DE1533347B1 - Tungsten-based ductile alloys - Google Patents

Description

The invention relates to alloys Tungsten base, which are characterized by transition temperatures from the ductile to the brittle state, the at temperatures below those of unalloyed tungsten.

It is known that the temperature for the transition can be reduced from the ductile to the brittle state of tungsten by adding rhenium can. Although tungsten wire already has a certain ductility at room temperature without additives Made by Rhenium: are used for the manufacture of sheet metal, pipes and other shaped Products made from tungsten have about 22 to 25% rhenium to achieve ductility at room temperature necessary. ., '.. ■ ..

Because of the rarity and the high price of rhenium, however, it seems cheap to use an alloy to make available that is ductile at room temperature or below, but less of contains this relatively rare metal. Furthermore, the alloy should have at least the same strength as unalloyed tungsten and a not lower recrystallization temperature than have this metal.

It is therefore an object of the invention to provide a tungsten-based alloy containing up to 1% rhenium and whose temperature for the transition from the ductile to the brittle state is, however, low.

Furthermore, the alloy based on tungsten is said to be be ductile at a lower temperature and still have essentially the same strength and strength Have high temperature properties like unalloyed tungsten.

The alloys according to the invention with such favorable properties consist essentially of 0.0001 to 0.0035% manganese, up to 1% rhenium, the rest Tungsten and inevitable impurities.

According to the invention, these tungsten-based alloys are produced by using tungsten powder with 0.1 to 0.3% manganese and possibly less than 1% rhenium, both in powder form, mixes (all% figures mean percentages by weight based on tungsten) and preferably the mixture Press this mixture into a block only at 1300 ° C pre-sintered in a vacuum or in an inert gas flow, i.e. under the same conditions. 1650 ° C and finally, as in the production of Sintered tungsten bodies known, sintered at 2350 ° G and, if desired, followed by hot deformation.

The pre-sintering at 1300 ° C serves to convert manganese with residual oxygen in the mixture to form manganese dioxide (MnO ₂ ), and during pre-sintering at 1650 ° C part of the manganese oxide and much of the remaining manganese evaporate. These two pre-sintering stages at 1300 and at 1650 ° C should generally depending. Last 4 hours, while the final sintering process at 2350 ° C preferably lasts 6 hours. The mixture is pressed into a block, preferably under a hydrostatic pressure of about 3500 kg / cm ² .

The pre-sintering at 1300 and 1650 ° C. is alternatively carried out either in a vacuum at a pressure of preferably 2 · 10 " ^e Torr or in flowing hydrogen or inert gas. In such an atmosphere, the flow rate of the gas should be sufficient to achieve both To remove both manganese and manganese oxide vapors so that their respective pressure in the block is lower than the normal vapor pressure of these substances at the pre-sintering temperature.

After the two pre-sintering stages, the mixture is at 2350 ° C for 6 hours under the same atmospheric conditions sintered as in pre-sintering. During sintering, the alloy is compacted, and almost all of the rest of the oxygen combines with manganese and escapes as manganese oxide. After sintering, the alloy is rolled to the desired thickness and cleaned.

Emission and mass spectrometric analyzes of samples of the resulting alloy show that it contains 0.0001 to 0.0035% manganese. That is significantly less than the amount originally Manganese introduced into the mixture, although it is more than the residual manganese content of 0.00003 to 0.00004% that is found in a typical unalloyed tungsten ingot. The% content of the Rhenium in the alloy remains essentially unchanged from that originally in the Mixture introduced amount. The oxygen content of the alloy samples is significantly lower than that of unalloyed tungsten, which contains between 0.005 and 0.01% oxygen

The temperatures for the transition from ductile to brittle behavior were at a number of Compositions determined by taking samples 25mm long, 10mm wide and 1mm thick across a radius of four times the sample thickness at an angle of 105 ° at different temperatures tried to bend. The minimum temperature at which the samples look low but noticeable Bending cracking (not ductile) was determined as well as the minimum temperature at which the specimens can be bent by 105 ° without cracking (ductile).

Alloys in sheet form with a thickness of 1 mm were mixed in the manner already described made of manganese, rhenium and tungsten in the amounts given in the table below. The (brittle -> ductu) transition stencils, the oxygen content, tensile strength and recrystallization temperature of samples were determined.

Table I.

