Patent Application
20180029117
The invention relates to a method for repairing a refractory sleeve of a metallurgical vessel according to the preamble to claim 1 and to an apparatus for implementing the method.
Refractory sleeves of the type specified at the start are, among other things, the inner sleeves of casting ladles containing molten metal. The inner sleeve is inserted into a perforated brick of the refractory ladle lining and adjoins the closure plate of a slide closure on the outside.
The inner sleeve forms the pouring channel of the casting ladle and so is subjected to a great deal of wear during operation. It is therefore often necessary to replace the worn sleeves with new, undamaged sleeves. However, this process is normally very laborious because one must first of all break out the worn sleeve, repair the damaged bearing surface of the perforated brick and then fit the new sleeve such that it is correctly centred within the vessel. This results in long down times for the vessels in question.
A method for repairing the tap holes of metallurgical vessels is known from patent AT-A-242 175 that is implemented with a section of pipe that can be introduced into the tap hole as a mortar dispenser. However, the known method is unsuitable for repairing spout sleeves because the section of pipe serving as the mortar dispenser has bore holes distributed around the circumference and has exactly the same outside diameter as the target diameter of the spout to be repaired. The result of this, on the one hand, is that the mortar is not applied evenly to the damaged channel wall, and on the other hand, is that after having applied the mortar to the spout there is the risk that the applied mortar layer will be damaged when the perforated section of pipe is removed.
The object underlying the invention is to devise a method for repairing worn sleeves such that, by means of this method, the operational reliability and dimensional accuracy of the repaired sleeves is guaranteed.
According to the invention, this object is achieved by the sleeve repair being carried out by applying mortar to the casting channel of the sleeve with a mortar dispenser that can be inserted into the casting channel in a way known in its own right, and which, when withdrawn from the casting channel, calibrates it over the entire length of the channel, the mortar dispenser being rotated coaxially to the casting channel during the application of the mortar and being withdrawn from the casting channel, still rotating, after a defined period of time.
The repair method according to the invention is characterised in that it can be implemented with relatively uncomplex apparatus because the rotating mortar dispenser provides even application of mortar to the channel wall and precise calibration of the latter.
Another advantage of the method is minimised expenditure of time because it can be implemented with a relatively high vessel temperature and because both the application of the mortar and the curing of the applied mortar mass take place quickly.
In addition, the method makes it possible to automate the function of the mortar dispenser and to adapt to essential parameters such as the composition of the sleeve or of the respectively used mortar.
These advantages are of particular significance if the method according to the invention is used to repair the inner sleeve of a casting ladle with a slide closure adjoining the ladle spout, maintenance of which is carried out automatically by a robot in a maintenance station of the casting facility. In this case the invention makes provision such that the repair to the inner sleeve is also carried out automatically here during the maintenance of the slide closure, preferably with the same robot.
In this way it is possible to repair the inner sleeve during the changeover process for every plate change instead of replacing it with a new sleeve after a small number of castings. In this way the cost of the refractory material is reduced and the time required for the maintenance of the ladle is minimised.
Within this context it is advantageous if when applying mortar to the casting channel of the sleeve the mortar dispenser is rotated with a relatively fast rotation speed which is such that the mortar mass is sprayed onto the channel wall of the sleeve with a strong centrifugal effect by virtue of the centrifugal force that is generated.
It is also advantageous for better adhesion of the mortar if the mortar dispenser is also rotated for a specific amount of time dependent upon the composition of the mortar after the start of the mortar curing process.
Furthermore, the invention makes provision such that upon removing the rotating mortar dispenser from the casting channel, the mortar mass sprayed onto the channel wall is wiped away helically by the mortar dispenser, the rotation speed of the mortar dispenser being able to be set dependently upon the composition of the mortar and the structure and composition of the channel wall. In this way the removal of the mortar dispenser from the casting channel is facilitated, and at the same time the latter obtains an immaculately smooth inner wall.
In order to optimise the application and smoothing of the mortar mass, the invention also makes provision such that the mortar is applied to the sleeve at a sleeve temperature of preferably over 300° C.
The apparatus according to the invention for implementing the proposed method is characterised in that the mortar dispenser is formed by a section of pipe rotating about the longitudinal axis and that has radially longitudinally directed blades the length of which corresponds to the casting channel length of the sleeve to be repaired and the outside diameter of which, defined by the blades, is equal to the target value of the casting channel diameter of the sleeve.
During the application of mortar the mortar mass is evenly centrifuged onto the channel wall of the sleeve by the rotating blades so that the channel wall is covered with a compact and well-adhering mortar layer. Within this context it is advantageous if the blades are slightly convexly curved in the direction of rotation of the section of pipe.
The blades that rotate helically when the apparatus is removed bring about precise calibration of the casting channel with an immaculately smooth channel surface.
