An Overview of Welding Machines - Gas and Arc Processes

This article sets out to outline the different types of welders used in the metal fabrication industry and their respective applications. Welders can be broken down into two categories: those that use a flame for their heat source and those that use an electric arc.

Flame welders consist of four major parts: compressed gas cylinders, regulators, hoses, and a handle. The gas cylinders contain a fuel and an oxidizer. Acetylene and oxygen are the most common fuel-oxidizer combination, but many people use propane for fuel because of Acetylene's relative instability. Each cylinder has a manual valve that when open allows gas to flow into the regulator. Each gas cylinder has an adjustable regulator that reduces the pressure of the gas from the higher cylinder pressure to a consistent pressure. Adjusting the regulators allows adjustment of the flame. The regulators are connected to the welding handle by rubber hoses. The handle contains on/off valves for both the acetylene and oxygen, and a threaded adapter to allow attachment of various welding, brazing, and cutting tips. Because of this design the gas welding outfit is the most versatile - with the right accessories nearly any operation can be completed. A skilled operator can also weld thin metal with precise control of the welding flame. Gas welding can easily result in a contaminated weld if the operator is not diligent and the flame is not properly adjusted.

Arc welding is broken down into three categories of machines, based on the electrode material and the shielding gas type. SMAW is the simplest process, which stands for shielded metal arc welding. An electrode holder clamps a long metal electrode coated in a flux mixture. An arc is struck between the electrode and the work piece. The electrode metal is deposited to fill the weld, and the flux burns and creates a shielding gas. GTAW welding, or more commonly referred to as TIG welding, stands for Gas Tungsten Arc Welding. GTAW welding employs an inert gas, usually a mix of argon and co2 to prevent the weld from being contaminated by oxidation. The Tungsten in GTAW stands for the tungsten electrode that is used to support the welding arc. The work piece forms the negative side of the circuit, and a tungsten electrode forms the positive side, which is contained in a handle, referred to as the 'torch'. The welding operator manipulates the arc using a voltage control foot pedal and by varying the distance of the torch from the work. The weld is filled in using welding rod. This technique is similar to gas welding. GTAW welding is slow, but it allows for a high degree of precision and the welding of exotic metals such as titanium. GMAW welding stands for gas metal arc welding, also known as MIG welding. Instead of a tungsten electrode and a separate filler rod the two are combined. A metal electrode is constantly fed out which both supports the electric arc and adds filler metal to the weld. Inert gas shields the weld and prevents contamination, as in GTAW welding. GMAW welding is fast as well as versatile. FCAW stands for flux cored arc welding. FCAW employs the same electrode feeding mechanism as GMAW welding, but instead of inert gas for shielding the welding wire contains flux, which when burned creates a shielding gas cloud around the weld.