US1503772A - Alloy for high-temperature use - Google Patents

Description

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PATENT @Ffiiifi.

WILLIAM H. SIVH'IH, OF EAST CLEVELAND, OHIO, ASSIGNOR TO ELECTRO MEETALLURG-I-- CAL. COMPANY, A CORPORATION 01E WEST VIRGINIA.

ALLOY FOR HIGH-TEMPERATURE USE.

No Drawing.

To all whom it may concern:

Be it known that I, WILLIAM H. SMITH, a citizen of the United States, residing at-East Cleveland, in the county of Cuyahoga and 5 State of Ohio, have invented a certain new and useful Improvement in Alloys for High-Temperature Uses, of which the following is a full, clear, and exact description. This invention relates to high-temperature l0 resisting devices and alloys for making the same. It relates particularly to the devices employed in the heat-treating of metals which devices are frequently made in the form of muflies, 'boxes or'containe'rs for the reception of small parts, although equally applicable to the construction of sides, walls, doors, floors and pipes of furnaces, and to the construction of rails, cars, trams, conveyors or the like devices movable in or through a heated space for the conveyance of the substances to be treated. Such treatment is of many diiferent kinds, such as tempering, annealing, cementation, carbon ization, case-hardening, crystal-growth, etc., and ordinarily necessitates a maintenance of the-work for a considerable time at temperatures up to 1,000 or 1,200 C. with in 'termediate coolings while the containers or furnaces are being emptied and refilled. Common iron and steel will withstand this treatment only a short time, the boxes, containers or other parts being promptly oxidized, warped, cracked, and disintegrated. Certain alloys, notably those containing a preponderance of nickel combined with a considerable amount of chromium, have been developed which serve these purposes with great success, but ofi'er the disadvantage of extremely high price owing to the great m- 40 trinsic value of the raw materials and the expense; of refining them and separating out the undesirable ingredients with which they occurin nature. The object of the present invention is the, provision ofan alloy for use in the above named purposes which shall possess a sufficient resistance to the severe conditions of use for most commercial purposes while being composed of much cheaper ingredients, and capable of being made .from ordinary commercial materials without e'xpensive treatments and refinings.

My improved alloy can be made. conveniently by melting together iron; an alloy Application filed November 8, 1919. Serial No. 386,696.

consisting largely or entirely of the elements iron, zirconium and'silicon; and forrochrome.

I have successfully prepared the alloy from the above named ingredients, which, in a specific example, had the following compositions:

The iron Was a very pure variety known as rivet stock, and contained about 0.20% to 0.24% of carbon, and only traces of silicon, phosphorous and sulphur.

The zirconium alloy was of the following approximate composition Per cent.

Zr 30 Si 47 Fe l8 Ti 3 This alloy was practically free from carbon.

The ferrochrome contained chromium, about 60%; iron, about 36%; and silicon and carbon, each about 2%.

With ingredients of the composition given above, the. charge melted down to produce the alloy may contain up to 25% of the ferrochrome, and 2 to 8% ofthe zirconium alloy, with the balance iron. A preferred alloy is made by using 20% of the ferrochrome and 8% of the zirconium alloy.

My improved alloy is preferably made in the electric furnace by first melting the requisite amount of iron, and adding thereto the zirconium alloy together with the ferrochrome in case the latter is used. The alloy melts readily, pours freely and produces uniform fine-grained castings in a sandmold. Ordinary dampness of the sand does not impede the casting operation. The resulting casting can be ground, drilled,- turned, or otherwise machined, the hardness depending largely upon the amount of carbon present. Machining appears tobe possible with any amount of carbon less than about .60 per cent. The alloy can also be made by the crucible process but in case graphitecrucibles are employed, it is necessary to reduce the amount of ferrochrome in order to compensate for the amount of carbon which will be dissolved from the crucible walls. This can be efiected either by using carbon-free ferrochrome (as made,

for example, by the alumino-thermic or Goldschmidt process) or by omitting the ferrochrome entirely. The alloy of iron and zirconium omitting ferrochrome is perfectly use of any amount of chromium lying be-.

tween 0% and about 8%. Unless the proportion of chromium in the resultlng alloy is at least about 8% its efi'ect in the h1 h temperature uses contemplated is very sma l,

but amounts between about 8% and 14% a are noticeably beneficial.

6O Y curacy for many purposes. The tabulation The titanium which in this case enters as an impurity of the zirconium has a beneficlal scavenging effect and is probably all employed in this Way and 'it is doubtfulwhether it occurs in the metallic. form in the resulting alloy. Likewise a considerable part of the zirconium is consumed in the process though generally a small percentage remains in the finished alloy and I prefer to elrlnploy enough of the same to accomplish t is.

In any event it is necessary that phosphorus and sulphur be restricted to the least possible limits.

It may be assumed that the finished alloy will contain everything which was present in the charge, and nothing else, and on this basis the composition of the alloy resulting from the melting of any given charge may be computed. It is well known to those skilled in the art, however, that the above assumption is never'strictly true when the alloy is prepared under ordinary conditions, for certain constituents tend to oxidize and slag off during the process, while other materials, notably carbon and iron, are practically always taken up by the alloy from crucibles and other utensils. In addition, chemical analyses are only accurate within certain limits, and in the case of some chemical elements the analytical figures are subject to considerable error, especially .where the elementto be estimated occurs only in small amount in the material imder analy- SlS.

Nevertheless, the composition of the ultimate alloy can be calculated from the composition of the charge with suflicient acbelow will illustrate the accuracy which can be attained inthis way. Materials uite-close in composition to the iron, zirconlum alloy and ferrochrome referr ed to above, were charges, as follows:

A. B. C. D.

Per Per' Per Per cent. cent. cent. cent. Zirconium alloy 8 2 8 2 Ferrochrome- 20 20 13 13 Iron .1.... 72 78 r 79 85 The relation between the calculated compositions ofv the final alloy and the actual analytical figures is shown by the following table: a

From the tabulation above, it will be noted that a large proportion of the zirconium present in the charge fails to enter the final alloy, but that even when only 2% of the zirconium alloy is present in the charge, zirconium is found in the final alloy.

- Charge A corresponds closely to my preferred charge andthe compositionof the resulting alloy is indicated by the analytical figures.

It will be understood that other ingredients, especially such as frequently or ordinarily occur with and are employed in the metallurgy of the named ingredients can be added without departing from my inventive idea, and generally that I do not restrict myself to the exact compositions or proportions or substances herein mentioned except as the same are recited in the claims hereto annexed or rendered necessary by the prior state of the art. 7

Having thus described my invention, what I claim is 1. An alloy containing 8% to 15% of chromium, at least 2.5% of silicon, and a fraction of one per cent of zirconium, with the balance principally iron.

2. An alloy containing 8% to 15% of chromium, at least 3% of silicon, and a small amount of zirconium, with the balance principally iron.

3. An alloy containing at least 3% of silicon, and a smaller percentage of zirconium, with the balance principally iron.

4. An alloy containing 12% to 15% of chromium, at least 3% of silicon, and a small amount of zirconium, with the balance principally iron.

alloy containing at least 3% of silicon, at least of iron, and 12% to made up into four 15% of chromium, said alloy being such as more than 3% of silicon, 12% to 15% of can be made by melting under the conditions chromium, and aifraction of one per cent of herein described, a char e comprising ferzirconium. 1o rochrome, pure iron, an 2% to 8% of an In testimony whereof, I hereunto affix my 5 iron-zirconium-silicon alloy containing more signature.

silicon than zirconium. 1 6. An alloy containing about 80% of iron, WILLIAM H. SMITH.