Posted by Robert Hernandez on Sep 16th 2026
| Term | Definition |
|---|---|
| I.D. | Inside diameter, the interior size of a pipe or tube, measured at its widest point. |
| Icicles | An undesirable condition where excess weld metal protrudes beyond the root of the weld. |
| Ignition temperature | The temperature at which a material will burn if enough oxygen is present. |
| Impact strength | The ability of a material to withstand impact or hammering forces without cracking or breaking. |
| Impact test | A test that carefully measures how materials behave under heavy loading, such as bending, tension, or torsion. Charpy or Izod tests, for example, measure energy absorbed when breaking a specimen. |
| Impurities | Undesirable elements or compounds in a material. |
| Inch switch | A switch on a welding machine that is used to slowly feed consumable wire through a combination cable to a TIG (GTAW) torch. |
| Incomplete fusion | Failure of weld metal to fuse completely with the base metal or the preceding bead. |
| Inclusion | A gas bubble or nonmetallic particle entrapped in the weld metal as a result of improper arc heat or filler material manipulation. |
| Inert gas | A gas which does not normally combine chemically with the base metal or filler metal. |
| Indentation | A depression left on the surface of base metal after a spot, seam, or projection weld is made. |
| Indenter | In a hardness test, the ball or diamond that is pressed into the surface being tested. |
| Inductance | In the presence of a varying current in a circuit, the magnetic field surrounding the conductor generates an electromagnetic force in the circuit itself. If a second circuit is adjacent to the first, the changing magnetic field will cause (induce) voltage in the second circuit. An application of this principle is the step-down transformer used in welding machines. |
| Infrared rays | Heat rays which come from the welding arc. |
| Inert gases | Shielding gases, such as argon and helium, that do not react with the weld. |
| Inorganic | Being or composed of material that was never living; mineral, as compared to plant or animal. |
| Inorganic fluxes | Welding fluxes that do not contain carbon. They are very corrosive, so they are not used on electrical or electronic parts. |
| Input power | Electrical power required to operate a given welding machine. |
| Inside corner weld | Two metals fused together; one metal is held 90 degrees to the other. The fusion is performed inside the vertex of the angle. |
| Inspection | The process of examining welds for suitability, without damaging or destroying them. |
| Insulation | A material that will not permit the flow of electricity, used as a covering on wires, cables, and electrode holders. |
| Intermittent weld | Joining two pieces and leaving un-welded sections or gaps in the joint. |
| Interpass heating | Heating or reheating a joint between the passes needed to complete the weld. |
| Inverter | Power source which increases the frequency of the incoming primary power source. |
