EP2013482A1

EP2013482A1 - Rotors or stators of a turbomolecular pump

Info

Publication number: EP2013482A1
Application number: EP07728626A
Authority: EP
Inventors: Rainer Hölzer; Michael Froitzheim; Lars Etschenberg; Ishan Roth; Gernot Fischer; Dieter Sauer; Gregor Terlinde
Original assignee: Otto Fuchs KG; Oerlikon Leybold Vacuum GmbH
Current assignee: Otto Fuchs KG; Leybold GmbH
Priority date: 2006-04-29
Filing date: 2007-04-27
Publication date: 2009-01-14
Anticipated expiration: 2027-04-27
Also published as: US20090180890A1; JP5274447B2; JP5274446B2; CN101438063A; WO2007125106A3; WO2007125104A1; RU2008146811A; EP2013483A2; RU2455529C2; RU2008146813A; CN101432525A; JP2009535550A; EP2013483B1; DE502007003011D1; RU2435076C2; EP2013482B1; WO2007125106A2; US20100199495A1; JP2009535551A

Abstract

The invention relates to the rotors or stators of a turbomolecular pump having rotor blades that are produced from a special aluminum alloy.

Description

Rotors or stators of a turbomolecular pump

The invention relates to rotors or stators of a turbomolecular pump with rotor blades made of a special aluminum alloy.

For the construction of rotors of a turbomolecular pump with rotor blades, aluminum has prevailed as a construction material, as this can best combine the demand for the lowest possible specific weight with high strength and good workability. Thus, M. Wutz et. al, theory and practice of vacuum technology, second edition, 1982, Friedr. Vieweg & Sohn, Braunschweig / Wiesbaden, page 207/208 known to produce the rotor or stator of specially selected aluminum alloys.

In order to build efficient pump rotors or stators, aluminum alloys with high heat resistance are predominantly used. Rotors made of such materials are usually produced by means of cutting processes, as described, for example, in DE 10210404 A1 or DE 29715035 U1, to which reference is made in their entirety. In particular, the shape of the wing contour is time consuming and costly.

DE 101 03 230 Al describes rotors in which a part of the rotor blades has a rear side which is convex on the suction side and concave on the pressure side, or that at least part of the Rotor blades has a front side, which is concave on the suction side and convex on the pressure side.

When using high-strength alloys, their low forming capacity has to be considered. As a result, the complete shaping of solid bodies or disks must take place with the aid of chip-removing methods, and less costly shaping processes by means of plastic deformation, such as twisting, embossing or stamping, can not be used.

In concrete terms, in the case of medium-strength alloys, the combination of chip removing (turning, milling) and / or thermal removal methods (erosion) with plastic deformation (twisting) methods has proved to be a more economical production method for rotors or stators.

First, individual disk-shaped segments are machined Span working in a cylindrical solid body, which are then slotted axially spark erosion. In this way, disk-shaped structures per disk segment, which receive a defined angle of attack by a subsequent plastic torsion about the wing longitudinal axis.

DE 100 53 664 A1 describes a mechanical kinetic vacuum pump with a rotor consisting of an Al alloy; to increase the hot and creep strength is proposed that the rotors material is a powder metallurgy produced light metal alloy, the main alloying component next

070545wo HPJ / ko 27.04.2007 Aluminum is copper which further contains magnesium, manganese, zirconium and silver, and optionally titanium.

By using a new high and heat resistant aluminum wrought alloy, which has an unusually high elongation at break in the cold outsourced state, it is now possible to use the above-mentioned cheaper molding processes, which were previously reserved only low to medium strength Al alloys ,

WO 2004/003244 A1 describes an Al-Cu-Mg-Mn alloy for the production of semi-finished products with high static and dynamic strength properties. Surprisingly, it has been found that the alloys described here, on the one hand, are particularly heat-resistant and, on the other hand, have such high ductility in the cold-aged state that cost-effective rotor production by chip removal or thermal removal processes and forming (for example twisting or bending) is possible.

The invention therefore relates, in a first embodiment, to rotors or stators of a turbomolecular pump having rotor blades of an aluminum alloy, which is characterized in that the alloy comprises an Al-Cu-Mg-Mn-Knet alloy.

