US1835791A - Process of preparing metal for casting - Google Patents

Description

Dec. 8, 1931. J UNABURY 1,835,791

PROCESS OF PREPARING METAL FOR CASTING Filed Aug. 20, 1926 2 Sheets-Sheet 1 Dec. 8, 1931. E, NAB RY 1,835,791

PROCESS OF PREPARING METAL FOR CASTING Filed Aug. 20. 1925 2 Sheets-Sheet 2 gn uzntoz Patented Dec. 8, 1931 UNITED STATES PATENT OFFICE JOHN E. UNA-BURY, OF PONTIAC, MICHIGAN, ASSIGNOR TO GENERAL MOTORS COR- PORATION, 013 DETROIT, MICHIGAN, A CORPORATION OF DELAWARE PROCESS OF PBEPABJN G METAL FOR CASTDSI'G- Application filed August 20, 1926. Serial No. 130,449.

This invention relates to the art'of metal founding-more particularly to methods of preparing a molten mixture designed to be poured in sand or other molds to form iron castings adapted to be rendered more or less malleable by heat treatment.

It is among the objects of the invention to obtain a molten metal in such quantities and at such intervals as to make it possible to operate mold conveyors, or operate a foundry on a continuous pouring basis, to reduce cost as compared with standard prior practice and to assure substantial uniformity of product.

In the manufacture of malleable iron castings it is necessary to melt iron with a proportion of silicon and carbons so balanced as to produce a castin when poured into a suitable mold that can lie annealed or made malleable by heat treatment. In the usual practice the metal is melted in air furnaces because of the adaptability of this type .of furnace to furnish a molten product of the accurate analysisv and high fluidity required for pouring castings susceptible of being rendered malleable by annealing.

In the usual ractice molten metal is taken from the air urnace and poured in sand molds. Bull ladles may receive metal from the melting furnaces and hand pouring ladles receive it from the bull ladles or the metal may be taken directly from the furnace into small pouringladles.

Air furnaces are not adaptable to continuous pouring, as each furnace can produce but two or three heats each working day, depending on the capacity of the furnace. The pouring from airfurnaces is therefore intermittent, and all of the work of the foundry dependent on the furnaces must be timed by the time of arrival of themetal in the furnaces to pouring temperature.

This invention contemplates the production of iron castings which can be annealed in the usual manner, by a continuous process instead of by the intermittent or batch process of the prior art. Instead of melting the iron in batches in air furnaces, it is proposed to melt it in cupolas; to draw the molten meta-It fromthe cupolas, as requlred, mto

fore hearths or other receiving reservoirs of relatively large capacity; to remove sulphur by treatment in the fore hearths; to take samples of metal from thefore hearths and analyze them at suitable intervals in order to'ascertain whether the metal in said fore hearths 1s of proper composition; to transfer charges of metal from the fore hearths to high heat furnaces, preferably electric, adapted to raise the temperature to the degree required for pouring; to make such additions in the fore hearths or electric furnaces as will assure the required proportions of silicon and carbon or other ingredients, and to then pour from the electric furnaces into the molds, or receive the metal into pouring ladles from which the molds are filled.

By this procedure it is contemplated maintaining always, throughout a working eriod, in each fore hearth and in each electric furnace, a residue or remnant pool of metal representing a substantial proportion of an entire charge, to which fresh metal is added,

continuously or at more or less frequent intervals, to mix with it and thus tend to maintain uniformity of the analysis of castings poured throughout the working period. If operations do not go on continuously, day and .night, it is contemplated that both fore hearths and electric furnaces be emptied at the end of each days work.

By the process of this invention any lack of uniformity and fluidity in the metal tapped from the cupolas is remedied by maintaining always a substantial residue in the fore hearths and electric furnaces, ingredients being added to the fore hearths or electric furnaces if necessary to get the desired composition and securing the necessary fluidity in the electric furnaces. Uncertainty respecting the proportions of the ingredients of metal drawn from a cupola during successive periods, and the comparatively low fluidity of it, are more than compensated for in this process by the susceptibility of continuous production that is characteristic of cupolas.

