CZ296639B6 - Metallic seamless tube and process for producing thereof - Google Patents

Abstract

The present invention relates to a metal-made seamless pipe (30) containing at least one metal having a melting point of 1,600 degC or more and being selected from the group consisting of Mo, W, Re, Ti, Hf and Zr metals. The metal-made seamless pipe has a porosity of 0.3 to 25 percent when the porosity is defined as a proportion of the open pores not perforating in the thickness direction of the pipe. Inside diameter of the pipe (30) ranges within 0.4 to 3,0ámm and thickness thereof is in the range of 0.05 to 1,0 mm. Disclosed is also a process for producing the above-described metal-made seamless pipe, which comprises: preparing a mixture containing 80 to 98 percent by weight of a powder of at least one kind of metal selected from the group consisting of Mo, W, Re, Ti, Hf and Zr metals, each having a melting point of 1,600 degC or more and a binder in a solvent, kneading the mixture for 0 to 3 hours and then extruding the kneaded material to form a pipe-shaped material (30), and drying the pipe-shaped material at -5 to 25 degC for a period of 10 to 48 hours from the completion of the extrusion and thereafter at 30 to 120 degC for a period of 0.5 to 8 hours and then firing the dried material at a lower temperature selected from a temperature between 1,000 to 2,100 degC or at a temperature being lower by 300 degC than the melting point of the metal.

Description

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a metal seamless pipe and to a method for manufacturing such a pipe. In particular, the invention relates to a metal seamless tube which is difficult to process but can be manufactured with a small thickness and a small internal diameter, which has better mechanical strength and airtightness and which can be advantageously used, for example, as a sealing member of a translucent sleeve (e.g. a translucent housing) which is part of, for example, a high-pressure discharge lamp (for example, metal halide lamps). The invention also relates to a method of manufacturing such a metal seamless tube.

BACKGROUND OF THE INVENTION

As shown in FIG. 5, the translucent ceramic tube 20 (translucent tube) is used as a translucent housing of a high pressure discharge lamp 10 (e.g., metal halide lamps) since the translucent housing contains a light-emitting material (e.g. dysprosium iodide) which is highly corrosive. therefore, the translucent housing must be corrosion-resistant.

For the purpose of sealing the translucent ceramic tube 20 (translucent tube), which is used as a translucent sleeve, a metal tube 30 (e.g. molybdenum tube) has been proposed as a sealing member - see EP 0 982 278 A1.

It should be noted, however, that the metals (e.g. molybdenum or tungsten) used in the manufacture of said metal tube 30 are very difficult to process, which in turn limits the manufacture of tubes of small thicknesses and small internal diameters.

Because it is difficult to process metals and is difficult to cut, the manufacture of metal tubes 30 from metals now consists of sintering metal ingots, subsequently rolling the metal ingot, drawing it or the like to obtain a tube-shaped material.

In such manufacturing processes, it is extremely difficult to obtain metal tubes 30 with small thicknesses and small diameters.

US 3,626,744 relates to porous tubes and generally relates to "open porosity" of tubes. The specific meaning of the term "porosity" in the context of this document is clear from the proposed use therein. Indeed, the tubes used here are intended to allow gas or liquid to pass from the inside to the outside of the tubes. Thus, this document defines the open porosity of the tube for flow from the inner part to the outer part. Further, the inner diameter of the pipe disclosed herein is much larger than that of the pipe of the invention.

Furthermore, US 5 910 007 discloses an exemplary embodiment of a pipe having an inner diameter of 1.2 mm. However, it does not contain any information about the thickness of this pipe. This document refers to bulk porosity as an important factor in the depth direction of a pipe. This document completely lacks information about the importance of open porosity on the tube surface. Therefore, here too the technical concept is completely irrelevant to the concept of the invention described below.

SUMMARY OF THE INVENTION

In the context of the above-mentioned problems, it is an object of the present invention to provide a metal seamless tube which is difficult to process but which can be manufactured with a small thickness and a small inside diameter which has very good mechanical strength and airtightness. it can be advantageously used, for example, as a sealing member of the translucent sleeve

(E.g., a ceramic translucent housing) that would be part of, for example, a high-pressure discharge lamp (e.g., metal halide lamps). SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing such a metal seamless tube.

