US2108048A - Alloy - Google Patents

Description

Patented Feb. 15, 1938 UNITED STATES armor Birger Egeberg, Merlden, Com, and Boy W.

Tindula, Buffalo, N. Y., asslgnors to Internatlonal Silver Company, Meriden, Com, a corporation of New Jersey No Drawing. Otisina 1934, Serial No. 759,053. plication April 20, 1937,

14 Claims.

.This invention relates to alloys and this application is a division of application Serial No. 759,053 filed December 24, 1934.

The object of the invention generally is a tarnish and corrosion resistant alloy which may be readily cold worked, may be melted and cast more easily than prior non-tarnish and non-corrosive alloys, and may be economically produced, and particularly an alloy adapted for use in the manufacture of tableware and various kinds of hardware where a complete or substantially complete resistance to weak organic acids, salt solutions, and organic sulphur compounds is necessary, or where superior resistance to many strong mineral acids, such as sulphuric and nitric, is desired.

A further object of the invention is an alloy which, being resistant to tarnish and corrosion by all ordinary materials found in foodstuffs, such as sulphur compounds, salt solutions, and.

weak organic acids, requires no superimposed non-tarnish coating for use in the manufacture of tableware, and which is characterized generally by its favorable chemical resistance, desirable physical properties, ease of cold working, ease of polishing to a high. luster, ease of treatment, low melting point, ease of production, and lowcost.

To these ends we have produced an alloy embodying chromium, nickel, copper, zinc and iron, all in substantially complete solid solution, and in proportions, coupled with special heat treatment whendesired, to endow the same with the desired characteristics above indicated.

The individual elements of the alloy may vary over a limited and prescribed range in percentage but the amounts of nickel, chromium, and iron must be carefully controlled and proportioned and the copper, and zinc contents carefully proportioned and balanced against the nickel, chromium and iron contents, with carbon and other impurities kept below predeter mined values.

In order to produce the alloy of our invention which offers substantially complete resistance to tarnish and corrosion by household reagents, foodstuffs, weak organic acids, sulphur com- 1 pounds, saline or industrial atmospheres, and

corrosive vapors, we find it necessary that about a one atom (or over) of every eight atoms in the alloy be of chromium (that is at least approximately 11 per cent by weight of chromium in solid solution) and furthermore that the other elements be so proportioned that the annealing treatment given will bring this amoun 01' ch 0- l application December 24,

Divided and this ap- Serial No. 137,913

mium into solid solution. For resistance to the more corrosive materials, such as nitric acid we have found a higher percentage of chromium than that which corresponds to the .125 atomic fraction (about 11% by weight) to be of great value, as for example up to 1'7 per cent and higher. In alloys for use in applications not involving acid corrosion, smaller proportions of chromium in solid solution may be employed, as for example as low as four or five per cent.

The nickel content serves to bring the other constituents of the alloy into uniform solid solution and preferably sufficient nickel must be incorporated for this purpose. It also substantially, along with chromium, favorably affects the. degree of resistance to various tarnishing and corroding media by affecting the solubility of chromium at various temperatures, and tends to improve the workability and give somewhat increased luster in the polished state, but these advantages are somewhat offset by increase in melting point, greater cost, darker color, etc. Ac-

cordingly, the nickel content is kept as low as is permissible, though it may vary from forty to seventy per cent by weight.

By incorporating zinc not only may the proportion of copper be thereby reduced, but the alloy becomes mdowed with certain of the special properties and characteristics above described. For example, while the melting point of pure nickel may be progressively lowered about 50 F. for each 10% of copper alloyed with it, 10% of zinc will lower' the melting point by approximately 125' F. Thus with a given chromium and nickel content the substitution of 10% zinc in place of 10% of copper produces an alloy with a melting point F. lower. This greatly facilitates melting and makes it possible to obtain a much more fluid melt and better ingots. The substitution of 5% to 10% zinc also results in an alloy with greater softness on annealing the cold worked alloy, 3, better surface on alloys whichof 10% and our alloy with a component of as much as 15% to 20% of zinc still possesses a limited degree of cold workability. For best results we prefer to use with an alloy contain- 'tlon by weight and preferably .that by alloying manganese and zinc with copper. (and the other elements) and for alloys of the higher chromium range limiting the copper to less than about 30%, with the corresponding proportions of nickel, chromium and iron above described, superior or complete resistance of the alloy to tarnish and corrosion by sulphur.compounds and organic acids is secured. The presence of copper also aids in the alloying of the zinc with the other elements. The copper content should not be less than 5% of the composiis substantially larger (around 15%), 5% to 20% for alloys of the higher chromium range, and in alloys oi' the lower chromium range copper maybe alloyed up to a limit of about 55% by weight.