The accompanying drawings illustrate diaammatically one arrangement of apparatus A y the aid of which the process of this invention may be practiced commercially. In said drawings- Figure 1 is a diagram illustrating, in plan, a plant comprising several pieces of apparatus useful in practicing the invention and a suitable arrangement of them, and Figure 2 is in elevation of the plant viewed from one en In Figure 1 are shown, displaced with respect to actual arrangement, two halves of a complete equipment adapted to produce molten iron of an analysis and fluidity suitable for pouring into molds to solidify into annealable iron castings. The initial half (with reference to the direction of movement of the metal) of the equipment is shown displaced on the sheet of drawings below the final half. Numeral 10 indicates cupolas, of which there may be any number dependent upon the quantity of output required. Each cupola is equipped with a conventional trough or launder 11 for directing the flow of molten metal from the tap hole thereof. Adjacent each cupola is a fore hearth, or other receiving reservoir, 12, disposed in position to receive the discharge from the trough 11'. For convenience in transferring metal the fore hearths may be suspended by trunnions 13 on stands 14, as shown in Fig. 2, and may be tilted to discharge their contents.

In the upper half of Fig. 1 are shown two furnaces of a type capable of heating metal to a higher temperature than is possible in cupolas. The furnaces preferred for this purpose are electric arc furnaces, indicated conventionally at 15. There may be any number of these high heat furnaces according to the requirements of production; two of them are shown with transformer mechanism 16 disposed between. Each furnace 15 has a receiving hopper 17 on one side and a pouring nozzle 18 diametrically opposite. It will be understood that the electric furnaces are so mounted that they may be tilted to any angle necessary to discharge any desired portion of their contents, are provided with the necessary means for tilting them, and that suitable movable closures are adapted to open and close the receiving and discharging orifices in communication, respectively, with the receiving hopper and pouring nozzle.

In the plant illustrated, a monorail 19 extends along the pouring side of the cupolas 10 and fore hearths 12, and along the receiving sides of the electric furnaces 15. In the diagram the monorail is shown curved somewhat, as at 20, (owing to the exigencies of the arrangement of cupolas and furnaces), in its course between the cupolas and fore hearths at one end and the electric furnaces at the other end: Movable along the monorail 19 is a wheel traveller 21 which supports, by means of an adjustable suspension or hoist 22, a transfer ladle 23, adapted to receive molten metal poured into it from any one of the fore hearths and transport it to a position adjacent any one of the electric furnaces. The monorail is shown in Fig. 1 as curved in toward the farther furnace 15, as at 24, so that the ladle 23 may be run close enough to the receiving hopper 17 to enable its charge to be poured directly into, said hopper and so avoid the use of an intermediate launder. In order to direct the ladle sufficiently near to pour directly into the re ceiving hopper ofthe nearer furnace a branch rail 25 may be disposed adjacent the hopper 17 thereof, and may be connected by a switch 26 with the main rail 19.

A pair of monorails 27 and 28 are shown disposed along the discharge side of the electric furnaces. One of the rails 27, leads from the furnaces to the molding floor (not shown) the other rail, 28, leading back from the molding floor to the furnaces. It will be understood that suitable switches, Ys or other transfer devices should be provided for enabling the traveller, from which the bull ladles designed to carry metal to the molding floor (one of which is indicated at 29) are sup orted, to be shifted from one rail to the ot er.

Each fore hearth 12 may be capable of holding 9 or 10 tons of metal and the electric furnaces may be of standard 8 or 10 tons capacity each. The transfer ladle 23 may be preferably of 3 tons capacity. Each bull ladle 29 may hold about 1000 pounds.

Although one plant has been diagrammatically illustrated as an aid in practicing the improved process, other arrangements are possible. For example, fore hearths might be arranged to pour into high heat furnaces, and the latter to pour into molds travelling past their pouring nozzles.

What I claim is:

1. A process of preparing molten metal suitable for making castings which consists of melting metal in a cupola; transferring molten metal from the cupola to a reservoir; treating the metal in the reservoir to remove sulphur; transferring purified metal from the reservoir to a high heat furnace, heating the metal therein to a temperature suit able for pouring, then withdrawing metal from the high heat furnace and pouring it into molds.

2. A process as'defined in claim 1, which comprises also testing the molten metal in the reservoir to ascertain the proportions of ingredients and thereafter adding such ingredients as may be necessary to correct deficiencies ascertained by the test.

3. A process as defined in claim 1, which comprises also testingmetal in the reservoir to ascertain the proportions of ingredients then transferring metal from the reservoir to the high heat furnace and add' ingredients to the metal in the high heat rnace as may be necessary to correct deficiencies ascertained by the test.

4. A process of preparing molten metal suitable for making malleable iron castings U which consists in melting metal in a cupola; transferring molten metal from the cupola to a reservoir; treating the molten metal in the reservoir to remove sulphur; transferring purified metal from the reservoir to s. furnace adapted to superheat the metal, then withdrawing the superheated metal from the high heat furnace and pouring it into molds, and repeating the process without removing all the metal from the reservoir or high heat furnace.

In. testimony whereof I afiix my signature.

JOHN E. LINABURY.

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