US1489023A - Pot or crucible - Google Patents

Description

Patented Apr.

'umrso sures 11,489,023 PATENT om n ARTHUR E. BELL-IS, OF SPRINGFIELD, MASSACHUSETTS, AND CHARLIE-SS COLLINS, OI

NEW YORK, N. Y., ASSIGNORS, BY MESNE' ASSIGNMENTS, TO THE BELLIS HEAT TREATING- COMPANY, OF NEW HAVEN, CONNECTICUT, A. CORPORATION OF CON- NECTIOUT.

row on cnUcIBLE.

Io Drawing.-

, States, and residents of Springfield, county.

" f Hampden, and State of Massachusetts, and borough of Bronx, city, county, and

State of New York, respectively, have invented certain new and useful Improvements in gPots or Crucibles, of which the following 110 is a specification.

This invention relates to pots or crucibles for use in the heat treatment of metals, and more particularly concerns such pots or crucibles as are designed for containing molten or liquid baths of metals or metal salts for the heat treatment of ferrous or non-ferrous metals at high temperatures.

In the art of heat treating metals, when treatment baths of the above character are used, it is generally customary to employ pots or containers for the bath materials which areconstructed of cast metal alloys ofierin a high resistance to oxidization.

Such a loys are. usually of nickel, chromium and. iron; of nickel, zirconium and iron; or

of silicon, chromium and iron, as in alloys of this nature when exposed. to an oxidizing atmos here at high temperatures, a protecting oxlde coating forms on the exposed so surface, which acts as a rotection to the metal a ainst further oxidiz ation and resultant eterioration .or destruction.

We have determined that it is exceedingly difiicult in actual practice ,toproduce pots as or crucibles of these alloys in the form of .castings having a uniforml homogeneous ph sical structure, so thatal such castings wi 1 be absolutely nonporous. With present foundry practice, it is possible by the exer- 40 cise of extreme care to'secure some non-porous castings. These pot castings when used at temperatures from 1200 F. to 1800 F., and containing salt baths or lead baths are known to 've. a useful service of from 3,000, 46 to 6,000 ours. On the other hand, -.the larger percentage of'such cast pots or'cruci-' bles o the same alloy material andcast under the same foundry supervision, when & used for the same purpose and at the same 50 temperatures have developed porosity durin the first; 300, hours of operation. Y en theincipient pores of-the cast metal pot. or crucible are enlarged under high duction of a pot or crucible for the treatment of metals at. high temperatures Application and November 16, .1920; Serial No. #124,567.

temperatures to such an extent that the bath umteri'al will seep therethrou h, this. bath material attacks the coating 0 oxide on the exterior surface of the pot or'cruoible .wall 4 and removes the same. The protection afforded by the coating of oxide having thus been destroyed, the process of oxidization is renewed and as fast as the oxide reforms, it is dissipated and consumed by the bath ma-' terial seeping through the pores of the ot Wall. A continuation of this process finagly results in a complete vbreakdown of the pot wall and the leakage of the bath material to such an extent that a new pot or crucible casting must be provided.

Among other alloy metals which have been commonly used in the art for making such cast pots, are chrome iron and chrome nickel. trade name Duraloy and may be obtained in varying degrees of hardness and is capable of being readily machined or worked. Chrome nickel is known in the art as. nichrome and likewise may be easily machined or worked in shape. It has been common practies to form pots or crucibles either in whole or in part of these alloy metals by the casting process. It will be understood that our present improvement in the art does not necessarily involve any specific composition of these alloy metals.

Crucibles of the special metal-alloy castings above referred to are very expensive, and the high percentage of porous crucible castings of this character renders their use The former is produced under the in the economicalhe'at treatment of metal prohibitive. In so far as we are aware no process or method has-yet been devised for eliminating the development of porosity in I zirconium metal allo which entirely elimi nates the inherent eficiencies of the cast metal alloy crucible above referred to. To

this end our invention consists in the reformed from alloys of, the above character,

