TUNGSTEN

Tungsten is a heavy (sp. gr. 19.3) and a highly refractory metal (malting point 34100 C). It has good corrosion resistance, good thermal and electrical conductivity and low co-efficient of expansion. At temperatures above 16500 C it has the highest tensile strength of all metals. These Properties determine its areas of application.

Different tungsten products are used for different applications. The major areas of applications are: -

  • As a cutting tool,
  • As an alloy constituent in high speed and tool and die steels.
  • An filaments and electrodes in the electrical industry
  • As a major constituent in the production of armor piercing ammunition.

Tungsten Carbide:

Tungsten carbide is used in cutting tools as well as in wear resisting material. Apart from industrial cutting tools it is used as a drill bit in the mining and petroleum industry.

Ferro Tungsten:
 Earlier tungsten carbide was used in the defense and tank ammunition and it has now been replaced by tungsten nickel iron alloy.

Tungsten Metal / Wires:
High purity tungsten metal drawn a wire in used as filament in electrical lamps and as cathodes for electrical tube lamps.

The other minor areas of used are chemicals, X-ray screens, television tubes, etc.

The Chief Tungsten minerals are tungstates of iron, manganese and calcium, the tungsten ore being wolfram (FeMn) O4 and scheelite, CaWO4.

Tungsten ore mined are beneficiation to yield desired grade concentrates which is the starting point for making other down stream intermediate products like tungsten acid, tungsten mental powder, ferro-tungsten, tungsten carbide, etc.

The concentrate specifications for commercial purpose are in terms of WO3 content. Any concentrates with 65% and more Wo3 content is considered saleable material. However, Low-grade concentrates products provided the product could be obtained at economic costs. As such specification for the lower grade concentrates can not be prefixed.

Tungsten Carbide:
The Specification of the major T. C. tool producers in the country viz. WIDIA AND SANDVIK along with US specification are given below:

Constituent

WIDIA%
Wolframite

SANDIVK
Scheelite %

Wolframite

US carbide
Scheelite %

Wolframite
%

WO3

Min. 65

Min. 70

65

65

Min. 65

Sn

Max. 1.5

Max. 2.0

0.50

0.1

Max. 1.5

As

Max. 0.25

Max. 0.1

0.10

0.1

Max. 0.25

S

Max. 0.50

Max. 1.0

1.00

0.50

Max. 0.50

Cu

Max. 0.05

Max. 0.50

0.50

0.10

Max. 0.50

Sb

Max. 0.10

Max. 1.00

--

0.10

Max. 0.05

Bi

Max. 0.20

Max. 1.00

1.00

0.25

Max. 0.50

Mo

Max. 0.20

Max. 0.15

--

0.10

Max. 0.10

Pb

Max. 0.05

Max. 0.50

--

0.10

Max. 1.00

Zn

Max. 0.10

--

--

0.10

Max. 1.00

P

Max. 0.05

Max. 0.05

0.05

0.05

Max. 0.05

Si

Max. 2.50

Max. 1.50

0.50

--

--

Ca

Max. 0.05

--

0.20

--

Max. 0.20

Mn

No. Limit

1.00

--

2.00

(Fe & Mn)

Fe

3.00

--

--

--

--

Ca+SiO2

--

--

1.00

--

--

F

--

--

1.00

--

--

Ferro-tungsten:

The BIS (IS: 5632 1970) has prescribed the following specifications of concentrates for ferro tungsten industry WO3 65% (min.) P 0.05% max. As 01% max., Sn 0.1% max., MnO 10 15% max.

Electrical Industry:

The industry imports tungsten bars and wires. No specification is available. The US specification of concentrate for pure metal making is given below:

WO3 - 65%, Sn 1.5%, Cu 0.5%, As 0.20%, Bi 0.5%, Sb 0.5%, Mn 0.025%, P 0.50%, S 0.50%, Pb 1.0%, Zn 1.0%, Ca 0.20%

MDB suggested the following specifications for wolframite and scheelite and scheelite concentrate for tungsten carbide industry.

Constituent

Wolframite %

Scheelite %

WO3

Min. 65

65 to 70

Sb

Max. 1.5

Max. 1.5

P

Max. 0.05

Max. 0.05

S

Max. 1.00

Max. 1.00

Cu

Max. 0.50

Max. 0.50

As

Max. 0.20

Max. 0.10

Bi

Max. 1.00

Max. 1.00

Ca

Max. 0.05

--

Mn

--

1.00

Fe

--

3.00

Si

Max. 1.50

Max. 1.50

Tungsten ore as mined is not used directly in the industry as mentioned above the end use classification of this mineral is not possible. In the inventory as on 01.01.1985 the following reserve classification has been followed:

It was noted that while the resources position of tungsten in India is much better now as compared to the late 70s, the grade of most of the deposit is very low. They are mostly around 0.1% WO3 levels except a few deposits like Degana Vain Load (0.5% WO3) Kobana 0.3% WO3 Burugubanda bloom 0.5% WO3. The working economics of the Indian deposits, therefore, depended mainly on (I) amenability of the ore to beneficiation and the beneficiation process and (ii) the quantity and number of co-products and by-products that could be obtained while mining and processing such deposits. While in the gold mines, tungsten is a by-product, in Burungubanda it occurs with graphite, in salda with fluorite and in kobana no-Ta may be available in the top laterite. In the granite in Deana the WO3 is only around 0.04% to 0.2%. However, it may be an economic preposition if the indicated lithium levels are confirmed and recovery of associated tin is also possible.

 The following grade-wise classification of reserves and resources may be of use.

 Reserves - WO3 0.30% and above average.

  1. Conditional Resources - WO3 0.1% and above but below 0.3%
  2. Resource - WO3 0.05% and above but below 0.1%
  3. Associated metals please specify.

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