage of coolant fluid into the furnace should however be avoided at all cost as it may lead to a significant risk of explosion. As no such plug is welded to the cooling plate manufactured according to the method of present invention, the risk of a leakage occurring through such a plug is avoided. Furthermore, the cooling plate manufactured according to the method of present invention also presents a more important material thickness on the front face in the first edge region, as compared to cooling plates manufactured according prior art methods. The increased material thickness also contributed to a longer lifetime of the cooling plate.

[0009] Preferably, after machining excess material from the front and rear faces of the slab, the method comprises the additional step of forming grooves and intermittent lamellar ribs in the front face of the panel-like body for anchoring a refractory brick lining.

[0010] To warrant a good anchoring function of the lamellar ribs and grooves structure on the front face of the cooling plate and a good thermal form stability of the cooling plate, the grooves are advantageously formed with a width that is narrower at an inlet of the groove than at a base of the groove. The grooves may e.g. be formed with dovetail cross-section.

[0011] Preferably, the method comprises the additional step of providing a connection pipe for each cooling channel formed in the panel-like body; aligning one end of each connection pipe with an opening to the respective cooling channel arranged in the rear face of the panel-like body; and connecting the connection pipes to the rear face of the panel-like body so as to create a fluid connection between each connection pipe and its associated cooling channel.

[0012] An adapter may be arranged between the panel-like body and the connection pipe, the adapter having the form of a hollow truncated cone. The smaller base of the adapter may have a diameter adapted for connection to the connection pipe. The larger base of the adapter is dimensioned so as to cover the whole opening of the cooling channel in the rear face. Indeed, due to the bending of the cooling channel and the subsequent machining of the rear face, the cooling channel may have an elongated opening in the rear face. The larger base of the adapter allows to ensure that a leakage at the rear face of the cooling plate can be avoided.

[0013] Preferably, the rear face of the panel-like body, the connection pipe and, if applicable, the adapter are connected together through soldering or welding.

[0014] According to a first embodiment of the invention, the method comprises the steps of providing the slab with a first cooling channel by drilling a first blind borehole into the slab, wherein the first blind borehole is drilled from the first edge towards the second edge; and providing the slab with a second cooling channel by drilling a second blind borehole into the slab, wherein the second blind borehole is drilled from the first edge towards the second edge. The first and second cooling channels are arranged in such a way that their ends in a second edge region meet and form a fluid communication between the first and second cooling channels.

[0015] The first and second blind boreholes are both drilled from the first edge towards the second edge at an angle with respect to each other, in such a way that their ends meet in the second edge region. The resulting first and second cooling channels thereby form a combined "V"-shaped cooling channel, wherein coolant flows through one of the cooling channels towards the second edge region and then, through the other one of the cooling channels, back to the first edge region. Such a "V"-shaped cooling channel allows both the inlet connection pipe and the outlet connection pipe to be arranged in the first edge region.

[0016] According to a second embodiment of the invention, the method comprises the steps of providing the slab with a first cooling channel by drilling a first blind borehole into the slab, wherein the first blind borehole is drilled from the first edge towards the second edge; and providing the slab with a second cooling channel by drilling a second blind borehole into the slab, wherein the second blind

borehole is drilled from the second edge towards the first edge. The first and second cooling channels are arranged in such a way that their ends meet and form a fluid communication between the first and second cooling channels.

[0017] The first and second blind boreholes are drilled from opposite edges towards a central region of the slab, in such a way that their ends meet in the central region. The resulting first and second cooling channels thereby form a combined cooling channel extending from the first edge to the second edge. This is of particular importance when a cooling plate with particularly important height is to be manufactured. Indeed, blind boreholes can only be drilled up to a particular depth. If the cooling channel is to exceed this depth, a second blind borehole is generally drilled from the opposite side. In this embodiment, both the first edge region and the second edge region are bent towards the rear face before removing excess material from the slab. Two cooling channel openings are thereby formed in the rear face without resorting to the necessity to provide plugs at either end of the cooling channel.

