US2563859A - Addition agent - Google Patents

Description

Patented Aug. 14, 1951 ADDITION AGENT Keith Dwight Millis, Rahway, Albert Paul Gagnebin, Red Bank, and Norman Boden Pilling, Westfield, N. J., assignors to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware N Drawing. Application August 3, 1949, Serial No. 108,424. In Great Britain March 22, 1947 Claims. 1

The present invention relates to a new article of manufacture comprising a new addition agent for the treatment of iron-base melts and to a process for treating iron-base melts, particularly cast iron melts, with said addition agent to produce ferrous products with improved properties and characteristics and to produce cast iron with graphite in a compacted form, particularly in a spheroidal form.

Heretofore, the art has taught that magnesium does not alloy with iron and, in fact, when attempts were made to introduce metallic magnesium into cast iron baths when the baths were at the ordinary casting heat required for successiul casting (e. g, about 2700" F.) a reaction of such explosive violence took place that the molten iron was blown from its receptacle. It is known that the boiling point of magnesium (2030 F.) is below the melting point of most cast iron baths (e. g., about 2200 F.) The problem of introducing magnesium into a bath of molten cast iron, and particularly of incorporating and retaining residual magnesium in said cast iron without explosive results, was a diflicult one to overcome.

It has now been discovered that magnesium can be incorporated controllably and successfully into cast iron melts by means of a special magne'sium-containing addition agent and that cast iron castings containing graphite in a spheroidal form can be produced through the treatment of cast iron melts with the addition agent.

It is an object of the present invention to provide a new article of manufacture comprising a magnesium-containing addition agent particu-, larly adapted to the treatment of cast iron melts to improve the castings produced from such melts. 2

Another 'object of the invention is to provide an improved process for producing cast iron containing spheroidal graphite which comprises the treatment of molten cast iron baths with the special magnesium-containing addition agent provided by the invention.

The invention also contemplates providing an improved process for producing magnesiumtreated cast iron containing spheroidal graphite wherein the introduction of magnesium and the inoculation of the cast iron are carried out simultaneously.

. It is a further object of the invention to provide a magnesium-containing agent which enables high recovery of contained magnesium in a cast iron melt and quiet addition of magnesium when said agent is added to a cast iron melt.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates a magnesium-containing addition agent comprising a special alloy of nickel, magnesium and silicon and containing controlled amounts of the constituents, to wit: about 30%,

i. e., 25%, to about 50% silicon, about 12% to about 20% magnesium, up to about 12% iron, and the balance essentially nickel. The invention further contemplates an improved process for treating molten ferrous baths; particularly molten cast iron baths, with the new addition agent provided by the invention to incorporate magnesium in said baths, to reduce the sulfur content thereof, and to provide'gray cast iron castings containing a small but efiective amount up to about 0.3% or 0.4% magnesium and containing graphite in a compacted or even, in a spheroidal form.

In its preferred embodiments, the agent provided by the invention contains about 14% to about 20% magnesium, about 25% to about 30%" silicon, and the balance essentially nickel.v Very good results are obtained when the magnesium content is about,l7% to about 20%. For example, a very satisfactory agent comprisesan alloy containing about 18% magnesium, about 28% silicon, about 8% iron and the balance essentially nickel.

As pointed out hereinbefcre, the addition of magnesium to molten cast iron baths in the past has been attended by an explosive reaction and by the burning and consequent loss of by far the greater amount of magnesium added to the molten cast iron bath. The foregoin preferred compositions possess the unexpected advantage as com-pared to other alloys of equivalent density and magnesium level that, when added to molten cast iron baths, ,quiet introduction of magnesium is promoted and high recovery of contained magnesium in the cast iron is achieved.

As a further advantage, small amounts of the special alloy can be employed for the purpose of' spattering of metal and consequent high losses of magnesium, while at magnesium contents lower than about 14% the size of the ladle addl 3 tion required becomes. too great. In addition to nickel, magnesium and silicon, the alloys may also contain up to about 12% iron, e. g 0.01% to 12%, iioto'ab'out 2% copper, e. g}, 0.01% to 2%, up to about 1% cobalt, e. g., 0.01% to 1%, up to about 1% manganese, e. g., 0.01% to 1%, up to about 0.5% aluminum, etc. percentages are preferred, it has been pointedout in our parent application U. S Serial No. 787,420, .noW U. 5. Patent No. 2,485,760, that theaddition alloys may contain not only nickel, ma},- nesium and silicon but eiscinaiigane se, copper and/or iron and that various amounts of these latter elements may be present in larger amounts than the foregoing preferred percentages, The nickel content of the alloy, however, must always be at least about 40%. Likewise, as pointed out hereinbefore, the magnesium content of the alloy must be about 12% to abdut 20% and the silicon content or the alley must beabcut 25% to about 50%. The essential characteristics of the additidfi eiiey are imparted by the presence or these an" -ii't's' of nickel, magnesium and silicon. In ddi ion to the'rorgoing, the agent provi ed by the' i-iiv'fn nn ay contain small amounts of incidntal impurities; e. g, phosphorus, sulfur and titaiiiii'fir. These impurities do not materially [the properties of the alley and must not To a total of abo t 0.5%. .The'ag''r'it provided byth'irlviitiorl is adapted to the treatment of cast iron baths for the "genmovement thereof, e. g., for deoxidatiorl, a n'za'tion, etc, leading .to the roduction 6f improved properties in'cas'tings made from-said baths. Improved pr'fperties' are obtained when ii" base fr'ielts, including cast iren melts, are tr ated with about 0.8% to about 3% of the magnesium-containing agent provided by the invention.