The above object is solved by a metal seamless tube comprising at least one type of metal as its main component having a melting point of 1600 ° C or more and selected from Mo (molybdenum), W (tungsten), Re (rhenium), Ti (titanium) ), Hf (hafnium) and Zr (zirconium), the tube having a porosity of 0.3 to 25%, the porosity being defined as the ratio of the area of the open pores present on the outer surface of the tube to the total area of the outer surface of the tube. The pipe has an inner diameter of 0.4 to 3.0 mm and a thickness of 0.05 to 1.0 mm.

A preferred embodiment of the invention is characterized in that at least one type of metal is selected from Mo, W and Re with a melting point of 2600 ° C or more.

Another preferred embodiment of the invention is that the tube further comprises at least one type of oxide selected from the group consisting of Al ₂ O ₃ (alumina), Y ₂ O ₃ (yttrium oxide), Dy ₂ O ₃ ( dyspersium trioxide), Gd ₂ O ₃ (gadolium oxide), Ho ₂ O ₃ (holmitium oxide) and Tm ₂ O ₃ (thulium oxide), in an amount of 0.02 to 5% by volume relative to 100% of the total volume of metal and oxide .

The object of the invention is further solved by a process for the manufacture of such a pipe, the process according to the invention comprising: a powder of at least one type of metal selected from the group of Mo, W, Re, Ti, Hf and Zr having a melting point of 1600 ° C or more, and an adhesive in solvent, stirring the mixture for 0 to 3 hours and subsequently extruding the mixed material to form tube-shaped material, and drying the tube-shaped material at -5 to 25 ° C for 10 hours to 48 hours after completion of extrusion, and then at 30 to 120 ° C for 0.5 to 8 hours and then firing the dried material at a temperature range between 1000 ° C and below either 2100 ° C or at a temperature 300 ° C below the melting point of the metal.

A preferred embodiment of the process according to the invention is characterized in that at least one type of metal is selected from the group Mo, W and Re with a melting point of 2600 ° C or more.

A further advantageous process according to the invention consists in adding at least one type of oxide selected from the group consisting of Al ₂ O ₃ , Y ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O ₃ Ho ₂ O ₃ and Tm ₂ O ₃ , in an amount of 0.02 to 5% by volume relative to 100% of the total metal and oxide volume.

Another preferred method of the invention is that the drying of the tube-shaped material is carried out in an atmosphere containing solvent vapors.

BRIEF DESCRIPTION OF THE DRAWINGS

Giant. 1 is a graph showing the relationship between porosity and airtightness of a metal seamless tube.

Giant. 2 schematically illustrates a cross-sectional view of a tear-off test arrangement consisting in tearing off a thin tungsten plate attached to an aluminum plate using an Al ₂ O ₃ -Y ₂ O ₃ -Dy ₂ O ₃ -La ₂ O ₃ type ceramic compound plates using a given force.

Giant. 3 is a graph showing the airtightness achieved when Mo, W, Re, Ti, Hf and Zr metals were used and all had a porosity of 5%.

-2GB 296639 B6

Giant. 4 is a graph showing the relationship between the thickness, inside diameter, and airtightness of a metal seamless tube.

Giant. 5 schematically illustrates a cross-section of a prior art construction in which a metal seamless tube is used as a sealing member of a ceramic translucent high-pressure lamp housing (e.g., metal shalide lamps).

DETAILED DESCRIPTION OF THE INVENTION

In the following, preferred embodiments of a metal seamless tube 30 and a method for manufacturing it according to the invention are described in more detail, using the accompanying drawings.

The metal seamless tube 30 according to the invention comprises as its main component at least one type of metal selected from the group consisting of metals, each having a melting point of 1600 ° C or more, and having a porosity of 0.3 to 25%, where porosity is is defined as the ratio of the area of open pores that do not perforate in the thickness direction of the tube 30 and are located on the outer surface of the tube 30 to the total area of the outer surface of the tube 30.

The metal seamless tube 30 according to the invention has a higher leakage reliability than the seam tubes, due to the absence of these seams. If a metal tube with seams were used as a sealing member of the translucent housing of the high-pressure discharge lamp 10 (for example, metal halide lamps), leakage (damage) would be highly likely, since the high-pressure discharge lamp 10 operates in the interior of the translucent housing. the size of several atmospheres (1 atm = 0.1 MPa). As a result, the reliability of the seamed tube 30 is then reduced compared to that of the seamless tube 30.

