US1816744A - Permanent mold - Google Patents

Description

i No Drawing.

Patented July 28, 193i UNITED STATES-PATENT; OFFICE NELSON .r. QUINN, or romino, omo, ASSIQNOB To run METAL enemas HOLDING conromrron, or 01.2mm, 01:10, a coaromrron or nmwm rnmumin'r mom) The present invention, relating as indicated to molds, is particularly directed to a so-called permanent, or, more accurately, .a long-life, mold' which may be used for the castin ofmetal therein. The principal object o the invention is the provision of a refractory mold which may be used for repeated castings and which shall have the desired and necessary characteristics ofconsiderable physical strength and the ability to retain in the cast metal, or at least to prevent the transference of, heat from the molten metal at such a rate as to produce an uncommerical grain structure in the castings.

To the accomplishment of'the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly-pointed out in the claims; the following description setting forth in detail certain steps embodyingthe invention, such disclosed steps constituting, however, but one of the various ways in which the principle of the invention may be used.

Molten, metal of various kinds has for centuries been cast in and against sand molds.

the required smoothness of the metal, and to.

cause the metal to conform to and lay against the mold. The use of sand molds is based upon the porosity in the sand, i. e. quartztransference of the heat from the molten metal which will produce a too sudden setting or chilling in the casting which causes the formation of an uncommercial grain structure and, in gray iron castings, extremely hard unmachinable spots. Inorder to form the mold from sand the latter is dampened.

with water, rendering the particles of sand sufliciently adhesive to hold the structure together until the molten metal introduced in Application filed November 28, 1927. Serial No. 235,898.

the mold has set. The heat from the metal destroys the slight bond between the particles of sand, however, and the mold disintegrates and in practice, therefore, must be reformed for each casting, the sand being dumped out of the molds, remixed and retempered with a substance rendering it adhesive, such as water, before it is again ready for use.

Close attention has been paid in modern foundries tothe condition of the sand which iscarefully graded to produce varying degrees of porosity in the molds formed theretirely possible to produce a permanent or non-sand mold of refractory materials united with considerable strength and having a sufficient refractoriness to withstand the temperature of the molten metal cast thereagainst, providing such material is given an effective porosity approximating that of the -sand mold to be used for casting the same metal. Successful casting depends entirely upon the porosity of the molds into which the metal is cast, and porosity in turn is merely another statement of the rate of heat transference into the mold from the molten metal. Therefore, if a permanent mold of some nonsand material can be produced having the same effective rate of heat transference there is no reason why such a mold will not be clearly effective in producing sound, smooth, commercial castings of uniform grain, and in alsohaving a life sufficient to cast a numberof castings therein. After numerous experiments I have succeeded in producing such molds, in which I have incor orated the same efiective rate of heat trans erence, or, statthe same thin in other terms, the same in eflctive blanketmg or insulation of the heat in the molten metal that is present variety 0 materials providingithe base ma terial em loyed is suificiently refractory to .withstan the temperature of the metal for which it is to be used as a mold, andis at pableof uniting with the otherpartielesi of' the samematerlal or other materialsem'PIoyZ ed therewith, with a bond sufliciently strong to withstand the disintegrating effect of the casting of molten metal thereagainst,i and, finally, is capable of producing structure containing a multiphcity of air cells or passages to provide the retarding effeet on the flow of the heat from the molten metal that is required to approximate "the heat transference rate that is required in the sand mold designed for use in casting the.

same metal intended to be cast in the permanent mold. By the term porous I include all structures which are provided either with separated closed cells or with separated or connected passages, such as those which are commonly referred to by the term fcellular, honeyeomb, or porous. Thus, one form of my improved permanent mold may cons1st of refractory material, such, for example, as porcelain clay, intimately mixed with a destruetible substance. This mixture is forced into the desired shape of mold and it may be fired, or if not, then the first castin made therein will cause the destruction an removal of the other substance,;pro dueing a multiplicity of cells or openings in the mold and giving a porosity, the amount of which can be readily determined and varied-b the amount of destructible' material original y introduced into the mixture. Thereafter soft castin s ofuniform grain can be made re-' peate ly in this same mold.

