AT520352A1 - Method for producing an endless belt with a band body comprising at least one sheet of duplex steel - Google Patents

Abstract

The invention relates to a method for producing an endless belt (1, 1a) with a belt body (5) comprising at least one sheet (2) of duplex steel, wherein the belt body (5) is welded by welding at least two edges (7a, 7b) of the at least one sheet (2) is formed together into a closed ring, wherein the welding of the at least two edges (7a, 7b) of the at least one sheet with a plasma welding process, wherein at least one plasma jet (19a, 19b) is generated, with which the duplex steel in the range a weld to be produced is melted.

Description

The invention relates to a method for producing an endless belt with a band body comprising at least one sheet of duplex steel, wherein the band body is formed by welding at least two edges of the at least one sheet together to form a closed ring.

Moreover, the invention relates to an endless belt with a band body comprising at least one sheet of duplex steel, wherein the belt body has at least one weld seam, by which the belt body is connected to a closed ring

By duplex steel is meant in the present context a steel having a two-phase microstructure composed of a ferrite matrix with austenite islands.

In the production of endless strips of duplex steel, there may be the problem that it may come with a welding of longitudinal or end edges for the production of the endless belt to a delay of the endless belt.

Another problem of conventional production methods is that in conventional methods, substantial changes in the microstructure in the region of the weld can occur with respect to the microstructure of the rest of the strip body, which leads to an increased susceptibility to corrosion in the region of the weld and, subsequently, to a mechanical weakening of the weld Endless tape can come.

It is therefore an object of the invention to enable the creation of an endless belt of duplex steel, which is characterized by a low distortion and good

Corrosion properties in the weld area and a high weld strength distinguishes.

This object is achieved by a method of the type mentioned in the present invention, that the welding of the at least two edges of the at least one sheet with a plasma welding process, wherein at least one plasma jet is generated, with which the duplex steel is melted in the region of a weld to be produced.

Due to the high energy density and the high convergence of the plasma jet, a very high energy concentration results in the area of the weld, whereby high welding speeds and a significantly reduced distortion can be achieved compared with conventional production methods of endless strips of duplex steel. In addition, it has been found that the method according to the invention has only slight changes in the microstructure of the welded seam in comparison to the base material and no contamination of the base material.

In order to close the band body to form a closed ring, the at least two edges can be front edges of two free ends of the at least one sheet and placed in a step ii) preceding the welding in an at least partially abutting position.

According to an embodiment, which allows the production of endless strips of any width of duplex steel, the band body may be formed of at least two sheets of duplex steel, wherein in a step ii) previous step i) longitudinal edges of the at least two sheets placed in an at least partially abutting position and welded together.

Another variant for the production of endless belts of any width of duplex steel, which is also characterized by a high mechanical strength in the tape longitudinal direction, is that the tape body is constructed of at least egg nem subband made of duplex steel, which is narrower than the endless belt, said at least a sub-band is connected by means of a helical circumferential weld to the endless belt.

According to an advantageous variant of the invention, it can be provided that at least one plasma torch is arranged opposite an impact region of the at least two edges, wherein the plasma jet is generated by means of the at least one plasma torch and directed to the joint region of the at least two edges.

In a further development of the invention, which generates a particularly symmetrical weld both on an inner side and on an outer side of the endless belt, at least two plasma torches can be used, the at least two plasma torches being arranged on opposite sides of the joint region and generating at least one plasma jet in each case in which the plasma jets generated by the at least two plasma torches melt the duplex steel from one another, facing one another, from mutually opposite surfaces of the belt body.

It has proven to be particularly advantageous with regard to the reduction of a distortion when the plasma jet at a surface of the at least one metal sheet produces a temperature between 10,000 ° C. and 12,000 ° C.

It is advantageous in terms of achieving only a slight change in the microstructure in the region of the weld, when the plasma jet at a speed of 50 mm / min - 2,000 mm / min is moved relative to the surface of the at least one sheet or vice versa.

To achieve an optimum energy concentration on the surface of the belt body during welding, a plasma nozzle with a diameter between 0.4 mm - 5 mm can be used to limit a diameter of the plasma jet. It has been found that it is particularly advantageous to achieve the desired result when the plasma nozzle is placed at a distance of 0.5 mm - 50 mm to the surface of the belt body.

To generate the plasma jet, according to a preferred variant of the invention, a welding current having a current intensity between 0.5 A and 400 A can be used. To generate the plasma jet, a plasma gas may be used, with between 0.1 l / min - 6 l / min of plasma gas flowing through the plasma torch.

According to an advantageous variant, which is characterized by a weld with a high mechanical strength, it can be vorgehsehen that the at least two edges are connected in sections with a first weld, wherein after reaching a predetermined length of the first weld or after reaching a predetermined Time of the welding operation is interrupted and the welding operation is restarted at a point that lies on the first weld, and a second weld is generated, which extends beyond an end point of the first weld, wherein the first and the second weld partially overlap.

