GB2181080A - Method and apparatus for reinstating outworn ingot moulds - Google Patents

Abstract

A method for reinstating outworn ingot moulds is characterized in a predetermined removal of stock from the inner mould surfaces affected by surface decarburization and/or having crater-like recesses. The removal of stock is performed by means of a suitable machining, especially a cutting process, preferably by face milling. The apparatus comprises a turning and height adjusting device 3 and a clamping device 2 for the ingot 9 to be treated. Both the turning and height adjusting device 3 and the clamping device 2 are, together with a slide guide 4, arranged within a rigid frame stand 1. The slide guide 4 is reciprocatably movable along the inner surface of the ingot mould 9 to be treated by means of a lead screw 13, and it is further equipped with at least one tool holder 14 for at least one rotary cutting tool, especially circular cutter 8. The apparatus also comprises a power unit 5 suitable for rotatably driving at least the cutting tool 8, and a control unit 7 by means of which the stock removing process of ingot mould reinstatement is duly operated. <IMAGE>

Description

SPECIFICATION Method and apparatus for reinstating outworn ingot moulds The invention relates to a method and an apparatus for reinstating outworn ingot moulds by suitably treating their inner surfaces.

Ingot moulds generally used in the field of metallurgy tend to surface decarburization and to showing crater-like recesses in their inner wall surfaces. These effects show a steady growing tendency with the increasing number of castings until a stage at which finally sticking of the cast ingots occurs. According to prior art technique, reinstatement, i.e. repair of such outworn ingot moulds has been performed by welding, i.e. by repair welding whereby the crater-like recesses are filled in with a suitable welding material.

It has been recognised that current norms allow a certain wall thickness reduction for the ingot moulds in general use. This allowance by norms offers a limited possibility for reinstating outworn ingots by applying an inner surface treatment other than used until now. It should, however, be noted that reparability and thus, the possible number of castings by using one particular ingot mould is always limited by the allowable wall thickness reduction.

In accordance with what has already been indicated above, it is prior art knowledge to reinstate ingot moulds for further use by face welding, i.e. by manual arc welding. This method is, however, applicable for treating inner mould surfaces having crater-like recesses of limited depths only. Outworn ingot moulds showing recesses of considerable depths in their inner surfaces are sometimes repaired by using a treatment called oxygen jet planing whereby the wall thickness of such ingots is significantly reduced. This known treating process shows a number of drawbacks. The amount of material removal from the treated surface shows a random pattern, i.e. it is not really controllable. Thus, the resulting new surface shows, after treatment, a rather rough texture which in many cases, renders the treated ingot mould irreparable and also, sometimes unsuitable for further use.Especially in wintertime, pipes and hoses conveying the gaseous agents used for oxygen jet planing are often blocked by freezing since the process involves a very high demand on such agents. Also because of the permanent danger of fire and explosion, said known process of oxygen jet planing has proved to be disadvantageous for ingot mould reinstatement since for its safe application specific cautionary measures are inevitably necessary.

The main object of the present invention is to provide a novel method and a suitable apparatus for carrying out said method for reinstating outworn ingot moulds for further use.

Another object of the present invention lies in the provision of a method for the same purpose whereby the service life of ingot moulds can be considerably increased.

In accordance with the above and other objects the present inventions provides a method for reinstating outworn ingot moulds, the method being essentially characterized in a predetermined removal of stock from the inner mould surfaces affected by surface decarburization and/or having crater-like recesses. The removal of stock is performed by means of a suitable machining, especially cutting process, preferably by face milling. Deeper recesses in the ingot mould wall surfaces will preferably be treated by face welding, particularly by repair arc welding before the stock removal process according to the present invention is performed.

In order to perform the above method the present invention provides an apparatus for reinstating outworn ingot moulds by removing a predetermined stock from the inner mould surfaces that had been affected by surface decarbuziation and/or have crater-like recesses. The apparatus provided by the invention comprises a turning and height-adjusting device and a clamping device for the ingot mould to be treated. Both the turning and height adjusting device and the clamping device are, together with a slide guide, arranged within a rigid frame stand. The slide guide is reciprocably movable along the inner surface of the ingot mould to be treated by means of a lead screw, and it is further equipped with at least one tool holder for at least one rotary cutting tool, especially a circular cutter.The apparatus further comprises a power unit suitable for rotatably driving the at least one cutting tool, and a control unit whereby the stock removing process of surface cutting is operated.

