HU179999B - Apparatus for producing seamless tubes - Google Patents

Abstract

A plant for manufacturing seamless steel tubes has a heating furnace for heating ingots which may be of square cross section, a piercing press for piercing the ingots to produce pierced circular section blanks, at least one roughing push bench immediately beyond and in alignment with the piercing press and a finishing push bench for producing a semi-finished tubular product suitable for subsequent skew-rolling.

Description

Apparatus for making seamless pipes

2

The present invention relates to an apparatus for producing seamless pipes, in particular steel pipes, comprising a heating furnace, a punching press and at least one sliding bench, as well as devices for releasing or dissolving the mandrel from the pre-pressed tubing.

The equipment outlined above is the so called. they are working on a treadmill process which has evolved over many years from the Ehrhardt process. The latter process makes it possible to produce a seamless hollow body of circular cross-section called a perforated body. Thus, it is possible to use the cheap square semiproduct as a starting material for tubing and thus not to refer solely to circular semiconductor, which is otherwise a requirement in the life of inclined tubular seamless tubing.

In the Ehrhardt process, a cylindrical inner die is molded into a semiconductor of a hot cross section temperature; the diameter of the semi-finished product is approx. equals the inside diameter of the sticker. A punch mandrel is then pressed into the workpiece in the center of its longitudinal axis, thereby filling the cavity between the initially flat outer surfaces of the workpiece and the cylindrical peripheral surface of the die within the material. In this way, a perforated body of circular cross-section is obtained which is closed at one end with a bottom portion.

Practical experience has shown that the ratio of the length of the punched body to that of the punch 5 cannot be selected to be greater than 8: 1, since the punch will bend at the side during injection and thus the wall thickness of the punched body will not be economical. from the point of view of 10 more bearable expenses cannot be eliminated. As a result, the perforated body is relatively short and thick-walled, and the pre-extruded tube can only be produced by relatively large stretching. The Ehrhardt process also used a tensile press to increase the above-mentioned length to diameter ratio from 8: 1, although not to a large extent, since, in order to achieve a uniform wall thickness, it was approx. A ratio of 6: 1 was chosen so that the subsequent drawing operation produced a punctured body with a length / diameter ratio of only slightly above said 8: 1.

In the case of a rectangular semi-finished product, the ratio of the inside diameter of the die 25 to the diameter of the punch mandrel is approx. 2: 1 as this will fill the voids originally between the die and the workpiece. Higher diameter ratios would lead to the sticker not being filled by a perforated body other than circular cross-section and this would

-1179999 would cause greater stretchability behind the punch press. If the ratio is lower, the consequence would be that the material would expand upstream of the piercing mandrel pressure, which, while providing the desired length of the perforated body, would also result in uneven wall thickness if the length of the perforated body relative to the perforated mandrel diameter its size significantly exceeds the 8: 1 value.

It follows from the above-mentioned relationships that the traditional Ehrhardt process produces well-defined dimensions for the punched body which cannot be crossed. This also results in the limitation of the amount of material that can be used as a workpiece.

The aforementioned tension press has evolved into a known push bench in which a pierced body is moved through a plurality of tensioning rings located one behind the other by means of a mandrel, and the inner mandrel is then stretched as the wall thickness decreases. Here, the limitations of the size and weight of the punched piece are not disturbing, since the performance of the pusher is the limit of the whole process. Slip friction in calibers requires high thrust, which is limited in design. The limited thrust only allows the use of a limited number of calibers, i.e. tensile rings, which simultaneously apply to the perforated body. In order to keep the number of calibers working at the same time within the range that does not make the thrust too high, the spacing between the calibers should be chosen at an appropriate size, which would require overly long bearings, which would require a very long stroke. Because the sliding speed due to the slip friction in the calibers is only approx. 2.5 meters / second, this results in a restriction on tube length, since at relatively low feed rates and relatively long strokes, the punctured body and the mandrel are in contact for a long time, causing the mandrel to overheat and the punch to cool down, and consequently, during the forming operation and the extraction of the mandrel from the finished pre-extruded tube, there are significant wear phenomena. The necessary restriction on the length of the pre-pressed tube thus eliminates the need for a heavier punched body.