.Magnes um retained in cast iron has been found to have by itself a very powerful whiteniiigfoi carbide-stabilizing effect which is usua'uy While the foregoing process embodying the present invention will have a lower hardness than similar castings produced by processes employing other magnesium-containing addition agents, e. g., nickel-magnesium alloys, c'cippef-iiiag'riesiurfi alloys, etc.

. Cast iron baths which may be treated according to the process embodying the invention are eutectiferous iron-carbon alloy baths usually containing about 1.7% to about 5% carbon and up to -'about 5.5% er 6% silicon with the balance essentially iron, said balance usually being 85% or 87% 'or more iron. The aforesaid baths are those which will produce gray iron castings when cast in an inoculated condition. Preferably, the baths to be treated according to the process embodyiiig'the invention contain about 2% to about 4.5% carbon or about 2.5% to 4% carbon. The silicon content of the bath to be treated is such that the final siliconv content of castings made according to the process embodying the invention Willbe about 1.5% to about 4.5%. The inch. ten "cast iron compositions to be treated may contain the commonalloying elements in the amounts usually found in cast iron, e. g.,the cast irciicompositions may contain up to about 36% nickel, u jte about 0. molybdenum, up to about 1% chromium, u 'to about 2.5% mange nese, etc. In order to realize the preferred effects obtainable t rough the introduction "of magnesium into cast iron; the copperc'oiite'n't is" versive' amounts of tin, lead, antimony, bismuth,

arsenic, selenium and tellurium, etc, as these elements have been found 'to be subversive to thfiesire'd fiects Of magnesium 'On the graphite form. Theimp rities hos horusand sulfur may be pies'enti n theu'sual amounts found various grades Of comr'ne'rcial CBLSfi 11011. Thus, the bath un esirable in gray 'iIOi'l castings. Adcfildiligly,

iii the production or magnesium-containing gray cast iron, ashsuaiiy; been necessary heretofdl'fe iii the g ll't majority of cases to inoculate fiiag'fl'es'iiifii cohtaihifig cast iiOll baths 'bffii eastirig and to cast the baths in al-iilifioulit'd condition to insure that the resulting castings wcuic be 'graphit'i. A feature of the pl'dss ffihodylng the present. invention is that magcesium intrdductiofi and inoculation are accompushed simuitaneotisiy. This feature has "many practical eaten gee including the fact that'ih pro jmtcayihg the invention provide an improved met od "for producing east iron tantamihg- 'spheroitiei graphite wherein onl the single add ate the cast iio'n bathis required. of course, other inoculatingjadditioiis such as ferrosilicomtnickel 'Silicide, calcium suicide, etc, an be'em'ployed along with or subsequently to the addition to a cast iron bath of the agent rovided by the invention.- .When inoculants such as the foregoing are employed (in addition to the agent provided by the invention) in the treatmerit or cast iron melts, amounts of from about to aboutf1% by weight or the bath" may be employed. When an improved inoculating effectis desired in the addition agent .cohtemplated by the-invention, itis preferred that calcium up to abo ut 1%be incorporated in said agents, e-.-g ,*0.25 to about 1%. in addition, cast-iron castings having thin sections, e. g., below about 0 5, i nch' in thickness,. produced from. magneslum-containing gray cast iron according to the to betreatedlmay contain up'to 0.5% or more fihsphbllis, although it iS' preferred "that the phosphorus cont nt he beicw" abci t-0.15%, g, about 0 .02% to 0.06%. Similarly, fihB'Sulfiifi content may be as high as 0.3% or more, e. g, 0.05%

' ent invention wherein gi'ay'cast iron containin to 013%, although it is prefrre'd that the sulmy content be below 0.15%, e. a, 0.03% to 0.1%.

