OPTIMIZATION OF MECHANICAL PROPERTIES IN ENGINEERING STEELS VIA HIGH-TEMPERATURE THERMOMECHANICAL TREATMENT

Influence of the deformation scheme. Up to
now, there are practically no more or less systematic data
on the use of stamping as a method for deforming austenite
in the HTMT (high-temperature thermomechanical
treatment) cycle. Apparently, this is due to the peculiarities
of the stamping process itself, primarily with the strong
non-uniformity of deformation in different sections of the
forging, which determines comparatively less
strengthening as a result of HTMT than in rolling or
drawing. Meanwhile, the widespread use of this method of
manufacturing parts in industry leads to the need to
determine the possibilities of their strengthening in the
case of using HTMT with stamping deformation. Such
work was carried out on 50KhFA steel; the increased
carbon content in this steel, as well as the presence of
chromium and vanadium, which delay the decomposition
of martensite during tempering and the recrystallization
process, determine the feasibility of using this steel for
HTMT strengthening. To determine the optimal conditions
for HTMT with stamping deformation, hardening was
studied under a wide range of process conditions. Various
stamps and blanks of different shapes and sizes were
tested. Forgings with diameters of 10 and 5 mm were
stamped at 900 0C in a shaped stamp on a 1000 -t highspeed
crank press, after which they were immediately
(within 1.5 s) transferred to an oil quenching tank. In this
case, one batch of samples was deformed with one blow,
the other - with two. When deforming with two blows, the
blank was first squeezed between flat dies, and then
quickly tilted at 90 0C and the sample was stamped in a
shaped stamp. After quenching, low tempering was carried
out.