The obtained results of heating of sand moulds with binders by means of a thermal radiation of liquid metal are presented in this study.
Standard samples for measuring Rg made of the tested moulding sands were suspended at the lower part of the cover which was covering
the crucible with liquid metal (cast iron), placed in the induction furnace. The authors own methodology was applied in investigations. The
progressing of the samples surface layers heating process was determined as the heating time function. Samples of a few kinds of
moulding sands with chemical binders were tested. Samples without protective coatings as well as samples with such coatings were tested.
The influence of the thermal radiation on bending resistance of samples after their cooling was estimated. The influence of several
parameters such as: time of heating, distance from the metal surface, metal temperature, application of coatings, were tested. A very fast
loss of strength of moulding sands with organic binders was found, especially in cases when the distance between metal and sample
surfaces was small and equaled to 10÷15 mm. Then, already after app. 15 seconds of the radiation (at Tmet=1400o
C), the resistance
decreases by nearly 70%. Generally, moulding sands with organic binders are losing their strength very fast, while moulding sands with
water glass at first increase their strength and later slightly lose. The deposition of protective coatings increases the strength of the mould
surface layers, however does not allow to retain this strength after the metal thermal radiation.