Abstract
A method for producing a tube (101-104), the method comprising: providing a preform (1a-c, 70) in a mandrel (2), the preform (1a-1c, 70) having two ends; flow forming the preform (1a-c, 70) with a plurality of rollers (4-5,31-38) such that in one flow forming pass neither one of the two ends of the preform (1a-1c, 70) is flow formed, thereby producing the tube (101-104); and mechanically forming mechanical connection ends on the two ends of the tube (101-104). Also, a seamless tube (101-104), a pipeline comprising a plurality of seamless tubes (101-04), and a machine for flow forming a preform (1a-1c, 70) into a tube (101-104).
Claims
1. A method for producing a tube, the method comprising: providing a preform in a mandrel, the preform having two ends; flow forming the preform with a plurality of rollers thereby producing the tube; mechanically forming mechanical connection ends on the two ends of the tube; wherein in one flow forming pass neither one of the two ends of the preform is flow formed.
2. The method of claim 1, further comprising: forming a recess on a portion of the preform not comprising any one of the two ends of the preform; and bringing into contact each roller of the plurality of rollers with the preform in the portion thereof; wherein the plurality of rollers is arranged such that each roller is spaced apart from remaining rollers in an axial direction of the mandrel; and wherein each roller of the plurality of rollers has a leading angle, and the plurality of rollers is arranged so as to flow form the preform with increasing leading angles.
3. The method of claim 2, wherein: the plurality of rollers comprises four rollers; a first roller of the four rollers has a first leading angle A, a second roller of the four rollers has a second leading angle B, a third roller of the four rollers has a third leading angle C, and a fourth roller of the four rollers has a fourth leading angle D, wherein A<B<C<D; and the first roller is diametrically opposed to the second roller in a radial direction of the mandrel, and the third roller is diametrically opposed to the fourth roller in the radial direction of the mandrel.
4. The method of claim 3, wherein the third roller is after the first roller and before the second roller in a rotation direction of the mandrel when viewed in the axial direction of the mandrel.
5. The method of claim 3, wherein A is greater than 1° and lower than or equal to 8°, B is lower than or equal to 15°, C is lower than or equal to 20°, and D is lower than or equal to 25°.
6. The method of claim 3, wherein a distance between the first roller and the fourth roller in the axial direction of the mandrel is greater than 0 mm and lower than or equal to 120 mm.
7. The method of claim 5, wherein the tube produced comprises an outer diameter greater than or equal to 200 mm and lower than or equal to 630 mm.
8. The method of claim 5, wherein the tube produced comprises a wall thickness greater than or equal to 15.0 mm and lower than or equal to 40.0 mm.
9. The method of claim 3, wherein the step of flow forming the preform with the four of rollers comprises flow forming the preform with the four rollers such that the tube produced at least comprises first one or more portions and second one or more portions, the first one or more portions comprising at least one of a first wall thickness and a first outer diameter, and the second one or more portions comprising at least one of a second wall thickness and a second outer diameter; and wherein each of the first and second wall thicknesses is greater than or equal to 15.0 mm and lower than or equal to 40.0 mm, and wherein each of the first and second outer diameters is greater than or equal to 200 mm and lower than or equal to 630 mm.
10. The method of claim 1, wherein the plurality of rollers is offset with 90° angles.
11. The method of claim 1, wherein the preform is a seamless preform.
12. The method of claim 1, further comprising: sensing pressures radially exerted on the preform by each roller of the plurality of rollers; and adjusting, for at least one roller of the plurality of rollers during the step of flow forming the preform, at least one of a position of the roller relative to the other rollers in the axial direction of the mandrel and a position of the roller relative to the preform in the radial direction of the mandrel, the adjustment being made with a controlling device and based on the sensed pressures radially exerted on the preform, the adjustment being made such that a sum of the pressures radially exerted on the preform and a sum of moments of force on the preform are both minimized.
13. A pipeline comprising: at least one seamless tube, each of the at least one seamless tube having: an outer diameter greater than or equal to 200 mm and lower than or equal to 630 mm; a wall thickness greater than or equal to 15.0 mm and lower than or equal to 40.0 mm; and a length greater than or equal to 5.0 m and lower than or equal to 20.0 m; wherein the seamless tube is of one of the following: an Austenitic Stainless Steel, a Martensitic Stainless Steel, an Austeno-ferritic Stainless Steel, an Austenitic Nickel base Alloy, and a Super-Austenitic Stainless Steel; and wherein both ends of the seamless tube have mechanical connection ends integrally formed thereon.
