US1889007A - Sand core for casting metal and method of making same - Google Patents

Description

i have been made to produce sand, cores 5 verfilly regarded as wholly cross kTEFERENCE UNI E STATES PATENT OFFICE mum I wanna. or amount, saw me; J i moon roii ammo mar. meme or Io Drawing.

This invention relates to the maniifacture of sand cores for use in the casting of metal in sand or metal molds and has for its particular objects the expeditious and economical production of a sand core that is selfsustaining during the casting o ration under the action of the molten meta is substantially free from organic ingredients that Wlll. generate a voluminous acrid smoke or objectionable gases during the casting of the metal, and furthermore, such cores will not adhere to the castings when the latter solidify, but on the contrary, can be expeditiously and easily disintegrated by simply ta ping or tumblin the castings when cool an the resultant isintegrated cores can i-ly removed througr usual openings forme in such casting. arious other'advanta'ges of my im roved cores and the core binder employed 1n the production thereof are hereinafter set forth.

Heretofore, as I am well aware, attempts from ordinary sodium silicate solution (water glass) by the admixture of moist sand therewith or if dry sand was employed, the same was first moistened with water to insure the thorough wetting of the sand by the silicate solution. However, such attempts have been invariably unsuccessful as either the sand particles were not efiectively bonded together y the silicate solution and as a consequence, the core would break down under the erosive action of'the molten metal in the ouring o the mold or else if the core was ma e stro r by increasing the ratio of the binder to t e sand employed so as to resist the action of the molten metal thereon, the core would solidify in the casting when cool and tenaciously adhere to the inner walls thereof so that its removal fromthe casting was extremely diflicult and often impossible. As a consequence the employmentof sodium si cate solutioris, as a core binder, haslififil limpracticable for foundry purposes. Y i

My investigations have led to the discovery that-entirely satisfactory sand cores can produced with sodiumsilicate as the essential bond thereof in lieu of organic bonds as then be read-- d removal of the core therefrom is elim f bling be acrid fumes in the foun Application fled Iebrury a, mi. semi Io. siuoo.

linseed oil, pitches, dextrine, etc. which are now commonly employed, provided certain conditions of operation are carefully observed durin such manufacture. For ex-. ample, the sodium silicate vehicle or hinder employed should preferably be hi hly alkaline as compared with the so-calle ordinary standard sodium silicate in which latter the roportions of SiO, to H820 approximate .25 to 1 as thereby, owingto the incre adhesiveness or bondin pro rties of the silicate, a smaller quant1t s ces to cement or bond the 'sand gartic es fiether and any ten ency for the core to adere to the interior of the casting when the latter has cooled and thus interfere withthe inated. Furthermore, the amount of silicate bond employed should not be so excessive as to cement the sand particles so firmly together that the core will not readil disintegrate when the casting is subjecte to the usual tumbling or like tapping operation.

On the other han the bond between the sand particles of the core should be suficiently strong to withstand the action of .the .hot molten metal while leaving a high percentageof'voids in the core to permit of the proper ventirlifi of same during the castin operation.- y improved product not on y es these advanta of being readily isintegratable when t e casting, .after cooling, is subjected to the operation, whereby the substantially complete removal of the entire sand-particles comprising the core can be accomplished without any objectionable adhesion-of the surface portions of the core to the casting, but, owing to the unusual cementitious pro rties possessed by my binder, the cores ma e therewith are more indestructible during the casting operation than those roduced with the aforesaid usual organic binders at resent employed and as a consequence rod- Sin and vent wiring of the cores is either ren ered unnecessary or is reduced to a minimum. Furthermore, the elimination of the serves to very substantially increase the e ciency and motale of the molders. i

