Filler Metal Glossary
Alloying – The process of adding elements to a base material or filler metal; it provides both with specific mechanical and chemical properties. Alloying can improve toughness at low temperatures, enhance corrosion resistance, increase strength and more.
Cooling rate – The rate at which a weld cools. It is largely impacted by welding heat input, but also preheat and interpass temperature. Slower cooling rates are preferred to minimize the risk of distortion and cracking and can be achieved by preheating the base material, controlling interpass temperatures and using moderate heat inputs.
Cycle time – The total amount of time needed to create a weld/produce a completed part from start to finish. It includes pre-weld activities, such as grinding, tack up and joint preparation; welding; interpass activities such as movement; and post-weld cleanup or any required rework.
Deposition efficiency – The ratio of the weight of metal deposited in a weld joint to the amount of filler metal used, expressed as a percentage.
Deposition rate – The amount of metal deposited in a joint in a given period of time. It is typically measured in pounds or kilograms per hour. It is different from melt-off rate, which is the amount of filler metal used/consumed in a given period of time and does not factor in deposition efficiency.
Ductility – The amount a weld can stretch and undergo deformation before it fractures. It is measured in terms of percent elongation.
Heat input – How much energy from the arc is directed to the base metal to create a weld. It is calculated by the following formula: (60 x amps x volts) / (1,000 x travel speed in in/min) = heat input (kJ/in). Slow travel speeds can cause high heat input, while faster travel speeds can cause lower heat input, rapid cooling and increased hardness of the weld.
Hydrogen-induced cracking (HIC) – Often called hydrogen-assisted cracking (HAC), or cold cracking, HIC occurs in steel weldments at temperatures below 600 degrees F (316 degrees C) within hours or days after completing the weld. HIC is often in the heat-affected zone (HAZ) or in the weld metal transverse to the direction of welding. It is the result of residual stresses from the base material restraining the weld combined with the presence of stress induced by retained diffusible hydrogen. HIC is particularly prevalent in thick materials.
Operator factor – The ratio of the amount of time a welding operator spends welding to total operation time; it is measured by arc-on time (in hours)/hours worked x 100 and expressed as a percentage. Operator factor is largely impacted by the welding process.
Post-weld heat treatment – Abbreviated PWHT, it is the application of heat for a specified period of time after completing a weld. Code and application requirements determine the need, amount and duration of PWHT, and it is often used to reduce the risk of hydrogen- and/or residual stress-induced cracking in steel weldments.
Toughness – It is a weld’s ability to permanently deform while absorbing energy before fracturing. When this stress is applied rapidly — typically, in under one second — it is called impact toughness. In other terms, toughness is how much rapid-impact energy a weld can take before it cracks. This measurement is expressed in foot-pounds (ft-lbs) or Joules (J) and determined through the breaking of a Charpy V-notch test specimen.
Ultimate tensile strength – Sometimes referred to as tensile strength or UTS, it is the maximum stress a material can withstand before it fractures. Tensile strength testing determines this stress in pounds per square inch (psi) or in megapascal (Mpa).
Weld cost – The combined labor and overhead cost of pre-weld, weld and post-weld activities, as well as the cost for electricity, shielding gas, filler metals and other consumables. Joint design, power source efficiency, and welding process and parameters contribute to weld cost. It may be measured in dollars per joint or dollars per foot (assuming all the welds are the same size).
Weld size –This is specified by the leg or throat for a fillet weld, the throat for partial joint penetration groove welds, or the material thickness for complete joint penetration groove welds. Weld size influences weld strength. It also influences cost — larger welds use more filler metal, take longer to create and cost more. Weld size is specified in welding procedures.
Yield strength – The amount of stress a weld can withstand without deforming permanently. It is measured in pounds per square inch (psi) or in megapascal (Mpa).