US229308A - Casting metal - Google Patents

Description

UNITED STATES PATENT OFFICE.

JAMES DUFF, OF PEORIA, ILLINOIS.

CASTING METAL.

SPECIFICATION forming part of Letters Patent No. 229,308, dated June 29, 1880. Application filed October 16, 1879.

To all whom it may concern:

Be it known that I, JAMES DUFF, of the city and county of Peoria, and State of Illinois, have invented a new and useful Improvement in Casting Metals; and I do hereby declare that the following is a full, clear, and exact description of the same.

To get rid of blow-holes and points of weakness caused by particles of oxide has long been a desideratum in the working of iron and steel. As the cause of the former I have discovered that a part of the small quantities of oxygen which remain in and are taken up by the hot iron and steel and their alloys, as they have heretofore been manufactured and east, leaves its union with the metals during the casting process and unites with the carbon contained in the metal, and forms small quantities of carbonic-oxide or other gas, which is imprisoned by the cooling metal, thereby making it porous when cast and destroying its solidity and strength. The gas-cells or blow-holes which are thus formed in the ingots or castings can seldom be entirely worked out, so as to make the metal as strong, homogeneous, and solid as if they had never existed. Otherjparts of the small quantities of oxygen so retained or taken up by the metal in its molten state, or by substances mixed or combined with the metal, remain in the metal in the form of metallic and other oxides, and are not and cannot be removed entirely by forging or any process of manufacture now in use, being simply flattened or lengthened out by such treatment to form lines of weakness. Such being the character of the ordinary merchantable malleable iron and steel, it renders them less homogeneous, more difficult to cast and manufacture, and less solid and strong when cast and manufactured, and, Ibelieve, more liable to further and future oxidation. These objections do not apply to such an extent to ordinary cast-iron, for the reason that the presence of silicon in large quantities permits solidity to be more frequently obtained, and from which fact cast-iron is in practice successfully cast into form direct. These objections apply to steel and malleable iron, however, to such an extent as to practically preclude the casting of these metals into form direct, necessitating, instead, the casting into ingots first, and then My complete process consists in first deoxi- I dizing the molten metal beneath a surface which shall protect it from the air, and then, while in this melted condition, pouring or castin g the metal into form in an atmosphere containin g no oxygen.

In the deoxidizin g process any ordinary crucible steel-furnace may be used and the metal melted, as is ordinarily done in such furnaces.

The deoxidizing is accomplished by putting the deoxidizing compound hereinafter described into the crucible with the metal. This may be done before melting or at any stage of the melting process. I prefer putting it in before and in the bottom of the crucible, or the melted metal may be poured upon the mixture. The metal should be retained in a liquid state, after the compound is put in, until the metallic oxide and other oxides existing in the metal are entirely absorbed by the deoxidizing agent and have had time to rise to.

the surface and be liberated from theiron or steel. This will be indicated by the ebullition ceasing and not recurring when the crucible is shaken or moved. The lid of the crucible should be kept closed as much as possible from the beginning of the melting until the metal is ready to be poured, in order to keep air and carbonic-acid and carbonic-oxide, or other oxidizing gases, from coming in contact with the heated metal, and the slag hereinafter described should be used as directed.

If the molds are of such a size and shape as to make it probable that the metal will not readily flow into all the parts it may be heated several degrees hotter than the melting-point just before pouring without injury to the metal, as it is never exposed to oxidation during the heated state in casting by my process.

The deoxidizing compound which I use is and other oxidizing gases.

composed of the following ingredients in the following proportions oxide of silicon, (clean sand,) five ounces; carbon, (pulverized charcoal,) two ounces; pulverized iron, (fine iron turnings,) thirty ounces. This should be well mixed together and placed in the bottom of the crucible, and will ordinarily be the proper quantity for a melt consisting of sixty pounds of ordinary scrap-steel comparatively free from coatings of rust and ten pounds of wroughtiron reasonably free from exterior rust or oxide. A greater proportion of wrought-iron, as compared with the steel, and a greater quantity of rust on the iron and steel,will make a greater quantity of the compound advisable. If an excess of the compound is used-that is, if more silicon is disengaged by the decomposition of the compound than can be taken up by the oxygen of the metals-it may unite with the metal. A small quantity of silicon is not usually considered injurious to the metal. This depends somewhat upon the purpose for which the metal is to be used.