Our alloy is essentially non-ferrous, but we have found it an advantage, to include in the alloy a small percentage of iron, since it increases the solubility of chromium'for a given nickel content and promotes a more homogeneous structure, or to put it difierently it also reduces the necessary quantity of nickel by an amount greater than the'iron content. Further, it is beneficial in that the copper content is reduced to a point where the corrosive resistant properties of the alloy are not lowered by the copper. It also renders possible a substantial reduction in cost of producing the alloy, since ferrochrome is much cheaper thanchromium metal and also is more easy to introduce into the melt because of its lower melting point. In this respect ferrochrome has a distinct advantage over pure chrome in that it minimizes evaporation losses during melting especially that of alnc. The iron content of the melt, however, is best limited to that which results from using ferro alloys as the original source of chromium, because the further addition of iron causes reduction in amount of those elements (copper and zinc) which assure the desired low annealing and melting points and otherwise con tribute to the advantages above described. The iron content should not exceed ten per cent by weight and preferably should be substantially lower. We have obtained particularlygood results with iron content of from 2% to 6% in a1- it must be kept below the upper limits described below because it may remove a considerable amount of chromium from efiective service in preventing tarnish, thus making a greater chromium content necessary than if it were not present. It tends to form a hard and insoluble constituent within the alloy that greatly impairs malleabllity and ductibility which can only be partly counteracted by higher nickel contents,

tions less than the below mentioned amounts,

increases the frictional wear resistance of the alloy and is consequently detrimental from the standpoint of ease of polishing and the amount of labor involved. We have found that the carbon content should not exceed 0.5 per cent at 35% nickel, .12 per cent at 50% nickel, .15 per cent at 60% nickel, or .20 percent at 70% nickel.

The following are examples of embodiments of our invention:

CHEMICAL Answers Group I Ni Cr Cu Zn Fe Si 0 09.5 11.7 7.2 5.5 4 s .14 10 00.2 12.4 i 12.2 8.3 0 a .07 05 53.2 15. 5 13.0 10.0 7 0 .32 07 55.2 10.9 11.2 9.5 7 2 .19 04 50.0 20.5 3.7 5.5 s 9 .33 07 Group II 52.9 10.9 15.0 14.9 5.0 .24 00 51.0 11.1 17.5 14.0 as 15 .074 51. 1 12. 3 14 9 15 1 a 2 .35 .040 51. 2 14. 1 19. 5 14. 0 1. 0 5 .22 055 Group III 50. 0 4. 7 20 22.3 2 1 0. 25 0. 04 50.2 7.4 102 1&7 4.3 0.27- 0.04 35 5. 5 a is 3 0. a 0.1

These examples of the alloy show' a range in proportions of chromium from around 4 to 17 per cent, nickel 36 to '70 per cent, zinc from 2 to 20 per cent, iron 1 to per cent and. the balance copper in excess of 5 per cent with the carbon content limited as described above.

Group I of the examples includes alloys whose condition of complete immunity to tarnish or corrosion by mayonnaise and vinegar or any other ordinary household agent is obtained by any annealing treatment of commercial duration. These alloys may also be used in the cast condition, after any commercial furnace annealing treatment or after soldering, etc.', with substantially complete immunity to tarnish or corrosion.

also to prolonged heating at temperatures somewhat below 1600 F.

Group II includes alloys which by means of high temperature final annealing treatment (generally from 1900 F. up followed by rapid cooling) can be rendered completely immune to tarnish or corrosion by mayonnaise and vinegar. After final anneallngs carried outat lower tem-' peratures, alloys in this class are very slightly attacked by these materials. For complete resistance to milder conditions as atmospheric tarnish, corrosion by salt spray, or tarnish by egg or hydrogen sulphide, this high annealing temperature will not be necessary.

Group III includes alloys which are not completely immune to attack by mayonnaise and vinegar but may be somewhat improved in this respect by heat treatment similarto the heat treatment for Group 11. However, any such attack that does take place is much slower and not as severe as would take place on any relatively inexpensive alloys now known to the art which do not contain chromium. At the same time, these alloys in Group III are substantially immune to atmospheric tarnish, corrosion by salt spray, or tarnish by egg or hydrogen sulphide,

- In the practical production of the alloy it is impossible to avoid traces of one or more other elements being present as impurities in the essential elements making up the charge or extracted. from the furnace lining or slag, such for example as traces of silicon, carbon, cobalt, tin, aluminum, etc., but it is understood that such impurities as described above with respect to carbon are reduced to the lowest practicable value.

Small additions of magnesium to the alloy are harmless, and preferably 0.1 per cent of magnesium as a copper. alloy is added to the melt just before pouring to remove oxygen and other harmful gases. For example, in order to produce asound ingot free ofexcessive blowholes, it is desirable to add to the melt a small amount of magnesium, aluminum, calcium, barium, lithium, or other strongly reactive metal or alloy. The preferred practice is to add about one-half pound of acopper alloy containing 20% magnesium to every 100 pounds of total melt one or two minutes before casting.