14. The pipeline of claim 13, wherein the at least one seamless tube comprises a plurality of seamless tubes, wherein each seamless tube of the at least one seamless tube is mechanically connected at each end thereof to another seamless tube by means of the mechanical connection ends of the seamless tubes, and wherein each of a first seamless tube and a last seamless tube of the at least one seamless tube is only connected to one seamless tube.
15. A machine for flow forming a preform into a tube, the machine comprising: a mandrel; and four rollers adapted to flow form the preform when it is provided in the mandrel; wherein a first roller of the four rollers has a first leading angle A, a second roller of the four rollers has a second leading angle B, a third roller of the four rollers has a third leading angle C, and a fourth roller of the four rollers has a fourth leading angle D; wherein A<B<C<D; wherein each roller of the four rollers is adapted to be spaced apart from remaining rollers in an axial direction of the mandrel, and wherein the four rollers are adapted to contact the preform in the mandrel with increasing leading angles; and wherein the first roller is diametrically opposed to the second roller in a radial direction of the mandrel, and the third roller is diametrically opposed to the fourth roller in the radial direction of the mandrel.
16. The machine of claim 15, wherein the third roller is after the first roller and before the second roller in a rotation direction of the mandrel when viewed in the axial direction of the mandrel.
17. The machine of claim 15, wherein the first roller is arranged spaced apart from the fourth roller, in the axial direction of the mandrel, by a distance, the distance being lower than or equal to 120 mm.
18. The machine of claim 15, further comprising a controlling device, a first plurality of sensors configured to measure pressure that each of the four rollers radially applies to the preform, and a second plurality of sensors configured to measure a position of each of the four rollers in the axial direction of the mandrel; the controlling device being configured to receive the measurements of both the first plurality of sensors and the second plurality of sensors; the controlling device being further configured to digitally compute position adjustments for at least one of the four rollers that minimizes each of a sum of pressures radially exerted on the preform and a sum of moments of force on the preform.
19. The machine of claim 15, wherein the machine is configured to flow form the preform with the four rollers a single time.
20. The machine of claim 15, further comprising four cooling ducts, each cooling duct being adjacent to a roller of the four rollers; the machine being configured to eject coolant fluid on the preform while the machine flow forms the preform with the four rollers.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0172] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be carried out. The drawings comprise the following figures:
[0173] FIGS. 1A-1E, 2A-2G, 3A-3F and 4A-4I diagrammatically illustrate the production of tubes with methods in accordance with embodiments.
[0174] FIGS. 5A-5B shows an exemplary flow forming machine of the prior art.
[0175] FIG. 6 shows leading and trailing edges of a roller for flow forming.
[0176] FIG. 7 diagrammatically shows an arrangement of rollers of a machine in accordance with an embodiment.
[0177] FIGS. 8A-8B shows an arrangement of rollers of a machine in accordance with an embodiment.
[0178] FIG. 9 shows an arrangement of rollers in accordance with an embodiment.
DESCRIPTION OF WAYS OF CARRYING OUT THE INVENTION
[0179] FIGS. 1A-1E diagrammatically illustrate the production of a tube 101 with a method in accordance with an embodiment. With reference to these FIGS. 1A-1E, and also to FIGS. 2A-2G, 3A-3F and 4A-4I, only for the sake of clarity these figures represent the flow forming process from a cross-section view corresponding to a vertical plane going through a rotation axis of a mandrel 2, therefore only two rollers are illustrated but it is readily apparent that the plurality of rollers comprises three, four or even more rollers. Further, the rollers are arranged as described in the present disclosure, that is, with increasing leading angles in the axial direction of the mandrel thereby contacting the preform with increasing leading angles, and with separations between the rollers in the axial direction of the mandrel.
[0180] FIG. 1A shows a preform 1a before being subjected to a flow forming process for producing the tube 101 shown in FIG. 1E. The preform 1a may have been subjected to several thermal and mechanical processes before being subjected to the process steps that are described with reference to FIGS. 1B-1D. The preform 1a has a preliminary length, that is the length before flow forming the preform 1a, and comprises a preform surface 10, a first end 11, and a second end 12 opposite to the first end 11.
[0181] FIG. 1B shows the preform 1a secured to the mandrel 2 and clamped to the support 3 of a flow forming machine by its first end 11. A tool 50, for instance a machining tool, forms a recess 13 (illustrated in FIG. 1C) on the preform surface 10. The recess 13 (which is shown in a magnified view at the right side part of FIG. 1C and in which the bottom roller 5 has not been illustrated for the sake of clarity) has a length L.sub.R (in the axial direction of the mandrel 2 and the preform 1a), does not reach any one of the first and second ends 11, 12 of the preform 1a, and the recess 13 is formed at a distance d.sub.R away from the second end 12. By not forming the recess 13 in the portion (with length d.sub.R) that comprises the second end 12, a mechanical connection end (e.g. a threaded connection, a mechanical connector) for connecting the resulting tube to another tube may be integrally formed in said portion. Preferably the length L.sub.R of the recess 13 is such that all the rollers of the plurality of rollers can be introduced therein when they are brought into contact with the preform 1a, therefore the length L.sub.R is greater than a distance (in the axial direction of the mandrel 2) between a first roller (i.e. a forward-most roller in the main direction D) and a last roller (i.e. a rear-most roller in the main direction D) of the plurality of rollers, more preferably is equal to or greater than said distance plus one time a length equal to the thickness of the rollers so that all the rollers completely fit within the recess 13.