[0018] According to a third embodiment of the invention, the method comprises the steps of providing the slab with a first cooling channel by drilling a first blind borehole into the slab, wherein the first blind borehole is drilled from the first edge towards the second edge, wherein an end of the first blind borehole is arranged in a second edge region of the slab; and, in the second edge region, drilling a connecting bore extending from the rear face of the slab to the end of the first blind borehole and forming a fluid communication between the first cooling channel and the connecting bore.

[0019] In the first edge region, the slab is bent towards the rear face and an opening to the cooling channel is thereby formed in the rear face. In the second edge region on the other hand, a connecting bore is provided for forming second opening to the cooling channel. The formation of this second opening to the cooling channel essentially corresponds the method used in the prior art methods. This embodiment is adapted for connecting an inlet connection pipe in the first edge region and an outlet connection pipe in the second edge region.

[0020] Preferably, the cooling plate is made of at least one of the following materials: copper, a copper alloy or steel.

Brief Description of the Drawings

[0021] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-section through a slab according to a first step of the method for manufacturing a cooling plate in accordance with the present invention;

Fig. 2 is a schematic cross-section through a slab according to a second step; Fig. 3 is a schematic cross-section through a slab according to a third step; and Fig. 4 is a schematic cross-section through a slab according to a fourth step.

Description of Preferred Embodiments

[0022] Cooling plates are used to cover the inner wall of an outer shell of a metallurgical furnace, as e.g. a blast furnace or electric arc furnace. The object of such cooling plates is to form: (1 ) a heat evacuating protection screen between the interior of the furnace and the outer furnace shell; and (2) an anchoring means for a refractory brick lining, a refractory guniting or a process generated accretion layer inside the furnace.

[0023] Referring now to the Figures, it will be noted that the cooling plate 10 is formed from a slab 11 e.g. made of a cast or forged body of copper, a copper alloy or steel into a panel-like body 12. This panel-like body 12, which is more closely described by referring to Fig.4 has a front face 14, also referred to as hot face, which will be facing the interior of the furnace, and a rear face 16, also referred to as cold face, which will be facing the inner surface of the furnace wall. Referring to Fig.4, the panel-like body 12 generally has the form of a quadrilateral with a pair of long edges (not shown) and a pair of short first and second edges 22, 24. Most modern cooling plates have a width in the range of 600 to 1300 mm and a height in the range of 1000 to 4200 mm. It will however be understood that the height and width of the cooling plate may be adapted, amongst others, to structural conditions of a metallurgical furnace and to constraints resulting from their fabrication process.

[0024] The cooling plate 10 further comprises connection pipes 26, 28 for a cooling fluid, generally water. These connection pipes 26, 28 are connected from

the rear side of the panel-like body 12 to cooling channels 30 arranged within the panel-like body 12. As seen in Fig. 4, these cooling channels 30 extend through the panel-like body 12 in proximity of the rear face 16. According to the proposed method of manufacturing, which will be described in further detail below, such cooling channels 30 are formed by drilling. Each cooling channel 30 is normally provided with an appropriate inlet connection pipe 26, through which the cooling fluid is fed into the cooling channel 30, and/or outlet connection pipe 28, through which the cooling fluid leaves the cooling channel 30.

[0025] Referring further to Fig .4, it will be noted that the front face 14 is subdivided by means of grooves 32 into lamellar ribs 34. The grooves 32, laterally delimiting the lamellar ribs 34, may be milled into the front face 14 of the panel-like body 12. The lamellar ribs 34 extend parallel to the first and second edges 22, 24, from a first long edge (not shown) to a second long edge (not shown) of the panel- like body 12. They are perpendicular to the cooling channels 30 in the panel-like body 12. When the cooling plate 10 is mounted in the furnace, the grooves 32 and lamellar ribs 34 are arranged horizontally. They form anchorage means for anchoring a refractory brick lining, a refractory guniting or a process generated accretion layer to the front face 14.

