Tube for Use in Conjunction with a Deep Drilled Hole

Abstract

A tube for use in conjunction with a deep drilled hole comprises a light metal tube made of an aluminium alloy, having sections of different wall thicknesses arranged in the longitudinal direction of the tube and a respective coupling at each end for connecting the tube to a further tube, wherein the light metal tube is produced from an aluminum alloy containing the following elements: 2.5-5.0 wt. % Cu, 0.2-1.0 wt. % Mg, 0.8-2.0 wt. % Li, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.5 wt. % Mn, max. 1.0 wt. % Zn, max. 0.1 wt. % Ti, max. 0.5 wt. % Ag, the remainder being Al and unavoidable impurities. Also described is a method for producing a light metal tube for a tube of this type configured for example as a bore tube. Said method comprises the steps of forming the light metal tube by means of an extrusion method and subsequent solution annealing, then drawing out the extruded tube over the entire length thereof, until the section or sections having the smallest wall thickness are drawn out by at least 2 to 2.5%, and the drawn light metal tube is artificially aged in a subsequent process step at a temperature of between 164 C. and 180 C.

Claims

1-14. (canceled)

15. A tube for use in conjunction with a deep drilled hole, comprising: a light metal tube made of an aluminum alloy, having sections of different wall thicknesses arranged in the longitudinal direction of the tube and a respective coupling at each end for connecting the tube to a further tube; wherein the sections of different wall thicknesses comprise sections of smaller wall thickness, sections of greater wall thickness, and transitional sections; wherein the light metal tube is made of an aluminum alloy which contains the following elements: 2.5-5.0 wt % Cu, 0.2-1.0 wt % Mg, 0.8-2.0 wt % Li, max. 0.15 wt % Si, max. 0.15 wt % Fe, max. 0.5 wt % Mn, max. 1.0 wt % Zn, max. 0.1 wt % Ti, max. 0.5 wt % Ag, remaining Al and unavoidable impurities.

16. The tube of claim 15, wherein the composition of the aluminum alloy of the light metal tube has the following composition: 3.5-4.5 wt % Cu, 0.2-0.8 wt % Mg, 0.8-1.3 wt % Li, 0.1-0.4 wt % Mn, 0.02-0.07 wt % Ti, max. 0.15 wt % Si, max. 0.15 wt % Fe, max. 0.5 wt % Ag, remaining Al and unavoidable impurities.

17. The tube of claim 15, wherein the composition of the aluminum alloy of the light metal tube has a silver content of 0.2-0.5 wt %.

18. The tube of claim 15, wherein the composition of the aluminum alloy of the light metal tube has the following composition: 3.0-3.5 wt % Cu, 0.28-0.25 wt % Mg, 0.9-1.2 wt % Li, 0.28-0.40 wt % Mn, 0.035-0.06 wt % Ti, max. 0.15 wt % Si, max. 0.15 wt % Fe, remaining Al and unavoidable impurities.

19. The tube of claim 15, wherein the composition of the aluminum alloy of the light metal tube contains one or several of the following elements: max. 0.2 wt % Cr, max. 0.2 wt % Zr, max. 0.2 wt % Sc, max. 0.2 wt % Hf, max. 0.2 wt % V, wherein the sum total of the elements Cr, Zr, Sc, Hf, and V does not exceed 0.3 wt %.

21. The tube of claim 16, wherein the composition of the aluminum alloy of the light metal tube has a silver content of 0.2-0.5 wt %.

22. The tube of claim 16, wherein the composition of the aluminum alloy of the light metal tube has the following composition: 3.0-3.5 wt % Cu, 0.28-0.25 wt % Mg, 0.9-1.2 wt % Li, 0.28-0.40 wt % Mn, 0.035-0.06 wt % Ti, max. 0.15 wt % Si, max. 0.15 wt % Fe, remaining Al and unavoidable impurities.

23. The tube of claim 17, wherein the composition of the aluminum alloy of the light metal tube has the following composition: 3.0-3.5 wt % Cu, 0.28-0.25 wt % Mg, 0.9-1.2 wt % Li, 0.28-0.40 wt % Mn, 0.035-0.06 wt % Ti, max. 0.15 wt % Si, max. 0.15 wt % Fe, remaining Al and unavoidable impurities.

24. The tube of claim 16, wherein the composition of the aluminum alloy of the light metal tube in addition contains one or several of the following elements: max. 0.2 wt % Cr, max. 0.2 wt % Zr, max. 0.2 wt % Sc, max. 0.2 wt % Hf, max. 0.2 wt % V, wherein the sum total of the elements Cr, Zr, Sc, Hf, and V does not exceed 0.3 wt %.

25. The tube of claim 18, wherein the composition of the aluminum alloy of the light metal tube in addition contains one or several of the following elements: max. 0.2 wt % Cr, max. 0.2 wt % Zr, max. 0.2 wt % Sc, max. 0.2 wt % Hf, max. 0.2 wt % V, wherein the sum total of the elements Cr, Zr, Sc, Hf, and V does not exceed 0.3 wt %.