[0182] In this particular example, the recess 13 is formed such that first and second portions are provided. The first portion has a length L.sub.Ri that is preferably at least as long as the thickness of the rollers 4, 5; also, the first portion of the recess 13 has a thickness T.sub.F of the preform 1a that is equal to or approximately equal to the wall thickness of the tube to be produced, this is so because one flow forming pass will be made in order to produce the resulting tube, thus the flow forming will start at the first portion of the recess 13 and will reduce the wall thickness of the preform 1a to the thickness T.sub.F. The second portion of the recess 13 has a length equal to L.sub.R minus L.sub.Ri, and preferably has a shape such that the wall thickness therein progressively reduces (with an angle gamma γ that has a value preferably selected from the range of 8° up to 30°, both endpoints being included) until it arrives to the first portion and has the thickness T.sub.F. The remaining part of the preform 1a has the wall thickness T.sub.C, including the portion corresponding to d.sub.R where a mechanical connection end will be formed.
[0183] FIG. 1C shows the preform 1a when the plurality of rollers 4-5 (only two rollers being illustrated as aforementioned) are brought into contact with the preform 1a in the recess 13. The top-most roller 4 may correspond to a first roller 31 of the machine of FIGS. 5A-5B or to a first roller 35 of the machine of FIGS. 7, 8A-8B and 9, and the bottom-most roller 5 may correspond to a second roller 32 of the machine of FIGS. 5A-5B or to a second roller 36 of the machine of FIGS. 7, 8A-8B and 9. Additional rollers not illustrated may be further staggered to the right of each of the top-most roller 4 and the bottom-most roller 5 and may correspond to one or both of third and fourth rollers 33-34 of the machine of FIGS. 5A-5B or to one or both of third and fourth rollers 37-38 of the machine of FIGS. 7, 8A-8B and 9. As described above, the recess 13 has the first and second portions, and the last roller (i.e. the one that is to be at the right-most part of the FIG. 1C and which is closer to the mandrel 2 in the radial direction) is to be brought into contact with the preform 1a in the first portion of the recess 13, thus as the length LRi is at least greater than the thickness of the rollers, said last roller fits in the first portion. The further rollers, including for instance the illustrated rollers 4, 5, are staggered to the left with respect to the last roller and are brought into contact with the preform 1a in the second portion of the recess 13, therefore the inclined shape of the second portion makes possible to better adapt to the increasing distance between the mandrel and the rollers 4, 5 in the radial direction. Owing to said recess 13, the flow forming pass may start with the rollers already contacting the preform 1a at portions thereof having different wall thicknesses, thereby making smoother the start of the flow forming pass. In some other embodiments, the recess 13 is formed with a single portion in which the wall thickness of the preform is T.sub.F, or in which the wall thickness of the preform has the progressive reduction explained with reference to the second portion of the recess 13, in these embodiments, however, the start of the flow forming pass is less smooth than in preforms having the recess 13 with the first and second portions shown in FIG. 1C because the wall thickness of the preform 1a is not adapted to the different distances between the rollers and the mandrel 2 in the radial direction.
[0184] The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1a in a main direction D, so that the preform 1a flows along a flow direction F which is opposite to the main direction D. The rollers 4-5 cause the metal to flow because they compress it and it is forced to flow in a direction opposite to the main direction D due to the clamping of the preform 1a to a support 3. During the flow forming process, the length of the preform 1a is increased, since no material is chipped, but is made to flow from the wall thickness of the preform 1a to the final length.
[0185] FIG. 1D shows the preform 1a at the end of the flow forming pass, when the rollers 4-5 have arrived near the first end 11. In this case, a portion of the preform 1a near the first end 11 is also left without flow forming and, thus, has the wall thickness T.sub.C (as shown in the magnified view of FIG. 1C). By not flow forming the portion comprising the first end 11, a mechanical connection end (e.g. a threaded connection, a mechanical connector) for connecting the resulting tube to another tube may be integrally formed in said portion.