Mn re W. Final Mn salary Transition temperature ⁰ C) des oxygen
salary brittle— * ■ ductile
( ⁰ Q ductile 0.10 0.00 rest (Weight Temperature ( State (Weight Base alloy (mixture)
(Weight percent) 0.10 0.20 rest percent) not duktEen 125 percent) 0.10 0.50 rest <0.0001 State 25th 0.0022 0.10 0.75 rest 0.0001 100 0 0.0009 0.15 0.00 rest 0.0001 10 0.0016 0.0002 - 5th 40 0.0038 0.0001 -20 - 25th

Table I (continued)

Mn re W- Final Mn salary Transition temperature ductile oxygen
salary brittle - »- ductile
( ⁰ C) State 0.20 0.00 rest (Weight Temperature (° C) des 70 (Weight Base alloy (mixture)
(Weight percent) 0.20 0.50 rest percent) not ductile 10 percent) 0.30 0.00 rest 0.0002 State 50 0.0013 0.30 0.50 rest 0.0004 50 10 0.0002 0.30 1.00 rest 0.0003 0 35 0.0028 0.0013 35 0.0026 0.0035 0 ■ "- 25th

The final Re content corresponded to the Re content of Base alloy.

The above alloys have a tensile strength at 1650 ⁰ C of about 9.80 kg / mm ² and recrystallization temperatures in the range from 1400 to 155o ao ⁰ C. These values are slightly higher than those prepared with unalloyed tungsten obtained by the process described will. The transition temperature (not ductile) of unalloyed tungsten is 75 ⁰ C, and the temperature is determined at the ductility at 8O ⁰ C.

The emission spectrometric analysis of the alloys showed that the residual manganese content was at most equal to 0.0035% in all of them. Mass spectrometric Analysis of selected alloys obtained by mixing elemental manganese and Rhenium in powder form with tungsten before pre-sintering show that the manganese residue increases with the addition of manganese, as shown in FIG can be seen in the table below.

Table II

salary the mix re W. Mn before sintering (%) 0.5 rest 0.0001 Mn 0.75 rest 0.0002 0.1 without rest 0.0003 0.1 0.5 rest 0.0013 0.3 0.5

Sintered Alloy (%) Re I

40

unchanged unchanged unchanged unchanged

Remainder remainder remainder

As the table shows, the mass spectrometer content of the final alloys was in manganese, 0.0001 to 0.0013%. The percentage of rhenium in the final alloy was also found to be essentially unchanged compared to the value by emission spectroscopy found in the original mix.

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Claims (7)

Patent claims: 1. Ductile alloy based on tungsten, consisting of 0.0001 to 0.0035% manganese, up to 1% Rhenium, the remainder tungsten and inevitable impurities. 2. Alloy according to claim 1, consisting of 0.0001 to 0.0002% manganese, 0.1 to 1% rhenium, Remainder tungsten and inevitable impurities. 3. Alloy according to claim 2, consisting of 0.0002% manganese, 0.75% rhenium, the remainder tungsten and inevitable impurities. 4. Alloy according to claim 1, consisting of 0.0001 to 0.0035% manganese, the remainder tungsten and inevitable impurities. 5. A method for producing the tungsten-based alloys according to any one of the preceding claims, characterized by the following Steps: a) Mixing tungsten with 0.1 to 0.3% manganese and optionally up to 1% rhenium, all in powder form, and preferably compressing this mixture under Pressure to a block, b) pre-sintering the mixture at 1300 ^° C. in a vacuum or in an inert gas flow until the manganese is reacted with the residual oxygen, c) Subsequent pre-sintering at 1650 ° C under the same conditions up to extensive Volatilization of manganese and partial volatilization of manganese oxide, d) sintering the mixture in a known manner for tungsten sintered body is 2350 ⁰ C before combination of alloying components, and e) if necessary, hot deformation. 6. The method according to claim 5, characterized in that the pre-sintering according to b) and c) is carried out within 4 hours and the sintering according to d) within 6 hours. 7. The method according to claim 5, characterized in that the pre-sintering and sintering according to b) to d) is carried out under a pressure of 2 · 10 ~ ⁶ Torr or in a hydrogen or inert gas flow, the flow rate for the removal of manganese and manganese oxide in Sufficient vapor form in quantities that their respective partial pressure in the mixture is kept below their normal vapor pressure at the temperatures considered.