US1586871A - Casting metals - Google Patents

Description

Patented June 1, 1 926.

UNITED STATES 1,586,871 PATENT OFFICE.

JOHN H. WHITE, CRANFORD, NEW JERSEY, ASSIGNOR TO wE srnnN nnnornIo-com PAN'Y, INCORPORATED, OF NEW YORK, N. Y., A

CORPORATION OF NEW YORK.

CASTING METALS.

No Drawing. continuation or application serial No. 683,320, filed December 29, 1923; This application filed December 29, 1924. Serial No. 758,584. I

This invention relates to casting of metals and metal alloys.

It is the general practice in the casting of metals and metal alloys to place the mass It to be melted in a crucible or other receptacle, raise the temperature to the meltin point of the metal, or to the highest, melting point of the constituent elements of an alloy, and to pour the molten metal into a mold. 1 If the cast metal is to be worked instead of being left in the form in which it is cast, the mold is usually of such shape as to produce a rod-like or plate-like ingot. At the open end or side of the moldinto which the molten W metal is poured, there is formed a depression as the metal solidifies, This depression, in the case of a rod-shaped ingot, is called a pipe and. may extend a third of the length of the rod, necessitating the discarding of a m third of the ingot at the top. If the entire ingot is rolled or otherwise worked, a seam develops from the pipe. It is customary to add molten metal as this depression forms for the purpose of filling, it, but at best this portion of the ingot is, of a different charac terthan the rest, and may result in the development of flaws 0r faults during subsequent working. The formation of the pipe is due, it is generally agreed, to the forcing W out of gas from the molten mass at the instant o solidifying. I

As an expedient sometimes adopted for preventing the formation of a pipe or other depression for example in the castlng of W iron, the molternlmetal is caused to drop rapidly in temperature so that the dissolved gases are entrapped when solidification occurs and, instead of separating entirely at one end of the ingot and forming a pipe,

m are disseminated throughout the mass of metal in the form of large or small blow holes. During subsequent working the blow holes are closed and a perfect welding of the metal takes place. But, as explained below, it has been. found that welding does not occur with all metals and metal alloys, and probably perfect welding in the case of alloys is the exception rather than the rule. A method which is sometimes used where it w is desired to avoid blow holes is to raise the temperature of the molten metal, add a f degasifying agent and then reduce the temperature very slowly. to permit the gases to escape completely. .But this method does if impurities are plpe are likely to character than the g deeper portion of the casting. This appears to be due to the uniting of the impurities with the principal metal or metals to form alloys or compounds having lower melting pornts than the principal metal or allo in which case they are segregated aroun the p1pe. For example, if sulphur and phosphorous are present in iron as im uritles a casting will have layers of iron p osphides and sulphides adjacent the pipe. A further difficulty experienced with alloy ingots formed by processes now in general use is that they the mold during of toughness. 1

It has heretofore been proposed to improve the uality of metal ingots by melting the meta or alloy in a gas-tight electric furnace cooling due to their lack the furnace to produce as high a vacuum therein as may be necessary for the metal to be treated, during the whole process maintaming the furnace at a substantially constant temperature depending upon the metal or alloy eingytreated,and exhausting the gases therefrom until, with the furnace hermetically closed, no increase of pressure therein is observed alloy has solidified; the metal being then cooled and removed from the furnace, remelted and cast in the usual manner. This process overcomes many of the defects noted above, but is very expensive.

It is the principal obejct of this invention to overcome some or all of the above noted defects in metal castings in a simple and cheap manner and to produce castings which are free from pipes and blow holes, are sound, tough and nearly or quite homogeneous in structure.

The invention is based upon the discovery that if -the molten metal is melted in the presence of air at atmospheric pressure and is permitted to cool until it solidifies and are likely to tear a art in .under sub-atmospheric pressure, exhausting even after the metal or then is very soon reheated and poured, the

resulting casting will be of the improved character just stated. If the metal after entrapped gas to escape.

.the preferred proportions of room temperature, many or all of the above noted defects will be present in the casting.

The reason for the improved result is not known, but it is thought that it may be due to an expulsion of occluded gas into the metal during the first solidifying, which forms gas pockets, the gas in which, however, is unable to escape, because almost coincident with the expulsion of the occluded gas the mass of metal becomes rigid and entraps it, and the subsequent melting permits the It is immaterial, however, what is the correct theory, since, to

ractice the invention it is only necessary to ow the results obtained and the process used in obtaining them. No noticeable additional benefit is derived from continuing this rocess of remelting beyond this first stage. t seems probable that the ill efiect of permitting the metal to stand even for a short time after solidifying and before being remelted, is 'due to a rapid absorption of air or gases. To obtain the best results, therefore, the remelting must be done immediately after solidification has occurred. Likewise, to obtain the best results, pouring should take ,place immediately after reheating, as otherwise gas is apparently absorbed by the molten metal. V.