[0186] FIG. 1E shows the tube 101 produced, which is longer than the original preform 1a and has first and second end portions 14, 15 with a wall thickness (i.e. thickness T.sub.C) greater than that of the rest of the tube 101 (i.e. thickness T.sub.F). In some embodiments, mechanical connection ends are then formed on the first and second end portions 14, 15 by means of a mechanical process, for example machining or grinding.
[0187] FIGS. 2A-2G diagrammatically illustrate the production of a tube 102 with a method in accordance with an embodiment.
[0188] FIG. 2A shows the preform 1b before being subjected to a flow forming process for producing the tube 102 shown in FIG. 2G. The preform 1b may have been subjected to several thermal and mechanical processes before being subjected to the process steps that are described with reference to FIGS. 2B-2F. The preform 1b has a preliminary length, and comprises a preform surface 10, a first end 11, and a second end 12 opposite to the first end 11. On the surface of the second end 12 of the preform 1b a recess has been formed (a magnified view thereof is shown at the right side part of the figure for the sake of clarity) so that the plurality of rollers may be brought into contact with the preform 1b and have the amounts of pressure radially exerted on the preform 1b by the rollers and, therefore, the amounts of pressure supported by each of the rollers substantially balanced from the start of the flow forming process, which results in a smoother start of the flow forming process.
[0189] A length L.sub.R1 of the recess at the second end 12 is such that some or all the rollers of the plurality of rollers can be introduced therein when they are brought into contact with the preform 1b. In this sense, the length L.sub.R1 is greater than a distance (in the axial direction of the mandrel 2) between a first roller (i.e. a forward-most roller in the main direction D) and a last roller (i.e. a rear-most roller in the main direction D) of the plurality of rollers, and is more preferably at least equal to or greater than said distance plus a length equal to 0.5 or one time the thickness of the rollers so that all the rollers completely or almost completely fit within the recess.
[0190] Preferably, the recess is formed such that first and second portions are provided. The first portion has a length L.sub.Re that is preferably at least as long as 0.5 times or even one time the thickness of the rollers 4, 5; also, the first portion of the recess 13 has a thickness T.sub.C of the preform 1b that is equal to or approximately equal to the wall thickness of the preform prior to a subsequent flow forming pass as will be described next with reference to FIGS. 2B-2G, thus the flow forming will start at the first portion of the recess and will reduce the wall thickness of the preform 1b to the thickness T.sub.C. The second portion of the recess has a length equal to L.sub.R1 minus L.sub.Re, and preferably has a shape such that the wall thickness therein progressively reduces (with an angle theta θ that has a value preferably selected from the range of 8° up to 30°, both endpoints being included) until it arrives to the first portion and has the thickness T.sub.C.
[0191] FIG. 2B shows the preform 1b secured to the mandrel 2 and clamped by its first end 11 to a support 3 of a flow forming machine. The plurality of rollers 4-5 is brought into contact with the second end 12 of the preform 1b. In order to have a smooth start of the flow forming pass, the forward-most rollers (i.e. the rollers that would be at the left-most part in the figure) contact the preform 1b at the second portion of the recess such that the inclined shape allows to adapt to the different radial distances between the rollers 4, 5 and the mandrel 2, whereas the rear-most roller (i.e. the roller that would be at the right-most part in the figure) partially or completely fits in the first portion of the recess, thereby contacting the preform 1b where the wall thickness is T.sub.C. In some other embodiments, the recess is formed with a single portion in which the wall thickness of the preform is T.sub.C, or in which the wall thickness of the preform has the progressive reduction explained with reference to the second portion of the recess.
[0192] The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1b in a main direction D, so that the preform 1b flows along a flow direction F which is opposite to the main direction D. The rollers 4-5 cause the metal to flow because they compress the preform 1b and hence the metal is forced to flow in a flow direction F opposite to the main direction D because the preform 1b is clamped by its first end 11 to the support 3.
[0193] FIG. 2C shows the preform 1b at the end of the first pass, when the rollers 4-5 have arrived near the first end 11. In this case, a portion of the preform 1b near the first end 11 is left without flow forming, thereby making possible to integrally form in said portion a mechanical connection end (e.g. a threaded connection, a mechanical connector) for connecting the resulting tube to another tube.
[0194] FIG. 2D shows a tool 50 for forming a recess on the surface 10 (after the first flow forming pass), thereby providing a recess 13 therein. The recess 13 has a length L.sub.R2, does not reach any one of the first and second ends 11, 12 of the preform 1b, and the recess 13 is formed at a distance d.sub.R away from the second end 12. By not forming the recess 13 in the portion (with length d.sub.R) that comprises the second end 12, a mechanical connection end (e.g. a threaded connection, a mechanical connector) for connecting the resulting tube to another tube may be integrally formed in said portion. Preferably the length L.sub.R2 of the recess 13 is such that all the rollers of the plurality of rollers can be introduced therein when they are brought into contact with the preform 1b (after the first flow forming pass). Albeit not illustrated with a magnified view, the same explanation given above with reference to the recess 13 of the embodiment of FIGS. 1A-1E also applies to this recess 13.
