Cryogenic treatment, which is sometimes called cryogenic tempering, utilizes ultra-cold temperatures to modify the microstructure of metals and other materials. It has been widely adopted as a cost reduction and performance enhancing technology. It is also used as an enabling technology. It ultimately improves the performance of the metal, alloy and other materials. The cryogenic treatment process uses sub-zero temperatures down to -184 °C to modify the micro-structure of the material. This treatment promotes additional transformations in metals, alloys and other materials. People usually relate heat treatments with high temperatures, but thermal treatments can also involve cooling. Cryogenic process is extension of heat treatment which further improves the properties of material. The basic CT process consists in a gradual cooling of the component until the defined temperature, holding it for a given time (freezing time) and then progressively leading it back to the room temperature. Depending upon the application of the temperature it may be classified as shallow cryogenic treatment (SCT), is to gradually cool the workpiece at about – 84 °C and deep cryogenic treatment (DCT) is to cool the work piece at about -184°C. The subzero heat treatment effect to mechanical properties of bimetal composite component used in crushing industry has been investigated. Two metal plates (working part: high chromium white cast iron, bearing part: low alloy steel) have been prepared by sand casting method. Both of the plates was subjected to diffusion annealing at 1040°C and then one of them has been subjected to tempering at 270°C, the other plate was subjected to subzero heat treatment at -80°C and then tempered at 270°C. Hardness values and metallography of pieces have been analysed and compared. A remarkable change were observed in hardness values, and metallography shows a great difference between two plates.
Anahtar Kelimeler: Subzero heat treatment, bimetal, metallography,hardness.
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