Any suitable method may be utilized-for bringing the constituents of the alloy of our invention into a melt of the desired proportions and the following is merely suggestive of one procedure. It is desirable to use a furnace or crucible lined with a material free or nearly free ofcarbon. It is very important that the metal come only in contact with non-carbonaceous materials during the melting period.

Chromium may be added in the form of low' melting point addition alloys such as a 50-50 chrome-nickel alloy, or 9. 38-37-25 chromium nickel-copperalloy, but low carbon ferrochrome may be added directlyto the melt without formation of a lower melting alloy previously. The method of adding the various ingredients to the melt of our invention may be varied in any way provided the ingot analyses produced be within the limits described above.

After the ingot casting is obtained it may be converted into strip, sheet, or any type of hollowware, flatware, hardware'or ornamental articles in essentially a similar manner to that now used by the art, viz: hot working, cold working and annealing. Cold rolling and annealing schedules will vary considerably for the various alloys, but in general it can be stated that most of the alloys embodied in our invention will withstand at least 50% reduction in thickness by cold rolling between successive annealings, and can be made sufliciently soft for further workingby annealing between 1600 and 2000" F.

We have thus set forth the relative proportions or our alloy and have given certain limited ranges in proportions together with certain specific examples and it is understood that the proportions may be varied within the limited range described depending on the particular use to which the alloy is to be put. Where an alloy of maximum workability, luster, and complete tarnish and corrosion resistance is desired, the higher chromium and nickel ranges are to be 'used. For any material which is to be soldered, brazed or welded into finished articles an alloy of our invention containing more than 54% nickel and 11% chromium by weight should be used.

An alloy within the Group I of our invention is suitable, as indicated, for use in the cast condition for tarnish and corrosion resistance, and, since mechanical workability is not a factor here, we may add about 1% of silicon to the alloy for improved sharpness in casting.

For manufacture of cutlery articles and other materials which require complete) or essentially complete non-corrosive and'non-tarnish properties, and where the material can be annealed at a high temperature just before or after final fabricating processes either of the embodiments Groups I or II can be used. For example, for manufacture into spoons, forks, knives, and other tableware an alloy of our invention containing more than 48% nickel, more-than 11% chromium and no greater than 30% copper is preferable. The final annealing treatment before or after fabrication into final form should consist of heating the alloy to a temperature between about 1900 and 2100 F. and cooling rapidly.

For manufacture of hardware and other articles where extreme corrosion resistance is not as important as strength, lower cost, and ease of manufacture, any of the alloys within the limits to 10% iron, 2 to 20% zinc and the balance copper, in excess of 5%, with traces of other elements including a small trace of carbon.

3. A cold workable, low melting point alloy having non-tarnish characteristics, consisting of chromium, nickel, copper, iron and zinc, wherein the chromium content is 10 to 20%, nickel 45m 10%, zinc 2 to 20%, iron 1 to 10% but not in excess of 60% of the chromium content, and the balance copper in excess of 5% and not greater ing a small trace of carbon.

4. A cold workable, low-melting point alloy having non-tarnish characteristics, consisting of nickel, chromium, copper, iron, and zinc, wherein the'chromium content is 4'to 10%, nickel 36 to 60%, zinc 2-to 20%, iron 1 to 10% but not in' excess of 60% of the chromium content, and the balance copper in excess of 13% and not greater than 55%, with traces of other elements including carbon with the carbon not in excess of 0.2%.

5. An alloy of the character set forth in claim 1 wherein the iron content is from 40 to of the chromium content.

6. A cold workable, low melting point alloy having non-tarnish characteristics consisting of 5.4 to 70% nickel, 11 to 20% chromium, 5.8 to 25% copper, 1.5 to 20% zinc, l to 10% iron, but not in excess of six-tenths the chromium content, with traces of other elements including carpen with the carbon not in excess of 0.2%.

than 30%, with traces of other elements includtween 1900 F. and the melting point consisting.

of 11 to 15% chromium, 48 to 54% nickel, 5.8 to 30% copper, 1 to of iron, but not in excess six-tenths the chromium content.

10. A cold workable, non-tarnish alloy consisting of 50 to 55% nickel, around 11% chromium, 10 to zinc, 1 to 10% iron but not in excess of 60% of the chromium content, and the balance copper in excess of 5%, with traces of other elements including carbon with the carbon not exceeding 0.2%.

11. A non-tarnish, cold workable alloy consisting bi 4 to 10% chromium, 35 to 60% nickel, 10 to zinc, 1 to'10% iron but not in excess of 60% of the chromium content, and the balance copper, zinc and iron in the approximate proportions of 50.2 nickel, 7.4 chromium, 19.2 copper, 18.7 zinc, 4.3 iron with traces of other elements including carbon with the carbon not exceeding 0.2%.

