Electric arc welding has been the most common and fastest means of joining metals when compared with gas welding. Most industries uses arc welding due to it effectiveness of joining metals and how it offers great speed of work. This operation is done using welding power supply to create an electric arc between the electrode and the base metal. Heat produce with arc welding are less expensive due to the source of heat been from electricity non like gas welding that uses oxygen and acetylene gas to produces it flames.
At the end this article, reader is expected to understand the followings listed below:
- What is electric arc welding
- Types of arc welding and how they works
- Advantages of arc welding
- Components and equipment of electric arc welding
- Procedure of electric arc welding
- Safety precaution to be taken in electric arc welding
Electric arc welding is a welding process that uses electricity as a source of generating heat to melt metal through a welding power supply, and create electric arc between the electrode and the metal materials. Or arc welding is a fusion welding method which allows the heat supply to fuse metal to obtained the electric arc between the base metal and the electrode.
The arc is produce when two conductors touches each other and current continues to flow when separated by a small gap of 2 to 4mm. Temperature produced by the electric arc is usually 4000°C to 6000°C.
Note: arc welder can use either Direct current (DC) or alternating current, consumable and Non – consumable electrode. All these has been extensively explain below just keep reading and don’t forget to share this knowledge…
Types of Arc welding
The following listed below are different types of arc welding:
- Flux-cored arc welding (FCAW)
- Gas metal arc welding (GMAW)
- Gas tungsten arc welding (GTAW)
- Plasma arc welding (PAW)
- Shielded metal arc welding (SMAW)
- Submerged arc welding (SAW)
- Shielded metal arc welding (SMAW)
This type of arc welding is simple, versatile and one of the oldest welding methods. It is commonly used in constructions, pipeline work and shipbuilding. The arc is obtained when the coated electrode tip touch the workpiece. heat generated melts the tip, coating, and base metal and the weld is formed out of that alloy when it solidifies.
2. Flux-cored arc welding (FCAW)
This type of arc welding are popularly used when welding heavy metal materials like thick tanks, to a higher weld-metal deposition rate. It uses cannular electrodes that are filled with flux and less brittle than the coatings on Shielded metal arc welding electrodes and protect most of the alloying benefits.
3. Submerged arc welding (SAW)
This type of arc welding has a granular flux that is fed into the weld zone that forms a thick layer, completely covering the molten zone and preventing sparks and spatter. It allows for deeper heat penetration since it acts like a thermal insulator. The process is limited to horizontal welds and used for high speed sheet or plate steel welding. It can be semiautomatic or automatic. The flux can be recovered and treated then used again. This method provides 4-10 times as much productivity as shielded metal arc welding.
4. Gas tungsten arc welding (GTAW)
This type of arc welding is also known as TIG welding. It gas contains argon and helium or mixture of the two. It uses tungsten electrodes as one pole of arc in order to create heat needed. Filler wires can also be provide to act as molten materials to the surface welding is required only if necessary. Gas tungsten arc welding is good for thin materials.
5. Plasma arc welding (PAW)
This is another type of arc welding that has ionized gases and electrodes, which generate hot plasma jets that are aimed at the welding area. Due to extremely hotness of the jets, the concentration of higher energy is good for narrow and deeper welding which can also lead to increase in welding speeds.
6. Gas metal arc welding (GMAW)
This type of arc welding is simple, competent and economical. It temperature are relatively low and can be use for thin sheet and section. The gas metal arc welding is also called MIG welding. Furthermore, gas metal arc welding shields the welding arc with a gas such as argon and helium or mixture of both. The electrode contains deoxidizer to prevent oxidation in order to weld multiple layer. This arc welding can be automated.
Arc Welding Electrodes
The following explained below are types of arc welding electrode, they are classified in two broad categories:
- Consumable electrodes.
- Non – Consumable electrodes.
- Non-Consumable Electrodes:
Non-consumable doesn’t consume any electrode during the welding operation. These types electrodes are made of carbon, graphite or tungsten. The non-consumable electrodes made of carbon and graphite can be used only on D.C welding, while The tungsten can be used on both A.C and D.C welding. In this type of electrode, filler material is added seperatly since the electrode doesn’t consumed and the arc is stable.
2. Consumable Electrodes:
The consumable electrode get melted during welding operation and apply the melted filler were the joining is required. Consumable electrode are made of two types, they are:
(i) Bare Electrodes:
Bare consumable electrode is designed in form of continuous rode or wires. It is also known as plain electrodes. It does not provide any molten or shielded metal supply from atmospheric oxygen and nitrogen. Bare electrodes must only be used with straight polarity in D.C. welding. However, welds obtained with bare electrodes are of lower strength, lower resistance to corrosion and lower ductility. This type of electrodes is not rarely in used but used to weld mild steel and wrought iron.
