Technical Field

The present invention relates to a device for melting metals, usually referred to as a box, which is useful in the field of manufacture and processing of metals, in particular steel. The device is most often located in the casing of an electric arc furnace (Fig.8a and 8b), where it serves as a passageway to the inner part of the furnace where steel is melted by the electric arc.

Background Art

There are known devices located in the casing of an electric arc furnace, which in established terminology are generally referred to as a "box" or "jet-box". This device serves as a passageway to the inner part of the furnace where the steel is melted by the electric arc.

Powerful burners are placed in this device to accelerate the melting of steel. Another reason for its use is to position the burner closer to the melted material and thus increase the efficiency of the burner. It is also possible to use this device as an injection port for steel additives or for temperature measurement and steel sampling. This device is exposed to high temperatures in the furnace and can also be mechanically impaired or punctured by falling scrap. Further damage can be caused by an oxygen stream from the burner itself being reflected from a large piece of scrap metal.

Tube boxes

The older and currently less frequently used so-called box is made of thick-walled tubes arranged side by side and connected at the ends by a fitting. In the end, everything is welded together to form a cooled box with an opening. The whole system must form a cooling loop. This is a known state of manufacture.

• The advantage is the cheap and relatively simple method of manufacture.

• The disadvantage is the limited product range of tubes. This method of manufacture, if used, creates open spaces through which liquid slag can exit from the furnace interior and flood the burner or even flow out of the furnace, thereby endangering other equipment.

Cast boxes

Another method of manufacture is casting of boxes made of pure electroconductive copper. These are copper castings up to 1000 kg in weight in the shape of a bevelled block. This is a known state of manufacture. The disadvantage is the fact that it is very demanding on the copper purity and the capacity of the foundry.

Machined and welded boxes

In most recent times, the manufacture of boxes has been carried out in an extremely demanding and expensive way. Grooves are milled into a thick rolled copper sheet to form the final cooling loop. Again, this is a known state of manufacture

The disadvantage of this method of manufacture is its price, which is up to 3 times higher than in the case of conventional casting.

The advantage is the higher quality of the material due to the use of rolled sheet and the direct contact of the cooling water with the main material, but the service life is not significantly higher than that of cast boxes considering the cost and complexity. Summary of the Invention

This invention relates to a device for melting metals, usually referred to as a box, which is useful in the field of manufacture and processing of metals, in particular steel. It eliminates the disadvantages of the prior art presented by the boxes described above, in particular by addressing the problems outlined below:

• The need to use large copper foundries and complicated technological processes.

• Complicated and expensive machining and complicated welding.

• High consumption of expensive materials such as copper.

• Large loss of heat from the furnace area due to the exposed surface of the box in the furnace.

The subject device according to the present invention consists in a specially designed shape and an internal cooling loop.

• The basic innovation is the shape of the profile, which is derived from a triangle rounded at the top. By this is in fact created a vault that is smoothly linked to the sides of the vault that are integrated into the bottom and the back wall. This results in a much more durable shape than that of the straight-sided box used so far. The back wall then transforms into a rectangle so that this box can be installed in the side wall of the furnace, where it is difficult to create a triangular passage.

• The innovation of the shape reduces the area exposed to heat radiation. This improves cooling and reduces heat loss from the furnace.

• The overall saving in material used for the manufacture of the device makes it possible to produce the device even in smaller factories with the necessary equipment. DESIGN SOLUTION

Ά) Ά device formed by casting:

Standard sand moulded casting technology is used in its production. The device serves as an equivalent replacement for conventionally manufactured boxes. The innovation consists in a compact shape which provides greater resistance to the furnace environment. Another innovation consists in variations of the design. While maintaining the same construction height, we can choose from three design variants.

The cooling circuit is made of thin-walled tube. Cooling loops are designed for the top and the bottom part in order to best cool the most exposed areas.

The device shown in Figs, la to Id is a basic design with two openings for injection ports. On the inside of the front wall there are thermometer wells. The basic shape can be seen from the attached figures.

The second variant is shown in Fig. 2a and 2b. Here, one opening of the injection port can be seen. To save material, the other side is tapered to the smallest possible dimension to save as much material as possible. Otherwise, all shapes are the same as in the basic variant. The injection port can be either in the left-hand or right-hand position.

Another variant of the device is presented in Figs. 3a and 3b, with a tapering to fit into smaller furnaces. However, this device can no longer be equipped with injection ports. The advantage of this design consists in its low weight, therefore, in lower consumption of electroconductive copper.

