US2950187A - Iron-calcium base alloy - Google Patents

Description

United States Patent RQN-(IALCHIM BASE ALLOY Tohei Dtotani, Tokyo, Japan, assignor to The Research Institute for iron, Steel and Other Metals of The Tohoku University, Sendai City, Japan No Drawing. Filed Sept. 5, 1958, Ser. No. 759,126

2 Claims. (Cl. 75-122) This invention relates to the production of iron-calcium base alloys adapted to be used for improving the physical and chemical properties of iron and steel, and to new alloys produced by such a method.

The iron-calcium alloy of this invention contains as the essential ingredients 10 to 70% of calcium and 5 to 55% of one or more elements selected from silicon, aluminum and manganese; O to 5% of nickel, and the balance being mainly iron.

The principal object of this invention is to improve the physical and chemical properties of iron and steel by the addition of this iron-calcium base alloy to the melt in a ladle.

The principle of this invention is to produce an iron alloy containing calcium by adding one or more elements which have strong afiinity to both of iron and calcium which do not make an alloy or compound with each other.

It has heretofore usually been considered that iron and calcium could not make an alloy or compound with each other, and it has been recognized that calcium is used for the purpose of deoxidation and desulfurization of iron and steel and shows remarkable eifects. For

this purpose calcium silicide has usually been adopted. But the calcium silicide is easily oxidized in air and results very poor yield as an addition alloy for adding calcium to the molten bath of iron and steel. If, on the other hand, calcium can be alloyed with iron and such an alloy is used for refining iron and steel, the calcium can be melted in the iron or steel melt with very good yield since the iron in iron-calcium alloy is the same element as the melt and also uniformly retained therein so that calcium can be more efiiciently reacted with iron. Known calcium alloys may be mentioned as follows: calcium-silicon, calcium-magnesium, calciumaluminurn, calcium-lithium, calcium-manganese-silicon, calcium-magnesium-silicon, etc., all of which do not contain iron. The inventor has selected nickel, silicon, aluminum and manganese as the element which has afiinity to both of calcium and iron, and added such element to a mixture of iron and calcium and tested these elements to make an alloy or not. As the result, the inventor has found that an iron-calcium alloy containing the added element is produced owing to the reason that the added element makes an alloy with calcium and also with iron.

It has heretofore not been known that nickel and manganese can make an alloy with calcium, while the inventor has found that these elements can make an alloy with calcium and also that either one element of nickel, manganese, silicon or aluminum can be alloyed with iron and calcium and two or more of these elements can be added with iron-calcium mixture to make an alloy or intermetallic compound.

Next, the alloys made by adding nickel and manganese respectively to iron-calcium mixture will be explained.

(i) Iron-calcium alloy made by adding nickel.-The nickel-calcium binary alloysystem is not only unknown,

g V 2,95%,187. Patented Aug. 23, 1960 ice but also their phase diagrams were not known same as iron-calcium binary alloy system. But according to the investigations of the inventor, it was made clear that calcium and nickel have solid solubility and form intermetallic compounds such as Ni Ca and NiCa which can produce binary alloy by eutectic or peritectic reaction. On the other hand, nickel forms alloys with iron over the range of full concentration.

Two elements such as iron and calcium can never alloy with each other, but when nickel is added to the melt of both elements an alloy of iron and calcium containing nickel is produced.

Among these ternary alloys, those within the range of Ca 10 to 56%, Fe 10 to and Ni 0 to 5% are most suitable for use as addition alloys.' The alloys having compositions outside of the above range are not suitable for industrial purposes as such alloys tend easily to de= compose into powders.

(ii) Iron-calcium alloys with added manganese.- Manganese-calcium binary alloys were unknown up to the present time, but it has been revealed that there exists chemical affinity between manganese and calcium and they can make an alloy by the present invention. As to manganese-iron alloy system, these elements make alloys over the total concentration range as is well known in the art. It manganese is added to the mixture of iron and calcium the manganese acts as a medium for alloying iron and calcium.

For iron-calcium-manganese ternary alloy system, the

following range is most suitable:

Percent Ca 10 to 60 Fe lOto 80 Mn 5 to 55 Alloys outside of the above range are unstable and liable to disentegrate so that such alloys can not be adopted for addition iron alloys of calcium.

Similarly the following compositions are suitable for different ternary alloy systems.

An alloy outside of the above range is unstable and liable to disintegrate so that it is unsuitable for addition iron alloys of calcium.