(ii) Coated Electrodes:
The coated electrodes are sometimes called conventional electrodes. This type of electrodes provides a shielding to the molten metal from the atmospheric oxygen and nitrogen, when a coating (thin layer) of flux material is applied all-round the welding rod. This flux also prevents formation of oxides and nitrides. Flux chemically react with the oxides present in the metal and forms a low melting temperature fusible slag.
The slag is float on the top of the weld and can easily be brushed off after solidification of weld. The quality of weld produced by coated electrode is much better as compared to that of bare electrodes.
Depending on the coating factor or thickness of flux coating, coated electrodes are divided in three groups:
(a) Lightly coated electrodes.
(b) Medium coated electrodes.
(c) Heavily coated electrodes.
Advantages of Arc Welding
- It gives concentrated heat
- Strong joints is produced with arc welding.
- It uses electric engine, such as renewable energy source.
- It produce higher temperature than any other type of welding
- Arc welding can be easily automated
Components of Electric Arc Welding
The various equipments required for electric arc welding are:
- Welding Machine
Welding machine is one of the most important equipment. It can be either A.C or D.C. The A.C welding machine has a transformer that reduce the input voltage of 220-440V to 80-100v. While the D.C welding machine has a transformer-rectifier welding set or an A.C motor-generator set or petrol/desel engine- generator set.
2. Electrode Holders
The electrode holder is design to clip the electrode with the teeth at desired angle, It is available in different sizes according to the ampere rating from 50 to 500 ampere. It function is to hold the electrode strongly at one position.
3. Cables or Leads
The cables plays an important role as it transfer the current from the machine to work piece. They are made of copper and aluminum. The cables could be 900 to 2000 fine wires twisted together for greater and stronger strength. The external surface of the cable are made of insulating layers like rubber, reinforced fibre or heavy rubber coatings.
4. Cable Connectors and Lugs
The cable connectors are purposely design to easily connect and diconnect the cable between welding machine and eletrode holder. These connectors are design according to the current capacity and the cable used.
5. Chipping Hammer
The chipping are used to remove unwanted welding oxide (slag) from the work piece. The chipping hammer is design in chisel shape and has a one pointed end.
6. Wire Brush, Power Wire Wheel
The wire brush is use after the chipping hammer has remove the slag particles. It function is to completly clear away slag from the workpiece. The wire brush is also used to remove dirt from the workpiece before welding. It is available as portable machine tools and manual wire brush.
7. Protective Clothing:
Protective clothing is one of the important equipment that must not left out because it all safety to the welder. It consists of the hand gloves, leather apron, cap, high ankle shoes, leather sleeves and etc. which protect the welder from heat, Spark, infrared and ultraviolet rays.
8. Screen or Face Shield:
The face shield are purposely design to protect the eyes and face from ultraviolet and infrared light produced during welding.
Safety precaution in arc welding
Welding as whole can be dangerous when it comes lack of knowledge on safety practice. These could lead serious injury or death for failures to obey these rules and regulations. With the advance technology, safety practice in welding has reduced and arrested. The following explained below are common safety precautions and regulations to be practice to avoid damage or destruction in arc welder.
Ultraviolet light is very effective when it comes to eye damaging. It causes inflammation of the cornea and burns the eyes retinas. this condition is called arc eye. To prevent eyes exposure to brightness welding goggles and helmet with dark face plates will be used. The advance technology has introduced auto darkening welding hood with 90×110 mm cartridge and 3.78×1.85 in viewing area. These electronic device (helmet) automatically darken when exposed to ultraviolet light from the arc light. To protect the welder, transparent welding curtains often surround the welding area.
Safety from fire, heat and explosion
Body needs to be protected from electric arc or flames produce during welding operation. To prevent these continuous heat and sparks, the welder is expected to wear protective clothing which includes, heavy leather gloves, leather apron, cap, high ankle shoes, leather long sleeves and etc. To avoid explosion and fire risk, the exposure of oxygen to air should be limited and all combustible materials should be kept always from the workshop.
Some types welding processes like shielded metal arc welding and flux-cored arc welding produces dangerous smoke that contains different types of oxides. In this situation serious safety need to practice to avoid greater danger to the welder. It is advisable for welder to work at open surrounding or workshop with adequate ventilation.
I hope you’ve enjoyed reading this electric arc welding article, we’ve discussed on different types of arc welding, arc welding electrodes and we revealed the meaning of arc welding, we’ve also examined on components of arc welding and safety precaution in arc welding. Now I believe you’ve understand electric arc welding but remember this piece of knowledge is made for you alone do me a favor by sharing via social media.
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