Ferro-tungsten is an alloy of iron and tungsten, obtained both by the furnace and by the out-of-furnace method (according to GOST 17293-93), used for alloying steel with tungsten, in order to increase its hardness, wear resistance, yield strength and strength and improve mechanical properties (heat resistance, resistance to tempering etc.). Ferro-tungsten is supplied in lumps or in the form of crushed and sieved particles. The fractional composition of the supplied material depends on the needs of the consumer and can be provided in the range from 0 to 100 mm.
Ferro-tungsten – a ferroalloy containing 65-80% W, is smelted by a combined silicothermal and carbohydrate reduction process from wolframite and scheelite concentrates, the resulting “block” is broken after cooling. Ferro-tungsten is one of the most important alloying elements in the production of special steel grades. The addition of tungsten to steel, in the form of ferro-tungsten, retards grain growth and, when heated, creates a fine-grained structure, increases hardness, tear resistance and elastic limit, and also contributes to maintaining high hardness and stability of the microstructure at elevated temperatures. The chemical composition of ferro-tungsten in table 1.
Table 1
| Brand | Mass fraction,% | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| W | Mo | Mn | Si | C | P | S | Cu | As | Sn | Al | Pb | Bi | |
| at least | no more | ||||||||||||
| FV80(a) | 80 | 6 | 0,2 | 0,8 | 0,1 | 0,03 | 0,02 | 0,1 | 0,04 | 0,04 | 3 | 0,01 | 0,01 |
| FV75(a) | 75 | 7 | 0,2 | 1,1 | 0,15 | 0,04 | 0,04 | 0,2 | 0,05 | 0,05 | 5 | - | - |
| FV70(a) | 70 | 7 | 0,3 | 2 | 0,2 | 0,06 | 0,06 | 0,3 | 0,06 | 0,08 | 6 | - | - |
| FV72 | 72 | 1 | 0,4 | 0,5 | 0,3 | 0,04 | 0,08 | 0,15 | 0,04 | 0,08 | - | 0,02 | 0,02 |
| FV70 | 70 | 2 | 0,5 | 0,8 | 0,5 | 0,06 | 0,1 | 0,2 | 0,05 | 0,1 | - | - | - |
| FV65 | 65 | 6 | 0,6 | 1,2 | 0,7 | 0,1 | 0,15 | 0,3 | 0,08 | 0,2 | - | - | - |
Ferro-tungsten is made crushed in pieces passing through a mesh with a square mesh size of 100×100 mm. Particle size ranges and tolerances should be in accordance with Table 2.
| Class | Particle size ranges, mm | Maximum mass fraction,% | |
|---|---|---|---|
| undersize product | oversize product | ||
| 1 | 2 - 100 | 3 | 10 |
| 2 | 2 - 50 | 3 | No slice should exceed 1.15 of the maximum specified range of particles in two or three directions |
| 3 | 2 - 25 | 5 | No slice should exceed 1.15 of the maximum specified range of particles in two or three directions |
| 4 | Up to 2 | - | |
