Effect Of RE Compound Modification Treatment On Microstructures And Properties Of Infinite Chilled Cast

Infinite chilled cast iron has good wear resistance and thermal crack resistance，it has been widely used in the field of roll. but in the process of using, it tends to appear coarse "Meteor spot", chip off-falling, desquamating such as defects, causing the service life of roll is shorter. To solve these defects in the roll and get the good organization and performance, microalloy, modification and heat treatment are used. In this paper, by metallographic method, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy spectrum analysis and a series of mechanical properties test method, the RE compound modification and heat treatment on the infinite chilled cast iron microstructure and performance were systematically studied. The composite mechanism of modification and heat treatment were discussed.The results showed that after RE-Nb compound modification ameliorated the cast organization of infinite chilled cast iron, refined grain, eliminate dendrite, the amount of Ledeburite form carbide was reduced, continuous network carbide was changed into discontinuous network and island shape. Tempering time of heat preservation for10hours, RE compound modification infinite chilled cast iron after250℃,300℃tempering treatment, the matrix organization was acicular bainite and a small amount of martensite, The temperature up to410℃, the organization matrix turned to upper bainite. As the temperature up to430℃, the tempered troostite was appeared, when the temperature reached450℃, almost completely transformed into tempered troostite matrix organization. In the as-cast and low temperature tempered, the matrix organization without secondary carbide precipitation, with the increase of tempering temperature, the granular secondary carbide was precipitated.At250℃heat treatment condition, the hardness of RE-Nb compound modification sample reached60.2HRC, its impact toughness reached4.9J/cm2, compared with uncompound modification infinite chilled cast iron the hardness slightly improved, the impact toughness was increased by28.9%, along with the increase of tempering temperature, the hardness of RE-Nb composite metamorphic infinitely chilled cast iron was decreased, the change of impact toughness was not obvious; when the tempering temperature at250℃, the infinite chilled cast iron had the highest hardness and impact toughness values; after compound modification, with the increase of tempering temperature, the tensile strength of sample reduced, heat treatment temperature at250℃, the tensile strength of specimen up to521MPa.The abrasive wear test results showed that under the condition of250℃heat treatment, infinite chilled cast iron abrasive wear weight of compound modification cast iron was obviously reduced, before modification it was0.2855g, after the modification it was0.1653g, RE compound modification treatment makes the infinite chilled cast iron got significantly improved wear resistance.It is meant that, RE compound modification and heat treatment process on the organization、mechanical property and abrasive wear performance of infinite chilled cast iron were different degrees of improvement, with250℃tempering processing conditions, RE compound modification infinite chilled cast iron has the favorable microstructure mechanical properties, friction and wear performance.