[0026] In order to warrant an excellent anchoring for a refractory brick lining, a refractory guniting material or a process formed accretion layer to the front face 14, it should be noted that the grooves 32 have a dovetail (or swallowtail) cross- section, i.e. the inlet width of a groove 32 is narrower than the width at its base. The mean width of a lamellar rib 34 is preferably smaller than the mean width of a groove 32. Typical values for the mean width of a groove 32 are e.g. in the range of 40 mm to 100 mm. Typical values for the mean width of a lamellar rib 34 are e.g. in the range of 20 mm to 40 mm. The height of the lamellar ribs 34 (which corresponds to the depth of the grooves 32) represents generally between 20% and 40% of the total thickness of the panel-like body 12.

[0027] The method for manufacturing the cooling plates 10 will now be more closely described by referring to figures 1 to 4, which represent the cooling plates 10 at different key steps of the manufacturing method. In a first step, shown in Fig.1 , a slab 11 e.g. made of a cast or forged body of copper, a copper alloy or steel is provided. Such a slab has a generally quadrilateral form with a front face

14, rear face 16, a pair of long edges (not shown) and a pair of short first and second edges 22, 24. It should be noted that the slab 11 has dimensions exceeding the desired dimensions of the panel-like body 12. At least one blind borehole 40 is drilled from the first edge 22 into the slab 11 and extends to a second edge region 42. The blind borehole 40 has an end 44 arranged in the second edge region 42. In a subsequent step of the method, illustrated by Fig.2, the slab 11 is deformed in such a way that a first edge region 46 is bent towards the rear face 16 of the slab 11. This results in a corresponding bending of the blind borehole 40. The bending angle α between a central axis 50 of the unbent blind borehole 40 and a central axis 52 of the blind borehole 40 at the first edge 22 may be between 30 and 45 degrees. This bending angle α should however not be understood as limiting. The bending angle α may e.g. vary considerably depending on the thickness of the slab 11 or the diameter of the blind borehole 40.

[0028] After the slab 11 is deformed, excess material is removed from the slab 11 along the cutting lines indicated by dotted lines 55 in Fig.2. The resulting panel-like body 12, shown in Fig.3, is again of a generally quadrilateral form with a front face 14, rear face 16, a pair of long edges (not shown) and a pair of short first and second edges 22, 24. A cooling channel 30, formed by the blind borehole 40, is formed in the panel-like body 12 generally parallel to the rear face 16. In the first edge region 46, the cooling channel 30 is bent and opens up into the rear face 16.

[0029] According to one embodiment of the present invention, the panel-like body 12 can be provided with a bore 60 in the second edge region 42, extending from the cooling channel 30 to the rear face 16.

[0030] After machining excess material from the slab 11 , the resulting panel- like body 12 is further subjected to a milling step, wherein grooves 32 and intermittent lamellar ribs 34 are formed in the front face 14 of the panel-like body 12. As explained above, these grooves 32 and ribs 34 form anchorage means for anchoring a refractory brick lining, a refractory guniting or a process generated accretion layer to the front face 14 of the cooling plate 10.

[0031] Finally, connection pipes 26, 28 are connected to the rear face 16 of the panel-like body 12. An inlet connection pipe 26 is fluidly connected to the opening of the cooling channel 30 in the first edge region 46 for feeding cooling

fluid into the cooling channel 30. An outlet connection pipe 28 is fluidly connected to the bore 60 in the second edge region 42 for evacuating cooling fluid from the cooling channel 30.

Legend of Reference Numbers:

10 cooling plate

11 slab

12 panel-like body

14 front face

16 rear face

22 first edge

24 second edge

26 inlet connection pipe

28 outlet connection pipe

30 cooling channel

32 groove

34 rib

40 blind borehole

42 second edge region

44 end

46 first edge region

CC bending angle

50 central axis of the unbent blind borehole

52 central axis of the blind borehole at first edge

55 cutting line

60 bore