Powder Metallurgy and Metal Ceramics. Vol. 35. Nos. 1-2, 1996
OF CERTAIN FERROALLOY
AND GRAPHITE POWDERS
I. N. Zegalo, Yu. N. Grishchenko,
A. P. Stovpchenko, and S. I. Zigalo
The thermophysical properties of certain ferroaUoy (FS3OR3M30, FSZr50, FTi-30) and graphite powders, used
for the composite microalloying of steel castings, were determined using an experimental--calculation method.
A substantial difference in the heat conductivity of powder and monolithic materials was revealed. The nature
of change of these properties with temperature was investigated.
In developing techniques for the manufacture of composite ingots microalloyed with ferroaUoy powders [ 1], it has been
established that the use of thermal conductivity coefficients for these materials in the compact (cast) state leads to significant
errors in calculating the heating rates of the materials in powder form.
The authors of the present work have determined the thermophysical properties of the powder materials using the
experimental--calculation method proposed by N. Yu. Taits and E. M. Goldfarb for steel . This is based on graphical
solution of the heat-conductivity differential equation, carried out with the aid experimentally determined heating rates for the
bodies. A schematic of the experimental equipment, constructed on the basis of a Tamman furnace, is given in Fig. 1.
The experiments were conducted as follows: a steel tube 2, filled with powder (or a monolith) of the investigated
material 4, and closed above and below by refractory plugs 3 (to decrease heat loss), was situated within a graphite block 1,
placed on a support and heated to 1100-1150°C." Temperature changes in the graphite block, in the center of the specimen,
and in the tube wall were measured with the aid of a system of type VR 5/20 thermocouples, and registered on the multipoint
self-recording potentiometer KSP-4. The measurement error at 1000*C was +4 degrees, according to the thermocouple wire
The dimensions of the specimens were chosen so that they could be located in the zone of constant temperature along
the length of the furnace ( - 150 mm), but be of a diameter large enough to provide a noticeable temperature difference through
the cross section in the initial period of heating. The steel tubes were 48 mm in diameter and 3 mm in wall thickness. The
length of the specimens was twice the diameter, which obviated the occurrence of heat loss through the ends.
Results of the temperature measurements during heating were transferred to special tables, in which the temperature
ranges were delineated. From the initial and final temperature differences At o and At, and the heating rate over the time interval
T, the criteria Ato/C T and At/C T were found. Then, using the graph
given in  for various values of At0/C T, the Fourier criterion F 0 =
where ~ = temperature conductivity, m/sec; r
= time, sec; R = specimen radius, m, was determined for the different values of