DE2120736A1 - Rotating anode for X-ray tubes - Google Patents

Description

It is already known to make rotating anodes for X-ray tubes from a disk-shaped base body made of molybdenum to produce, at least at the point of impact for the electrons with a layer of tungsten or a tungsten alloy, e.g. a tungsten-rhenium alloy, is covered. By using a molybdenum body for the rotating anodes compared to an anode consisting entirely of tungsten, the advantage achieved that because of the opposite Tungsten with a lower specific weight than molybdenum, the centrifugal forces that occur when the anode rotates are significantly reduced, so that higher speeds can be allowed. at However, the difference in thermal expansion between the molybdenum base body has an effect on high stresses and the tungsten alloy are disadvantageous. This is the reason for cracks to appear. ",;,"; .U iii ^ Wiuun ,; you already have to suppress it

. 2 - ^{27 A} P ^ril

C -; -_- thought of the strength of the molybdenum green>:.; Rpers a-ilurch to raise that same other uphill .j-.aile, such as tungsten, tantalum, niobium, rhenium and Osmium, can be added. It is already known Learn about molybdenum base alloy additions of 0.05 1.5 wt Add amounts of carbon. This will make the

"Thermal strength and the recrystallization temperature : It also increases the molybdenum body, but This means that cracks are caused by differences in design between the base body and the lframe support is not avoided in all cases.

the invention is described another way.:. to reduce the mechanical stresses that occur as a result of the thermal expansion differences. The r "· indung relates to a rotary anode for X-ray tubes. ^ E of a basic body of a molybdenum alloy -iteht on which at least at the impact for. I electrons, a layer of tungsten or a" .f. . "alloy, eg a tungsten-rhenium alloy, • .... ge" ..: - is right. The invention consists in that the molybdenum alloy forming the main body of the rotating anode contains 50-500 ppm, preferably 100-200 ppm, boron. The addition of boron not only increases the heat resistance and the recrystallization temperature of the base body, but above all its cold ductility. In addition, small boron contents have a strong icorn-refining effect. "· - 3 Secondary grain growth is also at the highest tem-

.-ati.ren suppressed so that the '.volfram edition - Spatially the grain size of the molybdenum supports only

ii _c ; differs. When the highly stressed rotating anode cools down, the internal stresses can therefore be balanced out, so that the risk of cracking is increased.

^ liend is degraded and the life of the tube.;. is increased. The heat resistance of the base body can be increased by more that of the alloy n-Tnium is up to an amount of 2 wt. $ Was added yet. "3ie rotary anode according to the invention can be prepared by powder etc.

metallurgical processes in a simple manner.

-.:-. An embodiment of the invention is still nüier explains:

Ir. Eire round die which is slightly greater than the herzu- -llende rotary anode is first molybdenum powder. lev el containing an additive of 0.1 fo boron. This additive can best be used in the form of an appropriate mixture of molybdenum boride. If an addition of hafnium is desired, then ? .- ~ 3ez. s: “Best be oeijvsmengt in the form of powdered hafnium hydride. A second, about 2.5 mm thick layer is placed over this about 10 mm thick sleeve, which consists of V / oIfram with a ratio of 10 % rhenium. Das.Pulver is pressed with a pressure of 4 t / cm to form a round disc. The pressed body is then sintered in hydrogen at a temperature of 2000 ° C. During sintering, some of the boron is converted into boron trioxide by oxygen residues in the powder and in the gas atmosphere, which evaporates. The achieved boron content is

1098HQ / 1076

SAO

therefore a little lower than the one used and amounts to for example only 0.03 # * The sintered body is then forged and ground to the final dimensions, which show rotating anodes manufactured in this way, as was determined by means of reed pictures, a good bond between the base body made of a molybdenum alloy and that made of a tungsten alloy existing top layer. Due to the boron contained in the molybdenum body, which is partly also in the Tungsten alloy diffuses, becomes an excellent fine-grained transition between these two layers created.

The invention is of course not limited to that shown Embodiment limited. In addition to boron and hafnium, other alloy additives, e.g. tungsten, titanium or zirconium can be added to the base body. Even those made from a tungsten alloy The existing top layer of the rotating anode can contain further additives, e.g. other refractory metals, such as osmium or iridium.

- 5 109850/1076

Claims (2)

2120706 Claims M.) Rotary anode for X-ray tubes, consisting of a round body made of a molybdenum alloy, on which a layer of V / oIfram or a tungsten alloy, e.g. a tungsten-rhenium alloy, is applied at least at the point of impact for the electrons, thereby marked that the liolybdenum base body contains 50-500 ppm, preferably 100-200 ppm, boron. 2. Rotating anode according to claim 1, characterized in that that the molybdenum body also contains up to 2 $ hafnium. y. Rotary anode according to Claims 1 and 2, characterized in that the base body also contains further alloy elements, such as tungsten, titanium or zirconium. ORiGINAl INSPECTED 10 9850/1