Welding Technology

Weld Descriptions

Gas Metal Arc Welding (GMAW)

Sometimes also referred to as MIG welding, is a welding process in which metals are joined by heating them with an electric arc between the base metal and a continuous consumable electrode. A shielding gas or gas mixture is used to prevent the atmosphere from contaminating the weld.

Gas Tungsten Arc Welding (GTAW)

A welding process in which an arc is struck between a tungsten electrode and the base metal. The tungsten electrode does not melt and become part of the weld. It is, therefore, referred to as a nonconsumable electrode.

The tungsten electrode and the molten weld pool must be protected from the atmosphere while welding. Oxygen in the atmosphere causes the electrode and base metal to oxidize. An inert gas is used to shield the arc area from the atmosphere. Inert gasses do not react with the electrode, arc, or molten weld metal. GTAW is considered to be a very clean process, since oxygen is kept away from the electrode and the molten metal.

Oxyfuel Gas Welding

A general term for a group of welding and cutting processes that use heat produced by a gas flame. Oxyacetylene welding is a type of oxyfuel gas welding. Fuel gasses are those that will support combustion when combined with oxygen. These gasses include acetylene, propane, butane, hydrogen, natural gas, and methylacetylene-propadiene gas.

Acetylene is commonly used for welding and cutting. When combined with oxygen in a neutral flame, it will produce temperatures around 5600æF (3093æC). This is the highest temperature produced by any combination of oxygen and fuel gas. Propane, butane, and natural gas do not produce hot enough flame for welding; however, they can be used for soldering, brazing, and cutting.

Shielded Metal Arc Welding (SMAW)

Sometimes also referred to as “stick welding,” is a process in which base metals are heated to fusion or melting temperatures by means of an electric arc. The arc is created between a covered metal electrode and the base metals. The base metals, arc, electrode, and weld material are shielded from the atmosphere while welding. A shielding gas is used to protect the weld area from the atmosphere. This gas is created when the covering on the electrode melts. The melting electrode wire furnishes filler metal to the weld.

The temperature of the SMAW arc is around 7000æF (3870æ C). Heat created by the arc will melt any weldable metal. Milled carbon steel melts at about 2500æF—2700æF (1370æ C—1480æC).

Shielded metal arc welding is used to construct buildings, ships, truck chassis, pipelines, and other weldments. SMAW equipment is fairly inexpensive and is widely used in many shops.

Contact

Bill Johnson
Bill.Johnson@nwc.edu
Associate Professor of Welding; Coordinator of Welding
307-754-6156