GB2139924A

GB2139924A - Producing powder filled tube

Info

Publication number: GB2139924A
Application number: GB08412401A
Authority: GB
Inventors: Anthony Gerald Cooper; William Henry Tomlinson
Original assignee: FULTON
Current assignee: FULTON
Priority date: 1983-05-18
Filing date: 1984-05-15
Publication date: 1984-11-21
Also published as: GB2139924B; GB8412401D0

Abstract

An apparatus for producing powder filled tube comprises means including a metering conveyor 15, a blender 17, a conveyor 14 and a nozzle 13 for feeding a metered amount of powdered material into a channel section 10; and means e.g. forming rolls 18 or drawing dies and welding means 20 for closing the channel section to form a powder filled tube and reducing the tube by reducing rolls 21 or drawing dies to compact the powder therein. The amount of powdered material fed into the channel section is varied to maintain the force required to reduce the tube, within specified limits, by control means 25 connected to torque controllers 26 and motors 22, and the variable speed conveyor 14. The channel 10 is formed for metal strip by rolls 11. <IMAGE>

Description

SPECIFICATION Powder filled tubes This invention relates to powder filled tubes and in particular to the apparatus for forming and filling the tubes.

When manufacturing steel, materials in powder form are added to the molten metal in a crucible. It is extremely difficult to add these powdered materials in loose form, as they tend to get scattered about. It has been found convenient to add the powdered material to the molten metal, packed into a tube. The tube which contains a controlled amount of additive per unit length, may be fed right into the molten metal. The tube itself may be formed from steel or from a material which also forms an additive to the molten metal.

Welding electrodes may also be formed as a closed tube filled with a core of powdered flux.

Such powder filled tubes may conveniently be formed on a tube forming mill, in which flat sheet is formed into a channel section. Powdered material is then introduced into the channel section and the channel is closed to form a tube. The abutting edges of the strip are then welded together and the welded tube is reduced to compact the powder.

In such mills, it is necessary to compact the powder sufficiently, so that it will remain in the tube, when the powder filled tube is being handled.

However, if the tube is overfilled, there is a high risk that the reducing section of the mill may be damaged or the tube may burst.

With the inoculating tube for steel manufacture and welding electrodes, it is necessary that the tube contains a metered amount of powdered material, at least within manufacturing tolerances. The powder is therefore normally fed into the channel section by a suitable metering means. However, the powdered materials involved are normally of varied particle size and even using a blender, it is difficult to accurately meter the amount of powder fed into the channel section. Furthermore, because of manufacturing tolerances in the strip, it is necessary to vary the speed of the strip through the forming section of the mill and also the speed of the welded tube through the reducing section.

According to one aspect of the present invention, an apparatus for producing powder filled tube comprises; a variable metering device by which powder material is fed into a channel section, closing means by which the longitudinal edges of the channel section are brought together to form a tube and a reducing section in which the diameter of the tube is reduced and the powder therein compacted; said reducing section including at least one reducing station, means being associated with that reducing station for monitoring the force required to reduce the powder filled tube as it passes through the station and for controlling the variable metering device, so that the amount of powder fed into the channel section may be varied to maintain the reducing force required at that station, within specified limits.

According to a further aspect of the present invention, a method of producing powder filled tube comprises; forming a channel section, metering powdered material into the channel section, closing the channel section to form a powder filled tube and reducing the powder filled tube to compact the powder therein, the force required to reduce said tube being maintained within predetermined limits by controlling the amount of powder material that is fed into the channel section.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawing which illustrates diagram metically, in plan view, an apparatus according to the present invention.

The apparatus illustrated is a rolling mill, in which various sections are arranged in line, so that strip metal 10 may be fed in at one end and tube 24 filled with compacted powdered material, emerges from the other end.

First in line, is a forming section. This section comprises a series of pairs of forming rolls 11, which are driven by a DC motor (not shown). The rolls 11 are profiled so that, as the strip metal 10 is fed between the rolls, it is gradually formed into a U-shaped channel section 12.

After the rolls 11, a nozzle 13 is provided for delivering powdered material into the channel section 12. The powdered material is fed to the nozzle 13, at a metered rate, by a variable speed metering conveyor 14. A conveyor 14 feeds the powdered material from a store bin 16 to a blender 17. This blender 17 ensures that the distribution of particle size of the powdered material is substantially uniform, before it is delivered to the metering conveyor 15.

Two further pairs of forming rolls 18, follow the nozzle 13. These rolls 18 are profiled to close the longitudinal edges of the channel section 12, so that they butt and form a tube 19.

Next in line is a DC, or other appropriate type of welder 20, which serves to weld together the butted edges of the strip.

A reducing section follows the welder 20. This reducing section comprises a series of pair of reducing rolls 21, one roll of each pair being driven by an individual DC motor 22. These rolls 21 are profiled so that, as the welded powder filled tube 23 passes through each pair of rolls, its external diameter is gradually reduced and powder within the tube 23 is compacted.

