US2743176A - Alloy and method of manufacture thereof - Google Patents

Description

United States Patent ALLOY AND METHOD or Minwurncrrnusv THEREOF Ralph w. Thomas ,andWarren c. Williams, Waukesha,

Wis.,.assignors to Waukesha Foundry Company, Wan

lr'esha, Wis.,, a corporation of Wisconsin Application December 6, 1954, Serial No. 473,484:

'3 No. Drawing the desired properties.

2,743,176 PatenteiApr. 24., 1956 Nickel, chromium, bismuth, tin and molybdenum are relatively expensive and selection of the particular for.- mula' may be. influenced by thedesirability of keeping. the cost of the materials. as. low as; inconsistent with issas follows:

Per cent Nickel '60 Chromuim ..e 1'2 Molybdenum 3 Ti'n 4' Bismuth 2 /2 Manganese 1 SIIHCOII Balance Iron Inpractie,. the proportions. may. be. varied and some of the ingredients omitted... For. example,. the use of molybdenum, is entirely. optional. While: tin playss an important part in the preferredialloy and thepreferred method of manufacture, even this element may be omitted for? certain purposes. To the extent that non-essential. in

nickel with about 1-6 bismuth, it being our discovery that v the additionxofi'bismuth. prevents galling. In its preferred embodiment, the alloy; desirably uses 2-6% tin to assist in incorporating and dispersing the. bismuth. It desirably also contains 10-25% chromium and other metals commonly used in .niclcel bfaseialloys. 1-4 molybdenum improves resistance to corrosion. Silicon Oel% and manganese 02% facilitate casting and improve mechanical properties. If'therei's any balance required, we useiron. w

The foregoing figures. areregardedontheibasis. of present information, as representing about the maximum appropriate range. The preferred range is as follows:

Per cent Nickel 50-70 Chrome .10-15 Molybdenum 2-3 Tin 2.5-5.0 Bismuth 2-4 Silicon .25-.75 Manganese .50-l.50 Balance Iron It is believed that the bismuth cannot advantageously be used in thedesired proportions in any alloy that does not contain very substantial quantities of nickeL We prefer that nickel be present to the extent of at least 40% to 50%, the exact minimum depending somewhat on. the proportions of other metals which are used.

In its method aspects, the invention involves the melting of all of the other ingredients except the bismuth and, in some instances, the tin. All slag must then be removed and the alloy must be in readiness to pour before the bismuth is added. In actual practice, we prefer to incorporate the bismuth in the tin as a master alloy and then add this master alloy just as the rest of the melt, previously skimmed of slag, is tapped from the furnace. By so doing, we prevent the bismuth from being vaporized at the high temperature required to melt the other ingredients. The tin seems to act as a dispersing agent to facilitate the uniform distribution of the bismuth throughout the alloy.

gredientsare omittedorreduced in percentage; thesemayi be'replacedwith additional" ironor nickel; or both r,

As already indicated,- the-essential ingredients of the;

alloyaarenickel-to a preferred of'50% of the totaLandbismuth, which should beat least- 1% of the total and. desirably 2% or more; in order that the alloy,

may have the.desired -non galling-characteristics? A com mercially. knownialloy which as a composition of" 7-8 6 v of nickel and. 14% of ch12,ornium,, pl-us ,miuonpercentages of; manganese and; silicon amiironis. very satisfactory from the standpoint of corrosion resistance, but it galls badly. That alloy becomes completely non-galling when bismuth is added in the indicated proportions of 1% or 2% or more. If the bismuth were added in quantities exceeding 4.5% there would be danger of segregation of this element, particularly if tin were absent or present only in nominal proportions.

The method of preparation which we prefer to use is as follows: p

The requisite amount of bismuth and the requisite amount of tin are first melted together. It is immaterial whether the master alloy be used in its liquid or solidified form.

