Varmeinnføring

Varmeinnføring refers to the amount of heat energy introduced into a material during a heating process. It is a central concept in materials science and engineering, where it is often described as heat input per unit length or per volume and used to assess how a process will affect a material’s microstructure, mechanical properties, and dimensional stability.

In welding, heat input is a key parameter that results from process variables such as voltage, current, and travel speed. It influences the size of the heat-affected zone, cooling rate, grain structure, dilution with the base metal, and the development of residual stresses and possible distortions. Excessive heat input can widen the heat-affected zone and promote coarse grains, while too little heat input may cause defects such as lack of fusion or hydrogen cracking. Welding procedures are typically optimized by balancing heat input with joint design, material type, and desired weld characteristics.

Control methods include adjusting arc voltage and current, changing the welding speed, using different welding processes (for example MIG/MAG, TIG, or stick welding), preheating the workpiece, controlling interpass temperature, and employing heat sinks or interpass cooling. Pulsed or controlled heat input waveforms can also be used to tailor cooling rates and microstructure.

Beyond welding, varmeinnføring is relevant in other thermal processes such as heat treatment, brazing and soldering, and even certain polymer processing scenarios where energy input affects viscosity, crystallization, or phase transitions.

In practice, varmeinnføring is estimated and monitored to ensure product quality, structural integrity, and process efficiency, often expressed as energy per unit length or per volume and derived from process parameters or calorimetric measurements.