These Figs, la to Id, 2a and 2b and 3a and 3b are not only for illustrative purposes, but also serve as technical drawings from which the specific shape and side ratios and sizes of the various parts of the device according to the present invention can be abstracted. The advantageous dimensions are as follows: height 750 mm, width 410 mm, depth 491 mm, wherein the inclination of the wall with the opening for inserting the burners from the bottom wall is 50 degrees and the inclination of the axis of the opening from the horizontal plane is also 50 degrees.

B) A device formed by bending and welding sheet metal:

This method uses standard sheet metal bending and welding technology to form a device according to the present invention in the form of a weldment, shown in Figs. 4a and 4b, wherein it consists of two parts, where the casing consists of the back wall, the upper part and the supporting vault, the back wall is connected at the bottom by a strut and constitutes the base part shown in Figs. 5a, 5b and 5c, and the bottom with the front wall constitutes the lower part, shown in Figs. 6a and 6b.

The main innovation consists in the use of a new cooling method. The whole design is made specifically to take advantage of the new way of flow of the cooling liquid, depending on the simplest possible manufacture of the device.

Another kind of innovation is the division of the device - the box - into two parts, as mentioned above. This division has several advantages. It allows better access to the burner, where only the lower part (bottom) with the burner (not shown) need be moved out of the casing. The division further facilitates the manufacture and testing of both parts of the box. The division has an advantage in case of damage caused to one of the box parts, so that it is not necessary to replace the whole box but only the damaged part. Manufacturing is cheaper than that of cast boxes. Its main use is for trial runs when implementing chemical energy with new customers.

The shapes and dimensions of individual boxes correspond to the shapes and dimensions of the cast boxes mentioned in the preceding section. Thus, mutual substitution is possible. The vault at the upper part is used again. A shape is then formed in the front and lower part suitable for inserting the bottom. The inlet and outlet of the cooling water is carried out by means of a longitudinally cut pipe to minimize the pressure loss of the box.

- Casing (the basic part of the device):

This part of the device is manufactured by welding. The two main parts are the supporting part and the cooling channels, which together form the upper cooling loop. The load-bearing part ("supporting vault") is precision-cut sheet metal bent into a U- shape using a press brake. Pre-prepared channels are then welded onto this metal sheet. Furthermore, the casing is equipped with an inlet and outlet for cooling water and a transition corner between the vault and the rectangular back part - See Figs. 5a, 5b and 5c.

- Bottom (the lower part of the device): Again, the same procedure as for the casing is used, where channels are welded onto the bent supporting part. Finally, these channels form the lower cooling loop. The bottom is also equipped with a cooling water inlet and outlet as well as burner holder. See Figs. 6a and 6b.

- The device as a complete unit (includes the casing and bottom mutually connected):

After installing instruments, the bottom is placed on the casing strut and slid into the box until the front wall meets the frame at the front of the casing, and then it is secured by an eccentric lever mechanism. The clearances between the two parts are adjusted for metallurgical operation. They will be fine-tuned after tests in actual operation.

- Shape variants:

Figs. 4a and 4b show a box corresponding in size to the variant according to Figs. 2a and 2b with one opening for the injection port and is usable as a full replacement.

Figs. 7a a 7b show a box identical in height with the box of the narrowed version according to Fig. 3a and 3b, without the injection port, and is usable as a replacement.

TESTS AND ANALYSES

The analyses are carried out for each product separately. After completion of the prototype production, a flow test with pressure measurements is performed.

Practical tests:

- After completion of manufacture The test is carried out at a local supplier. A flow test shall be performed with measurement of inlet and outlet pressures.

- Test in actual operation

In agreement with the operator of the arc furnace, actual deployment into operation is performed. Here the temperatures and pressures at the inlet and outlet of the device are measured. The condition of the device after a specified number of melts is also evaluated.

List of Figures

Fig. la shows an axonometric view of the front part of a device according to the present invention manufactured by casting.

Fig. lb shows a front view of the device according to Fig. 1.

Fig. lc shows a side view of the device according to Fig. 1.

Fig. Id shows an A-A section perpendicular to the vault of the device according to Fig. 1.

Fig. 2a shows an axonometric view of the variant with only one injection opening according to this invention manufactured by casting.

Fig. 2b shows a front view of the variant with one injection opening according to Fig. 2.

Fig. 3a shows an axonometric view of the narrow variant without an injection opening according to this invention manufactured by casting.

Fig. 3b shows a front view of the narrow variant without an injection opening according to Fig. 3.

Fig. 4a shows an axonometric view of the front part of the variant of the device with one injection opening according to the invention manufactured by bending and welding pieces of sheet metal. Fig. 4b shows an axonometric view of the back part of the device comprising a casing and a bottom section connected together and equipped with a single injection opening according to the invention produced by bending and welding pieces of sheet metal.

Fig. 5a shows an axonometric view of the back part of the device casing according to Fig. 4.