Multi-stage, one-piece rotors or stators are thus also available with the aid of the present invention, such as rotors or stators, which are composed of individual stages segments. The rotors or stators have a low specific weight with high strength and good processability.

070545wo HPJ / ko 27.04.2007 Particularly preferred according to the present invention, the kneading alloy used has the following composition:

0.3 to 0.7% by weight of silicon (Si), up to 0.15% by weight of iron (Fe),

3.5 to 4.5% by weight of copper (Cu),

0.1 to 0.5% by weight of manganese (Mn),

0.3 to 0.8% by weight of magnesium (Mg),

0.05 to 0.15% by weight of titanium (Ti),

0.1 to 0.25% by weight zirconium (Zr),

0.3 to 0.7% by weight of silver (Ag), up to 0.05% by weight of other, individually, up to 0.15% by weight of other, total and

Balance wt .-% aluminum (AI).

The kneading alloys used have a higher static and dynamic heat resistance and improved creep resistance with very good fracture mechanical properties compared to other prior art alloys and are therefore particularly suitable for the rotors or stators of turbomolecular pumps according to the invention. In particular, the kneading alloy used according to the invention has an elongation at break of at least 14%, in particular 17 to 20% in the cold-aged state, determined in the tensile test according to DIN EN 10002.

The term wrought alloy in the sense of the invention comprises a special treatment of the alloy used according to the invention, in which the cast structure is converted and "kneaded" by, for example, extrusion, rolling or forging at elevated temperature.

070545wo HPJ / ko 27.04.2007 becomes. The light metal is thereby ductile. Wrought alloys therefore also allow further cold working such as rolling, drawing or forging (for example, cold forging).

From WO 2004/003244 Al is known per se that these properties are achieved in particular at a copper-magnesium ratio between 5 and 9.5, in particular at a ratio between 6.3 and 9.3.

The copper content is preferably in the range of 3.8 and 4.2 wt .-% and the magnesium content in the range of 0.45 and 0.6 wt .-%. The copper content is clearly above the maximum solubility for copper in the presence of the claimed magnesium content. This has the consequence that the proportion of insoluble copper-containing phases is very low, even taking into account the other alloying and accompanying elements. This results in an improvement in the dynamic properties and the fracture toughness of the rotors made from such an alloy.

In contrast to aluminum alloys which are furthermore known in the prior art, the proportion of the claimed kneading alloy in silver is between 0.3 and 0.7% by weight, preferably 0.45 and 0.6% by weight. In conjunction with silicon (0.3 to 0.7 wt .-%, preferably 0.4 to 0.6 wt .-%) curing takes place via the same mechanisms as in silver-free Al-Cu-Mg alloys. For smaller silicon contents, however, the precipitation profile is different due to the addition of silver. Although the rotors made from such an alloy have good hot and creep resistance in cooler conditions; they correspond

070545wo HPJ / ko 27.04.2007 but not the desired requirements. Only silicon contents from 0.3% by weight suppress the otherwise typical change in the precipitation behavior of Al-Cu-Mg-Ag alloys, so that higher strength values can be achieved without loss of heat resistance and creep resistance at the Cu and Mg contents.

The manganese content of the alloy used is 0.1 to 0.5% by weight, preferably 0.2 to 0.4% by weight. For alloys with higher manganese contents, undesirable precipitation processes were found in a long-term high-temperature stress, leading to a reduction in strength. For this reason, the manganese content is limited to 0.5% by weight. In principle, however, manganese is an alloying constituent required for microstructure control.

To compensate for the reduced voids of the manganese in terms of microstructure control, the alloy contains zirconium in an amount of 0.10 to 0.25 wt .-%, in particular 0.14 to 0.2 wt .-%. The secreting zirconium aluminides are generally even more finely dispersed than manganese aluminides. Moreover, it has been shown that the zirconium aluminides contribute to the thermal stability of the alloy.

For grain refining, the alloy is added 0.05 to 0.15 wt .-%, preferably 0.10 to 0.15 wt .-% titanium. Conveniently, the titanium is added to the alloy in the form of an Al-5Ti-1B master alloy, whereby the alloy automatically contains boron. This results in finely divided, insoluble titanium diborides. These contribute to the thermal stability of the alloy.

