How Heat Treatment Contributes to Material Conductivity

03 December 2019

Metals harden when they’re heated, or they become more ductile when they’re heated then cooled at a specific rate. Interestingly enough, metal workpieces change in other ways when cooking in a furnace. With their grains realigning as the thermal energy sends the material into a state of atomic flux, the material becomes more conductive. No surprises here, clients have come to covet such materials.

Increasing A Material’s Electrical Conductivity

The principle isn’t all that different from what we see on a metal part that needs to become more workable. Phase state changes occur as an alloy part is heated, with the energy penetrating deep into the materials’ grain. The metal crystallizes in such a way that the slowly changing alloy develops precipitates, which then form thin grain boundaries. Electrons can now flow through the larger grains and thinner crystallized boundaries faster. Typically, we’re referring to an annealing process, an operation that holds a workpiece at or near its critical transformative temperature for a fixed amount of time, before the alloy is then slowly returned to room temperature.

Intelligently Altered Thermal Conductivity Coefficients

Essentially, when metal parts get hot, they readily conduct that energy. Sometimes this is a good feature to have available. Heat exchangers conduct thermal energies well, and that’s a good thing. Conversely, there are times when a low coefficient is desirable. Metal beams, which take on an important role as a structure’s support framework, need to be welded. A moderate degree of thermal conductivity is okay here, but high values will cause weld heat to dissipate too fast. Taking these issues into account, heat treatment professionals use phase state altering thermal loads to alter an alloy part’s martensitic matrix. With material impurities, heat soaking carbon precipitates, and alloy additives all negatively impacting material heat conductance ratings, tempering and normalizing control factors should be fine-tuned if this value is to be successfully preserved.

Two wholly different material conductance parameters are brought under control when different heat treatment processes are employed. Utilizing an annealing operation, metal parts soften and become more electrically conductive. Expect to find bus bar circuits and advanced semiconductor elements treated in this manner. Grains largen and homogenize when annealed. As for the thermal conductivity work described above, well, alloying additives can decrease a metal part’s heat transference properties. The way a heat-soaking portion of alloying carbon diffuses into a crystallizing metal workpiece is also a matter of some concern. Again, by tempering or manipulating a metal part’s martensitic matrix, a heat treatment operation can alter an alloy part until it transfers more, or less, heat.

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