Abstract
<p class="1Body">The aim of the research is to determine the properties and the structure of boron-alloyed iron used for rolls production. It was found that boron can form different carbides in iron, which significantly improve both hardenability and microhardness. Iron borides Fe<sub>3</sub>(B,C) are also formed in cast iron as only 40% of carbon atoms in cementite matrix can be replaced by boron. Besides, boron influences the temperatures of structural constituents decomposition (increases the rate of cementite decomposition), it also decreases the temperatures of developing phase transformations. The research group determined the kinetics of martensite decomposition, which is formed when chilled cast iron is poured into a metal mold and then undergoes thermal treatment to the temperature of 400 °C. In the temperature range of 210 – 400 °C the main process is decomposition of the retained austenite into bainite, while in the temperature range of 400 – 500 °C, the main process is decomposition of martensite and forming a ferrite-cementite mixture. In order to get the necessary properties of the roll face, it is necessary to provide its thermal treatment (tempering), when it is heated to the temperature of 400 °C to avoid martensite decomposition, because otherwise in the process of roll operation it can result in crack formation. </p>
Highlights
There is a number of well known research works about the effects of boron on steel, but the question of the impact of boron on iron is poorly studied
Having studied the influence of boron on the microstructure of the roll-foundry iron cast into а sandy-clay form and a chill mold, it was found that the microstructure consists of austenite matrix with a small amount of martensite needles and carbide constituent established in the matrix
- borides of Fe3(B,С) type, the so called "boride-carbide" of iron are of particular interest as only 40 % of carbon atoms in the cementite lattice of Fe3С can be replaced by boron and the microhardness of this compound is higher than that of conventional cementite;
Summary
There is a number of well known research works about the effects of boron on steel, but the question of the impact of boron on iron is poorly studied. In steels it is used as an alloying element that increases the wear resistance and high-temperature strength (Bolkhovitinov, 1958). Boron is one of the chemical elements, which has not previously been used in roll-foundry iron. That is why it is necessary to investigate behavior of boron in wear-resistance iron of the roll face, its interaction with other chemical elements and its influence on the structure and properties of roll-foundry iron. Boron has a larger diameter of the atom than carbon (0.067 nm) and oxygen (0.048 nm), that is why its solubility in iron is lower, but its impact on the iron lattice is stronger than the impact of the elements mentioned above (Vinarova, 1961; Krukovich, Prusakov, & Sizov, 2010)
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