Titanium Alloy Essay

841 Words 4 Pages
AC 2.3: Explain the method of making titanium alloy and investigate how the composition and structure of metal alloys, polymers and poly-matrix composites influence the properties of the parent material.

1. Extraction process.
2. Melting process.
3. Storage process.
Extraction of Titanium by Kroll process:

First titanium ore Rutile (TiO2) is taken. Rutile is converted into titanium sponge by the following process:

Titanium tetrachloride (TiCl4) – a colourless compound is obtained as a result when passing Cl2 gas through the ore. Titanium tetrachloride is purified by fractional distillation. To obtain titanium sponge, the liquid form of TiCl4 is reacted with Magnesium (Mg) or Sodium (Na) under an inert (argon) atmosphere while Magnesium
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Then the mixture is subjected to a hydraulic load to produce blocks called briquette. Briquettes weight about few kilos.

The columnar shape first melt (primary) electrode or stick is made by welding the briquettes together in an inert atmosphere. In the VAR furnace, the electrodes are double or triple melted to produce sound ingot. Like few tens to a few hundreds of briquettes – depending on the ingot size.

The VAR process ingot production flow is shown in this flow chart.

The primary electrode of titanium is connected to the cathode of the furnace. It is melted by the direct current arc produced between the water cooled copper crucible (which is connected to the anode of the furnace) and primary electrode (which is connected to the anode of the furnace).

Molten titanium is solidified in layers in the water cooled copper crucible to form an ingot. Melting of the primary electrodes in the VAR furnace is shown in this diagram.

The ingot can be further melted two more times in order to get a homogeneous ingot. The ingots produced by the VAR process weight about 4 to 8 tons.

Electro Slag Refining
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On the bottom of the hearth the high density inclusions are separated.

The molten form of titanium alloy must be store in some solid form so that we can use it when required.

Storage process: The molten pure form of titanium alloy is then solidified in blocks. Also as sheets, wires and pellets as they can be incorporated in any form as required.

Source: [3]

Based on the properties and constitution Titanium alloys are classified into three types:

1. Commercially pure (CP) titanium alpha and near alpha titanium alloys.
2. Alpha –beta titanium alloys.
3. Beta titanium alloys.
Commercially pure titanium alloys Alpha-beta titanium alloys Beta titanium alloy
Medium Strength Strength ranges from Medium to High. Very high strength
Corrosion Resistant Corrosion Resistant Corrosion Resistant
Good creep strength Good creep strength
Non heat treatable Heat treatable Heat treatable
Not weldable Weldable
Excellent mechanical properties at cryogenic temperature Good forming properties Readily Formable
Example: Ti-6Al-4V(Grade 5) Grade 19, Grade 21, AMS 4983.


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