There are no restrictions on the type of metal whose melting point is 1600 ° C or more and which is used in the invention. Preferred examples of metals include at least metals selected from the group consisting of Mo (melting point 2623 ° C), W (melting point 3422 ° C), Re (melting point 3186 ° C), Ti (melting point 1668 ° C) C), Hf (melting point is 2233 ° C) and Zr (melting point is 1855 ° C), all of said metals being resistant to corrosion caused by a substance encapsulated within the interior of the translucent housing.

It should be noted that Mo and W have a centered cubic crystal structure, a high melting point, as mentioned above, and also a very high Vickers hardness of 200 to 450. Re, Ti, Hf and Zr have a closed cubic crystal structure, high melting point and have few crystalline chutes. Therefore, these metals are difficult to machine.

In the terminology of the invention, the term "open pores other than through pores" refers to pores on the surface of a tube 30 that do not perforate the thickness of the jacket of the tube 30 (thus not causing leakage). Similar open pores can be detected by performing a helium leak test and performing an image analysis of the external surface porosity.

As shown in Table 1, the airtightness is low when the porosity of the metal seamless tube 30 exceeds 25%.

In this document, the "airtightness" is measured in a helium metal tube detector 30, with a sample of used metal seamless tube 30 having the following dimensions: outer diameter is 1 mm, inner diameter is 0.7 mm (thickness is 0.3 mm) and its the length is 100 mm. 10 tube samples are measured and if all 10 samples are gas-tight, the airtightness is 100%. By "gas-tightness" is meant a gas-tightness in a helium test, the leakage rate being 1.0 x 10 ^-10 atm / m ³ / s or less.

-3GB 296639 B6

The lower limit of the porosity of the outer surface is determined by the degree of possible wetting of another substance, in particular cement, ceramics, glass or the like. A lower limit of less than 0.3% is not preferred, as shown in the results of the following tear-off test.

Tear-off test

As shown in Fig. 2, a thin tungsten plate 3 was attached to the aluminum plate 1 by means of a ceramic compound of the type AbOsMACb-DysCy-I-C. Thin tungsten plate 3 was peeled from aluminum plate 1. Breakpoints and ratings are shown in Table 1.

Table 1

A break point Evaluation Porosity Thin W Plates (%) 0, 1 The surface of the thin W plate does not break ceramic X 0 .. 2 The surface of the thin W plate does not break ceramic X 0,3 - 0, 5 Thin W plate surface W ceramic plate: small Δ 1.0 Ceramic on W plate: small to medium O - O 3.0 W ceramic plate: medium O 5, 0 W ceramic plate: large 0

As can be seen from Table 1, the presence of ceramics, resp. ceramic compound 2 on tungsten plate 3 (the remainder of ceramic compound 2 on the surface of the thin tungsten plate 3 that is in contact with the ceramic compound 2 after tungsten plate 2 is broken) high wettability, in other words high adhesion between the tungsten plate 3 and the ceramic compound 2 Therefore, a large amount of the ceramic compound 2 on the tungsten plate 3 was evaluated as "0". The case where there was no ceramic compound 2 on the tungsten plate 3 was evaluated as X and the mean between them was evaluated as "A". Thus, it can be seen from Table 1 that a porosity of less than 0.3% results in low adhesion.

If a metal with a relatively low melting point is used, the sintering is performed earlier. Specifically, it is carried out until the glue gas is released. Inside, pores are formed in large quantities, and it can easily occur through the entire thickness of the metal tube 30. Before the porosity reaches 25% (upper limit of the specified range), the airtightness is lower due to this phenomenon.

When Mo, W, Re, Ti, Hf and Zr are used, the gas tightness is compared by determining the porosity size to 5% in all cases. As shown in Fig. 3, metals having a melting point of 2600 ° C or more, in other words Mo (melting point is 2623 ° C), W (melting point is 3422 ° C) and Re ( the melting point is 3186 ° C).

