Glossary - I

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Ignition

The action of firing an explosive mixture of gases or vapours by means of a flame, electrical spark, heating or sudden pressure change.

Inert

A substance which does not form compounds with any other element. The noble gases, which occupy Group 8 of the Periodic Table are totally inert.

Impact Strength

The impact strength of a material is a measure of its ability to withstand shock loads.
In the laboratory, it is evaluated by dynamic test methods, such as, the Charpy V Notch, and, less commonly nowadays, the Izod test. These tests measure the energy absorbed in breaking a pre-notched specimen, held at a known test temperature This absorbed energy is quoted in 'Joules' or 'Foot-pounds', and reference is always made to the temperature at which the test was carried out.

Infrared Radiation

Electromagnetic energy with wave lengths from 770 to 12,000 nanometers.

Injector Torch

A torch design which is ideal for use with low fuel gas pressures. The gases are mixed by allowing the oxygen flow to suck the fuel gas through the injector nozzle. This type of torch is ideal for equipment fitted with long hoses (greater than 50m).

Interpass Temperature

In multipass welding, the temperature of the weld metal before the next pass is started.

Ionic

A chemical bond in which one element loses an electron to another element. Elements in Group 1 of the Periodic Table, for example Lithium are extremely reactive because they readily give up their single electron in the outermost energy level to another element with an incomplete energy level thereby forming a stable compound.

Ionisation

The process by which gas molecules are converted into positively and negatively charged particles called ions. This process occurs when an arc is struck between an electrode and the workpiece.

ISO

International Standards Organisation. This organisation develops standards for worldwide use. Standards are denoted as ISO followed by a number and date.