Question

Q2.
a. List the difference between non-fusion and fusion forms of welding.
b. Describe how the rightward or backward welding technique is done and stating its advantages
and also when it is mainly used.
c. With the aid of a labeled diagram, describe the gas welding process.
d. (i) Give one major reason for the use of fluxes during welding. Give one example.
(ii) Mention any two hazards that may occur in the welding workshop.

Answer 1

Answer:2(a)

Difference between non-fusion and fusion forms of welding.

Non fusion welding is the process in which the metal which need to be joined or welded, is heated up to the semi molten or partial molten state and than for the complete welding pressure is applied. Spot welding, projection welding, flash welding, upset welding are the process of welding which comes under non fusion welding technique. All resistance welding are type of non fusion type of welding. It is generally the process of welding which doesnt include metlting or include just partial heating.

Fusion welding the process of welding in which the metal to be joined is heated up to molten state and after that when molten metal solidifies it results in the complete welding process.All arc, gas TIG, MIG are the fusion welding process. Complete melting of the metal take place in this process of welding.

(b) Rightward or backward welding technique:

This is the technique of welding process in which the welding torch is held in the right hand and the filler rod is placed in the left hand. In this process, welding starts from left hand end and goes towards righ hand side.

In this process, torch tip makes the angle of 40 to 50 degree with the work surface while filler rod makes angle of 30 to 40 degree with work surface.

Advantage of backward welding:

Some of the advantage of backward welding process is as given below:

• This techniqueis very economical for welding of heavy steel plates and section having thickness over thickness of 6 mm.
• There is no need of bevel preperation up to 8 mm thickness.
• This type of welding provides better shielding for the oxidation from environment.
• Welds produced by this welding process are stronger and tougher
• Metal deposition is very small.
• Better weld quality
• Less consumption of filler metal

When this process is used:

As in this process the flame is contant towards the V availbe ahead of the weld pool, so there is no side wise motion is required so it provides greater welding control. It is the process which is generally used for the heavier and thicker base metals which are above 5 mm thick. Weld with the 12 mm penetration can be acheived with this type of welding process.
(c) Gas welding process

For easy understanding, i will be explaining gas welding point by point as is given below as:

• Gas welding is the process in which heating and melting of the base metal is carried out with the use of chemical reaction of the gases
• Metal is heated up to 3300 degree centigrade
• Oxyacetelene is the mostly used gas iwelding technique in which mixture of acetelene and oxygen gases are used for the welding process.
• Flux is also used in this welding process which cleanse and deoxidise the weld metal
• The base metal is heated until it reaches to the molten state and than after melting solidifcation takes place which make the permamnet joint.
• This process of welding can be acheived with or without any application of external pressure.

Labelled diagram of gas welding process is given below

(d.1) Major reason for the use of fluxes during welding

Flux used in the welding is the combination of silicate and carbonates. Its main reason of use in the welding is to provide the shield to the weld zone from the harmful atmospheric gases. Iit prevents the oxidation and reactiion with nixtrogen as an example when the heat of the weld zone reach the flux, flux melts and the it sends the gases outside and the gases produced in the process do not allow and push the atmospheric gases towards outside.It also helps in thermally insulating the weld and to reduce the cooling rate

(d2) Two hazards that may occur in the welding workshop.

There are various hazards which can occur due to welding process but two main hazards which can occur is given below

• Electric shocks
• Gases and fumes
• Fires and explosions