Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D7/00—Bending rods, profiles, or tubes
  • B21D7/02—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment
  • B21D7/024—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment by a swinging forming member
  • B21D7/025—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment by a swinging forming member and pulling or pushing the ends of the work
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D7/00—Bending rods, profiles, or tubes
  • B21D7/16—Auxiliary equipment, e.g. for heating or cooling of bends
  • B21D7/162—Heating equipment

Definitions

• the invention relates to a method for Indudictionsbiegeumformen a pressure-resistant pipe with large wall thickness and large diameter, in particular a power plant and pipelined pipe, with the features of the preamble of claim 1, and a suitable for carrying out induction pipe bending apparatus having the features of the preamble of claim.
• tubes of steel are required, which have a large wall thickness to withstand the stresses.
• Such requirements apply, for example, to the transport of superheated steam in power plants, where pipe bends are required to adapt the pipelines to the structural conditions, or for the transport of crude oil or natural gas in pipelines over long distances, where double bends are used at regular intervals to thermal to compensate for conditional changes in length.
• a large opening cross-section and accordingly a large pipe outside diameter is required.
• Tubes to which the present method relates usually have nominal diameters greater than 300 mm and a diameter to wall thickness ratio of from 10: 1 to 100: 1, typically from 20: 1 to 70: 1.
• Such a method for induction bending forming has long been known, for example from DE2513561 A1, and has been continuously improved in order to produce very dimensionally stable pipe bends despite the enormous dimensions and wall thicknesses of the pipes. While the precise compliance of the predetermined arc angle for the pipe bend is controlled, two adverse form deviations remain in the Area of pipe bend. On the one hand this is the ovality, ie a deviation of the tube cross section from the desired circular ideal shape, and on the other hand a weakening of the wall thickness on the outer curve.
• Round tubes with the above size ratios are manufactured and delivered with ovalities of about 1%.
• a permissible out-of-roundness at the pipe bend after the induction bending process has been completed is 4% according to European and North American standards. Larger deviations are problematic because due to the internal pressure of the media conducted through the pipe bend, locally different tensile stresses occur at the pipe wall. In high-pressure applications for which these thick-walled tubes are particularly intended, such additional stresses occurring due to out-of-roundness are relevant.
• the wall thickness must therefore be chosen to be larger because of the geometric deviation often, as it would be mathematically necessary solely due to the fluid pressure.
• the other adverse influence on the tube during induction bending forming is the different wall thickness distribution on the outer and inner bow.
• the pipe wall is subjected to tensile stress in the region of the outer arch to be formed. Since the outer arch is longer than the undeformed pipe section, it inevitably leads to a reduction in wall thickness.
• compressive stresses are present during bending, and because of the necessary shortening of the arc length, wall thickness increases.
• these unavoidable effects also mean that the strength calculation for the high pressure application must always start at the most weakened wall, which is the wall at the outer arch. Also for this reason, the wall thickness of the entire pipe must be chosen to be much larger than on the straight sections, so that sufficient strength can be achieved in the pipe bend.
• the object of the invention is to reduce the strength of the pipe bend weakening geometric changes in the transformation such as ovality and wall thickness reduction.
• the solution according to the invention is provided by a method for induction bending with the features of claim 1 and an induction bending device for carrying out the method with the features of claim 8.
• the method according to the invention initially relies on an artificial ovality being imposed on the tube before the beginning of the shaping, specifically in the form of a so-called horizontal oval. Lying means that the longer diameter axis of the ellipse, which corresponds to the shape of the pipe cross section, lies in the bending plane. Since the induction bending deformation can be performed in practice only in a horizontal plane due to the large mass of the tubes and the required fixed arrangement of the bending arm, the long diameter axis is also aligned horizontally.
• the tube is vertically compressed prior to heating and thus before entering the forming zone in a press device by press ram and counter bearing or by two mutually opposed ram and guided laterally in the horizontal direction.
• the compression is preferably carried out by the same degree of out-of-roundness that would occur in the induction bending for a pipe bend with a certain arc angle on the same tube type. Particular preference is given to a continuous adjustment of the degree of ovality during the execution of the tube bending process, so that initially worked with lower pre-ovalities, which increase to the center of the tube bending, because without the inventive pretreatment process there would be the largest ovality.
• the second measure provided according to the invention for optimizing the tube geometry during induction bending forming is based on the approach of at least relocating the unavoidable, different wall thickness distribution on the inside and outside of the tube.
• the wall thickness in the inner arc increases even more due to the natural law volume constancy.
• this has no negative effects on the strength and the subsequent processability of the pipe bend.
• the wall thickness reduction can be reduced on the outside, so that according to the invention, a larger wall thickness is obtained, as it was previously possible when using a similar pipe.
