A high-frequency induction annealing machine is used to heat and heat treat metal materials. Improper operation can easily cause defects such as oxidation, decarburization, cracks, overheating, and overburning. These defects may at least affect the service life of the metal, or at worst may lead to the scrapping of the metal.
Various metal materials will produce overheating and overburning defects due to excessive heating temperatures.
1) Overheating
After the forging is overheated, the grains become coarse and the grain boundaries are thickened. The strengthening phase in the grains dissolves or merges, the particles become coarse, and the grain boundaries precipitate in strips or network phases. The overheating phenomenon is not only related to excessive heating temperature, long holding time and small degree of deformation, but also related to the purity of the alloy within a certain temperature range.
Since both forging and heat treatment heating may produce overheating, austenitic steels, high-temperature alloys, and aluminum, titanium, and magnesium alloys are often inspected after final heat treatment. The longitudinal plasticity and toughness of overheated forgings are reduced, and the fatigue properties and fracture toughness are significantly reduced.。
2) Overheated
The surface of over-burned forgings is rough, sometimes orange peel-shaped, with network cracks, and is easily broken during forging. In addition to coarse grains in the high-magnification structure, the grain boundaries are oxidized and melted and new phases are produced, and cracks appear, that is, overburning occurs. Overburned forgings must be scrapped。
This article briefly introduces overheating and overburning defects, hoping to be helpful to your heat treatment work.
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GS-ZP-1200
