DE1175887B - Use of a weldable titanium alloy for the production of welded, tubular bodies and processes for heat treatment - Google Patents

Description

Use of a weldable titanium alloy for the production of welded, tubular bodies and methods of heat treatment The invention relates to Use of a weldable titanium alloy with low alloy additions Aluminum and vanadium, in which the content of the two alloy additives is 5.5% amounts, due to particularly favorable and surprising properties for the Manufacture of welded, tubular bodies.

There are different alloys made of titanium, aluminum and vanadium known, in which the alloy components aluminum and vanadium in quite a wide range Areas can be changed. It is known that ternary alloys these Art on the one hand good weldability and on the other hand good deformability can. Any references to special alloys within these ranges, the unusual and prominent one due to its particular composition and treatment Have properties in terms of yield strength, weldability and ductility and are particularly suitable for the production of pipes, the information on these known alloys cannot be found.

So far, in the production of seamless or strip-shaped Material seam-welded pipes titanium of commercial purity used, as this the deformability and weldability desired for the manufacture of pipes owns. For the production of high strength pipes, titanium with a yield strength was used of at least 50 kg / mm2 used. Commercially available titanium with such a yield point has been obtained, for example, by using titanium sponge with a Brinell hardness of 225 kg / mm2 used.

Unfortunately, if the solid solution-forming elements 02, N2 and C exceed a minimum percentage of approximately 0.2% in commercially available titanium, affects the ductility of welds on this material.

For this reason, if the pipes had a yield strength of at least 50 kg / mm2 was required in the tempered condition, this with commercially available Titanium is only achieved at the expense of the weldability and ductility of the material will.

Further difficulties have arisen because the ends of titanium tubes often have to be expanded considerably, but that tubes are made of commercial titanium at the ends can be expanded up to a maximum of 15 "/ o.

Furthermore, titanium of commercially available purity can be subjected to heat treatment not subjected to quenching or hardening (aging) to increase strength will. Finally, the strength of titanium of commercial purity falls short a yield point of at least 50 kg / mm2 at high temperatures, so that at 425 ° C the tensile strength is only about 23 kg / mm2 and the yield point below of 14 kg / mm2.

The result of impairment of weldability, non-response on heat treatments, poor expandability and low strength have difficulties using titanium at high temperatures commercial quality for the manufacture of high strength pipes tight limits set, and there is a previously unsatisfied need for one for the Manufacture of pipes suitable material, which has good ductility and weldability made of commercially available titanium (yield strength 35 kg / mm2), but in a tempered condition has at least a yield point of about 50 kg / mm2 and at which the aforementioned Difficulties do not arise. The invention makes this Needs met. The invention is characterized by the use of a weldable Alloy consisting of 3% aluminum, 2.50% vanadium, the remainder titanium with a content of the usual impurities corresponding to a titanium sponge with a Brinell hardness from 100 to 140 kg / mm2 and that of a solution heat treatment with subsequent cooling in air or in water and optionally subjected to subsequent aging has been used to manufacture welded tubular bodies that at least can be expanded up to 3501o in diameter.

The alloy to be used according to the invention is particularly suitable for the production of seam-welded pipes, whereby the weld seams are not brittle exhibit. The lowest yield point can be achieved by air cooling and subsequent Hardening to 63 kg / mm2 and by quenching in water and subsequent hardening can be increased to 70 kg / mm2. The strength at high temperatures is also significantly higher than with the materials previously used. The expandability is at least 35 0/11, compared to a maximum value of 15 0/11 for commercially available Titanium.

The alloy composed and to be used according to the invention is subjected to a heat treatment process. A preferred heat treatment method is characterized in that the alloy is annealed at 850 or 900 ° C, in water quenched and then aged, expediently at a temperature of 480 ° C will. In this way, a material with a yield strength of 59.1 or 68.9 is obtained kg / mm2 and a tensile strength of 68.9 or 80.9 kg / mm2 and an elongation of about 18.5 and 14.011 / o, respectively.

Another preferred method of heat treatment according to the invention composite and to be used alloy is characterized in that the Alloy is rolled out hot to 1 mm thick sheets and - these sheets at a Annealed at a temperature of 700 ° C 1 / z hour and cooled in air. That in this Material obtained in this manner has a tensile strength at a temperature of 425 ° C of about 40 kg / mm2.

