JPS6137005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing hollow extruded aluminum profiles used in high vacuum conditions, such as particle acceleration pipes used in accelerators such as synchrotrons.

In this specification, aluminum includes aluminum and its alloys.

Up until now, stainless steel has mainly been used as the material for this type of particle acceleration pipe, but recently aluminum has been found to be suitable for this purpose and is being used more and more.
The reasons for this are that compared to stainless steel, aluminum is less likely to generate induced radiation, and even if it does, it decays quickly, has good thermal and electrical conductivity, and has a small surface gas release coefficient.
This is because it is excellent in terms of light weight and good workability. The inside of this particle acceleration pipe must be kept at a high vacuum in order to allow particles to pass through it at high speed. Therefore, an important issue is how to create a high vacuum inside the pipe.

Conventionally, in order to create a high vacuum inside a particle acceleration pipe, the inner surface of the pipe was degreased with an organic solvent, etc., and then heated and degassed at approximately 150°C for about 24 hours was repeatedly performed. Previously, discharge cleaning was carried out in hydrogen gas, argon gas, oxygen gas, etc., in combination with the was still not completely satisfactory.

By the way, in order to maintain a high degree of vacuum inside the particle acceleration pipe, it is important to reduce the amount of gas released from the inner wall of the pipe after it is made into a product. As a result of repeated experimental research on this point, the present inventors have found that the state of the coating on the inner surface of the aluminum pipe has a large effect on the degree of vacuum.

As is well known, aluminum is a metal that is very easily oxidized, and an oxide film is formed on the surface even if it comes into contact with a trace amount of oxygen. Furthermore, when placed in an environment containing moisture such as water or humidity, a hydrated oxide film is formed on the surface. The higher the temperature of the hydrated oxide production reaction, the more remarkable the growth of the hydrated oxide film.
In a high temperature environment, a hydrated oxide film such as boehmite or vialite is formed on the aluminum surface.
The quality of such a hydrated oxide film is much rougher and more porous than that of an aluminum oxide film formed in an environment without moisture, and the pores are also intricately shaped. In addition, the film thickness is also thick.

By the way, a hydrated oxide film is formed on the inner surface of an aluminum pipe formed by ordinary extrusion molding due to contact with the atmosphere containing moisture during molding. Moreover, this hydrated oxide film is exposed to high temperatures during extrusion, so
The formation reaction of the hydrated oxide film is promoted, resulting in a thick film. The film quality of this hydrated oxide film is as described above, and since it is a thick film, a large amount of water is adsorbed to the film. Moreover, because the film lacks consistency, moisture that remains in the atmosphere even after molding.
Vacuum reducing substances such as hydrocarbons, carbon dioxide and carbon monoxide are adsorbed onto the coating. Such substances that lower the degree of vacuum are still present to some extent even during discharge cleaning in the gas or during evacuation, and therefore are adsorbed to the film as described above. Moreover, since the hydrated oxide film is as described above, it is in the form of being occluded within the film. As a result, it becomes difficult to remove it, and it is difficult to remove it even by vacuuming. Therefore,
This is the cause of the impediment to improving the degree of vacuum in the particle acceleration pipe. In addition, in order to increase the mechanical strength of aluminum pipes after extrusion, quenching treatments such as water cooling and air cooling are performed after high-temperature heating, but the above-mentioned hydrated oxide film formed during extrusion is also As the film grows further, the vacuum-lowering substances that have already been adsorbed become incorporated into the film.

The purpose of this invention is to solve the above-mentioned problems and provide an inexpensive manufacturing method for vacuum extrusion aluminum hollow extruded sections suitable for applications such as particle acceleration pipes that require the interior to be kept in a vacuum. It is in.

The method for manufacturing a hollow extruded aluminum profile for vacuum use according to the present invention includes, when extruding an aluminum hollow extruded profile, supplying an inert gas containing oxygen as an impurity into the hollow part of the profile being extruded; This method is characterized in that a thin honey oxide film is formed on the inner surface of the hollow extruded shape due to the oxygen contained in the inert gas.

In the above, from the viewpoint of extrudability and mechanical strength, A6061 and
A-Mg-Si alloys such as A6063 are preferred.
Argon and helium are common inert gases. Furthermore, the purity of the inert gas currently available industrially is approximately 99.99%, and it always contains a small amount of oxygen as an impurity.

The reason why the degree of vacuum in aluminum acceleration pipes manufactured using conventional methods is not sufficiently high is that, as mentioned above, a hydrated oxide film is formed on the aluminum surface, and this hydrated oxide film This is because vacuum deteriorating substances that are occluded in the pipe are released into the pipe.However, according to the method for manufacturing a hollow extruded aluminum profile for vacuum use of the present invention, the hollow extruded aluminum profile is extruded. During molding, an inert gas containing oxygen as an impurity is supplied into the hollow part of the extruded shape, so the inner surface of the hollow extruded shape does not come into contact with the moisture-containing atmosphere. No problematic hydrated oxide film is formed on the same inner surface. On the other hand, due to the oxygen contained in the supplied inert gas, an oxide film is formed on the same inner surface. Since the film quality of this oxide film is honey and its thickness is thin, adsorption and occlusion of vacuum deteriorating substances is significantly less than that of a hydrated oxide film, and even if it is adsorbed or occluded, it can be easily removed by degassing treatment. Can be removed. Therefore, the amount of vacuum-degrading substances released into the pipe is extremely small, making it possible to maintain a high degree of vacuum, and eliminating or reducing the troublesome work required to increase the degree of vacuum as in the past. be able to.