In addition, it is also possible that the at least two edges are continuously welded together without interrupting the welding process. This variant of the invention is characterized mainly by a very low delay.

The above object can also be achieved with an endless belt of the type mentioned in the present invention that the band body between 20% - 35% Cr, in particular 25% - 32% Cr, and 1% - 8% Ni, in particular 7% -. 7 , 5% Ni, wherein the at least one weld has the same chemical composition as the rest of the tape body and has a ferrite to austenite ratio of between 0.4 and 2.3.

The endless belt according to the invention is distinguished not only by a high corrosion resistance and very low residual stresses, but also by a high mechanical strength.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

In each case, in a highly simplified, schematic representation:

Fig. 1 is a perspective view of an endless belt according to the invention;

Fig. 2 is a section along the line II-II in Fig. 1;

Fig. 3 is a plan view of an open band body of an inventive Shen endless belt;

4 shows a plan view of a surface section of a further variant of an endless belt according to the invention;

Fig. 5 shows an apparatus for producing an endless belt according to the invention and

Fig. 6 is a plan view of a surface portion of a belt body during the manufacture of the endless belt according to the invention.

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and these position information in a change in position mutatis mutandis to transfer to the new location.

According to FIGS. 1 and 2, a first variant of an endless belt 1 according to the invention has a belt body 5 produced from a sheet 2 of duplex steel. The sheet 2 is connected at frontal free ends by means of a transverse weld 6 to form a closed ring, so that a band outside 3 and a band inside 4 are formed. The sheet 2 may for example be between 1 m and 200 m long and between 0.5 m and 2 m wide and have a thickness between 0.3 mm to 2.5 mm.

At this point, it should be noted that the band body 5 of the endless belt 1 can also be formed by a plurality of individual pieces of sheet metal 2 of any width, which are connected to each other by transverse or oblique to a longitudinal extension of the endless belt 1 transverse welds 6 to an endless belt 1 of any width. Such an endless belt 1 may for example have a width of up to 10 m or more.

The duplex steel has a two-phase structure preferably with a ratio of ferrite to austenite between 0.4 and 2.3, in particular of 1. The band body 5 has between 20% - 35% Cr, in particular 25% - 32% Cr, and 1% - 8% Ni, in particular 7% - 7.5% Ni on.

The weld 6 has the same chemical composition as the rest of the belt body and has a ratio of ferrite to austenite of between 0.4 and 2.3. What has just been said for the weld 6 also applies to the welds 10, 11 and 16 mentioned in the exemplary embodiments described below.

The following are some examples of possible duplex steels, but to which the invention is not limited. Thus, for example, the duplex steel used may be a super duplex steel, for example X 2 CrNiMoN 25-7-4 with the EN number 1.4410. According to this embodiment, the material of the belt body has the following composition: C <0.030%, Si <0.8%, Mn <1.2%, P <0.025%, S <0.015, Cr = 25%, Ni = 7%, Mo = 4%, N = 0.3%.

Alternatively, the duplex steel may, for example, also be a steel with the EN number 1.4658. This steel has the following composition: C <0.030%, Si = 0.3%, Mn = 1.0%, P <0.035%, S <0.010, Cr = 27%, Ni = 6.5%, Mo = 4.8% or C 0.03%, Si 0.5%, Mn £ 1.5%, P <0.035%, S <0.01%, Cr = 27%, Ni = 6.5%, Mo = 4.8%, N = 0.4%, Co = 1.0%.

For example, according to another embodiment, the duplex steel of the belt body may also be a duplex steel of the following composition: C <0.030%, Si <0.8%, Mn <1.5%, P <0.035%, S <0.010, Cr = 32% , Ni = 7%, Mo = 3.5%, N = 0.5%.

The above statements on the duplex steels apply equally to all exemplary embodiments.

According to the variant shown in Fig. 3, the band body 5 may also comprise a plurality of sheets 2, 8, 9 of duplex steel, which may be connected to each other in the longitudinal direction of the belt body 5 extending longitudinal welds 10, 11. After production of the band body 5 from the sheets 2, 8, 9, the band body 5 can be closed to the endless belt 1 by welding the frontal free edges 7a, 7b.

As can be seen from Fig. 4, the endless belt 1a but can also be constructed from a sub-band 13 of duplex steel. The sub-band 13, which is narrower than the endless belt 1a, is connected by means of a helical circumferential weld 16 to the endless belt 1a. At the outer edges 14, 15 of the endless belt 1a subsequent regions of the sub-strip 13 are cut off, so that opposite outer edges 14, 15 of the endless belt 1a parallel to each other.