The other ingredients are melted. We have found that they do not melt below 2500 F. and in practice we heat them to about 2800 F.,-before pouring. At these temperatures, bismuth will vaporize in whole or in part. Accordingly, thenickel, along with the chromium, molybdenum, manganese, silicon, etc. is not only melted, but carefully skimmed to remove all slag before the bismuth is added. As aforesaid, the tin may be melted with the other ingredients, although the preferred practice involves the preparation of a master tin and bismuth alloy which is not added until justbefore pouring. The importance of removing the slag lies in the fact that a portion of the bismuth enters the slag layer if the bath is not skimmed. This reduces the percentage of bismuth remaining in the completed alloy.

In the preferred practice of the invention, we add the bismuth, or the bismuth tin alloy to the general molten mixture substantially coincidentally with the tapping of the furnace.

The resulting alloy, while not quite a strong as stainless steel nor quite as ductile, is amply strong for the manufacture of bearings or pump partsor the like, its

The precise composition, of the alloy preferred for'our particularsanitary: pumpipurposes;

alloy corrosion-resistant, and bismuth being present in v the approximate range of 1-6% to render the alloy nongalling, any required balance being selected from the group consisting of nickel and iron.

2. The alloy of claim 1 in which silicon is present in the approximate proportion of 0-1% of the total.

3. The alloy set forth in claim 1 in which tin is present in the approximate proportion of 2-6% of the total.

4. The alloy set forth in claim 1 in which molybdenum is present in the approximate proportion of 1-4% of the total.

5. The alloy of claim 1 in which manganese is present in the approximate proportion of 02% of the total.

6. A non-galling, corrosion-resistant alloy comprising the following ingredients in the approximate range of percentages indicated as follows:

7. A non-gelling, corrosion-resisting alloy for use in sanitary food handling machinery and comprising the 4 following ingredients in the approximate percentages in dicated:

Per cent Nickel Chromium l2 Molybdenum 3 Tin 4 Bismuth 2 /2 Manganese 1 Silicon /2 Balance Iron 8. The method of preparing a non-galling, corrosionresisting alloy of nickel, chromium and bismuth which comprises the steps of melting the nickel and chromium at one temperature, separately melting the bismuth at a lower temperature, dispersing the molten bismuth in the molten nickel and chromium and immediately cooling the resultant alloy before any substantial part of the hismuth has been lost through vaporization.

9. The method of claim 8 plus the intermediate step of skimming the slag from the molten nickel and chromium prior to adding the bismuth to preclude loss of any substantial amount of bismuth through reaction thereof with the slag.

10. The method of preparing a non-galling, corrosionresisting alloy of nickel, chromium, tin and bismuth which comprises the steps of melting the nickel and chromium at one temperature, separately melting the tin and hismuth at a lower temperature, and adding the tin and bismuth to the molten nickel and chromium in a step in which the tin constitutes a dispersing agent for'the bismuth in said molten nickel and chromium.

References Cited in the file of this patent UNITED STATES PATENTS 429,248 Singley June 3, 1890 FOREIGN PATENTS 152,303 Switzerland Apr. 1, 1932 OTHER REFERENCES Woldman: Engineering Alloys, Cleveland: American Soc. for Metals, 1936, page 133.

Claims (1)

1. A NON-GALLING, CORROSION-RESISTANT ALLOY CONSISTING ESSENTIALLY OF A NICKEL-CHRONIUM BASE IN COMBINATION WITH BISMUTH, NICKEL BEING PRESENT IN THE APPROXIMATE RANGE OF 40-80% OF THE WHOLE ALLOY, CHRONIUM BEING PRESENT IN THE APPROXIMATELY RANGE OF 10-25% TO MAKE THE ALLOY CORROSION-RESISTANT, AND BISMUTH BEING PRESENT IN THE APPROXIMATE RANG OF 1-6% TO RENDER THE ALLOY NONGALLING, ANY REQUIRED BALANCE BEING SELECTED FROM THE GROUP CONSISTING OF NICKEL AND IRON.