of the core tousual tum- EXAMINER",

In carrying out my invention,! preferabl proceed as follows tandard sodium silicate of a specific gravit of about 41 to 42 B6. and havm aforesaid ratio of about 3.25 to 1 about of its weight of solid ca ic soda XNaOIIII) until a clcfearvivlaitseogolution rbezu tts. sma amount- 0 soi ium ar na e (Na,CO-), bout 2.5% by 1 1h added to gelatinize the mass and the mixture is held at a boil until the desired viscosity, say about 52 to 54 Be. while hot, is attamed. The resultant viscous 'mass when cooled to room temperature will flow uite freely and in this form is particularly a apted for shipment to and handling in the found- A where the sand cores are to be made. n order to re are the sand cores utilizing the aforesai si icatebinder, the molder first thins the same with about 80% of water and mixes the solution in a muller, or. other suitable sand mixing machine, with about to arts of sand to each part of such thinned silicate hinder, the quantity of sand var ing with the character of the casting an the kind of core desired. The molder shapes the core desired from resultant sandand-binder mixture so obtained and subjects the core to a preliminary bakin at a temperature of say 220 0.. to 260 in the manner now customary in the reduction of cores containing organic bin ers and obtains the desired self-sustainin core which is then introduced into the mo d and utilized in the well known manner in the casting operation. Y

As above explained, the complete removal of the core from the cooled casting can be easily accomplished merely b tapping the casting and if necessary, po mg the core with rods introduced through the openings in the casting .that are customarily provided for the removal of the cores.

The castings obtained through the employment of my improved core which is, of course, adapted to be superficially coated with a usual core wash containing gra bite, or other suitable carbonaceous ingredients and a binder, are peculiarly rfect, being especially free from blow ho es which freguently result from the large amount of umes generated from other cores containing organic binders, and also owing to the small amount of volatiles generated from my improved cores, as well as on account of their remarkable porosity, the blowing of the casting during the pouring of the mold due to incomplete venting of the gases and fumes generated from the core, is eliminated.

Owing to the unusual adhesiveness of the binder employed in the production of my improved core, a very small quantity sufiices to produce the necessary nd and as a consequence there is no tendency for the molded weig t is en core to adhere to the walls of the core box such as would be the case were it attempted to employ ordinary water glass alone as such the b0 d com-' monly known as water glass) is boiled with n m agent.

Whi e I preferably employ a highly alkaline sodium silicate in which the proportions of SiO, to Na,O- therein are not in excess of about 1.58 to 1 because of its peculiar adhesiveness, nevertheless. without departing from the spirit of my invention as embraced within certain of the al llpended claims, sodium silicate of a lower a alinity, say 2 to 1 or even 2.75 to 1, may be employed with or without small amounts of other bondin agents suitable for the purpose provided t e siveness thereof is suficient to insure that the sand cores formed therefrom, owing to the small amount and character of the silicate bond, will not adhere to the core box and can be readil disintegrated and removed from the coole casting while at the same time such cores will effectively resist the erosive action of the molten. metal during the pourin of the mold. However, the adhesiveness o the bond employed, whether consisting solely of a sodium silicate compound or admixtures thereof with small amounts ofother suitable adhesive bonding agents should be at least as great as that of sodium silicate of an alkalinity corresponding to that of a 2.35 to 1 sodium silicate solution.

It is, of course, not essential that the sili-' cate binder should be first prepared with a While I preferably prepare my improvul binder from ordinary sodium silicate because of its availability, of course the same 'can be prepared directly from sand or other quartzlike raw material by fusion with the requisite quantity of alkali necessary to produce such abnormally alkaline sodium silicate and the fused mass is then digested with water to produce such binder of the desired concentration.

It is especially desirable that bank sand or thoroughly washed sea sand be utilized in the production of sand cores in accordance with my invention, since even the very small amounts of chlorides as sodium or calcium chlorides, such as are commonly present in beach sands or sea sands interfere with the production of such cores and impart objectionable properties thereto.

Various other changes within the scope of the appended claims may also be made adhe- 35 casting. 3. The method of making sand cores for Letters Patent is 1. The method of making sand cores for metal casting which comprises increasing the alkalinity of sodium silicate until the ratio of SK): to Na O thereof is less than 2 to 1,

70 but above that point at which the adhesiveness of such silicate is substantially impaired by reacting upon the same with caustic soda and effecting the gelatinization of the mass by the action of a soluble salt having an alkaline reaction and then mixing sand gelatinized silicate with sand in the presence of water, the amount of sand employed being in excess of 90% of the mixture, then (lesiccating said sand mixture to evaporate the moisture 2O therefrom and form a self-sustaining core without effecting the decomposition of such silicate.

