US1563573A - Heat-resisting alloy and structure, etc. - Google Patents

Description

Patented D... 1, 1925.

UNITED STATES NOAK'VIGTOB HYBINETTE, OF WILMINGTON, 'DELWARE.

HEAT-RESISTING ALLOY AND STRUCTURE, ETC.

No Drawing.

- To all whom itmay concern:

Be it known that I, NOAK VIo'roR HYBI- NETP'E, a citizen of the United States, residing temporarily at Wilmington, in the county of New Castle, State offDelaware,

have invented certain new and useful Improvementszin Heat-Resisting Alloys and Structures, Etc; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to. which it appertains to make and use the/same. This inventionrelates to heat-resisting alloys and structures adapted to withstand high temperatures for long periods of time. The heat-resisting alloys that have been used prior to my invention were mainly usedat temperature of 900 C. to 1000 C. and for the most part intermittently at these temperatures, and the alloys and products available on the market were not reliable for use over' long periods of time or were not uniformly reliable, one casting, for example, standing up satisfactorily in use,

5 Whereas others would fail without an visible reason. These previously known a loys and structures were, moreover, expensive to produce and were available only at a correspondingly high cost. These previously known alloys contained, for example, about 60% nickel, 12 to 20% of chromium,

and the rest iron; while certain alloys contained iron and chromium without nickel.

In comparative tests made with the commercially available alloys, it was found that. difficulties were encountered such that castings made therefrom were of limited life, for example, standing up for about three months or somewhat more, or would crack after a few days use. In particular, where castings were desired that would operate for long periods of time at elevated tempera- 4 Application filed June 11, 1923. Serial 110. 644,800.

time and which are reliable and uniform such that commerclal operations of a satisfactory character canbe based upon their use.

gation of heat-resisting alloys and structures and I have found that the cost of SfltlSr factory heat-resisting alloys can be greatly I have carried out an extended investireduced and at the same time the durability of the alloys and castings greatly improved. I have found that the high percentage of nickel previously used in heat-resisting alloys and structures is unnecessary and that improved alloys and structures can be provided with a considerably reduced percentage of nickle and with an increased percentage of iron over that previously considered permissible in such high temperature alloys and structures. In producing such alloys, I have also found that with proper proportioning of the nickel, chromium and iron, it is possible to avoid excessive losses of chromium by oxidation, and that the scrap can be resmelted without excessive loss of chromium and with replenishment of the chromium by the cheaper high carbon ferro-chromium, instead of the more expensive low carbon ferro-chromium. The proper control of the chromium content, in conjunction with that of the nickel and iron content, permits of lowering the melting point of the alloy, so that the work can be carried out in a furnace with an oxidizing atmosphere and at a lower temperature than with the alloys previously manufactured. The new alloys can advantageously. be produced in an open hearth furnace where the alloy contains 18% or less of chromium, and particularly with a chromium content of 15% or 12%, without excessive loss of chromium by oxidation and slagging, and with-important advantages of economy and control as compared with the manufacture of alloys in electric furnaces such as have commonly been used for the purpose.

carbon vmonoxide atmosphere of the eleced and unsound casting due to gas absorp- I tion practically eliminated. The use of an The troublesome 1.

open-hearth furnace also permits of handling greatly increased charges and insures a more uniform product, as compared with the small charges manufactured in an electric furnace and the increased number of charges made successively'for completing a large quantity. With a large oil-fired openhearth furnace, a sufficient charge for a large casting can. be. prepared and carefully adjusted as to composition and analysis before pouring. A large charge may thus be prepared in a days time, as compared with a series of successive smaller charges, say every three hours in an electric furnace. The provision of a considerably increased charge in an open-hearth furnace thus provides castings of greater uniformity and enables large castings to be poured from a single furnace charge. It also permits the utilization of large pieces of scrap as part, of the furnace charge.

The new alloys of the present invention are well adapted for manufacture and melting in open-hearth furnaces, with advantages such as those above mentioned. The new alloys and structures, moreover, are relatively free from tendency to scale when heated to high temperature, e. g. around 1150 C.

I have found that alloys with less than about 30% of nickel would tend to scale when heated to 1150 C., even when they contained as high as 20% or more of chromium. With 30% or more of nickel, however, this tendency to scaleis so reduced as to be unobjectionable, particularly where the alloy contains a proper content of chromium. With around 10 to 12% of chromium, the alloy is practically non-scaling with a content of 30% of nickel. With somewhat increased amounts of nickel and chromium, for example, 15% chromium, 35% nickel, and 50% iron, the resulting alloy and structures made therefrom were much stronger, both when hot and when cold, than alloys and structures containing less iron and more nickel, for example, alloys containing around nickel, such as were previously manufactured for high temperature Work. Instead of finding iron in increased amounts objectionable, I have found that it is of decided advantage and gives increased strength to the alloys and castings, as well as the other advantageous properties mentioned above.

