Arc Welding Consumable Parts: A Complete Guide
What is arc welding?
Arc welding uses a flow of electrons passing through air/gas known as the ‘arc’ to heat metallic workpieces in a localised area to create a molten puddle known as the ‘weld-pool’. Once the arc has moved on or is removed, the weld-pool solidifies to create a bond between previously separate parts.
There are two main types of welding consumables, one being the materials that form part of the weld itself (often described as ‘filler metal’) and the other being parts that are consumed to enable the welding process. In this article we will be concentrating on the consumable parts that enable the weld to take place, focusing on the MIG/MAG, TIG & MMA processes.
We put MIG/MAG welding first not because it’s the best way of welding in the sense of weld integrity but that it’s what most welders are familiar with. Its chief strengths are productivity, flexibility and the fact it is a relatively easy process to learn.
MIG/MAG welding is a process where the arc is struck between a continuously fed consumable wire (filler metal) and the work-piece. This wire is melted into the ‘weld-pool’ (molten ‘puddle’) formed by the arc on the work-piece and adds extra material to the weld. As most metals will burn in air at these temperatures, a shielding gas is introduced to keep oxygen (and other reactive gases) from the molten metal.
So the issues facing someone who wants to manufacture a MIG welding machine is not just how to produce the correct electrical conditions to enable a welding arc to be struck and maintained but equally critical is the delivery of the filler metal and shielding gas to the area welded in a precise and consistent manner.
The usual method of delivering the welding arc, shielding gas and filler metal to the work-piece is achieved by a welding torch (or ‘gun’) which commonly is 3 to 4 metres in length and attached to the positive electrical terminal of a welding machine. A wire feeding device pushes the filler metal (in wire form) along the torch through a ‘liner’ coming out the end via a ‘contact tip’ which gives an electrical charge to it. At the same time shielding gas is fed up the torch using the pressure from its compressed cylinder and this exits through a nozzle (or ‘shroud’) that surrounds the contact tip. An earth lead attached to the negative electrical terminal on the welding machine is clamped to the work-piece to provide complete circuit; both the welding torch and earth lead are commonly known as ‘secondary’ consumables.
MIG consumable parts might be a commodity but they play a critical role in achieving quality welding and can directly impact overall productivity and cost of the operation. A poorly designed MIG torch may not only be uncomfortable for the operator to use but also may create issues such as poor filler wire feeding and inconsistent gas shielding.
Moving on to the main consumable parts, these usually comprise of a liner, contact tip, gas nozzle and gas diffuser. It is these parts that are primarily responsible for consistent feeding of the welding wire, maintaining a gas shield and creating the electrical conductivity necessary for a good welding arc. Higher quality consumables are usually made from superior grade materials to more precise tolerances in order to maximise their life, increase weld quality and reduce operator frustration. Poor quality parts produce unnecessary issues for an operator in what can already be a demanding job role such as;
- Burn-back (wire end melting onto the tip) requiring time-consuming re-feeding
- Jerky wire feeding causing excessive spatter and poor weld bead appearance
- Extra downtime when having to frequently replace burnout parts
- Poor gas shielding causing porosity in the weld bead and therefore potential rework
It is estimated that consumable parts make up less than 1% of the cost of a metre of the weld as opposed to 76% being in wages. This makes an overwhelming case for buying quality manufactured parts rather than just going for the cheapest advertised.
TIG welding is one of the most common ways of producing high integrity and cosmetically nice weld beads. It is a very flexible process with the ability weld almost all metals with one type of machine and shielding gas (argon).
Like MIG/Mag welding, the TIG process joins metals by locally heating them to melting temperature with an electrical arc. However, in this case, the arc is struck between a temperature resistant tungsten electrode and the work-piece while filler wire is usually fed independently into the weld-pool. Again, a shielding gas is introduced to keep reactive gases present in the air away from the molten metal.
The electrical arc and shielding gas are delivered to the work-piece by a welding torch which is commonly 4 or 8 metres in length and a tungsten electrode from which the arc emits is held in a collet within the torch head. At the same time shielding gas is fed up the torch using the pressure from its compressed cylinder and this exits through a nozzle from which the tungsten protrudes. An earth lead completes the circuit, this and the torch are the ‘secondary’ consumables for TIG welding.
The main consumable parts usually comprising of a collet, collet body and ceramic nozzle need to be precisely dimensioned in order to keep the tungsten electrode concentric to the ceramic nozzle. An eccentrically mounted tungsten will tend to cause the welding arc to wander and will make control of the weld pool more difficult. As with MIG welding consumable parts, higher quality consumables are usually made from superior grade materials which can handle the intense heat better. This is particularly the case with collets for smaller TIG torches and also ceramic nozzles on high ampere applications. Again, poor quality parts produce unnecessary frustrations for operators that take pride in their work such as;
- Arc wander causing poor weld bead appearance
- Tungsten dropping into the weld pool caused by the collet deforming through heat
- Poor gas shielding causing porosity in the weld bead and potential rework
- Extra downtime when having to frequently replace burnout parts
- Ceramic nozzle ends cracking and falling off
MMA (Manual Metal Arc or ‘Stick’) welding is the original common method of arc welding. It is a simple and flexible process that can be used primarily on ferrous metals but does however require a good degree of operator skill.
MMA welding works by establishing an electric arc between a flux-covered metal consumable electrode and the workpiece. As with the other arc welding processes mentioned above, this locally melts the electrode’s metalcore and the work-piece producing a solid bond when it cools down. However, a fundamental difference lies in the electrode’s flux coating which ‘burns off’ during welding to create a gaseous shield from oxygen in the air. This process is very robust, able to give high integrity welds in outdoor atmospheric conditions which could not be achieved by either MIG or TIG welding.
The welding arc is delivered to the work-piece by means of a lead with a handle at one end to hold the consumable electrode. In a sense, there are no actual consumable parts in the MMA welding process. However, electrode holders, earth clamps and welding leads deteriorate with use causing issues such as;
- Worn electrode holder allowing the electrode to fall out or change position during welding
- Reduction of welding power due to poor earth and electrode conductivity
- Arcing out of machine sockets caused by worn welding lead connectors/plugs
- Welding lead insulation melting off due to connectors becoming loose
It is recommended that welding leads are replaced regularly and that correct size of cable, holders and earth clamps are used; a useful guide is shown below;
If you’re a welder or work in the industry then you know how essential the right consumables are for your welders. At PWP we aim to help assist the metal fabrication industry to be the absolute best it can. That means providing the best tools for the projects so every finished result is a perfect one.
Our extensive product ranges are focused on providing solutions that our customers can work with. After all, it’s our vision to put quality equipment in the hands of welders—to help them in all industries to become more efficient, productive and profitable.
Not to mention we offer fast delivery so that your delays and downtime are minimized whenever possible. Then again, that’s just part of our ambition to keep welders everywhere achieving their goals! So if you need expert advice or require a new welding machine or consumables, get in touch today. Call us on 01234 345111 or email [email protected] to place an enquiry or find out more from our knowledgeable, and dedicated team.
Bio of Author:
This article was written by Richard Fryer, a partner at PWP Industrial with 24 years of experience.
Passionate about supporting the professional welder and a demonstrated history of supplying products to the welding and fabrication industry, Richard is an invaluable asset to PWP Industrial and contributes toward the end goal of providing innovative solutions. Connect with Richard on Linkedin.