• the wall thickness reduction is up to 25% in the case of a 90 ° tubular bend produced by the conventional induction bending method, namely at a conventional ratio of bending radius to pipe diameter of, for example, 1.5: 1.
• the wall thickness reduction can be substantially reduced according to the invention, in particular be halved. This means that the wall thickness at the outer curve in the method according to the invention is 12.5% greater than in the prior art. This also means that either a higher operating load with the same wall thickness of the insert tube is possible, or that even a lower output wall thickness can be selected under the same operating conditions. This in turn results in a saving in weight and cost.
• the displacement of the neutral zone during tube induction bending forming is inventively achieved in that the pipe cross section between the Bo exact outside and the inside of the sheet is heated differently.
• the outside of the bow is heated less strongly than the inside of the bow. Due to the higher temperature, the resistance to deformation at the inner arc is lower than the outer arc, resulting in the intended displacement of the neutral zone in the bend to the outer bow out.
• the invention thus makes targeted use of the forming temperature interval available for the material.
• the deformation with altered temperature profiles is carried out according to the invention in a partial region of the arc angle. From the initial tangent into this subarea, there is a transitional program in which the displacement is gradually shifted outward from an initial position which is symmetrical to the center of the tube. From the subarea into the final tangent into it also applied a transitional program in which the temperature profile is again increasingly symmetrically aligned.
• Said subarea extends over about 80% - 90% of the intended arc angle.
• the partial area starts from the initial tangent at about 1 ° - 2 ° of the arc angle and ends about 1 ° -2 ° before the transition to the final tangent.
• the inventively provided displacement of the temperature profile is preferably based on an adjustment of the annular inductor in the bending plane, in particular to the outside, preferably coupled with an adjustment of the electrical power in the induction device, ie a change in heating power. Due to the inductor adjustment to the outside of the inductor is closer to the pipe inside the pipe than outside, so here is the stronger heating.
• the adjustment range is very small in relation to the used pipe diameters of more than 600 mm with about 5 - 50 mm. In order to effect a heating of large wall thicknesses by induction, the air gap, so the distance between the annular inductor as a current-carrying conductor and the pipe jacket, not be too large.
• the diameter of the inductor is preferably set at 1.05 D ROh r plus 25 mm .
• D ROh r 1000mm
• a targeted energy destruction by local cooling can take place.
• the temperature is measured without contact as the surface temperature on the inside and outside curves, and these values are fed to a control device.
• the temperature distribution can be tracked by the cooling capacity is increased on the outer arc and / or increases the heating power on the inner arc and / or the position of the inductor is changed in the transverse direction.
• a distance-controlled and at the same time a power-controlled method is provided.
• both the inside of the sheet and the outside of the sheet can be specifically influenced.
• the operator can preselect which side of the sheet is to be primarily distance-controlled and which is power-controlled, and specifies the desired surface temperatures including permissible tolerance fields.
• the control device then automatically changes the position of the inductor so that the desired relative distribution between inside and outside of the pipe bend is achieved and also adjusts the electrical power so that the absolute forming temperatures are achieved.
• FIG. 1 shows an induction tube bending device in a schematic view.
• Fig. 2 is a pipe bend in plan view
• FIG. 3 cross sections of the prior art in the marked in Fig. 2
• FIG. 4 cross-sections according to the invention in the marked in Figure 2 cross-sectional planes.
• Fig. 6 shows the different wall thickness distribution in the middle of the pipe bend in longitudinal section
• FIG. 7 shows a press device for pre-ovalization.
• FIG. 1 shows an induction tube bending device 100, which comprises a stationary machine bed 10, on which a holding device 11 for a tube 1 is arranged.
• the holding device 11 engages the tube 1 at its rear end and clamps it firmly.
• the holding device 1 1 in the direction of a pipe center axis 2, which also indicates the feed direction relative to the machine bed 10 slidably.
• the feed takes place via a hydraulic unit 12.
• a bending arm 30 is pivotally mounted on a vertical bending axis 32, wherein the distance of the bending axis 32 can be adjusted perpendicular to the tube center axis 2 to specify the desired bending radius.
• a bending lock 31 is arranged, with which the tube 1 can be gripped and clamped.
• a cooling device not shown here is arranged, with the z. B. over water, a cooling of the surface temperature is effected as soon as the corresponding length section has emerged from the forming zone.
• An induction device comprises an annular inductor 20, which is positioned with its center in the region of the tube center axis 2.
• a transverse adjustment device 21 is provided according to the invention, in order to be able to move the inductor 20 transversely to the longitudinal axis 2 of the insertion tube 1.
• a press unit 50 is provided, of which a preferred embodiment is shown in FIG. 7 in front view, viewed from the machine bed 10 in the feed direction.
• a frame 51 at the top and bottom of each at least one hydraulic ram 52, 53 are arranged, which are each provided with a pressure roller 54, 55 in the form of a double cone or a Rotationshyperboloids or otherwise concave, rotationally symmetrical body.