I have further found that the carbon and silicon contents of the alloys are important. In order for a casting made of the alloy to be machined, the carbon and silicon should not be above 2% each, and these percentages, while permitting machining in casting, make it somewhat brittle and for a serviceable castin capable of enduring quick tempera-v ture c anges, it is important to have the carbon and silicon content below about 1% where both are present 1n apprec able amount. If the carbon and silicon are sufficlently low, the alloys can be rolled and forged, but for this purpose the carbon content should be below about 0.1% and the.

silicon at the same time below about 0.5%. Such alloys, however, are too soft for prolonged high temperature where they are required to keep their shape when repeatedly heated and cooled and when having to carry bon. With this amount of carbon I find it important to keep the silicon content rela-' tively low, and below 1%, and I find it advantageous to use only the small amount of silicon normally present in the materials used and amounting, e. g. to about 0.2%. With this small percentage of silicon, and with around 0.5 to 1% of carbon, very satisfactory heat resisting alloys and structures can be produced having the important advantages already referred to.

t In manufacturing the alloys, I deoxidize them with a suitable deoxidizer or with more than one deoxidizer. Manganese can advantageously be used for this purpose as it acts as a good deoxidizer. It may also be present in small amount in the alloy. Aluminum and magnesium may also advantageously be used in small amount as deoxidizers.

Other metals such as cobalt, molybdenum and tungsten can also be used in small amount; when used in large amount they have a considerable modifying influence upon the alloys and castings. Titanium, zirconium, vanadium, etc. can similarly be used in small amount. All of these additions are of no particular advantage.

. sults I prefer to use around 0.5 to 1% of car- In manufacturing the castings, I have i found it of advantage to use a chill, although satisfactory castings can be manufactured Without their use.

In' the course of my investigations, I have made a'large number of alloys and have varied the different ingredients. Asa result of these investigations, I consider that in gen- The alloys made. with these pro ortions of the ingredients and suitably deoxidized have cylinders have been in been used in'the manufacture of cylinders for use at temperatures of 1000 to 1200 C. with carbonaceous material on the inside andoxidizing flame on the outside, and such practically continuous use for about one year s time and have been free from the limitations and objections of similar cylinders previously manufactured, and, faft er oneyear of continuous'use are still giving satisfactory service and have operated without noticeable deterioration. These cylinders were approximately 13% feet long,.15 inches in diameterand weighed about 2600 pounds each. The followin table gives the composition of certain of t ese cylinders and illustrates some of the variations of their composition:

No. Ni Cr Fe 0 Mn Various intermediate compositions were similarly used and were found equally satisfactory. The presence of manganese was not found essential. nickel objectionable scaling tends to take place, so that I consider that content of nickel as about the minimum The chro mium should be at least about 10% and I of nickel with 15% of chromium. In general, a nickel content of more than and a chromium content of more than 18% are unnecessary and undesirable as they increase the cost and the difficulty of the furnace operations and of the resmelting of the scrap metal; while increased amounts of iron appear desirable for giving increased strength to the castings made from the alloys.

The importance of being able to make a heat-resisting alloy in accordance with ordinary foundrypractice will be readily appreciated by those skilled in the art. With hi h nickel and high chromium contents, this isimpossible, as they require an electric Below about 30% of furnace and a molding and casting practice that is even more difficult than steel casting and resembles wrought iron casting. The

The alloys and structures of the present invention present the further im ortant ad-- vantage of small contraction an expansion on cooling and heating. This contraction is only about one-eighth of an inch per foot as compared with about one-fourth inch per foot or more for alloys as previously manufactured high in nickel and low in carbon.

Another advantage which the alloys of the present invention present isthe decreased trouble from gas-absorption and deoxidizing as compared with alloys containing, for example to. of nickel.

The new alloys and castings of the present invention, accordingly, present many practical advantages over similar alloys and structures previously known. They can be manufactured at a greatly reduced cost of manufacture; they are capable of withstanding high temperatures for long periods of time; they can be manufactured in an open hearth furnace; low priced ferro chrome high in carbon can be used in their manufacture and in resmelting the scrap; the alloys are much stronger both hot and cold than alloys containing less iron; the alloys have the advantage of a small expansion and contraction coeflicient; the alloys have proved uniformly reliable in operation; and the alloys and structures made therefrom present other important advantages such as those hereinbefore referred to.

I claim:

1. Heat resisting alloys containing from 10 to 20% of chromium, 30 to 40% of nickel,

from 0.4 to 1.5% carbon, less than 1% silicon and the remainder for the most part iron.

2. Heat resisting alloys containing 12 to 18% chromium, 30 to 40% nickel, 0.5 to 1% carbon, less than 1% silicon and the remainder for the most part iron.

3. Heat resisting alloys and containing from 10 to 15% of chromium, 30 to 40% of nickel, 0.4 to 1.5% carbon, less than 1% silicon and the remainder for the most part iron.

4. Heat resisting structures made of the alloys specified in claim 1.

5. Heat resisting structures made of the alloys specified in claim 2. p 6. Heat resisting structures made of the alloys specified in claim 3.

"7. C linders ada ted for high temperature whrk made of the alloys specified in claim 1.

8. Cylinders ada ted for high temperature work made 0 the alloys specified in claim 2.

9. Cylinders ada ted for high .temperature work made 0 I the alloys specified in claim 3.

10' 10. Heat resisting structnresmade of the v alloys specified in claim 1, said s'tructures being a a ted to withstand-a temperature of 1150 C. or more than one years time.

11. Cylinders adopted for high tempera- 4 ture work made of claim 1, said cylinders being adapted to withstand a temperature of 1150 (3. for more than one years time.

In testimony whereof I afiix my signature.

'NOAK VICTOR HYBIN TTE.

the alloys specified. in 11's