In a preferred embodiment of the apparatus according to the present invention a mechanically driven turning and height adjusting device is provided. Other preferred embodiments of the apparatus may be equipped either with a hydraulic power unit or with an electric power unit, as alternatives, for cutting tool driving. In embodiments where a hydraulic power unit is applied, the latter is preferably connected to the tool holder (comprising a hydraulic motor for tool driving) via suitable hose tubes.

The invention will be more particularly de scribed and shown, by way of example only, with reference to the attached drawing, in which Figure 1 shows a side elevation view of a preferred embodiment of the apparatus ac cording to the invention, and Figure 2 shows a cross sectional view of the apparatus, taken along a plane indicated by reference characters A-A in Fig. 1 of the attached drawing; The preferred embodiment of the apparatus according to the present invention, as shown in the attached drawing figures, comprises a rigid frame stand 1 to which a clamping device 2 for holding an ingot mould 9 to be reinstated during the machining of its inner surfaces is mounted.The rigid frame stand 1 also comprises--attached to its lower portion-a turning and height adjusting device 3 suitable for turning and lifting or lowering the ingot mould 9 to be treated into its predetermined positions during processing. On a slide guide 4 which is, by means of a lead screw 13, reciprocally movable along the inner ingot mould surface to be machined, a tool holder 14 is mounted to which a rotatably driven cutting tool, particularly a circular cutter 8 is attached. The circular cutter 8 is driven by a hydraulic drive system comprising a hydraulic power unit 5 which is connected to the tool holder 14 by means of hose tubes 6. The hydraulic power unit 5 is driven by an electric motor 10. The apparatus described above further comprises a control unit 7 whereby the stock removing process of surface cutting is duly operated.

The operation of the apparatus and the essence of the method according to the present invention are as follows: First, the clamping device 2 is attached to the bottom of the ingot mould 9 to be treated, i.e. reinstated, preferably by means of threaded screws (not shown). Following this the ingot mould is-by using a suitable hoisting device-placed on the turning and height adjusting device 3.

It is noted that-before doing this-it is important to check the wear and the general state of the inner mould surfaces, especially the depths of the crater-like recesses therein.

This is important because beyond a certain critical depth value, by a simple stock removal for arriving at a clean surface, the remaining wall thickness of the treated ingot mould would be less than allowed by current and valid standards. Hence, if the depths of certain crater-like recesses is found to be within or beyond the critical range, a treatment of such areas of the inner mould surface by well known face welding, preferably by repair arc welding, is necessary before machining.

The ingot mould 9 together with the attached clamping device 2 is placed on the turning and height adjusting device 3 and it is fixed in- its first position of treatment. After that, the slide guide 4, together with the tool holder 14 is fixed to the frame stand 1, and the power unit 5 for driving the circular cutter 8 is connected thereto by means of the hose tubes 6.

After performing the necessary checking operations such as checking the position of the cutting edge of the circular cutter 8 with re spect to the horizontal plane and the vertical side wall of the ingot mould 9 respectively, the depths of cut that is desired in accor dance with the wear of the surface treated is adjusted. For doing this, the turning and height adjusting device 3 is actuated in vertical directions as indicated by arrow 12 in Fig. 2.

The side direction of feed is adjusted as indicated by arrow 11 in Fig. 1.

Following the above, the circular cutter 8 is set into rotation and simultaneously, it is fed forward along the slide guide 4 by means of the lead screw 13. As a result, the surface layer of the ingot mould 9 affected by decarburization and/or showing crater-like recesses is removed, and a surface-finished clean metal surface is achieved. It is noted that the removal of stock as described above can also be performed in more steps of operation in sequence.