This situation has been altered by the use of tensile cavities formed from the roller rows, since this has greatly reduced or eliminated slip friction in the calibers and significantly reduced the thrust required for each caliber so that more calipers can be applied at the same total thrust. This also significantly shortened the distance between each caliber. The smaller stroke length required in this way and the more than twice sliding velocity of the roller pulling cavities 2 for roller calipers provided a significant reduction in the contact time between the punched body and the mandrel. Consequently, the limits of the overall process with respect to the length of the pre-extruded tube and performance were no longer determined by the sliding bench, but by the aforementioned limits on the size of the punched body and thus the amount of material that could be inserted. 10 Particularly at high wall thicknesses, they are very short pre-pressed tubes which are uneconomical for production and further processing.

In order now to make the sliding bench 15 economical even at higher wall thicknesses, an option has been explored to increase the weight of the perforated body. This was accomplished by the punching method described in DE-PS 1 298 494, in which a step punch was pressed into the workpiece, which was located in a downwardly tapered bottle-shaped die. The majority of the workpiece is thus punched with a diameter larger than the inside diameter required for the finished pre-pressed tube 25. This means that they may have started from a larger semi-finished cross-section, and the insert weight may have been higher accordingly. Essentially, the smaller diameter of the new mandrel corresponded to the diameter of the old mandrel 33. The punctured portion of the punched body serves to receive the respective internal centering tool, which is used for pre-stretching and pushing the tension press. With the stepwise punching described 35, the possible increase in insert weight results from the ratio of the steps of the punch mandrel diameter. This ratio is decisive for calculating the available deposit weight increase, which is definitely above 40%.

After stepping, only the short centering portion of the piercing mandrel 40 is passed through. its diameter corresponds to the inside diameter of the pre-extruded tube, and the actual diameter of the piercing mandrel can be freely chosen, so that the insert weight of the perforated body is practically independent of the mandrel diameter and thus of the larger diameter of the pre-extruded tube. and punched bodies of greater weight can be produced, so that the limits of the push bench process are again defined by the push bench.

These limits depend on various factors. Above all, the spacing of the roller racks has been extensively experimented and optimized so that further shortening of the current stroke length of 55 is hardly possible. In addition, increasing the thrust speeds does not appear to be very feasible, since the required thrust requires a relatively large rack of rack and other propulsion elements, which results in very high acceleration and retardation forces, which barely permit further increase of the thrust speed. Since calibers are already fitted with rollers and the shape and dimensions of the caliber apertures are also optimized, no further reduction in thrust is expected,

-2179999 so that weight reduction, which would again allow the thrust speed to be increased, cannot be achieved. Because the length of the rack bed for a given pre-pressed tube cannot be shortened for aforesaid reasons, nor can the pushing speed be increased, so a contact length between a mandrel and a pre-pressed tube is also given for a given pre-pressed tube. shortened. Since the contact time, due to the cooling of the pre-extruded tube and the heating of the mandrel, cannot be prolonged arbitrarily, but it increases with the increasing pre-extrusion tube length, which, however, cannot be allowed, as explained above. and the opportunities offered by the stepped perforation, which allow for greater deposit weight, cannot be exploited by known means.

And the demand for longer pre-pressed tubes is increasing. This is understandable, since the longer pre-pressed tubes, the further processing they have is less waste per tonne of tube produced, and the amount of commercially available remnants is also smaller.

It is an object of the present invention to provide a solution to the above problem and to develop an apparatus of the type mentioned in the introduction, which enables the pre-extruded tube to be produced in an otherwise advantageous manner, which, at a given wall thickness, is longer in length than previously available.

According to the invention, the object is solved by inserting at least one feeder bench into the production line after the punch press, in addition to a ready-made feeder. Here, the sliding benches do not need to be spatially aligned one behind the other, but should be thought of as forming and stretching each punctured body first on the sliding bench and then on the second and optionally further sliding benches without any intermediate heating. In the apparatus according to the invention, at least one feed bench is placed in front of the ready-to-push bench, which produces the pre-extruded tube having the required finished sizes, which advantageously relieves the stand from both time, thrust and temperature. Because the pushers work with different sized mandrels and need to be exchanged between the pushing operations, the contact time between the mandrel and the pre-pressed tube is significantly reduced. Advantageously, it is advantageous to prevent the pre-pressed body from shrinking onto the mandrel and causing unacceptable warming of the latter.