Examples when the iron-calcium base alloy of this invention is used for iron and steel will be described in the following:

EXAMPLE I The quantity of the iron-calcium base alloy added to hypereutectoid steel and that of retained calcium. If the iron-calcium alloy containing 28.3% Fe, 24.8% Ca, 46.1% Si is directly added into the molten mass of hypereutectoid steel and its quantity is increased, gradually calcium is positively retained in the steel and moreover its yield is 3 to 5 times as compared with usually used calcium-silicide, so that it is apparent that 5 it is splendid as the addition alloy of calcium.

[Iron-calcium alloy: (28.3% Fe, 24.8% Ga and 46.1% Si) Calcium silicide: I (2 9.4%Oa)], V

Analysis, Added quantity of percent Yield Melt N o. Ca-alloy, percent of Ga, a percent 1 FeOa-Si 0. 1.63 0. 007 5. 5 Fe-Ga- 1. 0 1. 62 0.009 3. 6 Fe-Ca--S 2. 0 1.59 0. 022 4.4 Fe-CaS1 .3. 0 1. 45 0.022 V 3.0 FeCaSi1 0. 5 1.40 0.007 5. 6 Fe-Ca-SL- 1. 0 1. 22 0.012 4. 8 Fe--Oa-Si- 2.0 1. 25 0. 024 4. 8 3. 0 1.17 0.032 4. 3 2. 0 1.45 0. 006 1. 0 5.0 1. 40 0. 018 1.2 7. 0 1. 45 0. 025 1. 2 2.0 1. 21 0.005 0.9 5.0 1.15 0. 011 0.7 7.0 1.13 0.023 1.1

- If the iron-calcium base alloy is added to hypereutectoid steel and about 0.007 to 0.03% of Ca is retained in the steel as in the above table, the graphite steel containing nodular graphite can be easily obtained under the cast state, and in case of steel ingots graphite steel can be produced without subjecting graphitizing heat treatment for a long period. If, on the other hand, calcium silicide is used and 0.007 to 0.03% of Ca necessary for the graphitization should be retained, the calci um silicide of about 3 to 5 times of the iron-calcium base alloy as above mentioned is necessary so that it is diflicult to add the alloy in a ladle and also it lacks the uni- :Eormity of products and the quantity of silicon to be added to the molten steel becomes considerably large as the silicon content in the alloy is large, so that it is unsuitable for steel since it can not be forged when the silicon content increases above about 1.5

When about 1.5% of the iron-calcium base alloy containing 34.5% Fe, 30.1%Ca, 13.3% A1, 21.2% Si which is crushed to the size of about 8 mesh gauze and mixed with about 0.5% of calcium fluoride is added to the molten steel' having the composition C=1.46%, Si=0.7%, Mn= 0.3%, P=0.01% and S=0.02% in a ladle, the obtained nodular graphite steel showed the following mechanical properties:

[Annealed after casting at 850 C. for 1 hour and at 700 C. for 2 hours] [Annealed after forging at 850 C. for 2 hours and at 700 C. for 2 hours] Graphite Tensile Elongation Contraction,

carbon, strength, in 50 mm., percent percent kgJrnrn. percent EXAMPLE H When the iron-calcium base alloy of this invention is used for eutectoid-, hypoeutectoidor alloy-steel.

The addition of the present base alloy to the above steel has special feature of producing very refined and clean steels.

The molten steel containing C 0.81% and Si 0.50% is killed with 0.5% of ferro-manganese, 0.2% of silicon and 0.05% of aluminum and then the calcium base alloy containing Fe 28.0%, Ca 23.9%, Mn 13.7% and Si 33.5% is added to the molten'steel and the steel ingot thus obtained is compared, with the ingot which is not treated with the addition of the calcium base alloy in chemical compositions and'grain sizes as shown in the following results.

Table I Steel Treatment 0 Si Mn P S Ca No. 1-- Addition of 0.05%

ofAl and 0.8% of V Fe-Oa base alloy. 0.82 0.50 0.49 0.001 0.010 0.010 No. 2.- Addition of 0.05% r Table II Grain coarsen- Steel ing tempera Grain size 1 ture, 0.

1 (A.S.T.M. grain size number) after heating at 1,000 C. for 3 hours and partially water quenched.

EXAMPLE 1n When the base alloy of this invention is used for cast iron. 7 Graphite gensilg hillllongation c n a The test results of the yield of calcium and the struccar on s engt 50 mm., ercent. I pemni kgJmmfi percent P ture of cast lron when the iron calcium base alloy is added to the molten cast 11'011 at various temperatures (L5 73 4 6 are shown in Table HI. The lron-calcium base alloy used contalned 25.4% of Fe, 20.7% of Ca and 53.3% of Si.