The invention will be described in more detail below by means of an exemplary embodiment with reference to the drawings. These show as follows:
During operation the sleeve 6 is subjected to a great deal of wear on its inner wall 6′ in the region of the casting channel 7. For this reason it is no longer serviceable after a certain number of castings.
According to the invention the sleeve repair takes place by applying mortar to the inner wall 6′ of the sleeve 6 with a mortar dispenser 9 that can be inserted into the casting channel 7 and through which the mortar is conveyed to the outside into a cavity 14 formed between the mortar dispenser 9 and the worn inner wall 6′ of the sleeve 6.
After subsequently removing the mortar dispenser from the casting channel 7, the sleeve is mortared with sufficient adhesion and calibrated over the entire length of the channel.
According to the invention, the apparatus 8 is actuated such that the mortar dispenser 9 rotates relatively quickly coaxially to the casting channel 7 for a defined time during the mortar application, and is removed from the casting channel, still rotating, during the curing of the mortar. The inner wall 6′ of the restored casting channel 7 is thus processed to be evenly smooth, and during casting molten metal that is flowing through is prevented from being retained and possibly adhering due to irregularities.
The rotational speed of the mortar dispenser 9 corresponds, for example, to that of a hand drill with approx. 500 to 1,000 rotations per minute. A drive shaft 19 coupled to the mortar dispenser for rotary drive is shown.
During trials relating to this it was established that it is advantageous if the mortar dispenser 9 is rotated for a total of, for example, 60 seconds, and if the mortar is applied to the inner wall of the sleeve at a sleeve temperature of preferably over 300° C. In this way the sleeve repair can be carried out while the casting ladle is still hot.
In order to repair the inner sleeve by the method according to the invention, the types of mortar commonly used for similar purposes are considered. The rotational speed of the apparatus can be set dependently upon the composition of the mortar and the structure and composition of the channel wall.
As can be seen from
By rotating the section of pipe 10 the mortar is centrifuged out of the spaces 13 and applied evenly to the worn inner wall 6′ of the sleeve 6 over the entire channel length, the centrifuging effect contributing to the mortar being able to adhere securely to the inner wall 6′ and the cavity 14 that is formed in between. In order to increase this centrifuging effect, it is advantageous if the blades 11 are slightly convexly curved in the direction of rotation of the section of pipe 10 so that the mortar can be pushed out over the outer edges 11′ that are formed, and these edges 11′ having a cutting effect.
The blades 11 that rotate with the section of pipe 10 also serve to wipe away the excess mortar and to calibrate the casting channel of the inner sleeve without the channel wall being damaged thereby. This also applies when removing the apparatus because then the section of pipe 10 that continues to rotate executes a helical movement that significantly supports the removal process.
Advantageously, these spaces 13 of the mortar dispenser 9 are dimensioned such that a pre-determined amount of mortar can be poured into the latter, for example by hand, the amount of mortar corresponding approximately to the cavity 14 formed between the mortar dispenser and the inner wall of the sleeve so that this wiping away of the excess mortar is made possible. These spaces 13 are therefore filled with mortar such that this mortar is poured in so that it is approximately flush with the outer circumference of the blades 11 and is evenly distributed here.
The sleeve repair method according to the invention is particularly suitable for casting facilities in which the maintenance and preparation of the slide closure of the ladles is carried out centrally by means of a robot in a maintenance station—the so-called ladle position.
In
The apparatus according to the invention can readily be designed differently than in the exemplary embodiment described. It is only essential that it functions as described above.
The sleeve repair method according to the invention is of course also suitable for other sleeves that are fastened in a refractory vessel lining and are subjected here to a large amount of wear, such as for those, for example, in a tap of a converter, an electric furnace or in a tundish. Perforated bricks, sleeve inserts, recovery nozzles or sleeve-shaped sprayed channels as sleeves could also be repaired by the method according to the invention.
However, the method is particularly advantageously suitable for repairing the inner sleeves of casting ladles because it offers the possibility of repairing the inner sleeve quickly with each plate change in the course of the automation of the casting operation and so of reducing the requirement for new inner sleeves. The cleaning of the perforated brick otherwise required when changing a sleeve is no longer necessary. The wear of the perforated brick is reduced, and no troublesome fusions occur.
The invention is sufficiently displayed by the exemplary embodiments described above. However, it could also be illustrated by other variants. A refractory replacement spout fastened in the mechanism of a slide closure or the like could thus also be repaired by the method according to the invention.
Instead of blades, other forms of means delimiting the spaces, for example thread-like elevations, could also be provided in the pipe section of the mortar dispenser.
In principle, this mortar could also be conveyed onto the inner wall of a sleeve by pushing to the outside, for example by means of a cylindrical, inflatable balloon-like body or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 00243/15 | Feb 2015 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/078719 | 12/4/2015 | WO | 00 |
