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Variation of the chemical composition of all phases and structural components (metallic matrix, eutectic and secondary carbides) in complexly alloyed cast iron is studied after crystallization and different variants of tempering. It is shown that several groups of secondary carbides may be distinguished according to their morphology and chemical composition.

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288Complex cast iron (alloyed with Ti, V, Cr, Ni, and Nb) is used to produce components subject to abrasive wear at high temperatures, including rollers of hot rolling mills. After solidification and cooling in ingots, considerable shrinkage and thermal stresses arise on account of the large size and low thermal conductivity of the cast iron components, together with phase hardening in γ → α transition. The final operation in roller production is tempering for stress reduction. The traditional treatment is one time moderate tem perature tempering for many hours, with slow heating and cooling to prevent crack formation [1]. In temper ing, the residual austenite decomposes to form bainite, which impairs roller performance [2]. This is accom panied by additional carbide deposition, with simulta neous redistribution of chemical elements between the metallic base and the carbides.The performance of cast iron rollers may be improved by changing the heat treatment [3]. How ever, that also changes the decomposition kinetics of the austenite and the redistribution of the chemical elements. Therefore, in the present work, we investi gate the change in structure and chemical composi tion of all the structural components of white cast iron after solidification and tempering in production con ditions.The table presents the chemical composition of the cast iron samples.The samples are taken from the working layer of the roller after solidification and tempering. The distribu tion of the chemical elements is determined on a Tes can VEGA II LMU scanning electron microscope with an INCA Energy 450 attachment for X ray microspectral analysis. To prevent the superposition of the spectra of the base and the secondary carbides because the excitation region of the X-rays (around 30 μm) extends beyond the secondary carbides, we use electrolytic etching of the samples in a 3% aqueous solution of hydrochloric acid, with a current density of 200 A/m 2 [4]. In Fig. 1, we show the resulting relief surface with an etching depth of 100-150 μm of the base.After solidification and cooling, the samples from the working layer of the roller consist of austenite den drites, of which 80% are converted to large martensite needles and also eutectic and secondary carbides (Fig. 2). The carbides differ in shape and size and in chemical composition.The austenite dendrites contain up to 0.7% Mn, 4.8% Ni, 1.0% Si, 0.9% Cr, and 1.3% Cu. The eutectic carbides contain 78.5% Fe, 3.6% Cr, 1.1% Mn, 0.6% V, and up to 1.5% Ni; the remainder is carbon. The sec ondary carbides differ in morphology and composi tion; on the basis of their Ni and Fe content, they may be divided into three groups.In the first group, the main carbide forming ele ment is niobium (67.0-68.0%), with 0.3-0.8% Ti, 2.0-2.5% V, 4.0-6.0% Fe, and up to 0.6% Cr. These carbides take the form of plates (thickness 0.8-2.0 μm) located within the dendrites. They are aligned with dendritic axes of first and second order and only some times reach the boundaries of eutectic carbides (sec Abstract-The chem...

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