As a result, the apparatus according to the invention enables the production of pre-pressed tubes of more than 20 meters in length, at least as many as the shorter tubes produced so far. Considering the known equipment to have a maximum pre-pressed tube length of about 16 meters, even if a shoulder roller is used between the punch press and the treadmill 5, it will be appreciated that pre-pressed tube lengths above 20 meters represent a significant increase in power. This is all the more true considering that in all seamless tube manufacturing processes, the yield is determined by the losses during the entire manufacturing process, including the stretch-reducing roll mill rolling the pre-extruded tube. For this reason, they always strive to obtain the maximum starting length of the breathable tube, which requires the largest possible pre-pressed tube length. For example, splitting the forming between a front and a ready-to-push treadmill, while also dividing the thrust among many drive gears, frees the entire production process from its limitations so far, particularly with regard to its tightly limited maximum tubular weight, while fully reaping the benefits of staggered punching can provide 25. Finally, it is also possible to pry extra-thick-walled pre-extruded tubes behind the feed bench for a separate prefabricated program, thus providing a greater wall thickness selection than the currently known equipment.

In a preferred embodiment of the apparatus according to the invention, where a pre-and a push-pull bench are used, the push-bench performs at least 50 percent, preferably 65-80 to 35 percent, of the total cross-section reduction behind the punch, percent - up to 50 percent - performs cross-sectional reductions. The advantage of this distribution is that the pre-extruded tube 40 that is formed on the feed bench is short compared to known pre-extruded tubing produced on the slide so that the extremely short stand length 45 is not required due to performance and contact time. too. As a result, the individual puncture reductions are very small, the rack spacing is relatively large, and the pushing speeds are relatively small, rather arbitrary, and can be optimized in a completely different way than was possible with currently known equipment. The smaller puncture reductions at relatively long rack spacing and the relatively short pre-extruded tube result in a relatively low thrust 55 on the feed bench, despite the larger puncture cross sections, since only the caliber is required at a time to grip or operate the punched body. Even the large puncture cross section 60 possible by step punching does not pose a problem since the greater overall cross-sectional reduction required is divided into a relatively larger number of calibers. For example, for punched bodies between 0.8 and 1 meter in length, a pre-pressed tube of 3 to 5 meters in length is obtained after the feed bench, while

For example, after the -3179999 ready-to-use treadmill, a pre-pressed tube length of 22 meters is available. Despite stretching three to five times, the work stroke at the feed bench remains very short, which of course also applies to contact time.

By reducing the feeder bench and the puncture cross section therein, the thrust is also reduced at the finished feedrate bench, thereby reducing the load on the pre-pressed tube bottom. Complete reductions can already be made in the first calipers of the ready-to-move bench, which, together with a smaller overall reduction than the ready-to-stand bench, improves the just-important ratio between pre-pressed tube length and rack length. This means that for the same pre-pressed tube length, the required stroke is shortened, or vice versa, for larger pre-pressed tube lengths of the same stroke. Due to the absolute reduced cross-sectional reduction, the pushing speeds can be sufficiently higher than the finished push-off bench, but there is no difficulty due to the mass forces, since the displaced masses may be smaller, since smaller cross-sectioning requires only less thrust. The higher feed rate, coupled with the more favorable relationship between pre-pressed tube length and rack bed, significantly reduces the contact time between the mandrel and pre-pressed tube at the finished slide so that larger pre-pressed tube lengths are available and / or a higher number of tubes per minute. improves the overall performance and yield of the equipment. ^x

Advantageously, the feeder bench has a mandrel * which is stepped at its front end section. In addition, it is advisable to design the step on the mandrel rod of the feed bench so that it corresponds to that of the punch press mandrel. This ensures that the bottom weight is determined by the forces of the ready-made push-off bench.

In another embodiment of the present invention, the front caliper or calibers of the feed bench perform smaller cross-sectional reductions than the following ones. In this way, it is possible to avoid tearing the bottom of the pre-pressed tube, or to prevent the mandrel rod from penetrating the pre-pressed tube bottom, which can occur primarily at the front caliber of the feed bench without this action. This is because the feed bar is fed into the front calipers with a pre-pressed tube having a particularly large puncture cross section, and at the same time the thrust is transmitted only in the front, relatively small stepped portion of the mandrel, while the thicker, rear portion of the mandrel. at that time, the perforated body is not in contact with the larger internal bore of the stepped compression and, as a result, the front guide portion of the mandrel has to transfer all thrust. However, with the proposed design, the thrust acting at this location, despite its large puncture cross-section, is relatively small, so that there is no fear of puncturing or tearing the bottom of the pre-pressed tube. Reducing the wall thickness reduction for the first racks in the apparatus of the present invention is accomplished without further ado, since there is a sufficient number of additional calibers to distribute the total cross-sectional reduction.

