Welding is a fabrication process that uses high temperature to melt and fuse two pieces of metal together. The process of welding does not merely bond the two pieces together but through the use of excessive heat and in some cases other metals or gases are added which makes the metallic structure of the two pieces of material to join together. Welding can even be done underwater. Welding can be applied in different kinds of industries such as; building and construction, oil and gas, marine, power generation, automobile and transportation. Materials commonly welded are metals; such as aluminum, mild steel and stainless steel. Plastics can also be welded. But In welding plastics, the source of heat used is an electric resistor or hot air.There are different energy sources that can be used during the process of welding. These include a gas flame (powered by a chemical like acetylene), an electric arc, laser, an electron beam, friction, and ultrasound. There are different welding techniques that fit open air, underwater, and even space settings.
In welding consumables market globally, it can be observed that there might be an increase in growth as a result of industrial outcome due to its usage as seen in transportation, automotive, construction and also in marine industries. However, in some countries that are still developing in the aspect of advanced technology, this growth phase might be observed at a slow rate.
In Welding, substances called filler materials or consumables are used. As the name implies, these substances provide a filler or a body of molten materials that provides a strong bond to be formed between the base metals used. Most welding processes will also require some form of shielding to protect both the main components and filler from being oxidized during the process.
Metal parts that are joined during welding are called the parent material. Consumables are the material added to help form this joint. The form of these materials may see them referred to as parent plate or pipe, filler wire, consumable electrode (for arc welding), etc.
Using the correct consumables or filler material in welding brings about a strong bond between the two metals involved. These are one of the four most important components involved in welding, others include, the metal to be used, the source of heat, and the shield from air. The consumable is added to the point that is to be linked together to form a single piece of metal when the metal is heated to its melting point while being shielded from air. In arc welding, consumable does not only act as a filler during the heating but also helps in stabilizing the flame.
TYPES OF WELDING CONSUMABLES
The type of consumable used during welding depends on the nature of the job intended. Electrodes draw the necessary energy in order to perform welding applications. Consumables includes;
- Stick electrode:
Stick welding requires a lot of skill and also some know-how about stick electrodes (also called welding rods). There are different types of stick electrode, some of them includes (According to the American Welding Society); The E6010, E6011, E6012, E6013, E7014, E7024 and E7018 electrodes. Variables such as storage techniques, electrode diameter and flux composition all contribute to stick rod selection and performance, with basic knowledge one can minimise difficulty which will ensure better outcome in the welding processes.
- Fluxes: Flux is commonly used to produce a shield of gas around the weld pool to prevent oxidation of the hot metals. Flux typically acts as a deoxidizer preventing the formation of porosity in the weld pool. Flux and filler metals together are known as welding consumables.When an arc is struck, the flux burns and produces a series of complex chemical reactions. As the flux ingredients burn in the welding arc, they release shielding gas to protect the molten weld pool from atmospheric impurities. When the weld pool cools, the flux forms slag to protect the weld metal from oxidation and prevent porosity in the weld bead.Flux also contains ionizing elements that make the arc more stable (especially when welding with an AC power source), along with alloys that give the weld its ductility and tensile strength.Some electrodes use flux with a higher concentration of iron powder to help increase deposition rates, while others contain added deoxidizers that act as cleaning agents and can penetrate corroded or dirty workpieces or mill scale.
- Solid wires: This provides deep penetration in the root and usually has little spatter
- Saw wires: These are consumables that are used in combination with flux which result in excellent productivity. It is very necessary to note how the wire and flux will interact with each other and the metals to be welded. Following extended postweld heat treatment, SAW wires are designed to maintain good mechanical properties, while others are less resilient.
- Flux cored wires; There are two types of flux-cored wires — gas-shielded and self-shielded. Gas-shielded flux-cored wires require external shielding gas, and the slag is easy to remove. Consider using gas-shielded flux-cored wires when welding on thicker metals or in out-of-position applications. Gas-shielded flux-cored wires have a flux coating that solidifies more quickly than the molten weld material. As a result, it creates a shelf to hold the molten pool when welding overhead or vertically up. Self-shielding flux-cored wire does not require external shielding gas because the weld pool is protected by gas generated when flux from the wire is burned. As a result, self-shielding flux-cored wire is more portable because it does not require an external gas tank.This has a larger ball type transfer and produces low spatter levels, it also produces a rounder penetration profile with excellent side wall fusion.Flux cored wires is wasted during the course of welding because it does not form part of the final weld.
