ABSTRACT
In this research work, the effects of different amounts of acid hardener (30%, 40%, 60%, 80% weighted to theresin) on the hardening characteristics and hot-distortion properties of no-bake furan and no-bake phenolic bonded sand cores were studied. Bending tests were conducted on test bars with storage times of 1, 2, 3, 5, 7, 24h. Hotdistortion tests were carried out on specimens with storage times of 4h and 24h. The bending tests revealed that in the case of the furan binder system, the acid hardener is best utilized in terms of higher bending strength, in an amount of 40–60%, while in the case of the phenolic binder system, the amount of 60–80% acid hardener resulted in higher bending strength of the sand specimens. Too low (30%) acid hardener (catalyst) level produced low bending strength. Too high (80%) amount of acid hardener decreased the strength of the no-bake furan sand samples, and as can be seen from the SEM analysis, it damaged the binder bridges between the sand grains.
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INTRODUCTION
Over more than 60 years, no-bake methods have been widely used in the foundry industry for producing expendable molds and cores during the manufacturing of medium and large-sized castings of nearly all alloys.1 During the no-bake process, two or more binder components cure at ambient temperature after they are blended with foundry sand. The curing process begins immediately after all components of the sand mixture are combined. The produced sand mixture is usable for a limited time, which allows filling of the core or mold boxes. After an additional time, when the curing reaction is advanced, the hardened core or mold can be removed from the box. The time difference between the two steps can range from a few minutes to several hours depending on the used binder system, the type and amount of curing agent, the sand temperature, and other environmental conditions
http://www.pfa.org.pk/wp-content/uploads/2017/04/The_Influence_of_Acid_Hardener_on_the_St.pdf