It is especially advisable not to place a loosening roller after the feeder bench, but only a device for pulling the mandrel rod out of the pre-pressed tube. The pre-extruded tube lengths there are only approx. They range from 3 to 5 to 10 meters and the wall thickness is still relatively high, so that the pre-pressed tube can be easily removed from the mandrel rigidly connected to the rack. Intermediate heating is usually not required here.

In addition, it is advisable to leave extensions in the roller range at the caliper openings of the front and / or backrest racks. These expansions have the advantage of facilitating loosening of the pre-pressed tube on the mandrel and greatly facilitating its removal.

According to a further feature of the invention, the feeder bench operates at a lower sliding speed than the finished feeder bench. In addition, the speed at the feeder bench should be about 2 to 4 meters per second, while the ready-made walker works at about 7 to 9 meters per second.

The invention will now be described in more detail with reference to an exemplary embodiment thereof, in which: - Figure 1 is a schematic top plan view of an apparatus according to the invention having a front and back slide;

Figure 2 is a diagram showing cross-sectional reduction in the range of the feed and ready feed 35 pads.

Figure 1 shows a transverse conveyor device 1 for guiding the perforated bodies to the feed platform 2. The punched bodies come from the arrow direction x, have a punch punch not known in themselves (not shown), and have the temperature required for hot forming. The shape of the perforated bodies is a thick-walled cylinder whose inner opening is closed at one end by a bottom. The punctured bodies pass through the transverse conveyor 1 to the feeding table 3 of the feeder bench 2, on which they are individually placed. The mandrel rod 4 is displaceable axially in the trunnion guide wire 4 and is moved by the axially displaceable toothed rod in the gas rod guide 5. The toothed rod is moved by the toothed gear drive 6, which consists essentially of two drive motors 7, a reducing gear 8, two clutches 9 and two small gearwheels 55 which are directly engaged with the toothed rod. Lubrication and compression oil supply is provided by the pump station 11.

When a perforated body is on the feed table 3, the toothed rod 60 is moved to the right of the toothed rod by means of the toothed pinion drive 6 in the toothed wire 5, with the first end portion of the mandrel until it engages 65 in its bottom. The perforated body is-4179909

Then, the mandrel rod is pushed through the calibrators of the roller stand 12, which are arranged one behind the other in the roller bed 13. The punched body is then formed into a pre-pressed tube (tubular bulb) which has a substantially smaller wall thickness and a greater length than the punched body. The pre-extruded tube thus produced then passes to a second transverse conveyor 14 after the mandrel bar has retracted and the tubular bar has been pulled out of it. The puller 15, which is located between the second transverse conveyor 14 and the roller bed 13, holds the tubular block on the second transverse conveyor 14 while the mandrel is pulled out of the tubular stack and roller stands by the drive 6 until the mandrel 4 is retracted. remains in standby until the next work stroke.

The tubular billet thus produced on the feeder bench 2 is passed through the second transverse conveyor 14 to the feed table 16 of the ready-made feeder bench. It also, like the feeder 2, has a mandrel guide 18 extending downstream of the feed table 16 and a roller bed 19 and roller stands 20 behind the feed table 16. Since the feed tube tubing 17 is already significantly longer than the feed tray 2, the installation parts 17 have substantially longer lengths. In addition, it is not always possible to work with the same needle bar at the ready-made push bar 17 as with the push bar 2, but a separate needle bar is required for each tube block. This is placed in the vicinity of the mandrel guide 18, shortly before the feeding table 16, from the side. The insertion is made from the stock 21, where the pins are kept on standby. In the case where it is necessary to preheat the mandrel, this may be in the mandrel 22, from which the mandrels may be individually placed on the stock bed 21, but only shortly before being inserted into the mandrel 18.

The mandrel rod is moved in the mandrel guide 18 by a rod which is axially slidable in the mandrel rod 23. The handle bar is driven or moved by a rack which is located in the rack 24. The drive of the 17 ready-to-go-off bench is indicated by 25. This consists of a total of four drive motors 26 that directly affect the four drive gears 27. The drive cog wheels 27 are connected directly to the rack. The pumping stations 28 provide each of the pipes, bearings and some cylinders with the required lubricating and compression oils. The gateways 29 allow the service personnel to pass dangerously over the ready-made push-off bench 17.