[0195] FIG. 2E shows the preform 1b when the plurality of rollers 4-5 are brought into contact with the same 1b in the recess 13. The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1b in the main direction D, so that the preform flows along the flow direction F. During this flow forming process, the length of the preform 1b is further increased.
[0196] FIG. 2F shows the preform 1b at the end of the second pass, when the rollers 4-5 have arrived near the first end 11. Again, the portion of the preform 1b near the first end 11 is left without flow forming so that a mechanical connection may be formed therein.
[0197] FIG. 2G shows the tube 102 produced, which is longer than the original preform 1b and has first and second end portions 14, 15 with a wall thickness greater than that of the rest of the tube 102. In some embodiments, mechanical connection ends are then formed on the first and second end portions 14, 15 by means of a mechanical process, for example machining or grinding.
[0198] FIGS. 3A-3F diagrammatically illustrate the production of a tube 103 with a method in accordance with an embodiment.
[0199] FIG. 3A shows the preform 1c before being subjected to a flow forming process for producing the tube 103 shown in FIG. 3F. The preform 1c may have been subjected to several thermal and mechanical processes before being subjected to the process steps that are described with reference to FIGS. 3B-3E. The preform 1c has a preliminary length, and comprises a preform surface 10, a first end 11, and a second end 12 opposite to the first end 11.
[0200] FIG. 3B shows the preform 1c secured to the mandrel 2 and clamped by its first end 11 to a support 3 of a flow forming machine. A plurality of rollers 4-5 are brought into contact with the preform surface 10, at a position (in the axial direction of the mandrel 2 and the preform 1c) which is at least 1% of the preliminary length away from the first end 11. The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1c in a direct direction R, which is opposite to the main direction D as described in the methods illustrated by FIGS. 1A-1E and 2A-2G. In this case, the preform 1c flows along a flow direction F which is the same as the direct direction R. The rollers 4-5 cause the metal to flow because they compress the preform 1c and hence the metal is forced to flow in this direct direction R and the flow direction F due to the clamping of the preform 1c to the support 3.
[0201] FIG. 3C shows the preform 1c at the end of the first pass, when the rollers 4-5 have arrived at the second end 12.
[0202] FIG. 3D shows the preform 1c when the rollers 4-5 are brought into contact with the preform surface 10, at a position (in the axial direction of the mandrel 2 and the preform 1c) which is at least 1% of the preform length away from the second end 12. It is to be noted that the preform length is greater than the preliminary length, since it has been increased in the step illustrated by FIG. 3B. This step may be performed quickly, since the rollers 4-5 are already located near the second end 12, because the previous step finished there. The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1c in the main direction D, yet the preform 1c flows along the flow direction F.
[0203] FIG. 3E shows the preform 1c at the end of the second pass, when the rollers 4-5 have arrived near the first end 11. In this embodiment, portions of the preform 1c near the first and the second ends 11, 12 are left without flow forming and, thus, have a greater wall thickness than the flow formed portion of the preform 1c.
[0204] FIG. 3F shows the tube 103 produced. In some embodiments, mechanical connection ends are then formed on first and second end portions 14, 15 of the tube 103 by means of a mechanical process, for example machining or grinding.
[0205] FIGS. 4A-4I diagrammatically illustrate the production of a tube 104 with a method in accordance with an embodiment.
[0206] FIG. 4A shows the same preform 1b of FIGS. 2A-2G before being subjected to a flow forming process for producing the tube 104 shown in FIG. 4I. This preform 1b may have been subjected to several thermal and mechanical processes before being subjected to the process steps that are described with reference to FIGS. 4B-4H. A recess has been formed at the second end 12 of the preform 1b for a smoother start of the flow forming process by the plurality of rollers 4-5.
[0207] FIG. 4B shows the preform 1b secured to the mandrel 2 and clamped by its first end 11 to the support 3 of a flow forming machine. The plurality of rollers 4-5 are brought into contact with the preform 1b in the recess at the second end 12 of the preform 1b. The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1b in a main direction D, so that the preform 1b flows along a flow direction F that is opposite to the main direction D.
[0208] FIG. 4C shows the preform 1b at the end of the first pass, when the rollers 4-5 have arrived near the first end 11, but without reaching it. Accordingly, a portion of the preform 1b comprising the first end 11 is left without flow forming.