The sub-band 13 may, for example, have a thickness of 0.3 mm to 3.5 mm, in particular of 0.8 mm to 1.2 mm, and at least a width of between 300 mm and 1000 mm. The produced endless belt 1a itself can have, for example, a width between 700 mm and 5,000 mm. The circumferential length of the endless belt 1a can also vary and be for example between 3 m and 50 m.

In order to achieve the desired length and width of the endless belt 1a, the sub-band 13 is correspondingly helically juxtaposed so that abutting portions of the longitudinal edge along a helical line. Then the abutting sections are welded together along the longitudinal edge.

The weld 16 is inclined in the longitudinal direction of the endless belt 1a and encloses with a longitudinal center plane 12 of the endless belt 1a an angle α. The angle α can be, for example, in a range of 1 ° to 25 °, in particular of 6 ° to 9 °.

As can be seen from FIG. 5, the welding of the two edges 7a, 7b of the sheet 2 or the production of the welds 6, 10, 11 and 16 takes place by means of a plasma welding process. Here, a plasma jet 19a, 19b is produced, with which the duplex steel is melted in the region of a weld seam 6, 10, 11, 16 to be produced.

In this case, at least one plasma torch 17, 18 for generating the plasma jet 19a, 19b is arranged opposite to an abutting region of the edges 7a, 7b to be connected to one another. The plasma jet 19a, 19b is directed towards the abutting region of the at least two edges 7a, 7b.

As further shown in Fig. 5, instead of just a single plasma torch 17 or 18, two plasma torches 17, 18 may be used which are disposed on opposite sides of the butt portion of the edges 7a, 7b. The two plasma torches 17, 18 each generate a plasma jet 19a, 19b. The plasma jets 19a, 19b generated by the two plasma torches 17, 18 melt the duplex steel from converging surfaces of the belt body 5 toward each other. When using two opposing plasma torches 17, 18 plasma beams 19a, 19b are preferably produced with identical parameters or properties.

The following explanations apply both to embodiments with two plasma torches 17, 18 and to those with only a single plasma torch 17 or 18.

The plasma jet 19a, 19b generates at a surface of the weld or the belt body 5, a temperature between 10,000 C ° - 12,000 ° C.

The plasma jet 19a, 19b can be moved at a speed of 50 mm / min -2,000 mm / min with respect to the surface of the at least one sheet 2 or the belt body 5 or vice versa. When two plasma torches 17, 18 are used, the movements of the two plasma jets 19a, 19b are synchronized with the two plasma jets 19a, 19b moving in such a way that they always melt the same section of the joint area of the edges 7a, 7b from different sides.

To limit a diameter of the plasma jets 19a, 19b, plasma nozzles 20, 21 having a diameter of a plasma exit opening 20a, 21a between 0.4 mm - 5 mm can be used.

The plasma nozzle 20, 21 can be arranged at a distance of 0.5 mm - 50 mm to the surface of the belt body 5.

To generate the plasma jet 19a, 19b, a welding current with a current intensity between 0.5 A - 400 A can be used. In addition, to generate the plasma jet 19a, 19b, a plasma gas is used, wherein between 0.1 l / min - 6 l / min of the plasma gas flow through the respective plasma torch 17, 18.

The current intensity of the welding current is proportional to a flow rate of the plasma gas. Thus, for example, to obtain a weld 6, 10, 11, 16 with a width of 0.5 mm - 5 mm and a sheet thickness of 1 mm, a welding current between 0.5 A - 50 A and a flow rate of the plasma gas of 0.1 l / min - 2 l / min. In order to achieve a weld 6, 10, 11, 16 with a width of 0.5 mm - 5 mm and a sheet thickness of 2 mm, the welding current, however, between 5 A and 200 A, wherein the flow rate of the plasma gas between 0.2 l / min and 4 l / min. For sheet thicknesses above 2 mm, to achieve a weld 6, 10, 11, 16 with a width of 0.5 mm - 5 mm, the welding current and the flow rate of the plasma gas between 10 A and 400 A and 0.3 l / min and 6 l / min. For example, pure argon could be used as the plasma gas. Alternatively, however, the plasma gas could also have the same chemical composition as a protective gas used. As a protective gas, for example, a gas with 98% argon and 2% nitrogen could be used.

As can be seen from FIG. 6, welding can be carried out discontinuously according to a variant of the invention. Here, the edges 7a, 7b are first connected to each other with a first weld. After reaching a predetermined length of the first weld or after reaching a predetermined time, the welding process is interrupted at a point P1. Thereafter, the welding operation is restarted at a point P2 that lies on the first weld, and a second weld is created that extends beyond the end point P1 of the first weld. As a result, the first and second welds partially overlap. The direction in which the welding takes place or in which the weld 6 is generated, is indicated in Fig. 6 with an arrow. In this direction, either the plasma torches 17, 18 or the belt body 5 are moved relative to the plasma torches 17, 18.

