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Актуальные проблемы в машиностроении
. Том 4. № 3. 2017
Материаловедение
в машиностроении
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FORMATION OF STRUCTURE HYPEREUTECTIC SILUMIN WHEN CASTING
INGOTS SEMICONTINUOUS PROCESS
Prudnikov A.N.
,
D.Sc.(Engineering), Professor, e-mail:
a.prudnikov@mail.ruPrudnikov V.A.
, Ph.D. student, e-mail:
vladpr88@gmail.comSiberian 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