US241718A - Process of manufacturing solid steel castings - Google Patents

Description

TED STATES:-

OFFICE;

JACOB REESE, OF PITTSBURG, PENN SYLVAlSlIA.

PROCESS OFMANUFACTURIINGISOLID STEEL CASTINGS.

sPEoIFIcArIoN'formin part of Letters Patent No. 241,718, dated May 17, 1881.

Application filed August 13, 1880. (Nomodeh) Toall whom-it may concern Be it known thatI, JACOB REESE, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, have inventedcertain new and use pertains to make and usethe same.

My invention consists'in a new and useful process 'for the production of tough, solid, and

malleable steel castin gs low in silicon it and free from blow-holes.

Itis known that blow-holes in cast=steelare dueto' the formation and absorption of 1 gases in the metal while fluid and to theimperfect 1 emission of the gases when castin g. Hard steel contains fewer blow-holes than soft steel, because it absorbs less gases and emits them again more perfectly, the fusion-point being lower and the steel remainingliquid for a longer time when cast and then solidifying suddenly. Soft steel, on the otherhand, requires a higher temperature in melting,and on solidifying it passes through a pasty state, which prevents thefree escape of the gases, and thereby causes an increased number of blow-holes in the interior of the casting. The formation and absorption of the gases principally take place during the ebullition and-boiling of the metal, whichis caused by the oxidation of thecarbon. In the open-hearth process themetal does not commence to boil until the silicon in the metal is reduced down to about .020, at which point oxidation of the carbon com mences.

, Heretofore highly-carbonized steel has been used (on account of the reasonsabove stated) in the production of steel castings. Th'esecastings were then subjected to an annealingopen ation to reduce the carbon and impart thene= cessary degree of toughness and malleability. This operation is very tedious and costly, as the metal is placed in cast-iron boxes, packed with oxides, and heated and held at a high temperature from one to eight days, according to the thickness of the casting and the de-' gree of toughness and malleability desired in the resultant product. a

con in the A metal.

Now, the objects of my invention are, first, to prevent the production and absorption of gases in the metal when 'treated in an open licarthby preventing thewmetal from ebullition and boiling, andyet produce a casting low in silicon; secondly, to subject the metal to a dead-melt while at a state of perfect restin the open hearth, to allow'the free and gradualescape of its gases-thatis to say, to preventas far as possible the; formation and absorption-of the gases when the metal is being treatedand to aid asfar as possible the emission of the gases previous to casting, and produce a strong, tough, malleable, solid steel casting, freefrounblow-holes and low in silicon, and which 'will not require the costly annealing operation: above mentioned.

In the practice of myimprovement I decarburize and desiliconize ordinary hot-blast silicious pi g-metal in the Bessemer converter; The metal is then treated with a charge of: ferro man ganeseto remove the oxygen and partially recarburize it and when thisloperationis finished-it is treated with silicious pig to bring the carbon up to the degree required .inthe resultant product and to incorporate into and secure a determined and fixed amount of sili- Whenvthe metal has s iliconized to a sufficient degree to prevent ebullition andboiling during its after treatment, it is run into an open-hearth furnace, excluded as much as possible from oxides, and treated with a carburizing-flame, in order 'to give it a dead-melt and keep at a state of rest until am= pletimehaselapsed for the free and gradual escape of the gases which then takesplace. In other words, I producea low Bessemer steel in theusual manner andthen add silicious pig to the metal in the converter in suificient quantities to prevent oxidation of the carbon during thewtime the metal istreated in the openhearth.

In order to-securc economy and facility of operation, I prefer to use a plant which consists of a smallconverter of about one ton capacity and of a pairof open-hearth furnaces of about five tons each.

