Actual Problems in Machine Building 2017 Vol. 4 No. 3

Актуальные проблемы в машиностроении . Том 4. № 3. 2017 Материаловедение в машиностроении ____________________________________________________________________ 83 FORMATION OF STRUCTURE HYPEREUTECTIC SILUMIN WHEN CASTING INGOTS SEMICONTINUOUS PROCESS Prudnikov A.N. , D.Sc. (Engineering), Professor, e-mail: a.prudnikov@mail.ru Prudnikov V.A. , Ph.D. student, e-mail: vladpr88@gmail.com Siberian State Industrial University, 42 Kirova st. Novokuznetsk, 654007, Russian Federation Abstract Investigated fracture surface, macro- and microstructure of ingots semi-continuous casting of binary hypereutectic silumin with a silicon content of 20%. Ingots produced in industrial conditions on the PN-2 machine with mold slip 165 mm. Ingot length was 100 cm and its weight - 60 kg. It is found that the break in the cross section of the ingot is characterized by the presence of significant areas of quasi-viscous and viscous destruction. These regions are formed in the ground breaking for the eutectic (Al + Si) and α-solid solution. Within this matrix are brittle cleavage facets located on the primary silicon crystals. Moreover, their size and the volume fraction greater in the central part of the ingot than at the periphery. The macrostructure characterized eutectic colonies distribution inhomogeneity (Al + Si), and portions of dendrites α-solid solution. It is shown that in the cross section of the ingot semicontinuous casting hypereutectic silumin formed peripheral, intermediate and central zones. These areas differ in the number, size and distribution of the primary silicon crystals and the eutectic structure.Аre shows the mechanical properties averaged over the cross section of ingots (σ ts ,= 88 MPa, δ, = 1,5 %). The average value of the coefficient of thermal expansion in the range of 50 - 200 ° C is 17.7∙10 -6 K -1 , which is comparable with the piston casting alloys such as AK21. Keywords silumin, ingot, semicontinuous casting, structure, primary crystal silicon, eutectic