26. The tube of claim 15, wherein the sections of different wall thicknesses comprise a section of smallest wall thickness, the tube has been drawn out by at least 2-2.5%, in the section of smallest wall thickness.

27. The tube of claim 26, wherein the tube has been drawn out by at least 3.5%.

28. The tube of claim 15, wherein the light metal tube comprises on each of its two ends a section having a greater wall thickness, wherein the sections having a greater wall thickness are each separated from one another by a section having a smaller wall thickness and wherein transitional sections in which the wall thickness continuously transitions from the one section to the other section are provided between sections having a greater wall thickness and those having a smaller wall thickness.

29. The tube of claim 28, wherein at least one further section having a greater wall thickness is arranged between the two end sections having a greater wall thickness, where the section having a greater wall thickness transitions into the adjacent sections having a smaller wall thickness via a transitional section.

30. The tube of claim 28, wherein the couplings are incorporated into the end sections of the light metal tube.

31. The tube of claim 15, wherein the tube is a drill tube for forming a drill rod assembly.

32. A method of manufacturing a light metal tube of claim 15, wherein the light metal tube is formed using an extrusion process and subsequently solution annealed; the extruded tube is then drawn out over its entire length until the section or sections having the smallest wall thickness are drawn out by at least 2 to 2.5%, and the drawn light metal tube is artificially aged in a subsequent process step at a temperature between 164 C. and 180 C.

33. The method of claim 32, wherein the extruded light metal tube is then drawn out in its sections having the smallest wall thickness by at least 3.5%.

34. The method of claim 32, wherein the drawn out light metal tube is artificially aged for 24-45 hours.

35. The method of claim 32, wherein the artificial aging of the drawn out light metal tube is performed within a temperature range between 168 C. to 172 C., for 32-38 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present disclosure is described below using an exemplary embodiment and with reference to the enclosed figures. Wherein:

[0034] FIG. 1: shows a schematic longitudinal section of a light metal tube,

[0035] FIG. 2: shows a diagram of the yield strength development over the artificial aging performed according to the present disclosure,

[0036] FIG. 3: shows a diagram of the yield strength development over the artificial aging time for artificial aging at conventional conditions, and

[0037] FIG. 4: shows a diagram representing the flow point or tear resistance of a tube in the present disclosure combined with its drawing-out ratio.

[0038] Before further explaining the depicted embodiments, it is to be understood that the invention is not limited in its application to the details of the particular arrangements shown, since the invention is capable of other embodiments. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting. Also, the terminology used herein is for the purposes of description and not limitation.

DETAILED DESCRIPTION

[0039] FIG. 1 shows a schematic longitudinal section of a light metal tube 1 for forming a drill tube as used for deep drilled holes. The longitudinal extension light metal tube 1 shown in FIG. 1 is not to scale. The length/diameter ratio is indeed much smaller than shown in this schematic drawing.

[0040] The light metal tube 1 has sections of different wall thicknesses in its longitudinal extension. The tube 1 of the exemplary embodiment shown is symmetrically configured with respect to its center towards its ends. The central section A.sub.1 of the light metal tube 1 has a greater wall thickness than its adjacent sections. Sections A.sub.2 of a smaller wall thickness are located on both sides adjacent to section A.sub.1. A continuous transition is provided between sections A.sub.1 and A.sub.2, wherein the wall thickness increases gradually from section A.sub.2 to section A.sub.1. An end section A.sub.3, which again has a greater wall thickness compared to section A.sub.2, is located adjacent to each of the sections A.sub.2. There is a transitional section between each section A.sub.2 and A.sub.3 as well, in which the wall thickness continuously and gradually transitions from the wall thickness of section A.sub.2 to the wall thickness of section A.sub.3. The difference in wall thickness between the section A.sub.1, A.sub.3, and A.sub.2 is about 2 times.

[0041] It will be appreciated that the light metal tube does not necessarily need to be configured symmetrically in the longitudinal extension with respect to its center.

[0042] The light metal tube shown in FIG. 1 is comprised of an aluminum alloy having the following composition:

TABLE-US-00001 Al Si Fe Cu Mn Mg Li Zn V Ti Zr Ag 94.27 0.02 0.04 3.86 0.01 0.38 0.8 0.02 0.005 0.03 0.1 0.36

[0043] The light metal tube, which was homogenized after continuous casting and then extruded, was solution annealed after forming and then drawn out to a draw-out ratio of 4.6 in the sections A.sub.2 with the smallest wall thickness. Due to the differences in wall thickness between the sections A.sub.2 and the sections A.sub.1 and A.sub.3, respectively, these sections remain unaffected by the drawing process.

[0044] The end sections A.sub.3 are thickened compared to their adjacent sections A.sub.2, since contours are to be machined into the outer circumferential surface to connect a coupling piece to the exemplary embodiment described. The light metal tube 1 forms the actual drill tube only with the coupling pieces not shown in the figure. It will be appreciated that the thickened sections A.sub.3 can also be used to incorporate the coupling geometries therein. The sections A.sub.3 are machined for incorporating the desired retention geometry, such as threads or the like, after drawing out and artificial aging. This utilizes the fact that the sections A.sub.3 of the light metal tube 1 are unaffected by the drawing process and did not become hardened by it.