Once the tubular billet has been crossed to the caliber of the roller stand 20, at the ready-to-reach stand 17, only the handlebar is retracted by means of a rack and a drive 25 while feeding the tubular billet 30 to the loosening roller mill. In the loosening roller mill 31, the tubular billet is shaped to such an extent that it no longer sits snugly on the mandrel but can be pulled down therefrom. Another roller track 32 located behind the loosening roller 31 takes over the tubular billet after the expansion operation, in which case the mandrel is still there, and an additional transverse conveyor 33, along with the mandrel that is still there, engages the tubular billet 34 with the extruder roller 34. , 10 which is located parallel to the roller track 32. Behind the loosening roller mill 31, but in line with the pull-out roller track 34, is a mandrel puller 35 which grips the rear end of the mandrel not covered by the tubular block 15 and pulls it out of the tubular block to the left in FIG. As the tubular bulb thus remains on the pull-out roller track 34, the mandrel puller 35 has a pull-out ring 36, the backside of which is pushed through the backside of the mandrel and the mandrel pulled out of the pull-out ring. The subsequently released mandrel rod is now inserted into the mandrel rod roller path 37 which is then transported to the mandrel rod furnace 22 or to the finished bed 21 or mandrel mandrel 38.

Figure 2 illustrates that the feeder bench 2 performs most of the cross-sectional reduction while the cross-sectional reduction is substantially smaller than that of the finished feedrate bench.

The axis of the graph is plotted with the length of the perforated body and the length of the tubular bulb, while the ordinate shows the cross-sectional projections in square millimeters.

The section A to B of the drawn curve shows the shaping on the feeder bench, while the curve between points B and C shows the cross-sectional reduction on the finished feeder 17. It goes without saying that in addition to the curve shown, many other curves of different origin are conceivable.

It will be apparent from the description of the exemplary apparatus that the apparatus according to the invention has only sliding benches and accordingly uses the sliding bench method exclusively, thus being able to produce a substantially longer pre-pressed tube than was possible with prior art apparatus. In the prior art, at most one sliding bench was used - and the highly expensive rolling mills were used in addition to the sliding bench - because it was the professional understanding that the sliding bench could not produce a sufficiently long tube for various objective reasons. Such a reason was, for example, 55 that insertion demand over a certain length is insurmountably high due to the large adhesive surface between the mandrel and the inner wall of the tube, and because of longitudinal contact between the mandrel and tube in contact with the long section. frustrates or further increases thrust demand.

The apparatus according to the invention has proved that the two successive sliding benches produce a pipe of a shared length, along which the

-5179999 There are no problems considered to be scary, but the end result is that you get significantly longer pre-pressed tubes than any known system of equipment. With the known equipment it was not possible to produce a pipe longer than 16 m, but with the device according to the invention pipes 22 m and even longer can be produced.

In the case of the apparatus according to the invention, the manufacture of substantially longer tubes does not require the intermediate heating of the workpiece tube.

It is a great advantage of the apparatus according to the invention that it utilizes only a sliding bench process which is known to provide the greatest amount of stretching, and hence cross-sectional reduction, in a single process. In addition, its production capacity is higher than that of other devices known, and its space requirements and investment costs are significantly lower than those of other similar devices.

Claims (8)

Apparatus for producing seamless pipes, in particular steel pipes, with a heating furnace, a punching press and at least one sliding bench, and means for dissolving the mandrel and withdrawing it from the pre-pressed tube, characterized in that at least one feeder bench (17) ) is queued. An embodiment of the device according to claim 1, characterized in that at least 50% - preferably 65-80% - of the total cross-sectional reduction of the device is behind the punching press. It has 5 transfer-feeder pads (2) and the remainder, preferably 20-35% but not more than 50% of the back-feeder (17). Embodiment according to claim 1 or 2, characterized in that the feed pad (2) has stepped mandrels at its front end. An embodiment of the device according to claim 3, characterized in that the stepping of the mandrel of the feed bench (2) corresponds to 5 press-mandrel steps. An embodiment of the apparatus according to any one of claims 1 to 4, characterized in that the front caliper or gauges of the feed bench (2) are designed for smaller cross-sectional reduction. 20 as the next in line. 6. An embodiment of the apparatus according to any one of claims 1 to 3, characterized in that, after the feeder bench (2), the mandrel is removed from the pre-pressed tube instead of a loosening roller (31). There are 25 pulling devices (35). 7. An embodiment of the device according to any one of claims 1 to 4, characterized in that the caliber recesses of the rear rack of the feeder bench (2) and / or the finished feeder rack (17) are provided in There are 30 extensions with extensions. 8. Figures 1-7. An apparatus according to any one of claims 1 to 6, characterized in that the pushing speed of the feeder bench (2) is lower than that of the ready-made feeder bench (17).