, BIRGER EGEBERG.

ROY W. EINDULA.

5 of six-tenths the chromium content, and. the recopper in excess of 5%, with traces of other 5 maincler zinc between 6 to 20% and traces of elements including carbon with the carbon not other elements including carbon with the carbon exceeding 0.2%. not in excess of 0.2%. p 12. A non-tarnish alloy of nickel, chromium,

8. A cold workable, non-tarnish, low melting copper, zinc and iron in the approximate proporpoint alloy which consists of chromium, nickel, tions or 53.2 nickel, 15.5 chromium, 13.0 copper, 19 copper, iron and zinc in the proportions of 4 to 10.9 zinc, 1.0 iron with traces of other elements 20% chromium, to 70% nickel, 6 to 18% zinc, including carbon with the carbon not exceeding and 1 to 10% iron, but not in excess of six-tenths 0.2%. the chromium content, with the remainder cop- 13. A non-tarnish alloy consisting of nickel,

15 per in excess 01' 5% and traces of carbon not in chromium, copper, zinc and iron in the approxi- 5 excess of 0.2%. mate proportions of 51.0 nickel, 11.1 chromium,

9. An alloy of the character set forth in claim 17.5 copper, 14.6 zinc and 5.6 iron with traces of 3 wherein the chromium content is from 10 to other elements including carbon with the carbon 16% by weight, the nickel content is from to not exceeding 0.2%. 20 and the iron content is from one-eighth to 14.-An alloy consisting of nickel, chromium, 20

, CERTIFICATE OF CORRECTION.

Patent No. 2,10 ,ou February 15, 19

' BIRGER EGEBERG, ET AL. 1

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1 first column, line 15, claim 8, before 'oarbon" insert the words other elements including carbon with the; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office... I

Signed and sealed this 12th day of April, A. D. 1958.

Henry Van Ar sdale iSeal) I Acting commissioner of Patents.

tween 1900 F. and the melting point consisting.

of 11 to 15% chromium, 48 to 54% nickel, 5.8 to 30% copper, 1 to of iron, but not in excess six-tenths the chromium content.

10. A cold workable, non-tarnish alloy consisting of 50 to 55% nickel, around 11% chromium, 10 to zinc, 1 to 10% iron but not in excess of 60% of the chromium content, and the balance copper in excess of 5%, with traces of other elements including carbon with the carbon not exceeding 0.2%.

11. A non-tarnish, cold workable alloy consisting bi 4 to 10% chromium, 35 to 60% nickel, 10 to zinc, 1 to'10% iron but not in excess of 60% of the chromium content, and the balance copper, zinc and iron in the approximate proportions of 50.2 nickel, 7.4 chromium, 19.2 copper, 18.7 zinc, 4.3 iron with traces of other elements including carbon with the carbon not exceeding 0.2%.

, BIRGER EGEBERG.

ROY W. EINDULA.

5 of six-tenths the chromium content, and. the recopper in excess of 5%, with traces of other 5 maincler zinc between 6 to 20% and traces of elements including carbon with the carbon not other elements including carbon with the carbon exceeding 0.2%. not in excess of 0.2%. p 12. A non-tarnish alloy of nickel, chromium,

8. A cold workable, non-tarnish, low melting copper, zinc and iron in the approximate proporpoint alloy which consists of chromium, nickel, tions or 53.2 nickel, 15.5 chromium, 13.0 copper, 19 copper, iron and zinc in the proportions of 4 to 10.9 zinc, 1.0 iron with traces of other elements 20% chromium, to 70% nickel, 6 to 18% zinc, including carbon with the carbon not exceeding and 1 to 10% iron, but not in excess of six-tenths 0.2%. the chromium content, with the remainder cop- 13. A non-tarnish alloy consisting of nickel,

15 per in excess 01' 5% and traces of carbon not in chromium, copper, zinc and iron in the approxi- 5 excess of 0.2%. mate proportions of 51.0 nickel, 11.1 chromium,

9. An alloy of the character set forth in claim 17.5 copper, 14.6 zinc and 5.6 iron with traces of 3 wherein the chromium content is from 10 to other elements including carbon with the carbon 16% by weight, the nickel content is from to not exceeding 0.2%. 20 and the iron content is from one-eighth to 14.-An alloy consisting of nickel, chromium, 20

, CERTIFICATE OF CORRECTION.

Patent No. 2,10 ,ou February 15, 19

' BIRGER EGEBERG, ET AL. 1

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1 first column, line 15, claim 8, before 'oarbon" insert the words other elements including carbon with the; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office... I

Signed and sealed this 12th day of April, A. D. 1958.

Henry Van Ar sdale iSeal) I Acting commissioner of Patents.