The invention is the outgrowth of an extended research to discover the best method of making nickel-iron alloy wire and tape, the alloy being about 80% of nickel and 20% of iron. When ingots werecast in accordance with usual methods, the results were very unsatisfactory. A deep pipe formed in the ingot necessitating much waste. When the ingots were rolled there. developed transverse cracks which did not weld during further working. Frequently the ingot was torn apart in the mold during cooling. 'The casting was not homogeneous'or tough and had to he annealed before it could be worked.

In the practice of the invention the preferred procedure in the case, for example, of a nickel-iron alloy, is as follows: The iron and nickel are placed in the crucible or other receptacle in the desired proportions and melted in the usual manner. The mass is then allowed to'cool until it has solidified, after which it is again immediately melted and poured into the mold preferably immediately after this second melting. The induction furnace is particularly well adapted for this process since it permits the reheating to be done at once after the solidification point has been reached. It is only necessary to stop the flow of current at the proper time and, after the required interval,

- to startit again.

tages over This process has several marked advanthat mentioned 1 above in which the ,meltin is done in a gastight -furnace an pumping during is carried vacuum furnaces require expensive auxiliary pumping apparatus and are not suitable for the final melting before casting; (2) the time required is very greatly reduced, not only because of the shorter time necessary before the charge is permitted to solidify, but also because it is not necessary to wait for the charge to cool before remelting. If a vacuum furnace is employed, the charge must be removed from the furnace and re heated in another so that the molten metal can bepoured. I

This invention will find its principal application in the manufacture of alloys which are designed to have some particular quality or characteris ie to a marked degree, such as permeability, So-called spec al steels are in this class. Steels which are now used as automobile parts, for example, are often flakey in structure, and this is thought to be due, in the light of the discoveries leadin ,up to this invention, to the minute blow holes or entrapped gas in the casting, the walls of which holes do not weld together perfectly would be the case if the casting were of iron alone. Larger faults in automobile parts may result from the lack of homogeneity in the casting, from larger blow holes, and from incipient cracks introduced by rolling.

toughness, hardness, etc.

subsequent Working-of the metal, as i When nickel-iron castings eight inches three inches byone inch having about 80% of nickel and 20% of iron were cast in accordance with this invention and compared with others made in the usual manner, it was found that the former could be rolled to thin sheets without being first. annealed, while the latter cracked after a few passes in the rolls, necessitating the discardin of all but a small portion of the sheets. T e castings made by the improved process were sound and tough.

In the preparation of special steels, so called, and other alloys of the kind mentioned above, induction furnaces ,are ordinarily employed, since other furnaces are likely to introduce impurities into the melt. This invention can therefore be practiced easily and cheaply in the manufacture of all such alloys. It is also applicable of course, though not quite. so readily, to other furnaces. While the greatest use of the invention is in connection with the manufacture of alloys or articles made from alloys, it is not limited to such use, as castings of pure metal, or metals of the de cc of purity used for ordinary commercia purposes, when made according to this invention are ofsuperior quality.

meant/i m This application is a continuation of an application of J. H. White, Serial No. 683,- 320, filed December 29, 1923.

What is claimed is:

t 1. The method of working a metallic composition containing large amounts of nickel which comprises melting together the component elements, cooling the melt until it solidifies, immediately remelting, casting 110 immediately after the remelting, and working the casting without first subjecting it to an annealing temperature.

2. The method of producing and Working an alloy consisting chiefly of nickel and w iron which comprises the steps of melting together the component elements, cooling the melt until it solidifies, immediately remelting, at once casting, and Working the casting without first subjecting it to an an- MD nealing temperature.

3. The method of producing and Working a nickel-iron alloy consisting chiefly of nickel and iron in which the nickel component greatly exceeds the iron component, which method comprises the steps of melting 25 together the com onent elements, cooling the melt until it solidifies, immediately remelting and at once casting, said steps being carried out without the use of a "vacuum, and cold workin the casting. to

4. The metho oil producing and Working an alloy consisting chiefly of nickel and iron, which comprises the steps of melting to gether the component elements, cooling the melt until it solidifies, immediately remelt- 38 ing, and at once casting, said steps being carried out without the use of a vacuum, and cold worhng the casting. V

In Witness whereof, ll hereunto subscribe my name this 26th day of December A. D, 4c 1924...

Jenner WHITE.