070545wo HPJ / ko 27.04.2007 As an unavoidable impurity, the alloy may have a maximum of 0.15% iron, preferably 0.10% iron.

The rotors or stators according to the invention of a turbomolecular pump with rotor blades made of the above-defined aluminum alloy can be produced, for example, by producing the rotor blades from individual disks or solid bodies by radial separation, which are subsequently formed by forming (for example twisting, bending, embossing, forging, etc.). be made to a desired angle of attack. The production of the desired angle of attack also includes, where appropriate, the production of a defined wing contour. Alternatively, the steps of cutting and forming can also be carried out in one operation, for example by stamping.

The steps of this method per se are known, but were previously limited to low and medium-strength aluminum alloys, since only these have the required forming capacity. However, with the aid of the present invention, this method is also applicable to the defined high-strength aluminum alloys.

Usually, one proceeds when forming disc-shaped blade stages, in which individual wing segments are previously produced by radial separation. Separation methods in the sense of the present invention include cutting methods, such as laser or water jet as well as eroding, machining, punching or stamping.

070545wo HPJ / ko 27.04.2007 The combination of chip-removing molding with plastic forming processes reduces the manufacturing costs of the rotors or stators.

EXEMPLARY EMBODIMENTS:

Example 1 :

Production of the adjustment of pump rotors of a TMP by forming

From a cylindrical solid body of the alloy AA 2016 (see WO 2004/003244) were concentrically stacked disc-shaped segments according to the desired number of pumping stages Span lifted out worked. This resulted in a rotationally symmetrical body, which consisted of superimposed, disc-shaped ribs, which were connected to each other in the hub area. The rib thickness corresponded to the later wing thickness. Each ribbed disc was now slotted circumferentially in the axial direction to the vicinity of the hub at regular intervals, creating individual wing segments.

The material was in the state "solution-annealed, quenched and cold-aged." In this state it possessed a high formability.

In the same state, the wing segments were now twisted about their longitudinal axis. The Tordierung took place with a fork-shaped gripper arm, the one wing segment concerned up close

070545wo HPJ / ko 27.04.2007 included at the Flügelfuß and then carried out a torsional movement about the wing longitudinal axis up to the desired angle of attack. The wing segment experienced a plastic deformation in the area close to the wings. In this way, torsion or angle of attack of about 45 [°] to the starting position was easily achieved without cracks in the wing root area being observed.

Such conventional angles can not be achieved with conventional heat-resistant Al alloys.

In order to obtain the strength required for later operation, a thermal aging was carried out to achieve maximum strength according to condition T6.

Example 2:

Punching of stator discs

From aluminum sheets of the material mentioned in Example 1, stator disks are produced by stamping as follows:

Semicircular ring segments are punched out of Al sheets in thicknesses between 0.5 and 1.0 [mm]. Condition of the sheets: "solution-annealed, quenched and cold-aged".

These ring segments are now inserted into a stamping die, which works out the wing contour by pressing the counter-mold on this stamping die.

070545wo HPJ / ko 27.04.2007 In this case, the leading edges of the radially symmetrically arranged wing segments are punched out, while the angle of attack of the wings, however, is formed by plastic deformation in the embossing mold. The maximum deformation occurs in the region of the transition of the free Flügelanströmkante to undeformed sheet.

In order to obtain the strength required for later operation, hot aging takes place to maximum strength according to condition T6.

070545wo HPJ / ko 27.04.2007

Claims

claims:

1. Rotors or stators of a turbomolecular pump with rotor blades of an aluminum alloy, which is characterized in that the alloy comprises an Al-Cu-Mg-Mn-Knead alloy.

2. rotors or stators according to claim 1, characterized in that they comprise a kneading alloy having the following composition:

0.3 to 0.7% by weight of silicon (Si) up to 0.15% by weight of iron (Fe) 3.5 to 4.5% by weight of copper (Cu) 0.1 to 0.5 % By weight of manganese (Mn) 0.3 to 0.8% by weight of magnesium (Mg) 0.05 to 0.15% by weight of titanium (Ti) 0.1 to 0.25% by weight of zirconium (Zr) 0.3 to 0.7% by weight of silver (Ag) up to 0.05% by weight of other, individually up to 0.15% by weight of other, total remaining wt% of aluminum (Al ).