As the tube diameter is reduced, it increases in length and consequently, each pair of reducing rolls 21 must rotate at a faster peripheral rate than the preceding pair. The speed of rotation of the first pair of reducing rolls 21 must also related to the speed of the forming rolls 11. The speed of the DC motors 22 and the motor driving the forming rolls 11, may be controlled by varying the DC currents by which they are driven. Each of the motors 22 and the motor driving the forming rolls 11 are interconnected through suitable control means (not shown), so that the necessary variation in speed between the motors 22 may be maintained automatically, even though the speed of the motor driving the forming rolls 11 may vary, to accommodate manufacturing toler ances in the incoming strip 10.

Each of the DC motors 22 is also provided with a DC torque controller 26, by means of which, for a given speed, the current may be varied to vary the torque on the rolls 21 by up to 10%, in order to accommodate, within manufacturing tolerances, variations in, for example, the dimensions, mass and mechanical properties of the strip and powdered materials.

These DC torque controllers 26 are also arranged to provide an output signal corresponding to the variation in torque. Each controller 26 is connected via suitable control means 25 to the motor (not shown) driving the variable speed conveyor 14, so that if the torque on any pair of rolls 21 starts to increase, the amount of powdered material delivered by the conveyor 14 may be reduced to a corresponding degree. Alternatively, if the torque of any of the pairs of rolls 21 starts to decrease, the amount of powdered material delivered by the conveyor 14 may be increased correspondingly. In this manner, the torque on the rolls 21 may be automatically maintained between the tolerance limits, thus avoiding under compaction of the powdered material. at one extreme, or damage to the rolls 21 at the other.

After leaving the reducing rolls 21, the tube 24 filled with compacted powdered material may be passed through further processing stations comprising, for example, further rolls for a final sizing operation and/or an annealing furnace which operates at a temperature which will not adversely affect the properties of the powdered material cores of the tube. Finally, the tube 24 filled with compacted powdered material may be coiled or cut to required lengths.

Various modifications may be made without departing from the invention. For example, drawing dies may be used in place of the forming rolls 18 or reducing rolls 21, in the embodiment described above. Where drawing dies are used in the reducing section, the welded tube may be drawn through the dies using for example, a traction drum. The torque applied to this drum may be monitored and used to control the feed of material into the channel section, in a manner similar to that described above. The number of pairs of rolls or drawing dies used at each section may be varied as required depending on, for example, the properties of the strip, the final size of the tube and the degree of compaction required.

Claims

1. An apparatus for producing powder filled tubes comprising; a variable metering device by which powder material is fed into a channel section, closing means by which the longitudinal edges of the channel section are brought together to form a tube and a reducing section in which the diameter of the tube is reduced and the powder therein compacted; said reducing section including at least one reducing station, means being associated with that reducing station for monitoring the force required to reduce the powder filled tube as it passes through the station and for controlling the variable metering device, so that the amount of powder fed into the channel section may be varied to maintain the reducing force required at that station, within specified limits.

2. An apparatus according to Claim 1 in which the variable metering device comprises; a variable speed metering conveyor which feeds the powder material, via a nozzle, into the channel section.

3. An apparatus according to Claim 2 in which the variable metering device includes a blender which ensures that a powder of substantially uniform particle size distribution is fed onto the variable speed metering conveyor.

4. An apparatus according to any one of Claims 1 to 3 in which the reducing section includes at least one pair of reducing rolls, one of the or each pair of rolls being driven by a variable speed direct current motor, said motor having a direct current torque controller by means of which, for a given speed, the current may be varied to vary the torque applied to the rolls within predetermined limits.

5. An apparatus according to Claim 4 in which a plurality of pairs of reducing rolls are provided in the reducing section, means being provided to control the speeds of direct current motors driving the reducing rolls, such that the speed is increased as the tube progresses through the reducing section, thereby accommodating the axial increasing length of the tube as it is reduced.

6. An apparatus according to any one of Claims 1 to 3 in which the reducing section includes a drawing die, a traction drum being provided to pull the tube through the die, said traction drum being driven by a variable speed direct current motor, said motor having a direct current torque controller by means of which, for a given speed, the current may be varied to vary the torque applied to the drum, within predetermined limits.

7. An apparatus according to any one of Claims 4 to 6 in which the or each direct current torque controller is arranged to provide a signal corresponding to the variation in torque, this signal being used to control the speed of the variable metering device so as to reduce the amount of powder delivered to the channel section if the torque increases and increase the amount of powder delivered to the channel section if the torque decreases.

8. An apparatus according to any one of the preceding claims in which the closing means comprises means for butting together the longitudinal edges of the channel section and for welding the butted edges.

9. An apparatus according to any one of the preceding claims in which a forming section is provided before the metering device, this forming section comprises a series of pair of rolls by which the channel section is formed from strip material.

10. A apparatus according to Claim 9 in which the forming rolls are driven by a variable speed direct current motor, this motor being coupled to the motors in the reducing section and the variable metering device so that the speeds of the motors may be synchronised as required.

11. An apparatus for producing powder filled tube substantially as described herein with reference to and as shown in the accompanying drawings.

12. A method of producing powder filled tube comprising forming a channel section, metering powdered material into the channel section, closing the channel section to form a powder filled tube and reducing the powder filled tube to compact the powder therein, the force required to reduce said tube being maintained within predetermined limits by controlling the amount of powder material that is fed into the channel section.

13. A method according to Claim 12 in which the longitudinal edges of the channel section are butted and welded together.

14. A method of producing a powder filled tube substantially as described herein.