Why phosphoric acid is mostly used as a curing agent for high nitrogen furan self-hardening resins, but seldom used as a curing agent for low nitrogen furan self-hardening resins?

EN-GJL-150 is one of grey cast iron in European standard EN 1561, it is also named as gray cast iron GG15 in standard DIN 1691 by Germany and Austria.

ASTM A216 specification covers carbon steel castings for valves, flanges, fittings, or ther pressure-containing parts for high-temperature service and of quality suitable for assembly with other castings or wrought-steel parts by fusion welding. ASTM A216, WCA, WCB, WCC will be selected as per the design and service conditions, mechanical properties, and the high temperature characteristics. Today, we would like to introduce ASTM A216 WCB carbon steel.

Gray iron castings in ASTM A48 Class 20