It is also possible to supply only oxygen into the hollow part of the shape, but if there is only oxygen, there is a risk of explosion if oil adhering to the die transfers to the hollow extruded shape, where the temperature is high during extrusion. There is sex. In order to eliminate this danger, it is preferable to use a mixed gas of oxygen and an inert gas, but this increases the cost. According to the present invention, there is no such fear due to the presence of an inert gas, and the above-mentioned oxide film can be sufficiently obtained with a small amount of oxygen, which has the advantage of reducing costs.

Note that the hollow extruded shape obtained by the method of the present invention can be used not only for particle acceleration pipes but also for products that require maintaining a high vacuum.

Embodiments of the invention will be described below with reference to the drawings.

Fig. 1 shows an extruder, in which 1 is a container, 2 is an aluminum billet inside the container 1, 3 and 4 are dummy blocks and stems that press the billet 2, and 5 is in the center. A male port hole die having a mixed gas injection port 6, 7 a female die, 8 a die holder, 9 and 10 gas passages formed in the male die 5 and the die holder 8, and 11 a die. - A gas supply port 12 provided on the holder 8 is a gas container, and a conduit 13 attached to this is connected to the gas supply port 11. 1
4 is a bolster.

The extruder shown in FIG. 1 is used to extrude hollow extruded sections 15, 16 used for particle acceleration pipes having cross sections as shown in FIGS. 2 and 3. Of course, the dies used for molding both have shapes that match the respective shapes 15 and 16 to be molded. Both extruded sections 15 and 16 of a predetermined length are alternately connected to assemble an endless particle acceleration pipe (not shown). In both figures, reference numerals 17 and 18 indicate a particle flow hollow part with an elliptical cross section (when incorporated into a particle acceleration pipe - the same applies hereinafter), 19 an adjacent hollow part for evacuation with a rectangular cross section, and 20 a hollow part for vacuum evacuation with a rectangular cross section. hollow part 17,
19 partition walls, in which communication holes are bored at predetermined intervals. 21 and 22 are particle circulation hollow parts 1
Cooling water circulation hollow portions 7 and 18 with a small circular cross section are provided on one side, and heating desorption portions 23, 24 and 25 are provided on one side of the particle circulation hollow portions 17 and 18 and the vacuum hollow portion 19, respectively. Seeds for gas processing
This is a groove for attaching heater wires.

The manufacturing order of the hollow extruded section 15 will be described. First, billet 2 of A6063, which had been homogenized at 560℃ for 3 hours after caustic cleaning of the die, was extruded at the extrusion temperature.
Extrude at 500℃ and extrusion speed of 10m/min. Do not use lubricant at this time. At the same time as the extrusion, argon gas 26 containing oxygen as an impurity is ejected from the gas container 12 through the conduit 13 and the passages 10 and 9 from the ejection port 6 at a pressure of 2 to 3 kg/cm ² to remove the shape 15 that is being extruded. Supplied into the hollow part. Then, the tip opening of the slightly extruded section 15 is pressed and sealed with a press to form one sealed end 27 as shown in FIG. After that, the mixed gas 26
After continuing to supply the material and extruding it to a predetermined length, the shape material 15
is cut with a shear and the cut end is sealed at the same time to form the other sealed end 28 (see FIG. 4). After that, the profile 15 with the mixed gas 26 sealed is
Forced air cooling to 250℃ followed by natural cooling followed by tensile straightening. Next, aging treatment is performed at 180°C for 6 hours in that state. Finally, the two sealed ends 27, 28 of the profile 15 are cut off without oil and without air blowing to obtain a hollow extruded profile of the specified dimensions. Other hollow extruded sections 16 can also be manufactured in the same manner as described above, only by changing the die.

Note that the sealed end portions 27 and 28 may be cut and removed after being sent to the place where the hollow extruded shape is used after extrusion molding.

A thin honey oxide film was formed on the inner surface of the extruded shape.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a longitudinal sectional view showing a state in the middle of extrusion molding, Fig. 2 is a sectional view taken along the line - in Fig. 1, and Fig. 3 is a particle acceleration pipe. Figure 2-equivalent cross-sectional view of other shapes used in combination with the shapes shown in Figure 2 when making
The figure is a longitudinal sectional view of a profile sealed with an inert gas containing oxygen as an impurity. 15, 16...Hollow extruded shape.

Claims (1)

[Claims] 1. When extruding an aluminum hollow extruded section, an inert gas containing oxygen as an impurity is supplied into the hollow part of the extruded section, and the oxygen contained in this inert gas causes the hollow extruded section to be formed. A method for manufacturing hollow extruded aluminum shapes for vacuum use, which is characterized by forming a thin oxide film with honey on the inner surface of the material.