[0209] FIG. 4D shows a tool 50 for forming a recess on the surface 10 (after the first flow forming pass), thereby providing a recess 13 therein. The recess 13 is at a position of the preform 1b (after the first flow forming pass) that is between 40% and 60% (the endpoints being included in the range) of the preform length (the length after the first flow forming pass) away from the second end 12. It is to be noted that the preform length is greater than the preliminary length, since it has been increased in the step illustrated by FIG. 4B. As explained with reference to the recesses 13 of the embodiments of FIGS. 1A-1E and 2A-2G, the recess 13 has a length L.sub.R that is preferably equal to or greater than a distance (in the axial direction of the mandrel 2) between a first roller (i.e. a forward-most roller in the main direction D) and a last roller (i.e. a rear-most roller in the main direction D) of the plurality of rollers 4-5, and preferably has said first and second portions.
[0210] FIG. 4E shows the preform 1b when the rollers 4-5 are brought into contact with the same 1b in the recess 13. The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1b in the main direction D, the preform 1b thereby flowing along the flow direction F. This pass has been performed along approximately half of the length of the preform 1b, but there is still another portion of the preform 1b that has not undergone the second pass.
[0211] FIG. 4F shows the preform 1b at the end of the second pass, when the rollers 4-5 have arrived near the first end 11. In this case, the portion of the preform 1b near the first end 11 is left without flow forming; if the resulting tube shall have a mechanical connection integrally formed on the first end 11, such mechanical connection may be provided thanks to the greater wall thickness in this portion.
[0212] FIG. 4G shows the preform 1b, which has been unclamped from the support 3 and clamped again but by the second end 12 of the preform 1b. The portion of the preform 1b that has not undergone the second pass is now arranged onto the mandrel 2 so that the second pass may be performed on this portion. The rollers 4-5 are displaced with respect to the mandrel 2 and the preform 1b in the main direction D, so that the preform 1b flows along the flow direction F. This pass has been performed along the portion of the preform that was not subjected to this second pass.
[0213] FIG. 4H shows this preform 1b when the whole preform, except the portions that comprise the ends, have undergone the flow forming process.
[0214] FIG. 4I shows the tube produced 104. In some embodiments, mechanical connection ends are then formed on first and second end portions 14, 15 of the tube 104 by means of a mechanical process, for example machining or grinding
[0215] The method corresponding to FIGS. 4A-4I makes possible to manufacture a tube with a length that may be two or three times the length of the mandrel 2. The length of the mandrel 2 is limited because of technical and structural requirements, but longer tubes are advantageous as they may form a pipe with fewer tubes and, thus, fewer joints.
[0216] FIGS. 5A-5B show an exemplary flow forming machine of the prior art for manufacturing a tube out of a preform 70. The preform 70 processed by the machine comprises a first end 11, and a second end 12 opposite to the first end 11. In FIGS. 5A-5B are illustrated 3D axes (X, Y and Z) for an easier understanding of the representation of the machine only; it is readily apparent that different 3D axes or naming thereof could be provided.
[0217] The machine comprises: a mandrel 2 adapted to secure the preform 70, the mandrel 2 having a mandrel or rotation axis 21 (shown with dashed lines for illustrative purposes only) extending in an axial direction of the mandrel (along the Y dimension illustrated); a support or jaw chuck 3 adapted to clamp the first end 11 of the preform 70; and a plurality of rollers 31-34 that may be brought into contact with the preform 70 for flow forming thereof, each roller 31-34 adapted to rotate around a roller axis thereof. The plurality of rollers 31-34 is provided in a carriage 7 of the machine.
[0218] The rollers 31-34 are arranged such that a leading angle thereof is incremental in a counterclockwise direction when the rollers are seen from the support or jaw chuck 3, as illustrated in FIG. 5B (in which the support or jaw chuck 3 is not illustrated for the sake of clarity). That is, when seen from said support or jaw chuck 3, a first roller 31 at the top has a first leading angle, a second roller 32 at the left has a second leading angle greater than the first leading angle, a third roller 33 at the bottom has a third leading angle greater than the second leading angle (and, thus, greater than the first leading angle), and a fourth roller 34 at the right has a fourth leading angle greater than the third angle (and, thus, greater than the first and second leading angles). Accordingly, from the first roller 31 to the fourth roller 34 in the counterclockwise direction, the leading angles of the rollers 31-34 increase. The rollers of other prior art machines may be arranged in a similar fashion, and/or with increasing leading angles in clockwise direction. In addition, the distance from each roller 31-34 to the rotation axis 21 of the mandrel 2 (the distance being measured from a contact point of each roller 31-34 that contacts the preform 70) may be different; for example, the greater the leading angle is, the closer the respective roller is to the mandrel 2 or rotation axis 21 of the mandrel 2.
