Analysis of Spent Moulding Sands with Binders of Various Thermal Degradations, in an Aspect of a Possibility of a Directional Mould Degassing

Abstract

The results of investigations of spent moulding sands taken from the mould in which the metal core cooling system -to increase the cooling rate of the ladle casting -was applied, are presented in the hereby paper. The changes of the spent moulding sand at the casting external side being the result of degradation and destruction processes of organic binder, were analysed in this publication. Since the reclaimed material, obtained as a result of the mechanical reclamation of spent sands of the same type, is used as a grain matrix of the moulding sand, the amount of a binder left from the previous technological cycle is essential for the sound castings production. On the bases of investigations of the thermal analysis, ignition losses, dusts contents and pH values of the samples taken from the spent sand the conditions under which the process of gases displacing in the casting mould was realised as well as factors limiting the efficient mould degassing -were considered in this study. The possible reason of a periodical occurrence of an increased number of casting defects due to changing gas volume emission, being the reason of the realised technological process, was indicated.

Influence of Weather Conditions and Mechanical Reclamation on Molding Sand with Alkali-Phenolic Binder for Manganese Cast Steel

“…The high content of organic compounds in the molding sand is degraded or destroyed as a result of contact with liquid metal, causing the formation of When looking for the optimal composition of the molding sand, with regard to the amount of resin and hardener, one should follow the rule that the less organic binder in the sand, the better. The high content of organic compounds in the molding sand is degraded or destroyed as a result of contact with liquid metal, causing the formation of gases in the mold cavity, which in turn affects the quality of the castings [21,22]. Therefore, an analysis of the amount of gases emitted was carried out.…”

“…After 24 h, the cured binder was crushed and prepared for gas emission tests. Gas emission measurements of the samples were carried out on a stand equipped with a pipe furnace type PRC 30M/1300 by CZYLOK, a peristaltic pump type BT100-2J by LongerPump and a control and recording unit [18][19][20].…”

State of Spent Molding Sands in the Mold Large-Size Cast

“…It was shown in other publications of the author [2,7,8], that the burning state of a moulding sand depends on a temperature, time and air, necessary for the complete burning of the binder. In case of the binder applied by the Company (resin FR 75A mixed with hardener PU-6 according to the ratio recommended by the producer -resin/hardener=2) a temperature of app.…”

“…In case of the binder applied by the Company (resin FR 75A mixed with hardener PU-6 according to the ratio recommended by the producer -resin/hardener=2) a temperature of app. 520°C is required for the binder complete burning (destruction) in the oxygen atmosphere [2]. The temperature distribution in the core is shown in Figure 3, while in Figure 4 the temperature distribution in the mould of another casting, in dependence on the distance from the metal and from the place at the casting height.…”

“…The solution of such situation is creation of systems carrying away of gases from moulds, especially from cores, where mainly occur unfavorable conditions related to gases flows as well as to increased thermal influences of metals on moulding sands reproducing the casting inner surface. The system realizing this task was presented in paper [2].…”