Welding

Welding Buyer's Guide

The Welding Process

Welding is a process for joining or fastening two pieces of similar metals (work-pieces) by melting and fusing 1) the base metals being joined and 2) the filler metal applied. Most commonly, work-pieces are welded by melting both of them and adding more molten metal or plastic to form a pool that cools to form a strong joint. The energy to form the joint between metal work-pieces most often comes from a flame (e.g.: oxy-acetylene) or an electric arc. Most welding involves ferrous-based metals such as steel and stainless steel. Welding covers a temperature range of 800º C - 1600º C. Weld joints are usually stronger or as strong as the base metals being joined.

Manual Metal Arc (MMA) Welding

Manual Metal Arc or "Stick" welding is very popular in fabrication, agricultural repair and maintenance and pipeline applications. The self-sufficient welding electrodes - also called "sticks" or "rods" are flux-coated, therefore they do not require any shielding gas.  In "stick" welding, two types of power source are available: AC electro-mechanical and DC inverter.  DC inverters are lightweight and more portable than electro-mechanical sets.  DC is much easier to weld with than AC.

Metal Inert Gas (MIG) Welding

MIG Welding is probably the easiest way to weld due to its automated nature and it is highly productive.  This makes it ideal for vehicle restoration and industrial fabrication applications.

Tungsten Inert Gas (TIG) Welding

TIG welding is the preferred choice in applications where strength and the visual finish of the weld is most important.  Heat is provided by an electrical arc, but TIG allows the welder greater control of the addition of filler rod and speed of weld, which can result in strong, x-ray quality welds when mastered.  Many welders use TIG for stainless steel and aluminium applications.  For stainless steel, a DC inverter power source is suitable, for aluminium an AC/DC set is required.

Plasma Cutting

Widely used in industrial and body-shop applications, plasma is popular because it allows shapes to be cut out, enables keyhole cutting and removes the need to start a cut at the edge of a plate or panel.  Plasma cutters are ideal for cutting and fabricating metal — from thin sheets, to thick beams. Plasma cutting employs a torch which uses a powerful electric arc to create plasma, made by boosting a gas (nitrogen, argon or oxygen) to a very high temperature. This creates a stream, or cone, of directed plasma that can reach a temperature of 16,500º C. Handheld torches can usually cut up to 13 mm (1/2 in) thick steel plate, and stronger computer-controlled torches can pierce and cut steel up to 300 mm (12 in) thick. Unlike laser cutting, for example, the process of plasma cutting is only effective on materials that conduct electricity.

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Arc Welders

Inverter Welders

Mig Welders

Other Welders

Understanding the Welding Process

Manual Metal Arc Welding (Stick/Arc) - MMA

This process uses a consumable electrode to support the arc. MMA is achieved by the melting of the outer flux coating on the electrode. Filler metal is obtained from the electrode core.

• Good for windy, outdoor conditions
• OK to use on dirty or rusty metal

Recommended metal: Steel, stainless steel, cast iron
Skill Level: Moderate

Metal Inert Gas Welding - MIG

A process used with a wire feed welding machine. Metals are joined by heating them with an arc, which is between the continuously fed filler metal electrode (solid wire) and the work-piece. Externally supplied gas or gas mixture provide shielding.

• Easy process to learn
• Better control on thinner metals
• Cleaner welds with less slag to clean
• Equipment can be used for Flux Cored welding

Recommended metal: Steel, stainless steel, aluminum, cast iron
Skill Level: Low

Tungsten Inert Gas Welding - TIG

This process uses welding equipment with a high-frequency generator. The arc is created between a non-consumable tungsten electrode and the work-piece. Filler metal may or may not be used, and argon inert gas or inert gas mixtures are used for shielding.

• Provides high-quality, precise welds
• Highly aesthetic weld beads

Recommended metal (AC TIG): Aluminium, magnesium alloys (DC TIG): Steel, stainless steel, copper, brass, titanium
Skill Level: High

Resistance Spot Welding (RSW)

Two separate pieces of metal are joined by passing current between electrodes positioned on opposite sides of the work-pieces. No arc is used; rather, it is the resistance of the metal to the current flow that fuses the pieces.

• Portable and easy to operate
• Ideal for light industrial applications
• Typical use would be car body panels

Recommended metal: Steel, stainless steel
Skill Level: Low

What to look for when choosing a welder

Typical Applications

Consider the most common uses and applications for your welder: construction, farm, general maintenance/repair, home, auto body/repair, etc. Welders are designed for certain applications, depending on rated output, duty cycle and other features. For example, heavy-duty repairs in the field requires a welding package that can handle different types and sizes (thickness) of metal, whereas repairing a wrought iron railing can be done using a stick welder.

