US1886249A - Mold for high temperature castings - Google Patents

Description

Patented Nov. 1, 1932 UNITED STATES PA ENT oFFics LE sun 1 BENSING, or LEBANoN, PENNSYLVANIA, AssIQN mg LEQANQN 5W FOUNDRY, or LEBANON, PENNSYLVANIA, A CORPORATION qsgmmsxw MOLD son men TEMPERATURE q sriNqs N0 Drawing.

This invention relates to a molding sand for foundry purposes that will form molds into which molten metals or their alloys can be poured to form successfully shapes WhlCh '5' have been very difiicult or impossible to form satisfactorily heretofore in commercial practice. By this invention molds are formed into which steel, for example, can be cast even though sections of the forms or shapes desired are thin in places, or small amounts of the molding sand used are surrounded by large amounts of the poured metal.

While this invention has been found to be particularly useful in casting high melting point metals such as steel, it is not restricted to this material, since it is also applicable to other metals and alloys for which molds have been made of ordinary sand, that is,

silica sand.

Heretofore silica sand has been used both for making .molds proper, as well as cores for such molds. Different varieties of sand are used for these purposes, such as river, bank and sea sands, these sands usually being obtained in the vicinity of the place where the foundry is located to save freight charges.

Such sands contain various amounts of clay,

which may be fusible at the pouring temeratures of the metals that are being cast mto forms. This is satisfactory for metals and alloys which are cast at relatively low temperatures, but with metals and alloys which are cast at very high temperatures, as for example, carbon steel castings and alloy steel castings, the clays occurring in such sands flux too readily and burning in of the sand is caused to take place, making the castings unsatisfactory. If the sand has little or no clay mixed therewith bonding materials such as wheat flour, dextrine, bentonite, et cetera are mixed with the sand to 've suificient plasticity and strength to it or holding the shapes.

In carrylng out the present invention, zircon,- which is zirconium silicate that is found in the natural state in many places of the earths surface, is used for making the molds or is used for lining molds that may be made of ordinary sand or a mixture of ordi-' 60 nary sand and zircon. Zircon is very hard Application flied October 4, 1930. Serial No. 48( !,5 2(

' and has a much higherfusion. ointthan silica. It does not become pow ered-byusing it as a molding sand and it has a higher specific gravity than silica sand, thusiadaptmg it betterfor heavy castings. :The grams of zircon are usually round and 1 polished, being ordinarily obtained from alluvial deposits, so that the ca'stings that arepoured into molds made of, or lined with, zircon, are smooth and .are not injured.by.burning in-the same. The following are given astwo examples of mixtures that can be used for making molds containing zircon, but it is to be understood that the invention is. not restricted to these examples. I may, for example, use 3% of water, 2% of bentonite and" 95% of ZlI'COll sand, or I may use 1% of water 1% of wheat flour, /47 of dextrine 97%% of zircon sand.

Zircon that is found in natural deposits is suitable for use in my invention, although it may contain only about 95% of zirconium silicate with a small amount of silica sand and organic impurities. The impurities may be removed, however, in large part or entirely, still leaving a very excellent and satisfactory sand for foundry purposes.

By using zircon as themolding sand the danger of burning in occurring is practically eliminated and less scabbing of the castings takes place; the castings can be molded to closer dimensions, thus reducing machining costs; the metal may be poured in hotter than with silica sand and the gates that are used with silica sand may be eliminated and the castings poured down through risers. Also it is possible to pour heavier castings, as the metal penetrates the high specific gravity zircon less than it penetrates ordinary sand molds. The zircon sand is suitable for use not only as the molding sand, but also for making cores for molds, the usual binders, such as oil, farinaceous materials, rosin, et cetera being used. For example, by using zircon cores only three eighths of an inch square may be removed easily in cast steel blocks that are six inches square at the base and 12 inches high, as the core does not form with the metal a hardened adherent composition. It has also been found that M with the use of zircon sand as a mold for casting a block the block can be gated into the bottom with cores that are placed about two inches above the gate in a horizontal position having a head of ten inches or more of metal above them. It has been found that the cores can be readily removed from such a block even though the steel is cured excessively hot. This would not e feasible with silica sand molds.

When desired, the zircon cores and molds may be washed with fine suspension'of silica to give extraordinarily smooth surfaces while retainin the advantages above mentioned. In most mstancesfihowever, it is not necessary to use such a was with the zircon sand cores or molds.

I claim: a

1. A mold for castings in which the metal contacting surfaces are formed substantially of zircon and a binder.

2. A mold for castings in which the metal contacting surfaces are formed substantially of smooth grains of zircon.

LE RUE P. BENSING.