By my process of casting the presence of silicon and ofmanganese and some other alloys of a like nature, if injurious at all, is rendered less injurious than when the metals are cast by other processes. It is not so much the presence of these substances that injures the iron or steel as the presence of the oxides of them imprisoned in the cooling metal before they have time to rise to the surface. If the compound is not used in excess the silicon will not unite with the iron or steel, but will ounces; carbon, (pulverized charcoal,) one and one-half ounce; oxide of manganese, (black,) two ounces; pulverized iron, (fine iron turnings,) twenty ounces. Mix these well together. Use this quantity as a substitute for the foregoing quantity of the first compound, and use in the same way.

, Steel and iron containing a considerable per cent. of carbon, silicon, manganese, or other (leoxidizin g agent, may be deoxidized by maintaining it in its molten state while protected by the slag hereinafter described, or other similar slag, and as much as possible by the lid of the crucible.

I place upon the metal in the crucible a compound composed of one pound of aluminous clay and one or two ounces of lime, as it may be desired to have the slag more or less liquid. The larger portion of lime makes the more liquid slag. This compound will melt and form a complete protection to the metal from contact with the air, carbonic acid, Small globules of the metal'will be thrown into the slag, and by the ebullition be carried to the top of the slag, and for this reason it is desirable to keep the cover of the crucible closed as much as possi- 1016 during the process. This slag will remain After thorough deoxidation, as before described, the metal is carried to the pouringchamber, conveniently situated near the meltin g-furnace.

The pouring-chamber is constructed as described in a patent issued to me hearing date the 28th day of May, A.D. 1878; butother pouring-chambers may be constructed to accomplish the same purpose. The metal is putinto said molding-chamber and poured into the molds as described in that patent.

Iron and steel should be poured in an atmosphere of nitrogen gas. Any gas that does not contain oxygen, or does not have a direct affinity for the metal in its heated state to form a salt, may be used. Nitrogen is the best, according to my present knowledge and experience, it being odorless, not injurious to the lungs of the workmen, not explosive, and not injurious to the metal.

Among other gases not containing oxygen which may be successfully used are hydrogen and carbureted hydrogen. Such gases as chlorine, although not containing oxygen, could not be used on account of their direct affinity for the metal.

Great care must be taken to have the molding-chamber and the gas free from dampness and the molds perfectly dry and free from oxide of iron and every other substance that will be decomposed by the heat or heated iron or the carbon in the iron, and give off oxygen. Iron molds must be, and it is better that all molds should be, carefully luted with some substance entirely free from oxygen. A mixture of lamp-black and spirits of turpentine is good.

In defining my invention more clearly, I would state that I do not claim, broadly, deoxidizing iron or steel by the compositiondescribed, 'as I am aware that substantially similar deoxidizing compounds havebeen heretofore employed. 1 am aware also of the English Patent to Bessemer, N 0. 1,292 of 1856, and the United States Patent to Ghubb, No. 65,473, granted June 4, 1867. I therefore do not claim, broadly, casting iron or steel in an atmosphere containing no oxygen. I do not know, however, that iron and steel have ever been deoxidized and then, while in the same melted condition in which said deoxidation took place, immediately poured or cast in an atmosphere containing no oxygen, and from these successiveand coacting steps there results the perfect product which has not been. heretofore obtained-4. 0., a perfectly dense homogeneous casting of steel or malleable iron entirely free from holes, particles of oxide, and lines of weakness, which renders practical the casting of such metals into form direct. That these two steps, practiced under the same melt, do coact to produce this result is evidenced by the fact that neither of these steps, conducted separately, can give such result, For if, leaving out the first step, we pour iron or steel containing more or less oxide in an atmosphere containing no oxygen, the particles of oxide decompose at the high heat at which these metals are poured and the oxygen of said oxide unites with the carbon in the steel or iron and forms in little globules a gas (carbonic-oxide) which is im prisoned in the casting, and renders it porous,

notwithstanding the fact that no air or oxygen had access to it during the melting and, casting. On the other hand, if the second step of casting in an atmosphere containing no oxygen is dispensed with, no matter how thorough the deoxidation is, if the metal has any