Oxy-acetylene welding will use for welding of wide selection of metals.
Acetylene mixed with oxygen and then burnt under a controlled environment produces large amount of heat giving higher temperature rise.
It will produces carbon dioxide that helps in preventing oxidation of metals being welded.
Highest temperature that may be produced by this welding is 3200oC.
Concerned chemical reaction in burning of acetylene gas is
2C2H2 + 5O2 = 4CO2 + 2H2O + Heat
Oxy-acetylene welding is categorized as high pressure welding on the basis of supply pressure of gases.
In this system both gases oxygen and acetylene supplied to welding zone are high pressure from their respective high pressure cylinders.
The other one is low pressure welding in which oxygen is supplied from high pressure cylinder but acetylene is generated by the action of water on calcium carbide and supplied at low pressure.
In this case high pressure supply of oxygen pulls acetylene at the welding zone.
CHARACTERISTICS :
The oxygen and acetylene gases stored under pressure in steel cylinders.
Melting the materials to be welded together.
The ability to regulate temperature by adjusting gas flow.
GAS WELDING EQUIPMENTS :
1. Gas cylinders
2. Regulators
3. Pressure gauges
4. Rubber hoses
5. Welding torch
6. Safety goggles
7. Gloves
8. Spark lighter
9. Wire brush
GAS CYLINDERS :
Oxygen and acetylene gases are stored in separate cylinders and used for gas welding.
Oxygen cylinder color is black and therefore acetylene gas cylinder color is maroon.
Pressure of oxygen is keep at 125Kg/cm2 &Pressure of acetylene is keep at 16 Kg/cm2 in the cylinder.
REGULATORS :
It is used to control the operating pressure of the gases. Separate regulators are fitted for each cylinders.
Oxygen operating pressure is 1Kg/cm2 and acetylene is 0.15Kg/cm2. Working pressure of these gases is altered according to the thickness of the metal parts of the joint.
PRESSURE GAUGES :
Two pressure gauges are fitted on each cylinder. One of the pressure gauges indicates the pressure of the cylinder and the other gauge indicates the working pressure of the specific gas.
HOSES :
Separate hoses are used to connect the two cylinders with the welding torch through regulators. Oxygen cylinder hose color is black and acetylene cylinder hose color is red. These hoses carry the gases to the welding torch.
WELDING TORCH :
Oxygen and acetylene reach the welding torch through hoses. These gases are mixed in the mixing chamber of the welding torch. Flame is produced at the tip of the torch when the gases are ignited. There are two control valves present in the torch to control the quantity of oxygen and acetylene. By this control, the grade of the flame can be altered.
WELDING GLOVES :
Protective hand gloves are utilized by the operator to prevent possible damages which will be caused by high temperatures.
SPARK LIGHTER :
It is used to ignite the oxy-acetylene gas at the tip of the welding torch.
WIRE BRUSH :
It is used for cleaning the weld before and after the welding process.
FILLER RODS USED IN GAS WELDING :
It is used in gas welding supply the additional metal in making joints.
These rods are melted by the gas flame and deposited over the components of the joint.
Usually the filler rods are made of the same metal as that of the parts of the joint.
The diameter of the filler rod depends upon the thickness of the parts to be welded.
ADVANTAGES OF GAS WELDING :
Suitable for different classes of work.
The cost of the welding unit is less.
Welding temperature is controlled easily.
The number of filler metal added in the joint can controlled easily.
The cost of maintenance is less.
LIMITATIONS OF GAS WELDING :
Intended for welding thin work pieces only.
The process of welding is slow.
The time taken by the gas flame to heat the metal is more when compared with electric arc.
The strength of the joint is less.
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