The operation is as follows: Hot-blast silicious pig-metal is melted in a suitable cupola and run into'the converter, where it is blown until the carbon and silicon are entirely eliminated. A charge of ferro-manganese is then added, and the metal is deoxygenized andpartially recarburized, and as soon as this operation is finished the metal is treated with silicious pig, preferably containing about ten per cent. of silicon, and just sufficient carbon to bring the carbon in the metal up to the degree required in the resultant product of the process. The amount of silicon to be incorporated into the converted metal will depend upon the length of time of the after treatment of the metal. It is desirablethat as little silicon should be used as will be sufficient to prevent the oxidation of the carbon during the time the metal is to be treated in the open hearth, as the percentage of silicon should be kept down in the castings in order to secure greater toughness and malleability. In ordinary prac-. tice .25 of silicon will be suflicient to hold the metal in a state of rest for one hour, and this amount may be lessened if the metal is treated only with a carburizing-flame and kept free from oxides, or if the time of after treatment is shortened. Ordinarily the metal should be charged with sufficient silicon to prevent oxidation of the carbon for about thirty minutes after the open-hearth furnace has been fully charged for the after treatment of the metal. After the charge has been siliconized in the converter it is run into the open-hearth furnace and treated with a carburizing-flame to keep down oxidation, and kept as free from oxides as possible, in order to keep it at rest and allow the free escape of the gases. As soon as the first blow has been treated and run into the open hearth another charge of metal is treated as in the preceding case and run into the furnace, and this operation is repeated until the first-furnace is charged to its full capacity. The metal is then subjected to a deadmelt to allow further escape of the gases, the time of treatment generally lasting about one hour from the time of the introduction of the first blow of metal until the last blow is in troduced, and then about thirty minutes longer for the further escape of the gases. When the first furnace has been fully charged the next five blows are run into the second furnace and treated as in the preceding case.

The principal object of treating a comparatively small amount of metal in the converter, and in the employment of open hearths of much larger capacity, is as follows If at any time during the treatment of the metal it is found that the silicon is being reduced down to the boiling-point while sufiicient time has not elapsed for the free escape of its gases, a fresh charge of partially-'desiliconized metal may be added from the converter; or, if it is found that the percentage of silicon is too high after the metal has been treated for a sufficient time to allow the escape of its gases, a fresh charge of desiliconized metal from the converter may be run in, and in this manner the ebullition and boiling may be entirely prevented, and yet the proportion of silicon kept down in the metal and in the castings which are produced.

7 About five tons of steel per hour maybe pro duced by the use of the plant which I have mentioned, about one hour being consumed in charging and one hour in treating the metal in and casting from each furnace. Hence the plant will produce about one hundred tons in twenty-four hours, leaving four hours for contin gencies and repairs. The chief advantages of the plant when used by my method are low cost of apparatus, facility and economy of operation, and the cheapness with which the castings may be produced; and the chief advantages of the product of my invention are its solidity,freedom from blow-holes and porosity, and its toughness and malleability, thus obviatin g the necessity for the costly and tedious process of annealing heretofore in use.

When the metal is being treated in the con verter it is preferable, but-not necessary, to treat it first with ferro-manganese and afterward with the silicious metal; but the materials may be added in one charge as a ferroa silicate of manganese; and while I have described my improvement only as applicable to the manufacture of steel castings it is also applicable to the manufacture of solid in gots,free from blow-holes, for tool and other purposes, wherein the metal, after having been worked, requires to be tempered or hardened, in which cases blowing and cracking will be prevented, and the material will be uniform in texture and free from physical imperfections; but for these purposes metal of suitable grades must be used for the process.

I am aware that it has been heretofore proposed totreat a bath of cast and wrought iron in the open-hearth process by the addition of fog ferro-manganese'and silicon to free the metal of oxides, and to retain it in a fluid condition for the escape of gases during the casting, and do not claim the same, as no provision is made for the elimination of any or all of the silicon so added, and steels lower in silicon than onequarter of one per cent. (.25) were not contemplated or obtainable by such process; whereas by my process steel as low in silicon as onefortieth of one per cent. (.025) can be obtained, and the essential difierence of the process lies in this, that the molten metal, after the addition of the silicon, is submitted to a deadmelt under a neutral flame, which retains the heat and fluidity of the metal not only while the gases are escaping, but permits the oxidation of the larger portion of the silicon without decarburization of the bath, so that a steel casting practically free from silicon is obtainable.

Having described my invention, what I claim, and desire to secure by Letters Patent, 1s-

1. The method herein described for obtainin g solid cast-steel castings low in silicon, which consists, essentially, in the following steps: first, decarburizingand desiliconizingthe molt- TIC en metal; secondly,'adding carbon and silicon to the molten metal in such proportions as shall give definite per cents.of carbon and silicon to the molten metal; and, thirdly, subjecting the molten metal, after the addition of carbon and silicon, to a dead-melt under a neutral flame until the silicon shall be oxidized to the required degree, substantially as and for the purpose specified.

2. The method herein described for manufacturing solid cast-steel castings, which consists, first, in desiliconizing and decarburizin g a portion of the metal; secondly, adding there to a portion of metal which has been partially desiliconized and deoarburized; and, thirdly, 15 subjecting the molten mixture to a dead-melt under a neutral flame until the silicon added in the second step has been oxidized to the desired extent, substantially as and for the purpose specified.

J AOOB REESE. Witnesses:

FRANK M. Emma, L. E. JOHNS.