-4GB 296639 B6

The metal seamless pipe 30 according to the invention preferably has an inner diameter of 0.4 to 3.0 mm and a thickness of 0.05 to 1.0 mm.

As shown in Fig. 4, leakage does not occur (and thus improved airtightness) in certain areas when the inner diameter and thickness sizes are within the above ranges.

For example, if the inner diameter is 3 mm and the thickness is 0.05 mm, the inner diameter is too large and a sufficient density increase is not achieved when sintering. Thus, leakage occurs in a situation where the thickness is comparable to 0.05 mm.

If the inner diameter is 0.4 mm and the thickness is 1.0 mm, the thickness is too large and the unevenness of the drying rate is manifested in sintering. This results in cracks caused by uneven drying (micro-cracks), which eventually causes leakage.

The metal seamless tube 30 according to the invention preferably further comprises at least one type of oxide selected from the group consisting of Al ₂ O ₃ , Y ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O ₃ , Ho ₂ O ₃ and Tm ₂ O ₃ , in an amount of 0.02 to 5% by volume, preferably 0.05 to 2% by volume, based on 100% of the total volume of metal and oxide. If the amount of oxide is less than 0.02% by volume, the effect of increasing the strength is small. If the amount of oxide is greater than 5% by volume, adverse effects such as airtightness reduction, brittleness and the like may occur. Of the above oxides, Al ₂ O ₃ oxide is preferred as it has good corrosion resistance.

The method for manufacturing a metal seamless tube 30 according to the invention comprises:

preparing a mixture comprising 80 to 98 wt. a powder of at least one type of metal selected from the group consisting of metals each having a melting point of 1600 ° C or more and an adhesive in a solvent,

- agitating the mixture for 0 to 3 hours, preferably 1 to 2 hours, and subsequently extruding the mixed material into a tube, and

- drying the tube-shaped material 30 at a temperature of -5 to 25 ° C (preferably 2 to 15 ° C) for (at least) 10 hours to (at most) 48 hours (preferably 24 hours) after completion of extrusion and subsequent drying at 30 to 120 ° C, preferably at 80 to 100 ° C, for 0 to 8 hours, preferably 0.5 to 4 hours, and then firing the dried material at a lower temperature selected from a temperature range of 1000 to 2100 ° C, and at 300 ° C below the melting point of the metal.

According to the method of manufacturing a metal seamless tube, a slight drying is performed over a period of time to complete the extrusion. This mild drying is necessary to eliminate the extrusion tension and similar phenomena existing after extrusion is completed (at the beginning of drying). When drying the material, especially in the form of a tube, the drying speed is inevitably higher than the drying speed of the monolithic (non-hollow) material and must therefore be moderate immediately after the extrusion is complete. Residual extrusion stress is a major cause of firing distortions and the like.

There are no restrictions on the preparation of the mixture. If, at this stage, the metal powder content is less than 80% by weight, cracks may occur due to uneven drying (micro-cracks). If the metal powder content is greater than 98% by weight, the overall dispersion of the metal particles may be insufficient.

Neither the method of mixing nor the extrusion in the extrusion step are subject to any particular restrictions.

-5GB 296639 B6

Also, no particular restrictions apply to the method of drying.

The firing process in the corresponding process stage is carried out in a non-oxidizing atmosphere or in a vacuum. In the firing stage, sintering may be insufficient if the firing temperature is below a temperature selected from a temperature of 1000 ° C and a temperature that is 300 ° C below the melting point of the metal.

If the firing temperature is higher than a lower temperature selected from a temperature of 2100 ° C and a temperature 300 ° C lower than the melting point of the metal, firing deformations may occur, the type and nature of which depend on the metal used.

Using a similar manufacturing process, it is possible in a simple manner to obtain a thin metal seamless tube 30 with a small diameter, which would be difficult to manufacture using conventional manufacturing techniques. It is therefore possible to achieve improved productivity and, consequently, cost reduction.

The drying of the seamless metal tube 30 material is preferably carried out in an atmosphere containing the solvent vapors used in the compositions.

By using the above production method, it is possible to carry out fine drying and to reduce the occurrence of the extrusion tension.

In the following, the invention is described by way of examples. However, it is to be understood that the invention is not limited to these exemplary embodiments.

