Tungsten powder. Grades, chemical composition.
General Characteristics
Tungsten is a hard refractory metal, element number 74 in the Mendeleev table, designated as W, has a density of 19.25 g/cm³, a melting point of 3422 °C and a boiling point above 5500 °C. Tungsten powder is a heavy fine mass with high hardness and refractoriness. It serves as the basis for compact metal. At first, stacks are produced, which are the blanks of tungsten rods, wires, sheets, as well as the basis for sintering hard heat-resistant alloys by powder metallurgy.
| Atomic (molar) mass g/mol | Oxidation state | Density [g/cm3] | Melting point t°C | Boiling point t°C | Melting point kJ/kg |
|---|---|---|---|---|---|
| 183,84 | 0, 2, 3, 4, 5, 6 | 19,25 | 3422°С | 5500°С | 191 |
Grades of tungsten powder
The main grades are: VP, PVV (highly active tungsten powder), PVN (low-active tungsten powder), PVT (technical tungsten powder). They are produced according to TU 48−19−72−92 «Tungsten Powder. Tech. conditions». Average grain diameter of PVN and PVT powders is 3,5 — 6 microns (not more than 40% of PVN tungsten powder grains are over 4 microns in size), PVV 0,8 — 1,7 microns.
Use
Hard and refractory tungsten is used as the basis for tool and high-speed steels, wear-resistant and heat-resistant steels, non-fusing electrodes and electrical lighting equipment. Tungsten powder is used as the main component of tool and high-speed steels or as an alloying agent as well as heat-resistant and wear-resistant alloys (such as stellites). Tungsten carbide is the basis of a hard tungsten-cobalt alloy of the BK type. Tungsten powder is used to produce tungsten non-consumable electrodes for welding.
Tungsten powder is produced in three grades, depending on the application and raw material: Tungsten powder TU-48−19−72−79
| grade | Powder name | Feedstock |
|---|---|---|
| PVV | High-active tungsten powder | Tungsten anhydride of ammonium paratungstate, A grade or high-purity ammonium paratungstate. |
| PVN | low-active tungsten powder | Tungsten anhydride of ammonium parafframate, grade, A or low molybdenum ammonium parafframate. |
| PVT | technical tungsten powder | Ammonium tungstate anhydride or ammonium paratungstate. |
| Impurity | PVN | PVV | PVT |
|---|---|---|---|
| Al | 0,001 | 0,001 | 0,002 |
| Fe | 0,008 | 0,006 | 0,02 |
| K | 0,02 | 0,02 | 0,02 |
| Ca | 0,005 | 0,002 | 0,005 |
| (O2 and moisture) | 0,25 | 0,35 | 0,2 |
| Si | 0,003 | 0,002 | 0,005 |
| Ni | 0,005 | 0,005 | 0,008 |
| Na | 0,015 | 0,01 | 0,02 |
| Mo | 0,04 | 0,02 | 0,2 |
| As | 0,005 | 0,003 | 0,03 |
| S | 0,004 | 0,004 | 0,004 |
| C | 0,003 | 0,003 | 0,003 |
| P | 0,005 | 0,004 | 0,005 |
Note:
Mass fraction of tungsten is the base metal and undetectable associated impurities.
Dispersity of tungsten powder, characterized by the average particle diameter according to Fischer, and must comply with the following standards.
| Mark | Fischer mean particle diameter, μm |
|---|---|
| PVV | 0.8 to 1.7 |
| PVN | 3.5 to 6.0 |
| PVT | 3.5 to 6.0 |
Note
— In PVN powder grain content of more than 4 microns should be up to 40%.
— Bulk specific weight of PVN and PVT powder grades = 3.0 to 5.5 g/cm³.
— Bulk density for PVV grade is not a rejection criteria and may not be determined.
Buy at a bargain price
Evek GmbH stocks a wide range of high-quality metal powders at optimal prices. Tungsten powder is supplied in tins with gross weight up to 70 kg. The warranty shelf life is 24 months from the production date. All products have a quality certificate of compliance with the requirements of standards and specifications. The certificate indicates the manufacturer, powder grade, chemical composition and properties. Implementation of orders — in the shortest possible time. Preferential discounts are offered to wholesale buyers.