• a load distribution is obtained on two spaced-apart lines at the outer circumference of the tube 1 which are sufficient to each other. Traces on the outer tube shell due to excessive surface pressure can be avoided.
• the hydraulic rams 54, 55 are operated after a single adjustment to a center which is located on the tube center axis 2, with the same stroke, so that the pressure rollers 54, 55 simultaneously contact the tube shell and then cause the same deformation forces.
• the tube thus remains centered in the vertical plane throughout the bending-forming process.
• two more hydraulic ram 56, 57 are mounted, each having at least one guide roller 58, 59 at its end.
• the tube 1 is also centered so that it is exactly on the center axis 2 through the top and bottom arranged punch 52, 53 with the pressure rollers 54, 55 compressed and no eccentricities occur.
• the lateral guide rollers 58, 59 convex ball or cylindrical to avoid a shape related fixing of the tube 1 to the guide rollers in the vertical direction.
• the compression takes place exclusively in the vertical direction, so that the cross section of the tube 1 takes the form of an ellipse, that is to say the long diameter axis runs horizontally.
• the ovality is shown exaggerated in the illustration of Figure 7 as well as in Figure 3 below explained for illustrative purposes.
• the imposed runout is only about 1% of the pipe diameter at the beginning, 1.5% at the end, and up to 4% of the pipe diameter in the middle of the pipe bend, so that it is barely visible to the naked eye.
• the frame 51 of the press unit 50 is annular, in the sense that it is self-contained, so endless, is formed.
• the outer shape is preferably rhombic in plan view, wherein at each vertex one of the punches 52, 53, 55, 56 is arranged.
• Figure 2 shows a pipe bend 3 with a Wegsstangente 2 and a tangent 4.
• Figure 2 shows a pipe bend 3 with a Wegsstangente 2 and a tangent 4.
• three different sectional planes AA, BB and CC are marked, the sectional plane BB is located in the middle of the pipe bend 3, because there the largest deviations of the wall thicknesses Inner bow and the outer bow present.
• FIG. 2 The cross sections at the points marked in FIG. 2, which would result from an induction bending process according to the prior art, are shown in FIG. Accordingly, the cross section is only in the area AA, that is to say at the end tangent. te 4 on the undeformed insert tube 1, still circular. Due to the forming process results as a cross section BB in the middle of the arc 3, a so-called standing ovality, which also has the consequence that in the area CC, ie at the transition to the initial tangent 2, a lying ovality is given.
• FIG. 5 shows, in a further cross-sectional drawing in the plane B-B, the different wall thickness distributions on the pipe bend 3.
• the wall thickness is significantly thicker than at the pipe outer bend 3.1.
• a vertical axis 3.3 which characterizes the neutral zone, does not lie in the center of the tube cross-section, but according to the invention is offset towards the outer pipe bend 3.1. This is achieved, for example, by the following asymmetrical temperature distribution in the forming zone according to the invention:
• FIG. 6 shows the wall thickness distribution in a horizontal longitudinal section through the pipe bend 3.
• the dot-dash line in the middle represents the pipe center axis 2. Parallel to this, the neutral zone 3.3 runs.
• the dashed lines in the region of the pipe inner bend 3.2 and the pipe outer arch 3.1 represent the wall thicknesses on the undeformed pipe 1.
• the solid lines show the adjusting wall thicknesses after carrying out the bending deformation. Again, the deviations shown exaggerated.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)

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• 2015
  • 2015-04-28 DE DE102015106571.1A patent/DE102015106571A1/de active Pending
• 2016
  • 2016-04-21 CA CA2979430A patent/CA2979430A1/en not_active Withdrawn
  • 2016-04-21 PL PL16731774T patent/PL3288694T3/pl unknown
  • 2016-04-21 JP JP2017556525A patent/JP2018514387A/ja active Pending
  • 2016-04-21 RU RU2017134400A patent/RU2679502C1/ru active
  • 2016-04-21 EP EP16731774.2A patent/EP3288694B1/de active Active
  • 2016-04-21 BR BR112017022211-6A patent/BR112017022211B1/pt not_active IP Right Cessation
  • 2016-04-21 SG SG11201707655PA patent/SG11201707655PA/en unknown
  • 2016-04-21 CN CN201680018768.9A patent/CN107567358A/zh active Pending
  • 2016-04-21 KR KR1020177034346A patent/KR20170141766A/ko not_active Application Discontinuation
  • 2016-04-21 MX MX2017012647A patent/MX2017012647A/es unknown
  • 2016-04-21 ES ES16731774T patent/ES2744610T3/es active Active
  • 2016-04-21 US US15/556,837 patent/US20180043410A1/en not_active Abandoned
  • 2016-04-21 WO PCT/DE2016/100189 patent/WO2016173584A1/de active Application Filing

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