[0219] In some prior art machines (not illustrated), the rollers 31-34 are arranged such that they are spaced apart in the axial direction of the mandrel 2.
[0220] As illustrated in FIG. 5B, the preform 70 comprises a first portion 71a closer to the outer diameter thereof, and a second portion 71b closer to the inner diameter thereof. The four rollers 31-34 contact the first portion 71a such that the wall thickness of the preform 70 is reduced while, at the same time, the length of the preform 70 is increased. With dashed circumferential lines within portion 71a are illustrated the wall thickness reductions due to the different rollers 31-34.
[0221] The machine of FIGS. 5A-5B may be suitable for carrying out methods as described with reference to FIGS. 1A-1E, 2A-2G, 3A-3F and 4A-4I.
[0222] FIG. 6 shows leading and trailing edges of a roller 4 for flow forming, the roller may be any one of the rollers 31-34 of the machine of FIGS. 5A-5B, or any one of the rollers 35-38 of the machine of FIGS. 7, 8A-8B and 9. The roller 4 comprises a leading edge 42 intended to roll the preform 70 when the roller 4 is displaced relative to the mandrel 2, and also comprises a trailing edge 43 intended to achieve a near net shape in the tube. A leading angle, represented as angle alpha (α), is defined as the angle that the leading edge 42 forms with respect to the mandrel axis 21, and a trailing edge angle, represented as angle beta (β), is defined as the angle that the trailing edge 43 forms with respect to the mandrel axis 21.
[0223] FIG. 7 diagrammatically shows an arrangement of rollers of a machine in accordance with an embodiment. Four rollers 35-38 as described in the present disclosure are illustrated, but all of them are shown at a top-most portion of the preform 70 only for the sake of clarity of the leading angles and distances represented therein.
[0224] The first 35 of the four rollers comprises a first leading angle A, the second 36 of the four rollers comprises a second leading angle B, the third 37 of the four rollers comprises a third leading angle C, and a fourth 38 of the four rollers comprises a fourth leading angle D. As shown in FIG. 3, A<B<C<D. The four rollers 35-38 are arranged with increasing leading angles in a direction along a mandrel 2 or rotation axis 21 of a mandrel 2 on which the preform 70 is arranged. That is to say, the first roller 35 contacts any given point of the preform 70 (the given point being along a length of the preform 70) first, the second roller 36 contacts the same given point of the preform 70 after the first roller 35, the third roller 37 contacts the same given point of the preform 70 after the second roller 36, and the fourth roller 38 contacts the same given point of the preform 70 after the third roller 37.
[0225] Further, the four rollers 35-38 are spaced apart in a direction along the mandrel 2 or the rotation axis 21. The first roller 35 is spaced apart from a support or jaw chuck (not illustrated, but it is further at the left of the figure) of a flow forming machine by a distance x.sub.1 and from the second roller 36 by a distance d.sub.1, the second roller 36 is spaced apart from the support or jaw chuck by a distance x.sub.2 and spaced apart from the third roller 37 by a distance d.sub.2, the third roller 37 is spaced apart from the support or jaw chuck by a distance x.sub.3 and from the fourth roller 38 by a distance d.sub.3, and the fourth roller 38 is spaced apart from the support or jaw chuck by a distance x.sub.4; the distance x.sub.2 is equal to x.sub.1+d.sub.1, the distance x.sub.3 is equal to x.sub.2+d.sub.2, and the distance x.sub.4 is equal to x.sub.3+d.sub.3. Even though it is not illustrated, a carriage of the flow forming machine may be adapted to stagger the four rollers 35-38 as indicated, and may be further adapted to allow adjustment of the distances.
[0226] Also, in some embodiments, the machine comprises a controller or controlling device for automatically and dynamically adjusting a position of one or more rollers 35-38 in axial and/or radial directions of the mandrel 2. The controller or controlling device receives from sensors the amount of radial pressure (illustratively shown with arrows FR.sub.1, FR.sub.2, FR.sub.3 and FR.sub.4, all pointing upwards in this representation in which all the rollers 35-38 are shown above the mandrel 2, but it is readily apparent that in a real case these arrows are pointing outwardly from the preform 70 in accordance with the position of the rollers 35-38 around the preform, for instance as shown in FIGS. 8B and 9) supported by each of the rollers 35-38. The controller or controlling device digitally computes which position adjustments are necessary so as to balance the sum of amounts of radial pressures FR.sub.1, FR.sub.2, FR.sub.3 and FR.sub.4 and the moments of force resulting therefrom.
