- Acetone
- A highly flammable organic compound in which acetylene is dissolved to enable it to be safely stored and transported.
- Acetylene
- A fuel gas comprising two carbon atoms and two hydrogen atoms, C[2]H[2]. If acetylene is compressed on its own it can lead to a highly exothermic reaction. For this reason acetylene is supplied dissolved in acetone. Acetylene cylinders are made up of a porous mass capable of storing the acetone-acetylene solution.
- Annealing
- A heat-treatment designed to fully soften a metal or alloy.
- Anodising
- A method of artificially thickening the oxide film on an aluminium alloy by an electrolytic process. The component to be treated is made the anode in a tank of electrolyte, and on the passage of electric current, oxygen is produced which reacts with the metal surface to form a tightly adherent oxide coating. Dyes may be added to the electrolyte to produce colour anodised surfaces.
- Arc Air Gouging
- A competitive process to Flame Gouging. It uses a hollow carbon electrode through which compressed air is passed. The electrical arc generated between the electrode and workpiece melts the metal which is then blown away by the compressed air. Arc air gouging has poor environmental performance.
- Arc Energy
- See Heat Input.
- Arc Stability
- Arc stability is the term used to describe the regularity at which droplets detach from the consumable wire or rod during welding. Processes with good arc stability have droplet detachment rates that are regular, and of consistent size, these create a minimal amount of disturbance to the weld pool. Similarly processes that have poor arc stability are characterised by irregular droplet rates, with droplets of different sizes. One consequence of this is an increase in the amount of spatter produced.
- Arc Wander
- Movement of the arc column caused by the arc attempting to find the path of least resistance to earth. Exhibits itself as the arc moving from one edge of the welded joint to the other.
- Argon (Ar)
- A colourless and odourless monatomic gas, density relative to air 1.38. Its most useful property is its total inertness to all substances at all temperatures and pressures. It is the most widely used shielding gas in arc welding.
- Artificial Aging
- An age-hardening process which takes place at elevated temperature.
- Asphyxia
- Unconsciousness or death produced by failure of the blood to become properly oxygenated. This failure may be due to inability of air to reach the lungs, as in suffocation, or because of chest injuries.
- Atmospheric Pressure
- Atmospheric Pressure is the pressure exerted by the air in the atmosphere on the earth's surface. Standard atmospheric pressure is quoted in a variety of units: 1.01325 kPa, 760 mm Hg (Mercury), 1.01325 bar or 1 atmosphere.
- Austenite
- A solid solution of iron and carbon, with the carbon diffused uniformly throughout the structure. Austenite has a face-centred cubic (F.C.C.) structure.
- Automatic Welding
- Welding with equipment that performs the welding operation without adjustment of the controls by a welding operator. The equipment may or may not load and unload the workpieces. See also machine welding.