Another preferred method for heat treatment according to the invention consists in that the alloy annealed at 940 ° C for 112 hours, then quenched in water and finally subjected to a heat treatment at 480 ° C for 2 hours and then is cooled in air. In this treatment method, for example, a A tensile strength of 90.7 kg / mm2 can be achieved.

In the alloy used according to the invention, the aluminum content should be must not be higher than 311 / o, as there is a higher aluminum content in the pipe production the deformability of the material is impaired.

Furthermore, the vanadium content should not be more than 2.5%, since a higher vanadium content increases the weldability of the material during manufacture impaired by seam-welded pipes, so that during subsequent treatment of the material, cracks can occur in the weld seams.

On the other hand, in the alloy to be used according to the invention existing contents of 3% aluminum and 2.5 0/11 vanadium fell short of within certain limits will.

Furthermore, the oxygen content must not be higher than that in a titanium sponge with a Brinell hardness of 140 kg / mm2 is present, otherwise the The deformability and weldability of the alloy are adversely affected. For The manufacture of the alloy can be either commercial grade or titanium Titanium of a high degree of purity can be used. In the case of commercially available titanium titanium sponge with a Brinell hardness of 100 to 140 kg / mm2 (hereinafter referred to as For simplification referred to as HB) is used; this gives the alloy a precisely weighed content of aluminum, vanadium and oxygen, the highest possible Deformability and satisfactory weldability with a yield strength of at least 50 kg / mm2 guaranteed in the tempered condition.

The alloy to be used according to the invention is produced preferably by means of an electric arc in a water-cooled copper crucible under a protective gas atmosphere, for example an argon atmosphere or under Vacuum; the material is melted and the alloy additives become the melt added. After melting and casting the alloy, it can be used in the usual Way can be further processed, for example by the fact that the desired profiles or semi-finished products are forged or rolled. The product can be bar-shaped or be plate-shaped. For example, ingots of the alloy can be forged into slabs or rough-rolled, which is then hot-rolled into sheets of the desired thickness be further deformed. Furthermore, the slabs can be closed according to the usual method strip-shaped material of the desired thickness are rolled. On the other hand you can Blocks of the alloy rolled into a square shape and then rolled into bars of the desired Size to be deformed.

Rods formed from the alloy can be made seamless in a conventional manner Pipes are processed. According to the invention, the alloy is in particular in the form of strips Shape used for the manufacture of seam-welded pipes.

Typical properties to be used in the invention Alloy found are shown in the tables below.

Typical properties of the alloy with the composition of 3 Al and 2.5 V (nominal value) made from titanium sponge of 140 HB and tempered at 725 ° C. for 1 hour and then air-cooled are typical properties of rod-shaped material with a diameter of 2.5 cm shown in Table I. Table I. Tensile strength, kilograms per square millimeter 69.50 Yield strength (0.20I0), Kilograms per square millimeter ......... 61.20 Elongation, 0io ............................. 15.0 Reduction in area, 0/11. . . . . . . . . . . . . . . 46.7 Typical properties of the same alloy with 3 Al and 2.5 V (nominal value). which is made from titanium sponge of 120 HB are shown for 1 mm sheet metal in Table I1 for two types of heat treatment. Table 1I annealed annealed at 700 ° C at 725 ° C 1 / z hour at 1/9 hour at Air cooling air cooling Tensile strength, kilograms per square millimeter .... 58.30 56.90 Yield strength (0.2%), kilograms per square millimeter ................................... 56.20 52.70 Elongation (5 cm), a / o. . . . . .. ... . . . . . . . . . . . . ... . . . 21.6 23.1 Bend, Tx-L ................................ 4.6 4.2 Bend, T, partly ................................ 4.5 4.2 Higher values for the tensile strength and the yield point than those given in Table II can be achieved for sheet metal by using harder titanium sponge up to 140 HB. The effect of various heat treatments on the mechanical properties of the material on which Table II is based are shown in Table III. Table III Mechanical properties of 1 mm sheet metal Tensile strength yield point (0.2%) elongation bending T, Heat treatment kilograms kilograms (5 cm sample) per square millimeter per square millimeter% LIT 850 1 C at 1/2 hour LK 63.30 56.20 21.3 4.3. 3.7 480 ° C for 2 hours LK 850 ° C for 1/2 hour WA 6890 59.10 18.5 4.1 3.8 480 ° C at 2 hours LK 875 ° C at 1 / z hour LK -,. 3.6.; 6 480 ° C at 2 hours LK} 68.20 59;, 80 21J; $ 875 ° C at 1/2 hour WA 76.60 64.00 16.4 3.8 3.7 4801 C at 2 hours LK 900 ° C at 1/2 hour LK J 73.00 62.50 15.7 3.3 3.5 480 ° C at 2 hours LK 900 ° C at 1/2 hour WA 80.90 68.90 14.0 3.3 3.7 480 ° C at 2 hours LK 925 ° C at 1/2 hour WA 88.70 78.00 8.6 4.1 4.2 480 ° C at 2 hours LK 940 ° C at 1/2 hour LK 77.30 63.65 13.9 4.8 4.8 480 ° C at 2 hours LK 940 ° C for 1/2 hour WA l 90.70 77.30 6.1 5.4 5.5 480 ° C at 2 hours LK J The values in Table III show that the yield strengths of the annealed material with air cooling (LK) and subsequent hardening from 52.70 kg / mm = to 63.30 kg / mm 2 and with quenching in water (WA) and subsequent hardening to 66.80 kg / MM2 can be increased.

