What is a Tempering Furnace?
A tempering furnace is a type of industrial oven designed to heat treat a ferrous metal product and increase its toughness. In metallurgical terms, the toughness of an alloy describes its capacity for elastic deformation and energy absorption before the material fractures. It is part of a complex relationship between a metal’s ductility and its strength, with high toughness values requiring a delicate intersection of the two.
Typically, high strength materials are not ductile – and vice versa – but heat treating certain materials in a tempering furnace can unlock beneficial values on both axes of this mechanical dynamic.
How Does Tempering Work?
Tempering is a process that dates back millennia, and the theory behind it has remained relatively unchanged in the centuries since. It is the process of accessing the highest possible intersection of strength and elasticity of a ferrous, or iron-based, metal product by heat-treating it to a limited degree, typically after the quenching process.
Modern tempering processes may be theoretically like their ancient counterparts, but the equipment currently used is vastly improved. Quenching, for example, which once required a homogenous liquid such as mercury to appropriately precipitate hardening of a ferrous metal alloy, can now be accomplished using vacuum or gas flow techniques. Tempering furnaces have similarly enabled new capabilities for ‘softening’ a ferrous metal after the product has been quenched.
Iron-based metal products are uniformly heated to temperatures ranging up to 1,650°F (900°C), and are then soaked in a liquid bath or an air furnace. Typically, the material will be allowed to soak in the quenching environment for a period of minutes before it is quenched in a liquid material to encourage the formation of high strength martensite within the material. After the product has been cooled, it will be transferred to a tempering furnace to reduce its strength and brittleness to a desirable degree.
A tempering furnace uses ceramic heating elements lined with electrical wires or coils to uniformly heat a sample chamber to different heating ranges depending upon the desired material characteristics of the product. An iron-based metal is heated in a tempering furnace to between 300 – 750°C (572 – 1382°F), to encourage phase transitions within the martensite structures and reduce the hardness of the material while improving its ductility. It is crucial that the tempering furnace can accurately maintain temperature levels and temperature uniformity throughout the sample chamber to negate the likelihood of metal warping or fracture.
Tempering Furnaces from Thermcraft
Thermcraft is a leading supplier of heat treatment equipment and services for a broad range of sectors. We provide a robust range of industrial ovens and kilns, including tempering furnaces to improve the physical properties of iron-based products such as aluminum.
Tempered aluminum is regularly used in the aviation sector, where materials must be extremely strong but flexible enough to exhibit plastic deformation at varying pressures.