Silver Tungsten Contacts Produced by Infiltration Method
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- Category: Tungsten Information
- Published on Wednesday, 08 July 2015 16:26
- Written by Yahong
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The process of silver tungsten contacts produced by infiltration method:
Firstly, pressing the silver blank and tungsten skeleton without silver or porous skeleton with partial-induced silver; then, pre-sintering the porous skeleton at high temperature; after stacking up the two parts together, putting them in a special melt infiltration sintering furnace, and then liquid sintering, the sintering temperature is controlled above the melting point of silver. Silver under the molten state fills the pores of the porous skeleton by capillary action, forming silver tungsten contacts with high density eventually. The main process of silver tungsten contacts are as follows:
Tungsten powder + a small amount of silver, adding additional elements → mixing powder → pretreatment →skeleton molding + pure silver → pre-sintering (temperature > melting point of silver + 100 ℃) → infiltration → cold treatment
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Main Performance Index of Silver Tungsten Contacts
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- Category: Tungsten Information
- Published on Wednesday, 08 July 2015 16:24
- Written by Yahong
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Different tungsten contacts material have different characteristics, different proportions of the same tungsten contacts material also own different characteristics, their density, hardness, specific resistance have a different scope.
Main performance index of silver tungsten contacts (with different proportions) can be seen as follows:
|
Material name |
Specific resistanceμΩ·cm) |
Hardness(HB, MPa) |
Density(g/cm³) |
|
silver tungsten contacts（75） |
3.93-4.15 |
1629-1654 |
15.54-15.71 |
|
silver tungsten contacts（70） |
3.13-3.23 |
1681-1714 |
15.37-15.41 |
|
silver tungsten contacts（65） |
3.25-3.48 |
1535-1649 |
14.54-14.71 |
|
silver tungsten contacts（60） |
2.80-2.97 |
1419-1482 |
14.39-14.68 |
|
silver tungsten contacts（50） |
2.45-2.52 |
1145-1175 |
13.14-13.68 |
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Tungsten Copper Electrode Classification
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- Category: Tungsten Information
- Published on Wednesday, 08 July 2015 15:53
- Written by renge
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Tungsten copper electrode can be classified into 3 types.
1. Tungsten copper (Class 10) is used for flash and butt welding electrodes in applications in which high heat resistance, higher electrical and thermal conductivity, high malleability, and low thermal expansion are required. This metal is created by combining 45% copper and 55% tungsten, resulting in a dense and hard metal with superior wear resistance and strength.
2. Tungsten copper (Class 11) contains 25% copper and 75% tungsten. Like Class 10, it has superior wear resistance and strength and good thermal and electrical conductivity. However, it is harder than Class 10 and used in applications that require moderate pressure.
Common uses include projection welding electrodes, flash and butt welding electrodes, light upsetting and seam welding bushings, and spot welding low conductivity steels. It is also widely used in chip carriers, substrates, flanges, and frames for power semiconductor devices.
3. Tungsten copper (Class 12) contains 20% copper and 80% tungsten, being stronger than Class 10 and 11 tungsten copper, it is commonly used in heavy duty projection welding electrodes, and cross wire welding. It is also used in the liners of some specialty shaped explosive charges for the defense and oil and gas industries.
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EPR of High-Spin Fe 3+ in Calcium Tungstate, CaWO 4
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- Category: Tungsten Information
- Published on Wednesday, 08 July 2015 16:18
- Written by xinyi
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The geff=30/7 isotropic signal in the EPR of high-spin Fe3+ compounds is discussed for both tetragonal rhombic crystal fields by reference to the resonance in calcium tungstate. The Fe3+/CaWO4 EPR signals are shown to arise from Fe3+ in two slightly different interstitial sites in the crystal; the crystal field in both sites is predominantly rhombic. Highly anisotropic signals arising from transitions within the other two Kramers' doublets were positively identified leading to an unambiguous calculation of the spin Hamiltonian parameters. The results are likely to be of great value in analysing similar Fe3+ spectra in crystals of biological importance.
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Site Occupation in Gadolinium-Doped Calcium Tungstate
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- Category: Tungsten Information
- Published on Wednesday, 08 July 2015 15:46
- Written by xinyi
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The electron spin resonance spectrum of the S-state ion Gd3+ in a calcium tungstate host lattice has been examined at 37.5 GHz over the temperature range 290 K to 4.2 K. Low concentration Czochralski-grown single crystals having gadolinium concentrations of about 100 ppm were used to ensure substitution by Gd3+ in calcium sites; the crystals were vacancy compensated. Although the general features of the 290 K spectrum agreed well with that reported previously by Hempstead and Bowers, extra lines were observed very close to the main ΔM=1 transitions. Examination in theφ-plane showed that the extra lines were most pronounced nearφ=55° and that their intensites relative to those of the main transitions increased as the temperature was reduced. The extra lines are explained in terms of the ordering of oxygen vacancies.
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