Available Power Input

• Single-phase products require single-phase input power usually found in homes and garages (welders operate off either 115V or 230V).
• If electrical hook-up is not available, a petrol-powered, engine-driven welding generator can supply welding and auxiliary power.

Portability

• Can the welder be brought to the work-pieces, or do the work-pieces need to be brought to the welder?
• Accessories can be used to make most welders portable.
• Hand-portable welders are typically 30kgs or less.

What to look for in a welding helmet

Auto-Darkening vs. Standard Glass Lens

Auto-darkening allows easy starting and positioning in welding. With standard glass, the welder needs to be able to flip the helmet down at the moment the weld starts, and flip the helmet up to view the work-piece before beginning again. The downside of this type of helmet is a potential loss of torch position on starts, and at times the helmet cannot be flipped because of space restrictions.

Solar Power vs. Battery (how about both?)

Most solar-powered helmets have either a rechargeable or non-replaceable battery, or they maintain the lens in the shade mode. Solar-powered helmets typically require a charging period prior to their first use as well as after extended periods of storage. Dual-powered lens (solar with replacement battery) enable users to weld right out of the box and can last up to 2000 hours of use on MIG.

Lens Reaction Time/Switching Speed

The switching speed is the time it takes the lens to react to the weld arc. The sooner a welder’s eyes are shaded from the highly intense light, the better. Too slow a reaction time will cause eye discomfort. Some switching speeds are 1/12,000, 1/16,000, even 1/25,000 of a second.

Adjustable Sensitivity and Delay Controls

Sensitivity will set the helmet to trigger on the amount of light hitting the helmet. Delay sets the lens to stay dark after the weld arc goes out.

Helmet Weight

A lighter weight helmet can minimize strain on the user’s neck.

Fixed vs. Adjustable Shade

If welding on one type of material with the same thickness, a welder may opt for a fixed-shade helmet. If welding using multiple processes, for example stick, MIG and TIG, a welder will want to adjust the helmet shade to get the best view of the puddle.

ANZI Z87.1-2003 Standard

Make sure the helmet meets ANSI Z87.1-2003 standards. This means the helmet will filter out ultraviolet (UV) and infrared (IR) rays, even in a non-shaded state. This standard requires helmets to be tested through an independent laboratory. The testing includes impact testing with pointed/ball-shaped objects at speeds of up to 45meters per second, ultraviolet and infrared testing, and switch speed testing in extreme temperatures (-20° C to 55° C).

Glossary of Welding Terms:

Arc [Arc Length] - The physical gap between the end of the electrode to the point where the arc makes contact with the base metal.

Duty-cycle - The porportion of a 10-minute period an arc welder can be operated at maximum rated output. For example, a 60% duty cycle @ 300 Amps means that the welding machine can be used for 6 minutes (at 300 Amps) and then must be allowed to cool with the fan running for 4 minutes. This reduces the chance of heat damage to the system.

Electrode - A coated metal wire having the same composition as the material being welded.

Flux - The coating on arc-welding rods and in flux-cored welding wire that is consumed in the arc to produce a shielding gas. The gas displaces air and impurities from around the weld.

Ground Lead/ Work-piece Lead - The conductor cable or electrical conductor between the arc welding machine and the work.

Rated Output - The Amps and voltage the power source will produce for a given duty-cycle period. For example, 300 Amps, 32 load volts @ 60% duty-cycle.

Shielding Gas - Protective gas used to prevent atmospheric contamination of the weld pool. Usually a mixed gas or CO2.

Slag - A layer of flux soot the protects the weld from oxides and other contaminants while the weld is solidifying (cooling). Slag is to be removed after cooling.

Spatter - Metal particles thrown from the weld, often cooling and hardening on the work surface. A spatter-resistant spray applied to the work-piece can minimize spatter.

Torch - A device in the TIG process to control the position of the electrode, to transfer current to the arc and to direct the flow of shielding gas.

Tungsten - A rare metallic element with extremely high melting point used for manufacturing TIG electrodes.

Wire Feed Speed - Expressed as mm/sec or in/min and refers to the speed and amount of filler metal fed into a weld. The higher the wire feed speed, the higher the amperage.