Two of the most basic and commonly used welding techniques go by the name of shielded metal arc welding and gas metal arc welding — or SMAW and GMAW for short. For those who don't work as welders, the differences between SMAW and GMAW can be quite confusing — if not downright inscrutable.
Unfortunately, such a lack of understanding often makes it hard for consumers to choose the right type of welding for their metal project. While you should always consult a professional welder for their opinion, a basic understanding of common techniques is helpful. On that note, this article takes a closer look at three key differences between SMAW and GMAW.
1. Shielding Method
Both SMAW and GMAW rely on a consumable material known as the electrode to create the weld. When exposed to intense heat, the electrode melts, leaving behind a puddle of molten metal. This metal hardens as it cools, ultimately resulting in the formation of a tough joint between the two pieces of metal.
In order to produce a strong and reliable joint, the electrode must be protected from oxidizing forces during the welding process. SMAW and GMAW differ in how they shield the molten electrode from atmospheric gases.
SMAW encases the electrode in a layer of material known as flux. As the electrode melts, the flux turns to a gas that forms a protective layer around the molten weld pool. In recognition of the flux-covered electrode used in SMAW, welders also refer to it as stick welding.
GMAW works by a very different technique. Here no layer of flux exists. Instead, the consumable electrode feeds through a tool known as the spool gun. Not only does the spool gun guide the location of the electrode, but its tip also contains holes that emit a special shielding gas — most commonly argon, helium, or carbon dioxide.
This shielding gas covers the molten electrode as it pools onto the weld surface, thus protecting it from oxidation. The shielding gas has a chemically inert nature, which means that it does not interact with the weld pool in any other way. For this reason, GMAW also goes by the name of metal inert gas welding, or MIG welding.
SMAW and GMAW both utilize quite basic techniques, meaning that even less experienced welders can usually get good results from these welding styles. Yet when it comes to laying down welds as quickly and efficiently as possible, GMAW comes out the clear winner. Several different factors contribute to the efficiency of GMAW.
First of all, the process can be undertaken with far less interruptions. In SMAW, welders must periodically stop to change out for a fresh electrode. In GMAW, by contrast, the wire electrode feeds automatically into the spool gun. This boosts productivity by eliminating the need for constant stopping and starting.
GMAW also promotes better efficiency thanks to its ability to lay down cleaner welds. With SMAW, the vaporizing flux often leaves behind unwanted deposits of slag on the weld surface. This slag must be painstakingly removed once the weld has hardened, thus increasing the total project time. The welds produced by GMAW require much less secondary cleaning.
GMAW tends to carry a somewhat higher overall cost than SMAW. This increased cost stems from the greater expense of both GMAW machines and the types of electrodes used in GMAW systems. In addition, the welder must maintain an appropriate stock of shielding gas, which increases the overall operations costs yet more.
Welders today still routinely use both SMAW and GMAW techniques. For more information about which welding style would best suit your project needs, please contact the metal experts at Sam's Welding Inc.