05-11-2016, 11:04 AM
1465048127-1re11me061150421060604conversiongate02.pptx (Size: 1.05 MB / Downloads: 7)
INTRODUCTION
The plasma arc machining process was introduced to the industries in 1964 as a method of bringing better control to the arc welding process in lower current ranges.
Plasma-arc machining (PAM) employs a high-velocity jet of high-temperature gas to melt and displace material in its path.
Today, plasma retains the original advantages it brought to industry by providing an advanced level of control and accuracy.
Working Principle of PAM
Gases are heated and charged to plasma state.
Plasma state is the superheated and electrically ionized gases at approximately 5000⁰C.
These gases are directed on the workpiece in the form of high velocity stream.
Plasma Gun
The plasma gun consists of a tungsten electrode fitted in the chamber.
The electrode is given negative polarity and nozzle of the gun is given positive polarity.
A strong arc is established between the two terminals anode and cathode.
There is a collision between molecules of gas and electrons of the established arc.
Gas molecules get ionized and plasma state is formed.
Plasma is directed to the workpiece with high velocity.
Power Supply and Terminals
Power supply (DC) is used to develop two terminals in the plasma gun.
A tungsten electrode is inserted to the gun and made cathode and nozzle of the gun is made anode.
Heavy potential difference is applied across the electrodes to develop plasma state of gases.
Cooling Mechanism
Hot gases continuously comes out of nozzle so there are chances of its over heating.
A water jacket is used to surround the nozzle to avoid its overheating.
Work piece
Work piece of different materials can be processed by PAM process.
Ex: aluminium, magnesium, stainless steels and carbon and alloy steels.
Applications of PAM
In tube mill application.
Welding of cryogenic, aerospace and high temperature corrosion resistant alloys.
Nuclear submarine pipe system.
Welding steel Rocket motor case.
Welding of stainless steel tubes.
Welding titanium plates up to 8mm thickness.