Table III [Chemical composition 0! the cast iron base alloy to which calcium alloy additions are made: 2.8% O, 3.0% Si, 0.004% P and 0.007% S.]

7 Added Temp., Retained Recovery Oa-alloy and its added amount 0., Ca, perof Ca, Shape of graphite quantity, percent of Ca, when cent percent percent added Fe-Ca base alloy.- 5 1.0 1, 520 o. 015 1. 5 Almost nodular.

Do 5 1.0 1,480 0.025 2.5 Nodular.

5 1. 0 1, 440 0. 020 2. 0 D0. 5 1.0 1,400 0.029 2.9 Almost nodular. 5 1. 5 1, 520 0. 007. 0. 5 Do. 5 1. 5 1,480 0.008 0. 5 D0. 5 1.5 1,440 0.009 0.6 Eutectic. 5 1. 5 1, 400 0. 017 1. 1 D0.

In case of calcium-silicide, the yield of Ca in cast iron is very bad and moreover considerably large amount of calcium-silicide should be added in order to obtain nodular graphite cast iron. On the other hand, when the Fe-Ca base alloy of this invention is used the yield of Ca is about 3 to 5 times better than that when calcium-silicide is used and nodular graphite cast iron can be easily produced at a comparatively low temperature such as 1440" C., but with calcium silicide the nodular graphite can never be obtained at such a low temperature. 7

As another example, a melt of hypo-eutectic cast iron containing 2.8% of C, 2.2% of Si, 0.35% of Mn, 0.02% of P and 0.02% of S is prepared and added to it 4% of Fe-Ca base alloy containing 27.3% of Fe, 23.9% of Ca, 20.8% of Mn and 37.7% of Si mixed with 0.7% of calcium fluoride in a ladle and the melt was inoculated. The resulting cast iron showed nodular graphite structure, the tensile strength 56.4 kg./mm. elongation 3% 50 mm, gauge length and Brinell hardness number 230.

To the same melt as above is added 7% of calciumsilicide containing 29.8% of Ca together with 2% of calcium fluoride in a laddle and the resulting melt was inoculated with 0.3% Si. The cast iron thus obtained showed nodular graphite structure, but accompanied with semi-flake graphite and very non-uniform structure. The lining of ladle was attacked to practically objectionable extent.

In the manufacture of the alloy of this invention, when Ca is reduced from the raw material containing Ca a small amount of alkali metals, alkaline earth metals or rare earth elements such as sodium, potassium, lithium, barium, strontium, magnesium and the like elements is also reduced at the same time, and accordingly even when the base alloy of this invention containing a small amount of such alkaliand alkaline earth-metals and rare earth elements is used, the Fe- Ca alloys as above mentioned can easily be obtained. The object of this invention can be attained if the amount of one or more elements of alkali metal, alkaline earth metals and rare earth elements other than calcium is less than one-fifth of the total quantity of calcium. Accordingly the above range should be included in the scope of this invention.

What I claim is:

1. An iron-calcium base alloy to be added to a melt of iron and steel for improving the physical and chemical properties of iron and steel, which consists of 20 to of calcium, 10 to of manganese, 5 to 40% of silicon and a balance essentially of iron.

2. An iron-calcium base alloy, which consists of 15 to 30% of Ca, 10 to 50% of Mn, 5 to 20% of Al, less than 20% of Si and a balance essentially of Fe.

References Cited in the file of this patent UNITED STATES PATENTS 1,790,552 Meehan Jan. 27, 1931 2,280,283 Crafts Apr. 21, 1942 2,290,273 Burgess July 21, 1942 2,762,705 Spear et al. Sept. 11, 1956 2,767,084 Chandler Oct. 16, 1956

Claims (2)

1. AN IRON-CALCIUM BASE ALLOY TO BE ADDED TO THE MELT OF IRON AND STEEL FOR IMPROVING THE PHYSICAL AND CHEMICAL PROPERTIES OF IRON AND STEEL, WHICH CONSISTS OF 20 TO 40% OF CALCIUM, 10 TO 5% OF MANGANESE, 5 TO 40% OF SILICON AND A BALANCE ESSENTIALLY OF IRON.

2. AN IRON-CALCIUM BASE ALLOY, WHICH CONSISTS OF 15 TO 30% OF CA, 10 TO 50% OF MN, 5 TO 20% OF AL, LESS THAN 20% OF SI AND A BALANCE ESSENTIALLY OF FE.