Investigation results by the method of the steady heat
flow
A series of measurements of the thermal conductivity of
moulding sands with furan resin was performed. The matrix of
the tested moulding sands was high-silica sand either fresh or
reclaimed. Furanol FR75A resin in amounts of 0.81.0% was
used as a binder, while PTS acid as a hardener in amounts of
0.450.55%. Investigations of moulding sands with graphite
additions in amounts up to 10% in relation to a matrix as well
as with steel shots additions in the same amount were also
performed. Additionally, for comparison assessments of the
matrix influence on the thermal conductivity, investigations of
moulding sands with chromite and magnesite matrices were
performed. Also for comparisons the moulding sand with in-organic binder – water glass, which was added in amount of
3.5%, was investigated. The moulding sand was prepared in
the ester technology – with Flodur, as a hardener added in
amount of 10%, in relation to the water glass amount.
All samples were prepared for measurements in the same
way: before testing their thermal conductivity, they were dried
at a temperature of 120C for two hours. The dependence from
the equation (3) was used in the developed measuring method-ology of determining the thermal conductivity coefficient.
The instantaneous intensity of the heat flux generated by
the heating plate and flowing through the sample was deter-mined by means of the wattmeter. The heat flux intensity (q)
was calculated as the ratio of the measured heating power
to the contact surface: moulding sand sample/heating plate.
The obtained results of the thermal conductivity of moulding
sands with chemical binders, including sands with additions
intensifying heat exchanging, are shown in Figure 5. Mould-ing sands were heated up to a temperature of app. 450C.
A higher temperature caused a destruction of moulding sand
with resins, which renders difficult and – in practice – makes
the proper measurement impossible.