Fig. 5b shows a side view of the device casing according to Fig.

4.

Fig. 5c shows a perpendicular section of the vault of device casing according to Fig. 4.

Fig. 6a shows an axonometric view of the back part of the device bottom according to this device produced by bending and welding pieces of sheet metal.

Fig. 6b shows an axonometric view of the front part of the device according to Fig. 4;

Fig. 7a shows an axonometric view of the narrow variant without an injection opening according to this invention produced bending and welding pieces of sheet metal.

Fig. 7b shows an axonometric view of the narrow variant of the device without an injection opening according to Fig. 7a.

Fig. 8a shows an axonometric view of the device according to this invention, i.e., the box located in the furnace.

Fig. 8b shows the cross-section of the box located in the furnace.

Examples of the Embodiments

Example 1

The device with two injection openings 8.as shown in Figs, la to Id, produced by casting, is suitable for large furnaces where it is necessary to supply large amounts of additive materials or where only one such device can be installed. The device comprises a casing comprising a back flat wall 1_1 of rectangular shape, a bottom 6 and an upper part 1, wherein the upper part 1 has a smaller surface area than the bottom 6_, wherein from the back wall 11 and the upper wall 1 there extends a supporting vault 2 provided with reinforcements ' which is adjoined in the lower part of the device by a front wall A_provided with an opening 1_ for mounting a burner and one opening 8 for an injection port, wherein from a side view imaginary vertices of the front wall A and the supporting vault 2 form a triangle. The sides 5 of the vault are smoothly linked to the back wall 1_1, the front wall 4 and the bottom 6, while in a perpendicular section through the vault the imaginary vertices of the back wall 11_and the sides of the vault 5 form a triangle. The back wall 11_includes the inlet and outlet of the upper cooling loop 9 and the inlet and outlet of the lower cooling loop 1_0, wherein these loops 1_0, 1_1 pass through cooling channels 13 in the walls of the casing and the lower part of the device.

The front wall _ contains a thermometer well 12.

Imaginary vertices of the front wall 4_ have an approximately triangular shape in the frontal view, which follows the triangular shape of the vault, whereby the device is symmetrical when viewed from the front.

Example 2

The device as shown in Figs. 2a to 2b with one injection opening is suitable for large furnaces and medium-sized furnaces where it is advantageous to inject material into several places at the same time. This device is identical to the device shown in Example 1, except that from a frontal view the device is asymmetrical due to the provision of only one opening 8 for the injection port.

Example 3

The device without an injection opening as shown in Figs. 3a to 3b is suitable for medium and small furnaces where the additive material is supplied by other means or as a supplement to the previously mentioned devices for the installation of an additional burner.

This device is identical to the device of Example 1, except that it does not include an opening _8 for the injection port.

Example 4

The single-opening injection device as shown in Figs. 4a to 4b, formed by the sheet metal bending and welding method, is designed for large furnaces and medium furnaces as a cheaper replacement for cast boxes.

This device is the same as the device according to Example 1, except that it consists of two mutually connected parts independent of each other, wherein the casing is formed of a back wall 11, an upper part 1 and a supporting vault 2, wherein the back wall 1_1 is connected in the lower part by a strut 1_6, and the casing thus formed constitutes the basic part, further illustrated in Figs. 5a, 5b and 5c, and where the bottom 6 with the front wall A constitute the lower part, shown in Figs. 6a and 6b.

For the purpose of connecting the two parts together, the lower part comprises a lever mechanism 1_5. The lower part further comprises a burner holder 14. Furthermore, in contrast to the device according to Example 1, the lower cooling loop 10 is formed in the lower part.

Example 5

The device as shown in Fig. 7a and 7b is the same as the device shown in Example 4, except that it does not include the injection port opening 8_and is suitable for medium and small furnaces as a lower cost replacement for cast boxes.

Example 6

A device according to any of the above examples shown in Fig. 8a and 8b seated in a furnace.

Industrial Utilization

The invention is industrially exploitable in the metallurgical industry to produce metals more efficiently, particularly in furnaces.

List of Reference Marks

1 - UPPER PART

2 - SUPPORTING VAULT

3 - REINFORCEMENT

4 - FRONT WALL

5 - VAULT SIDE

6 - BOTTOM

7 - OPENING FOR BURNER MOUNTING

8 - OPENING FOR INJECTION PORT

9 - UPPER COOLING LOOP - INLET/OUTLET

10 - LOWER COOLING LOOP - INLET/OUTLET

11 - BACK WALL

12 - THERMOMETER WELL

13 - COOLING CHANNEL

14 - BURNER HOLDER

15 - LEVER MECHANISM

16 - STRUT