[0045] The alloy used is an alloy which is sensitive to drawing, which means that the wall sections that were indeed drawn out were hardened depending on the draw-out ratio. In an illustrated embodiment, these are primarily the sections A.sub.2 and, to a successively decreasing extent, the transitional areas towards the respective thicker wall section. Drawing out the light metal tube 1 before machining the ends has the result that the tube is given sufficient strength and dimensional stability.

[0046] In a subsequent step, the light metal tube 1 was subjected to hot curing by artificial aging. Artificial aging was performed at 170 C. for 36 hours. In the process of artificial aging, the strength set by drawing in the A.sub.2 sections was minimally reduced, however the sections not hardened by the drawing processsections A.sub.1, A.sub.3 and the transitional sections that were not drawn outwere hot cured by the artificial aging process.

[0047] Samples were taken from sections A.sub.1, A.sub.2 and A.sub.3 of the light metal tube 1 to determine the strength values. The strength values determined in this context can be seen in the table below:

TABLE-US-00002 Draw-out R.sub.p02 R.sub.m A.sub.g A.sub.5 Pos. Direction ratio [MPa] [MPa] [%] [%] A.sub.3 L 0.8 525 575 5.2 9.8 A.sub.2 4.6 573 604 4.5 11.8 A.sub.1 0 498 539 4.7 9.5 A.sub.2 4.6 572 602 4.6 11.2 A.sub.3 0.8 523 574 4.5 8.8 A.sub.3 LT 0.8 515 556 4.2 7.2 A.sub.2 4.6 556 585 4.2 7.9 A.sub.1 0 497 542 5.5 9.3 A.sub.2 4.6 548 580 4.3 7.3 A.sub.3 0.8 515 556 4.2 7.2

[0048] The strength values listed in the table include the 0.2% yield strength (R.sub.p02), tensile strength (R.sub.m), uniform elongation (A.sub.g), and elongation at break (As).

[0049] The strength values listed in the table, which were achieved for the light metal tube, exceed those strength values that were determined for a comparison tube made of an AA 2014 alloy by 20% to 30%. These strength values also make it apparent that even the non-drawn section A.sub.1 is of sufficient strength after artificial aging and that the difference in strength between sections of smaller wall thickness A.sub.2 and those of greater wall thickness A.sub.1, A.sub.3, while existing, is not critical. The lower strength values determined in the sections of greater wall thickness are easily compensated by their greater wall thickness.

[0050] FIG. 2 shows the yield strength development over the artificial aging time of a tube according to the one shown in FIG. 1 having a different draw-out ratio. Artificial aging was performed at 170 C., as explained above. The curves indicate that increasing the artificial aging time to over 40 hours no longer has any positive effects. It can therefore be kept short. But above all, the curve referring to a drill tube section that has remained non-drawn shows that the strength was increased to a sufficiently high level in the course of artificial aging. It will be appreciated that the strength of the tube in the non-drawn sections is more than compensated by the respective thicker walls.

[0051] FIG. 3 is a comparison of analogous samples after an artificial aging test, wherein artificial aging was performed using parameters from conventional practices, namely at 153 C. It is apparent, on the one hand, that the non-drawn sample or non-drawn tube section achieves acceptable strength properties after an unacceptably long artificial aging time (>200 h) only. In the aging time needed for artificial aging at 170 C. for achieving acceptable strength properties, the non-drawn tube sections do not reach sufficient strength properties if artificial aging is performed at 153 C.

[0052] FIG. 4 shows the drawing behavior, flow point and tear strength at the transition from a section of tube 1 having a thinner wall thicknesssection A.sub.2- to a section having a thicker wall thicknesssection A.sub.1. When the tube 1 is drawn out as described above, the sections of thinner wall thickness are drawn out to the desired extent (here: 4%). This draw-out ratio decreases successively in the transitional area from section A.sub.2 to section A.sub.1. The tube is no longer drawn out after just of the transition length towards wall section A.sub.2.

[0053] The curves for flow point and tear strength are shown in comparison to the curve for the draw-out ratio. The increase in flow point and tear strength from the tube section A.sub.2, having a thinner wall thickness, to the tube section A.sub.1, having a greater wall thickness, makes it clear that an increase in wall thickness more than compensates for the disadvantages of non-drawing in these sections. It is also due to the artificial aging method described above that the tube 1 has a significantly higher tear strength and flow point in the sections of greater wall thickness.

[0054] The invention was described based on exemplary embodiments. A person skilled in the art will derive numerous embodiments for implementing the invention without departing from the scope of the present claims. While a number of aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations therefore. It is therefore intended that the following appended claims hereinafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations, which are within their true spirit and scope. Each embodiment described herein has numerous equivalents.

[0055] The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. Whenever a range is given in the specification, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and sub-combinations possible of the group are intended to be individually included in the disclosure.

[0056] In general, the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art. The above definitions are provided to clarify their specific use in the context of the invention.