H - Foundry Additives Glossary
HALITE (See: SALT)
HEMATITE (See: FERRIC OXIDE-IRON ORE OXIDE-IRON OXIDE-KLEAN SURF IRON OXIDE)
HEVI-SAND (See: CHROMITE OR CHROMITE-SPINEL)
HEXA (See: NOVALAK)
Is a compound of formaldehyde and ammonia. It is used as a catalyst for the two step novalak resin binder in amounts of 10% to 17 % of the resin weight. Hexa is used with a lubricant (usually calcium stearate) in amounts of 4% to 6% of the resin incorporated into its weight. Hexa may also be added separately to the sand mixture during the coating process.
HEXAMETHYLENE-TETRAMINE (See: HEXA-RESINS)
Also known as Metheneamine [C6H12N4] and Hexamine or Hexa. Its molecular weight is 140.2. It is a compound from reactions of formaldehyde and ammonia. It occurs as a crystal or powder. Hexamine sublimes at 263°C. (506°F.) without melting. It is highly soluble in water, while sparingly soluble in alcohol. It is used in the manufacture of resin and also used as a white powder catalyst with phenolic resins for precoating the sand grains. In water, it is used as a quench during the hot sand coating operation for shell molds or cores.
HEXAMINE (See: CATALYST-HEXA-HEXAMETHYLENE-TETRAMINE-RESINS)
It is called a powder catalyst in the foundry for use with phenolic resins for precoating sand grains. Several commercial grades are available.
HI-EARLY PORTLAND CEMENT (See: CEMENT)
A special blend of Portland Cement designed to reach ultimate strength in 3 to 7 days, as contrasted to regular Portland Cement that requires 28 days for complete curing. Such a rapid curing cement depends upon its composition, fineness and environment to create this more rapid curing.
HOT BOX BINDER (See: HOT BOX RESIN-RESINS)
Any resin binder designed to cure from the heat generated in a metal core box. They consist of copolymers of (urfuryl alcohol, urea and formaldehyde or phenol, urea and formaldehyde.
HOT BOX RESIN (See: HOT BOX BINDERS-PHENOLIC MODIFIED FORMALDEHYDE-FURFURYL ALCOHOL-RESINS-UREA-FORMALDEHYDE-FURFURYL RESIN -UFFA)
Urea-formaldehyde-furfuryl alcohol resin (UFFA) is a liquid type used in the Hot Box process. A phenolic modified formaldehyde furfuryl. alcohol (PFFA) is also a liquid type used for the Hot Box process. There is still a resin manufactured by polymerizing phenol - urea -furfuryl alcohol with formaldehyde which can be used for the Hot Box process. A typical sand binder composition may be 30-80 parts of a urea compound to methaldehyde (HCHO). 5 to 50 parts may be furfuryl alcohol. Sugars, or other such additives may be added for specific reasons. Foundries having a high volume core production are more interested in the Hot Box process than smaller production foundries. There are various combinations of urea, phenol, and furfuryl alcohol used in certain systems. Acid salts such as ammonium chloride are used as catalysts, or activators.
HOT COATING BINDER (See: RESINS-SHELL MOLDING)
One binder used is a flaked, phenolic, novalac resin. The resin melts and coats the sand surface. Hill and Griffith offers a full line of Core And Mold Coatings - Refractory coatings provide molds and cores with an impervious barrier between the sand surface and the molten metal. This ensures excellent sand peel from casting with improved casting finish.