After the circular cutter 8 has arrived at its end position near the bottom of the ingot mould 9, the apparatus is switched off, and the position of the finished new surface with respect of certain reference bases is checked again. Following this, the tool holder 14 is fully removed from the inside of the ingot mould. By means of the turning and height adjusting device 3 the ingot mould 9 is turned around its longitudinal axis, and the starting position of the cutting tool, i.e. of the circular cutter 8 with respect of the next surface to be treated is adjusted. Having done this, the removal of stock from the next surface is performed in accordance with the above described sequence of operational steps. The above is repeated in sequence until the whole inner mantle surface of the ingot mould 9 is finished and thus, the ingot mould 9 is fully reinstated.

From the above detailed description will be apparent that the apparatus, shown by way of example only, is especially laid out and suitable for the renovative treatment of ingot moulds having a cross section other than circular. It should be noted, however, that by slight modifications within the scope of the invention and the attached claims, also embodiments suitable for the renovative treatment of ingot moulds with circular or tapered conical inner cross section can be designed and constructed.

Figure 2 shows a cross-sectional view of the embodiment of Fig. 1 taken along the by reference characters A-A in Fig. 1. In Fig. 2 the relative position of the circular cutter 8 and the mode of operation are particularly well illustrated. Also in Fig. 2, a very simple mechanically driven design of the turning and height adjusting device 3 can be well seen.

The major advantages of the method and apparatus according to the invention are as follows: Since the slide guide carrying the tool hol der, together with the circular cutter is controlled movable in all directions, the cutting tool can readily follow the original shape of the ingot mould's inner surface. Thus, the in ner cross-sectional shape of the reinstated in got mould is very similar to that of the original. The depths of cut can be adjusted very accurately. As a result, deviations from the side wall plane between the opposite ends of the ingot mould can be maintained within the tolerance limits of + 1 mm. The quality of the finished surfaces shows a smoothness that can be achieved by milling, in general.

The removal of stock is very accurate.

Thus, the increase of weight of the cast ingots due to reinstatement of the ingot mould is very little when compared with results of the known prior art techniques.

A further advantage of the invention lies in the fact that besides global reinstatement of the ingot moulds including all and the whole inner wall surfaces, also partial, local finishing of certain surface areas having crater-like recesses is possible. When doing this, smooth intermediate, connecting areas to the untreated surrounding surface parts can be maintained. Finally, for performing the method according to the present invention, no special measures of caution are needed because there exists no danger of fire or explosion.

Claims (9)

1. A method for reinstating outworn ingot moulds characterized in a predetermined removal of stock from the inner mould surfaces affected by surface decarburization and/or having crater-like recesses, said removal of stock being performed by means of a suitable machining, especially cutting process, preferably by face milling.

2. A method as claimed in Claim 1, wherein said removal of stock is performed after having treated said inner surfaces of the ingot mould by face welding, preferably by repair arc welding.

3. An apparatus for reinstating outworn ingot moulds by removing a predetermined stock from the inner mould surfaces affected by surface decarburization and/or having crater-like recesses, said apparatus comprising a turning and height adjusting device and a clamping device for the ingot mould to be treated, both said turning and height adjusting device and said clamping device being, together with a slide guide, arranged within a rigid frame stand, said slide guide being reciprocatably movable along the inner surface of the ingot mould to be treated by means of a lead screw, said slide guide being further equipped with at least one tool holder for at least one rotary cutting tool, especially a circular cutter, said apparatus further comprising a power unit suitable for rotatably driving at least said cutting tool(s) and a control unit whereby the stock removing process of surface cutting is duly operated.

4. An apparatus as claimed in Claim 3 characterized in having a mechanically driven turning and height adjusting device.

5. An apparatus as claimed in Claim 3 or 4 characterized in having a hydraulic power unit for cutting tool driving.

6. An apparatus as claimed in Claim 5 characterized in said hydraulic power unit being connected to said tool holder via suitable hose tubes.

7. An apparatus as claimed in Claim 3 or 4 characterized in having an electric power unit for cutting tool driving.

8. A method as claimed in claim 1, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.

9. Apparatus as claimed in claim 3, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.