2. A smokeless sand core for casting metal, comprising a maj or percentage of sand particles bound together by a very small percentage of abnormally alkaline sodium silicate, said core being free from ingredients capable of generating voluminous smoke fumes, being capable of resisting disintegration by molten metal during the pouring of the mold,

being free from any tendency to stick to the core box during formation of same and being capable of being readily disintegrated and removed through small openings in the cooled use in casting metal, which comprises mixing sand with a highly alkaline sodium silicate solution, the alkalinity of which solution is greater than the ratio of 2.75 parts of SiO to 1 part of Na O but not sufficient to seriously impair the adhesiveness of such silicate, shaping the core and desiccating the same to obtain a self-sustaining mass of the form desired without effecting the decomposition of such silicate.

4. The method of making sand cores for use in casting metal, which comprises mixing sand with a highly alkaline sodium silicate solution, the alkalinity of which solution is greater than the ratio of 2.40 parts of SiO to 1 part of Na O but not sufficient to seriously impair the adhesiveness of such silicate, shaping the core and desiccating the same to obtain a self-sustaining mass of the form desand with a highly alkaline sodium silicate solution, the alkalinity of which solution is greater than the ratio of 2 parts of SiO to 1 part of Na O but not sufiicient to seriously impair the adhesiveness of such silicate, C5 shaping the core and desiccating the same to form a self-sustaining mass of the form desired without effecting the decomposition of such silicate.

6. The method of making sand cores for use in casting metal, which comprises reducing to a gelatmized mass :1 solution of sodium silicate of an alkalinity substantially greater than the ratio of 2.75 parts of SK) to 1 part of Na O but not sufiicient to serious] impair the adhesiveness of such silicate, an mixing said gelatinized silicate with water and sand, the amount of sand employed being in excess of of solid content of the mixture, then desiccating said mixture to evaporate the excess moisture therefrom and form a self-sustaining core without affecting the decomposition of such silicate.

7. A substantially smokeless sand core for use in casting metal, comprising in excess of 90% of sand and asmall percentage of a highly alkaline sodium silicate bonding agent, the alkalinity of said sodium silicate being in excess of the amount corresponding to a ratio of 2.75 arts of SiO to 1 part of Na O but not su cient to seriously impair the adhesiveness of such silicate, said sand core being capable of resisting disintegration by the molten metal during the pouring of the mold, being substantially free from any objectionable tendency to stick to the core box during the forming of the core and bein capable of being readily disintegrated an removed through openings in such castings upon the completion and cooling of such cast- 1n A sand core for use in casting metal, containing highly alkaline sodium silicate as the principal bonding material, said core being capable of resisting disintegration by the molten metal during the ouring of the mold, being substantially smo eless'a-nd substantially free from ingredients yieldin acrid fumes, being free from any objectionable tendency to stick to the core box during the forming of the core and being capable of being readily disintegrated to a powder upon the cooling of the casting whereb its expeditious and effective removal rom the casting can be accomplished.

9. The method of making sand cores for cess of 48 B. when hot, then thinning the mass with water and mixing the same with a large percentage of sand and in excess of 90% J. u M

by weight of the mixture, shapingthe core and heating the same to a high temperature to volatilize the moisture without efiectin the decomposition of adhesive qualities 0 such silicate.

10. A sand core for casting metal, containiing a small percenta e of sodium silicate as the principal bond t ereof, said core bein free from any objectionable tendency to stic to the core box when formed, being substantially smokeless and substantiall free from ingredients which evolve acrid mes when such cores are employed in metal casting operations and said core being highly resistant to disintegration or erosion by molten metal during such casting operation while being readily disintegratable to a powder and easily removable through small openings provided in a casting when a casting formed therewith has cooled.

11. A sand core for casting metal being characterized by its freedom from any objectionable tendency to stick to the core box when formed, being substantially smokeless and substantially free from ingredients which evolve acrid fumes when such cores are employed in metal casting operations and said core being highly resistant to disintegration or-erosion by molten metal during such casting operation while being readily disintegratable to a powder and easily removable through small openings rovided in a castin when a casting formed t iierewith has coole Signed at New York in the cit county and State of New Yor this 30t day of January, 1931.

BENJAMIN F. WALLACE.