or analogous metal alloys, offering vhi hl' resistance to oxidation and characterized y the formation of a protective oxide coating eat on the pot wall at high temperatures. This metal alloy is forged, rolled, pressed, or otherwise wrought and from the Wrought alloy the pot or crucible of the desired shape and capacity is fashioned. We have found from actual experience that pots or crucibles 'of this character, in contradistinction to a pot of the same metal alloy in the form of a casting, is absolutely nonporous and efiectually prevents deterioration of the pot structure in service. While the serious objection to such cast metal alloy pots has been generally recognized in the art, in so far as we are aware, such pots have never been produced from wrought, alloy metals for the purpose of overcoming the objection. Our improved wrought metal alloy pot or crucible in actual practice is capable of withstanding exceedingly high temperatures and of giving continuous'service for a maximum period of 6,000 hours. As all of the pots or crucibles thus produced h ve a uniformly homogenous structure, wa te is wholly eliminated so that the initial cost of producing the pots or crucibles is materially reduced, in addition to the economy realized in the actual use of the pots.

- patents of Arthur E. Bellis, filed December 10, 1919, Serial No. 343,760, or Charles S. Collins, filed August 30, 1920, Serial No. 406,870. The internal wall or liner of the crucible may be constructed of pressed steel or pressed or wrought iron, both of which can be produced with practicalcertainty of the absence of incipient pores. Therefore, as the bath material cannot pass through the internal wall or liner, there will be no deterioration of the expensive alloy metal of which the external wall is I formed, even though the latter 'may develop porosity.

After the oxide coating forms upon the outer surface of the external wall it will be protected against further oxidation.-

gain, we may use a pot or crucible having an internal wall or liner of cast iron or cast steel and while the possibility ex- 1s'ts that these cast internal walls may de velop porosity when subjected to high tem removed e cost of peratures they may be read'; and replahe'd by a new liner.

such replacement is considerably less than would be incurred in the replacing of 'the more expensive cast crucible of the special oxidization resisting alloys. Vfith careful foundry. supervision sufficient non-porous cast iron or cast steel liners may be obtained to warrant the use of this construcfoundary practice a thin wall of cast iron or steel may be more readily cast with certainty of a non-porous structure than a thick wall pot or crucible.

Of course, it is very well known in the art that a pot or crucible of cast steel or iron will oxidize on its exterior surface, and such pot or crucible may be non-porous. But, the thin oxide coating which forms on the wall readily scales ofi'and the process of oxidization goes on practically continuously until the metal structure is entirely consumed. The chromium or zirconium oxide of-the alloy metals herein mentioned does not, however, scale 01f but adheres with great tenacity and, therefore, provides a protective coat on the exterior of the pot wall which it is desirable to retain. Ac.- cordingly, it will be appreciated that we have made a very distinct advance in the art in producing such pots or crucibles from a wrought alloy metal which is absolutely non-porous, instead of in the form of a casting which develops porosity after a short period of use, resulting in the seepage of the bath materials and the destruction of the protective oxide coating.

-What we claim is: 1. A pot or crucible for the heat treatment of metals at high temperatures, comosed of a wrought, non-porous metal aloy highly resistant to oxidizing atmospheres.

2. A pot or crucible for use in the heat treatment of metals at high temperatures composed of wrought-metal having asubstantialy non-porous hysical structure and characterized by the ormation on the outer exposed surface of the pot; or crucible of a tenacious oxide coatin when the crucible wall is subjected to a 'gh temperature in the presence of oxidizin atmosphere.

3. A pot or crucible or use in the heat treatment of metals at ,high temperatures comprising anexternal wrou ht metal alloy wall having a substantial y non-porous physicalistructure and offering high resist Leeaoae anee to oxidizing atmospheres at high temperatures, and an inner potwall of cast ferrous metal,

4:. A pot or crucible for use in the heat treatment of metals at high temperatures composed of a Wrought non-porous metal alloy having as one of its constituents; a metal of the chromium group.

5. A pot or crucible for use in the heat treatment of metals at high temperatures composed of a wrought non-porous metal alloy having as one of its constituents a metal of the chromium group and characterized by the formation of a permanent oxide coating on the exposed; surface of the pot or crucible in the presence of an oxidizing atmos here.

In'testimony t at We claim the foregoing as our invention,'we have signed our names hereunder.

THUR E. BELLIS. @HARLES S. CULLINS.