We were discussing Plumbing tools and their use, Carpentry tools and their use and Types of Carpentry Machines and their applications in our previous post.
Now its time to go ahead and understand a new topic in engineering field i.e. Welding. I hope you are very much aware with the term i.e. Welding. Let us get more in to deep and understand each term associated with welding practices.
Welding
Welding is basically defined as the process of joining similar metals with the application of heat, with or without the application of pressure or filler metal, in such a way that the joint is equivalent in composition and characteristics of the metals joined.
Welding is basically a joining process where metals are heated, melted & mixed in order to produce a joint with similar properties to that of the materials being welded or joined.
Welding tools and resources
Let us now see the various important welding tools and their accessories that we need to be aware of in order to execute the safe welding activities.
1. Welding transformers or welding machine
2. Welding Electrodes
3. Welding Electrode holder
4. Welding cables
5. Safety and cleaning accessories
The various welding tools and safety accessories those are required for safe arc welding are
Described and displayed here in the following figure as follows.
Welding machine
The welding machine used for arc welding could be completely either an AC or DC welding machine.
The AC welding machine will have a welding transformer set, whereas the DC welding machine will have an AC motor-generator set of diesel engine-generator welding set or a transformer rectifier welding set.
Both direct current (DC) and alternating current (AC) welding machines are used for arc
welding, but the DC welding machine is usually preferred.
The DC welding machines get their power from a DC generator or from a solid state rectifier.
The capacity of DC machines can be up to 600 amperes and open circuit voltage ranges from 50 to 90 volts.
When welding is carried out on a closed circuit, voltage ranges from 18 to 25 volts. The workpiece as anode (+ve) and the electrode as cathode (±ve) constitute a straight polarity (DCSP) welding. The electrons flow from the negative terminal to the positive terminal of the arc with straight polarity and strike the workpiece faster than the electrode. This helps in welding huge workpieces.
For AC welding machines, the current is drawn from the main supply or through an AC
generator set. It consists of a transformer which steps down the voltage of 220±440 volts to the
normal open circuit voltage of 50 to 90 volts. The AC welding machines may have air cooling or
oil cooling, depending upon the ampere rating. Bigger size transformers are normally oil-cooled.
An AC welding machine gives smoother arc at higher arc-currents and there is no arc blow. Once the arc is established, it can be controlled and maintained easily, that is why it is suitable for welding thicker plates. The melting rate of the electrode cannot be controlled because the heat generated at the workpiece and at the electrode end is the same.
Welding Electrodes
The filler rods used in arc welding are called welding electrodes. The electrodes are made of metallic wire also known as core wire. The size of the electrode selected depends upon the weld size required.
Electrodes are uniformly coated with flux. There are two types of electrode. One is a consumable electrode and the other one is a non-consumable electrode.
Welding electrode holder
It is used for holding the electrode and also conducts the current to the electrode. It is connected to the end of the welding cable. The jaws of the holder are insulated to avoid any electric shock.
Ground clamp
It is connected with the workpiece to be welded.
Welding Cables and connectors
They are used to conduct electricity from the welding machine to the end of the electrode and to the workpiece. Cables are highly insulated by a rubber cover. Connectors are the devices used for connecting the ends of cables.
Chipping hammer
It is used to remove the slag after the metal weld has solidified. It is chisel-shaped and is pointed on one end.
Wire brush
It is used to remove small slag particles from the workpiece after welding.
Face shield or screen
It is used to protect the eyes and face of the welder from the dangerous effect of ultraviolet and
infrared radiations of the arc during welding.
Flux-coated electrodes
They produce better welds as compared to the bare metal electrodes. The flux prevents the formation of undesirable oxides by forming a gas shield around the arc and covering the weld metal with protective slag during welding.
Protective clothing
Hand gloves are used to protect the hands of the welder from electric shock, hot sparks and hot
molten slags. Aprons protect from heat and spark not to injure the body of the welder.
Now we will see another topic i.e. Arc Welding in our next post.
No comments:
Post a Comment