Example 1

To 1000 g of tungsten powder (melting point 3422 ° C) was added 12 g of ethyl cellulose (binder), 30 g of butylcarbitol acetate (solvent) and 10 g of admixtures containing Al ₂ O ₃ . The mixture was mixed ten times in a three-roll mixing mill.

The mixture was formed in an extruder. The extruded material was dried at 80 ° C for 2 hours.

The dried material was fired with hydrogen at 1900 ° C for 3 hours. In order to remove the binder while avoiding molybdenum oxidation, humidification to a dew point of 0 ° C was performed.

A molybdenum tube having a porosity of 8% and a leakage rate of 1.0 x 10 ^-10 atm / m ³ / s or less was measured by the helium leak test as described above.

As already mentioned in the above description, it is possible by the present invention to produce a metal seamless pipe 30 that is poorly machinable, but can be manufactured to have a small thickness and a small inner diameter which is characterized by improved mechanical strength and airtightness. it is possible, for example, to use, for example, a transparent ceramic tube 20 or a glass tube 20 as a sealing member. a translucent housing (e.g., a ceramic translucent housing), for example, in a high pressure discharge lamp 10 (e.g., a metal halide lamp). The invention also provides a method for producing a similar metal seamless tube 30. The metal seamless tube 30 of the invention can be advantageously used, in particular, as a sealing member of a translucent ceramic tube 20, for example in a high pressure discharge lamp 10 (e.g. Said metal seamless tube 30 can also be advantageously used as a metal tube 30 made of poorly machined metal and with a low thickness and small inside diameter, characterized by high heat resistance, high mechanical strength and good airtightness. An example of a possible application of such a tube 30 is, in particular, a fine tube 30, located, for example, in the heat exchangers used

-6E 296639 B6 in extreme situations and environments such as space applications, aerospace or military applications, and the like.

PATENT CLAIMS

Claims (7)

CLAIMS 1. A metal seamless tube, characterized in that it comprises at least one type of metal having a melting point of 1600 ° C or more and selected from the group of Mo, W, Re, Ti, Hf and Zr, wherein the tube (30) has a porosity of 03-25%, the porosity being defined as the ratio of the area of open pores present on the outer surface of the tube (30) to the total surface area of the outer surface of the tube (30). (30), and the tube (30) has an inner diameter of 0.4 to 3.0 mm and a thickness of 0.05 to 1.0 mm. A metal seamless tube according to claim 1, characterized in that at least one type of metal is selected from the group of Mo, W and Re with a melting point of 2600 ° C or more. The metal seamless tube according to claims 1 and 2, further comprising in addition to the metal at least one type of oxide selected from the group consisting of Al ₂ O ₃ , Y ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O ₃ , Ho ₂ O ₃ and Tm ₂ O ₃ , in an amount of 0.02 to 5% by volume relative to 100% of the total metal and oxide volume. A method for manufacturing a metal seamless pipe according to any one of claims 1 to 3, characterized in that it comprises: preparing a mixture containing 80 to 98 wt. a powder of at least one type of metal selected from the group of Mo, W, Re, Ti, Hf and Zr having a melting point of 1600 ° C or more, and an adhesive in a solvent, - agitating the mixture for 0 to 3 hours and subsequently extruding the mixed material to form a tube-shaped material (30), and - drying the tube-shaped material (30) at -5 to 25 ° C for 10 hours to 48 hours after completion of the extrusion and then at 30 to 120 ° C for 0.5 to 8 hours and then firing the dried material at a temperature of a range between 1000 ° C and below either 2100 ° C or at a temperature 300 ° C below the melting point of the metal. A method for producing a metal seamless tube according to claim 4, characterized in that at least one type of metal is selected from the group of Mo, W and Re with a melting point of 2600 ° C or more. Method for producing a metal seamless tube according to claim 4 or 5, characterized in that at least one type of oxide selected from the group consisting of Al ₂ O ₃ , Y ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O ₃ , Ho ₂ O ₃ and Tm ₂ O ₃ , in an amount of 0.02 to 5% by volume relative to 100% of the total metal and oxide volume. Method for producing a metal seamless tube according to any one of claims 4 to 6, characterized in that the drying of the tube-shaped material (30) is carried out in an atmosphere containing solvent vapors.