- Rod electrodes
- Others including gases etc.
Welding consumables are differentiated based on the technique applied, the consumable type, the region it is used, and the end user.
Welding consumables are segmented into:
- Arc welding.
- Resistance welding.
- Oxy Fuel welding.
- Ultrasonic welding.
- Others (laser beam welding, etc.).
Some materials are considered 'unweldable,' a word not found in the dictionary but useful and descriptive in engineering, while other materials require particular techniques or processes to be employed.
HOW TO CHOOSE WELDING CONSUMABLES
In considering the choice of consumable to use for a particular welding job, the composition of the consumables must be similar to that of the parent materials used, which will yield a weld that is homogenous. In some cases, like when welding brittle cast irons, a filler that has a different properties from the parent materials can be used. The joint created is called a weldment and the weld formed is known to be heterogeneous.
It has been approved that when welding materials that have different tensile strengths, the consumable chosen should match the material with the lower tensile strength while the preheat temperature used should match what is required for the material with the higher tensile strength.
Welding has been used in the science of metals for thousands of years. Although, forge welding, carried out by blacksmiths was the only viable technique used for a while. Later on, it all changed when advanced technological methods like oxy fuel and arc welding was introduced.
There are a number of different welding methods, including spot welding, metal inert gas (MIG), and tungsten inert gas (TIG), which are forms of gas metal arc welding, arc welding, and gas welding, to name a few.
- MIG Welding - Gas Metal Arc Welding (GMAW); MIG welding is an arc welding process where a continuous solid wire electrode is fed through a welding gun into the weld pool, joining the two base materials together. A shielding gas sent through the welding gun protects the weld pool from contamination. It uses a wire consumable with a wire spool feeding the wire into the weld joint. It is usually pretty fast and provides a long arc time even when the electrodes are not fully charged.
- Stick Welding - Shielded Metal Arc Welding (SMAW); This uses a powder-coated electrode (flux). When it burns off, the coating shields the weld from oxygen. Filler metal is often added to the coating to speed up the process.
- Gas Tungsten-Arc Welding; It uses a non-consumable tungsten rod to heat the metal and filler metal. The rod just heats the metal and doesn’t add to the filler material.
- TIG Welding - Gas Tungsten Arc Welding (GTAW)
- Flux Welding - Cored Arc Welding (FCAW)
- Energy Beam Welding (EBW)
- Atomic Hydrogen Welding (AHW)
- Plasma Arc Welding
Welding machines produce heat that melts metals. However, bigger machines can be seen in industries while smaller ones are used for domestic and little jobs. There are five main types of welding machines. These are:
- MIG welding machines; They are some of the most outstanding types for welding purposes, whether in an industry or at home. They can handle various metals including mild steel, stainless steel, and even aluminum.
- Thyristor Type MIG welding machines; These brands of machines are best suited for welding solid core and flux material, fixing or mounting objects on a suitable surface. They are able to handle mild steel, alloy steel, low carbon steel etc. They are easy to control because they produce a small amount of spark.
- TIG welding machines; They are great for repairing damaged parts but not good for fieldwork. It gives a pure and neat weld without creating any form of sparks or fumes. They are more distinct than the rest. These machines can handle stainless steel, brass, gold, magnesium, aluminum, copper, and nickel alloys.
- Spot welding machines; They are mostly found in motor automobile industries and are quite cheaper than others. They are used to join overlaps between sheets of steel. The metal sheets are protected using a pair of electrodes by passing a direct current through them. They utilize power very effectively, with simple automation and have a high manufacturing rate.
- Shielded Metal Arc Welding Machine
However, there are different factors that should be considered when choosing the right consumable for a welding job. When a right consumable is selected for a job, it increases weld strength, gives a good quality to the work and also produces clean weld and finishing. Before any welding process is carried out on an equipment, the technician should go through the manual that is provided for that equipment in order to know the particular tools required, gases, consumables, as well as techniques to be used.
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