Tensile strengths of annealed 1 mm sheet of the type on which the table values in Table 11 are based at 425 ° C. are listed in Table IV. Table IV Tensile strength, kilograms per square millimeter 39.35 Yield point (0.2%), Kilograms per square millimeter. .... . . . 33.75 Elongation, ° / o. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.0 The value of 39.35 kg / mm2 for the tensile strength of 1 mm sheet metal at 425 ° C is a considerably better heat resistance than the value of 23.00 kg / MM2 at 425 ° C for commercially available products made from titanium sponge of 225 HB Titanium with a yield strength of 50 kg / mm2.

Another indication of the better heat resistance from the According to the invention to be used alloy existing sheet metal, its properties in Table IV is that the breaking strength at 400 ° C was 35.15 kg / MM2 for a continuous load of 100 hours (fracture occurred after 106 hours a).

Welding tests and investigations of the tables II, III and IV underlying sheet showed that the invention to be used alloy is suitable for all types of welds. The welds are just as strong or stronger than the alloy material itself, and determined by bending tests The ductility of the welds is as good or better than that of the alloy material self.

In a further test, a tube formed from a rod-shaped material of the alloy to be used according to the invention was subjected to a heat treatment in order to achieve a tensile strength of 90.70 kg / mm −1 and a yield strength of 78.00 kg / mm =. The tube was then widened at its end by increasing its diameter by 53117a, which is an extremely favorable value compared to the widening of 15.0, which can be achieved with tubes made of commercially available titanium with a yield point of 50 kg / mm-1.

The alloy to be used in the present invention lies essentially in the a-phase before, and the evaluation of the test results shows that the transition to the f3 phase with this alloy made of titanium sponge of 120 HB at 930 to 950`- ' C lies.

The "nominal value" of the alloy additives means that in the Practice aimed at producing the specified composition of the alloy that} but the proportion of the alloy in the cast ingot is different Places of the same can deviate from the desired value upwards or downwards. Thus, in one block, the composition in the upper part was 3.00 Al and 2.53 V during it was 3.19 Al and 2.32 V in the lower part of the block.

Claims (4)

Claims: 1. Use of a weldable alloy consisting of 3 1% aluminum, 2.5 '% vanadium, the remainder titanium with a content of the usual impurities corresponding to a titanium sponge with a Brinell hardness of 100 to 140 kg / mm-' and which has been subjected to solution heat treatment with subsequent cooling in air or in water and, if necessary, subsequent aging, for the production of welded, tubular bodies which can be expanded at least up to 35% in diameter. 2. Heat treatment method the alloy composed and to be used according to claim 1, characterized in that that the alloy is annealed at 850 or 900 ° C, quenched in water and then, is expediently aged at a temperature of 480 ° C. 3. Heat treatment method the alloy composed and to be used according to claim 1, characterized in that that the alloy is rolled out hot to 1. mm thick sheets and these sheets annealed at a temperature of 700 g C '/ z hour and cooled in air. 4. A method for heat treatment of the alloy to be used and composed according to claim 1, characterized in that the alloy is annealed at 940 ° C '/ z hour, then quenched in water and finally subjected to a 2-hour heat treatment at 480 ° C and then cooled in air will. Documents considered: French Patent Nos. 1092 641, 1094 616, 1 141 963.