Inthe preferred process pr'ovided'by the'presante eseentieiiy ren. oas'tingemeee ty adding futile aforesai bath the -tir'l0lii1ts' of a'.dditib'n agent (30111156ill'lblatt'6. by thei'nverifiioh Will contam about 2% to about 2.5% sitcom. When a cast 'irdh "bath of the fore oing composition is employed, no additional inoculating agents are required to. produce magnesium-containing gray cast iron other than the agentprovided by the in ention.

or the purpose er giving those skilled lathe art a better understanding of the invention, the

following illustrativeexample isgiven:

A graycast iron melt containing about i' carbon, about 035% manganese, about 0.06% phosphorusand about 0.04% sulfurwas .estabe l-is'hedand the temperature-of the bath was adfv justed to permit successful casting. "To a portion of said bath held in a ladle, a 1.5% addition of an agent containing about 18% magnesium, about 27% silicon, about 47% nickel and about 8% iron was made. The thus treated metal was then cast. In l-inch keel sections, the castings had hardness values of 215 to 230 Brinell, tensile strengths of 87,000 to 92,000 pounds per square inch and elongations of 5% to 7.5% in the as-cast condition.

The proportion of the magnesium content of a given addition alloy which will be introduced into a particular iron-base bath depends upon a number of factors. Thus, the temperature of the bath is an important factor as it has been found that the magnesium recovery from a given addition alloy is reduced at a very marked rate when the temperature of the bath is elevated. A preferred bath temperature to be employed in the addition of the alloy provided by the invention, particularly in the treatment of the preferred bath composition set forth hereinbefore containing about 3.4% to about 4% carbon, is about 2700 to about 2760 F. As magnesium has been found to be a powerful desulfurizer even under acid conditions and in the absence of a slag, the sulfur content of the bath is also a factor. When magnesium is introduced into a sulfur-containing cast iron melt, the sulfur content will be reduced and magnesium will be consumed in the resulting reaction. Generally speaking, when suflicient magnesium is introduced into a cast iron containing more than about 0.02% sulfur (e. g., 0.03% to 0.1% or more) to produce a retained magnesium content of 0.03% or more, the sulfur content will be reduced below about 0.02%. Practically speaking, about one part by weight of magnesium must be introduced into the bath for each part by weight of sulfur removed. The technique employed in adding the addition agent provided by the invention to the cast iron bath will also effect the magnesium recovery. It has been found that satisfactory results have been obtained when the addition agent provided by the invention is added to the molten stream of hot metal flowing into a ladle or other container. It has been found that magnesium recovery is usually greater when additions are made on a large scale as in a commercial foundry than when additions are made on a small scale, e. g., on a laboratory scale.

The magnesium addition agent provided by the invention can be prepared by a method which comprises melting down nickel and ferro-silicon (e. g., an alloy containing about 75% silicon, balance essentially iron), introducing magnesium into the resulting bath, and casting the metal from said bath.

This application is a continuation-in-part of our co-pending U. S. application Serial No. 787,420, filed November 21, 1947, now U. S. Patent No. 2,485,760.

Although the present invention has been described in conjunction with preferred embodiments, it is understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Variations and modifications apparent to those skilled in the art are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. As a new article of manufacture, an addition agent adapted for the treatment of cast iron baths to desulfurize said baths and to improve the quality of castings made therefrom, and comprising an alloy containing about 18% magnesium, about 28% silicon, up to about 8% iron, and the balance essentially nickel.

2. As a new article of manufacture, an addition agent adapted for the treatment of cast iron baths to desulfurize said baths and to improve the quality of castings made therefrom, and comprising an alloy containing about 17% to about 20% magnesium, about to about silicon, up to about 12% iron, and the balance essentially nickel.

3. As a new article of manufacture, an addition agent particularly adapted for the treatment of cast iron melts and comprising an alloy containing about 14% to about 20% magnesium, about 25% to about 30% silicon, up to about 12% iron, calcium up to about 1%, and the balance essentially nickel.

4. As a new article of manufacture, an addition agent comprising an alloy containing about 30% to about 50% silicon, about 12% to about 20% magnesium, up to about 12% iron, up to about 1% calcium, and the balance essentially nickel, with the nickel constituting at least about of the alloy.

5. As a new article of manufacture, an addition agent for the treatment of molten cast iron and comprising an alloy containing about 12% to 20% magnesium, about 25% to silicon, up to about 12% iron, and the balance consisting essentially of nickel and constituting at least about 40% of the alloy.

KEITH DWIGHT MILL-IS. ALBERT PAUL GAGNEBIN. NORMAN BODEN FILLING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,322,158 Becket -l Nov. 18, 1919 1,376,113 Pistor Apr. 26, 1921 1,922,037 Hardy Aug. 15, 1933 2,485,760 Millis et a1 Oct. 25, 1949 FOREIGN PATENTS Number Country Date 100,848 Great Britain Apr. 19, 1917

Claims (1)

1. AS A NEW ARTICLE OF MANUFACTURE, AN ADDITION AGENT ADAPTED FOR THE TREATMENT OF CAST IRON BATHS TO DESULFURIZE SAID BATHS AND TO IMPROVE THE QUALITY OF CASTINGS MADE THEREFROM, AND COMPRISING AN ALLOY CONTAINING ABOUT 18% MAGNESIUM, ABOUT 28% SILICON, UP TO ABOUT 8, IRON, AND THE BALANCE ESSENTIALLY NICKEL.