Where greater strength is required than can be obtained by the use of a refractory matenal of the character referred to above, irregular metal' particles, such as chi s, borings, cuttings, shavings and the e may be formed nto the desired mold sha either alone or w th a material such as s um silicate, or magnesium chloride, for example, to act as a binder. If the metal particles are used alone they may be integrated or united in any suitable manner by incipient fusion on the contacting point or by heavy pressure to produce a single unitary structure ofhigh strength and, by reason of the irregularity of shape of the particles, of considerable poros 1t y, the latter characteristic being varied as desired by the type of shavings or chips that are em loyed. A porous metal structure may be p ucedgyeolnpressing together a mass of well mix bormgs, turnings and metal '5 In the use of my permanent mold a part- 'molds is such capae1t in operation.

normal or room tem 'chips under y Y pressure or this same of metal partic es ma a g them to just the fuslng temperature} suflicient to cause a slight union between the contacting pointsforsi es of the'p'articles.

ing or facing material may advantageou y be employed on the inner surface of the mold inv the same manner andfor the same purpose as. the; same is now emlployed .on sand molds,

ow of the metal, and to namely, to assist the 1 facilitate the removal of theica'sting. It will alsovbe understood that while I have usedthe term fmold throughout the present deSCllp? tion, this obviously includes bothmolds and what are commonly termed cores, but

beunited by;

what are actually an inner mold introduced into the mold proper in some spaced relation to roduee a hollow casting therebetween.

t will be apparent that the essential qualities or characteristics of the present mold are the considerable mechanical strength or bond between the particles ori inally employed to produce the mold and t e capacity of transferrin heat at a rate apfproximating that of a san mold intended or the same casting. Various-other compositions in addi-' tion to those alread named may be employed to produce a mol having these characteristics. Thus, a refractory material such as porcelain clay, -or metal particles with or without material such as clay, may be mixed with destructible material, such as sawdust, to produce a composition which, upon being raised to high tem rature, will cause the destructible materia to leave the mold, forming the required insulated openings or cells throughout the material. Or acellular material maybe employed in conjunction with a refractory material. Diatomaeeous earth, which is itself cellular, may bemixed with metal particles or with metal particles and refractory material, or with refractory material alone, the porosity in'this case being" secured fromthe inherent characteristics of diatomaceous earth and, as in the previous cases, the porosity may be varied by the amount of diatomaceous earth'employed.

It should be understood that the equivalent capacity for the transference of heat in the present mold as compared with that of sand There is of course a certain ifl'erence' in the operating conditions to which sand molds, and the present molds, will be subjected, since the present molds will be used repeatedly and without sufliciently long intervals between pourings to permit the mold toeool to the rature of the foundry while ordinarily san molds are at the atmos pheric temperature of the foundry, although in -certain eases sand molds may be heated but this is not the usual practice.

By the term refractory, which has been throughout the specification, I include all materials whichare refractory to the metal being cast. Thus, if metals of low melting point are being cast many substances, materials and other metals are refractory as regards that particular metal which would not be refractory if used with metals of high melting point, such for example, as iron or steel.

The present mold, whether formed of refractory material, such as a'clay, refractor material and metal particles, or metal part1.

cles alone, is required to have the characteristic of a rate of heat. transference approximating that'of a sand mold for the same metal which is to be cast, and a strength sufficient to withstand the erosive and disintegrating efl'ects of the wash of the molten metal thereagainst and the rapid and repeated sudden changes in temperature. This last characteristic is of course secured by-the unitary or integrating condition of the material which forms the mold. The original particles or pieces of material which enter mto the mold structure must be united with suflicient strength to resist the washing action of the metal as well'as the disintegrating efiect of the rapid temperature changes.

The field for the present invention is of course the entire foundry field wherever castings are produced rapidly, and particularly where the same casting is made over and over again, since under the latter circumstances immense savings can be effected by the use of the same mold and the avoidance of the labor and material necessary to reform the molds for each casting.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made asregards the composition herein disclosed, provided the ingredients or steps stated by any of the following claims or the equivalent of such stated ingredients or steps be employed. w

I therefore particularly point out and distinctly claim as my invention 1. A permanent porous mold metal consisting of permanently united particles of metal having a rate of heat transfor the same casting operation, and a mechanical strength capable of re eatedly withstanding the erosive efiect o the flow of molten metal thereagainst and the disintegrating action of repeated rapid changes of temperature.

for casting 3. A permanent metal mold of unitary cel- 4. A permanent porous mold of unitary structure comprising united metal particles.

Signed by me this 22d day of November,

NELSON J. QUINN.