For the sake of order, it should finally be pointed out that for a better understanding of the construction, elements have been shown partially unevenly and / or enlarged and / or reduced in size.

REFERENCE SIGNS LIST 1 endless belt 1a endless belt 2 metal sheet 3 belt outside 4 belt inside 5 belt body 6 transverse weld seam 7a edge 7b edge 8 sheet 9 sheet 10 weld 11 weld 12 level 13 subband 14 outer edge 15 outer edge 16 weld 17 plasma torch 18 plasma torch 19a plasma jet 19b plasma jet 20 plasma nozzle 20a plasma exit opening 21 Plasma nozzle 21a plasma outlet opening

Claims (15)

claims 1. A method for producing an endless belt (1, 1a) with a belt body (5) comprising at least one sheet (2) of duplex steel, wherein the belt body (5) by welding at least two edges (7a, 7b) of the at least one sheet (2 ) is formed together into a closed ring, characterized in that the welding of the at least two edges (7a, 7b) of the at least one sheet with a plasma welding process, wherein at least one plasma jet (19a, 19b) is generated, with which the duplex steel in Area of a weld to be produced is melted. 2. The method according to claim 1, characterized in that the at least two edges (7a, 7b) end edges of two frontal free ends of the at least one sheet (2) and placed in a preceding welding step ii) in an at least partially abutting position become. 3. The method according to claim 2, characterized in that the band body (5) from at least two sheets (8, 9) is formed from duplex steel, wherein in a step ii) the preceding step i) longitudinal edges of the at least two sheets (8, 9) be placed in an at least partially abutting position and welded together. 4. The method according to claim 1, characterized in that the band body of at least one subband (13) is constructed of duplex steel, which is narrower than the endless belt (1a), wherein the at least one subband (13) by means of a helically circumferential weld seam (16 ) is connected to the endless belt (1a). 5. The method according to any one of claims 1 to 4, characterized in that an impact region of the at least two edges (7a, 7b) opposite at least one plasma torch (17, 18) is arranged, wherein the plasma jet (19a, 19b) by means of at least one Plasma torch (17, 18) is generated and directed to the joint area of the at least two edges (7a, 7b). 6. The method according to any one of claims 1 to 5, characterized in that at least two plasma torches (17, 18) are used, wherein the at least two plasma torches (17, 18) are arranged on opposite sides of the joint area and in each case at least one plasma jet ( 19a, 19b), wherein the plasma jets (19a, 19b) generated by the at least two plasma torches (17, 18) melt the duplex steel from one another facing surfaces of the belt body running towards one another. 7. The method according to any one of claims 1 to 6, characterized in that the plasma jet (19a, 19b) generates a temperature between 10,000 C ° - 12,000 ° C on a surface of the at least one sheet. 8. The method according to any one of claims 1 to 7, characterized in that the plasma jet (19a, 19b) is moved at a speed of 50 mm / min -2,000 mm / min with respect to the surface of the at least one sheet or vice versa. 9. The method according to any one of claims 1 to 8, characterized in that for limiting a diameter of the at least one plasma jet (19a, 19b) at least one plasma nozzle (20, 21) having a diameter of a plasma outlet opening (20a, 21a) between 0.4 mm - 5 mm is used. 10. The method according to claim 9, characterized in that the at least one plasma nozzle (20, 21) at a distance of 0.5 mm - 50 mm to the surface of the belt body (5) is arranged. 11. The method according to any one of claims 1 to 10, characterized in that for generating the at least one plasma jet (19a, 19b), a welding current with a current of between 0.5 A - 400 A is used. 12. The method according to any one of claims 5 to 11, characterized in that for generating the at least one plasma jet (19a, 19b), a plasma gas is used, wherein between 0.1 l / min - 6 l / min of the plasma gas through the plasma torch ( 17, 18). 13. The method according to any one of claims 1 to 11, characterized in that the at least two edges (7a, 7b) are connected in sections with a first weld, wherein after reaching a predetermined length of the first weld or after reaching a predetermined time of the welding process is interrupted and the welding operation is restarted at a point (P2) lying on the first weld, and a second weld is produced, which extends beyond an end point (P1) of the first weld, wherein the first and the second weld partially overlap. 14. The method according to any one of claims 1 to 11, characterized in that the at least two edges (7a, 7b) are continuously welded together without interrupting the welding process. 15. endless belt (1) with a at least one sheet (2) of duplex steel having belt body (5), wherein the belt body (5) has at least one weld (6, 10,11, 16), through which the belt body (5) is connected to a closed ring, characterized in that the band body (5) between 20% - 35% Cr, in particular 25% - 32% Cr, and 1% - 8% Ni, in particular 7% - 7.5% Ni comprises wherein the at least one weld (6, 10, 11, 16) has the same chemical composition as the rest of the belt body and has a ferrite to austenite ratio of between 0.4 and 2.3.