[0227] FIGS. 8A-8B show an arrangement of rollers of a machine in accordance with an embodiment. In FIG. 8A the machine and, thus, the arrangement of the rollers (in FIG. 8A the separations between rollers in the axial direction of the mandrel 2 have been exaggerated for illustrative purposes only) are shown from a side view, whereas in FIG. 8B the machine and the arrangement of the rollers are shown from a different side view, particularly the arrangement of the rollers is seen from a support or jaw chuck 3 of the machine (the support or jaw chuck 3 not being illustrated for the sake of clarity). The same 3D axes of FIGS. 5A-5B have been used for the sake of clarity.
[0228] The first roller 35 has the first leading angle A, and the second roller 36 has the second leading angle B and is arranged diametrically opposed to the first roller 35 in a radial direction of the mandrel 2 (along the X dimension illustrated), although displaced in a longitudinal direction of the mandrel 2 (along the Y dimension illustrated) by a distance d.sub.1. The third roller 37 has the third leading angle C, and the fourth roller 38 has the fourth leading angle D and is arranged diametrically opposed to the third roller 37 in the radial direction of the mandrel (along the Z dimension illustrated), although displaced in a longitudinal direction of the mandrel 2 (along the Y dimension illustrated) by a distance d.sub.3. The second and the third rollers 36-37 are offset 90° and are spaced apart by a distance d.sub.2. The first and the last (i.e. fourth) rollers 35, 38 are separated by a distance d.sub.T in the longitudinal direction of the mandrel 2, the distance d.sub.T being the sum of d.sub.1, d.sub.2 and d.sub.3. The distance d.sub.T is always greater than 0 mm and lower than or equal to 120 mm, and in some cases it is lower than or equal to 80 mm. Each of the distances d.sub.1, d.sub.2 and d.sub.3 is greater than 0 mm and lower than 80 mm.
[0229] In this example, the mandrel 2 rotates in a counterclockwise direction when seen from the view of FIG. 8B. The third roller 37 is after the first roller 35 and before the second roller 36 in the rotation direction of the mandrel 2, thus as seen in FIG. 8B it is at the left of the mandrel 2. In another example, the mandrel 2 rotates in clockwise direction when seen from the same view and the third roller 37 is at the right of the mandrel 2 thereby being arranged after first roller 36 and before the second roller 36 in the rotation direction.
[0230] In other examples, the third roller 37 is after the second roller 36 and before the first roller 35 in the rotation direction of the mandrel 2.
[0231] The four rollers 35-38 contact the first portion 71a such that the wall thickness of the preform 70 is reduced while, at the same time, the length of the preform 70 is increased. With dashed circumferential lines within portion 71a are illustrated the wall thickness reductions due to the different rollers 35-38.
[0232] Although in FIGS. 8A-8B the first roller 35 is arranged such that it is above the mandrel 2, it is readily apparent that in other embodiments the first roller 35 is arranged such that it is below the mandrel 2 (like where the second roller 36 is illustrated) and the second roller 36 is arranged such that it is above the mandrel 2 (like there the first roller 35 is illustrated), and that in other embodiments the four rollers 35-38 are arranged with some rotation with respect to the arrangement of FIGS. 8A-8B, for instance as shown in FIG. 9.
[0233] In some embodiments, the flow forming applied by the four rollers 35-38 to the preform 70 produces a tube with a constant wall thickness and/or constant outer diameter. In some other embodiments, for example as explained with reference to FIGS. 1A-1E, 2A-2G, 3A-3F and 4A-4I, the flow forming applied by the four rollers 35-38 to the preform 70 produces a tube with a variable wall thickness and/or variable outer diameter.
[0234] FIG. 9 shows an arrangement of rollers of a machine in accordance with an embodiment, which is seen from a side view similar to FIG. 8B (the support or jaw chuck 3 of the machine not being illustrated for the sake of clarity).
[0235] In comparison with the machine of FIGS. 8A-8B, the machine of FIG. 9 has the rollers 35-38 arranged with a 45° offset, but the first roller 35 is also diametrically opposed to the second roller 36, and the third roller 37 is also diametrically opposed to the fourth roller 38.
[0236] The machine of FIGS. 8A-8B or 9 may be suitable for carrying out methods as described with reference to FIGS. 1A-1E, 2A-2G, 3A-3F and 4A-4I.
[0237] Even though the terms first, second, third, etc. have been used herein to describe several devices, elements or parameters, it will be understood that the devices, elements or parameters should not be limited by these terms since the terms are only used to distinguish one device, element or parameter from another. For example, the first roller could as well be named second roller and the second roller could be named first roller without departing from the scope of this disclosure.
[0238] In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.
[0239] On the other hand, the invention is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.
