Messer Group GmbH (Krefeld, Germany):

Schmidt H.-P., Technology Manager Metallurgy, e-mail: hans-peter.schmidt@messergroup.com

It is stated that transformation of residual austenite has been occurred practically completely in the material after quenching in order to get wear-resistant components with stable form. This step can be considered as a decisive one to provide steel quality, if we consider hardness and service life of cutting tools or precision of outline dimensions of casting forms. Transformation occurs mainly as a result of long-term secondary heating and cooling. Low-temperature processing is the alternative characterized by time and power saving and allowing to realize complete transformation of residual austenite. The presented method is not only economically efficient, but also provides quality improvement of products. E.g., positive effect caused by cooling is manifested in comparison of service life of steels used for wood cutting tools. It is shown that holding temperature made –150 ºC and low-temperature processing decreased compressing stresses in the cutting tool and provided origination of especially fine martensite needles and it can be ex-plained as the prerequisite for increased strength of crystal structure of cutting tool material. As for cooling technology, usage of liquid nitrogen guarantees efficient and resource-saving operation of cooling chambers and provides rapid achievement of required cooling temperature and uniform temperature procedure.