US2467406A - Method of obtaining predetermined physical constitution in iron - Google Patents

Description

Apnl 19, y1949. H. A. REI-:CE 2,467,406

METHOD OF OBTINING PREDETERMINED PHYSICAL CONSTITUTION IN IRON Filed sept. 25, 194e IN V EN TOR.

Patented Apr. 1949 animos METHOD OF OBTAIN-ING PREDETERIVIINED PHYSICAL CONSTITUTION IN IRON Herbert A. Reece, Cleveland Heights, Ohio Continuation of application Serial No. 617,747,

September 21, 1945. This application September 25, 1946, Serial No. 699,200

.s claims. (ci. '1s-13o) This invention relates to the production of iron for use in the manufacture of cast iron products and, as one of its objects, aims to provide a method by which a base iron having a predetermined physical constitution can be uniformly obtained.

It has been recognized that when a base iron of a given physical constitution is subjected to graphitization or other known process steps and castings are poured from the treated or processed iron, they will have a desired tensile strength and certain other desirable physical properties but, so far as- I am aware, there has never been heretofore any known way of obtaining a base iron for such subsequent treatment which will uniformly have a desired predetermined physical constitution. Because of the inability heretofore to control the physical constitution of the base iron, the castings obtained from the processed iron did not uniformly possess the desired physical properties.

By the present invention it is possible to uniformly obtain a predetermined physical constitution in a base iron and since this physical constitution of the iron is retained through subsequent graphitization steps, or other process steps, the castings poured from the processed iron will inherit the desired physical constitution and will therefore possess corresponding desirable physical properties. In accordance with this invention the predetermined physical constitution is obtained in the base iron by controlling the combined carbon content of the materials charged into the melting furnace.

Another object of the invention is, therefore, to provide a method for controlling the physical construction in a base ironby controlling the amount of combined carbon charged into the melting furnace.

Other objects and advantages of the present invention will b e apparent from the following description and "the yaccompanying drawing.

'Ihis application is a continuation of my earlier application Serial No.'617,747, led September 21, 1945, now abandoned.

In the accompanying drawing Fig. 1 is a diagram illustrating the 4resultant tensile strength in iron castings where the physical constitution of the base iron is not controllable.

Fig. 2 is another diagram illustrating the resultant tensile strength in iron castings when the physical properties as regards tensile strength are based on total carbon and silicon percentage values, and

Figs. 3-6, inclusive, are diagrams showing the uniformity of results obtainable in the physical constitution of base irons by controlling the combined carbon content of the mixture of ferrous materials charged into the furnace.

As already indicated in a general way above, v

a feature of prime importance in the `present invention is the discovery by this applicant that predetermined and can be conveniently designated by values expressed in terms of the measureto an".

ment of the carbide formation of the iron. In obtaining this measurement a casting of wedgeshaped cross section is first poured from a base iron whose physical constitutional value is to be determined. The wedge-shaped casting has an acute angle at its apex defining a. knife-edge and which angle may range approximately from 20 The back face of the wedge-shaped cast- `ing can be of any convenient width such as 1",

2", 3" or 4". This wedge-shape has been found to be very convenient for obtaining the desired measurement but obviously this invention contemplates that other shapes could be employed.

After the wedge-shaped casting is poured and has cooled, it is broken in two transversely so that the carbide balance may be observed on the broken surface of the casting at the line of demarcation between the metal of white apearance and the metal of grey appearance. The width measured across the broken surface of the wedgeshaped casting at the line of demarcation is taken as an indication of the physical constitution of the base iron and the indication or value t thus obtained is usually expressed in for convenience and is referred to as' the constitutional carbide wedge value of the iron.

Generally speaking, a melter operating a metal- A '4 -f centages of the total carbon and silicon content are indicated by the plotted points Il. The tensile strength values plotted in Fig. 2 were also obtained from tests made on standard 1.21" seglurgical furnace has at his disposal'a variety of 5 tion test bars conforming to the specications of raw materials such as those represented by the the American Society for Testing Materials and following tabulation and which contain. the perknown thereunder as B bars. centages of combined carbon, graphitic carbon The iron on which the tests of Fig. 2 were made and total carbon specied therein. was in the form of castings or test bars having Approximatsla'omtages anime-ai 1 combined o from Carbon man Carbon s' of'ff .30:0 .so *.soto '.00 flusuuawnmdrmo-rnnrmm. .ino .20 .uw .u :,aorstooxmosmmgoto .10m .00 .1000 .00 n. con summum scoonooo... .e zo 1.15 .e0 zo 1.13 aoustook no .aototvo .soto .70 Llsuolgmlnmozo .1000 .40 .1Mo .03 .0200 '.20 morons 1.00xoa40 .esto .00 morons l1.30ioa00 .0000 .43 1.0000170 1.0000040 .atomo asoman 3.4500020 .30:o1.00 .00:02.40 1.000oa00 .00:03.00 .40002.00 aootoaoo .esto .s0 100003.10 azotoaw .zato .1s aoszoaus 3.100oa00 .-0000 .00 0:03.00 0:03.00 .soto .10l zooltoaio anomalo .2000 .so acuosa morosa: .30 to .ao 2.40 to aio aio zo 0.00

Pceenltegedvarlosyitlh alloy points Il. The tensile strength values plotted in y Fig. 1 were obtained from tests made on standard 1.21 lsection test bars conforming to thespeclilcations` of 'the American Society for Testing Materials and known thereunder as B bars.

The ironon which the tests of F18. 1 rwere made was obtained from furnace charges which, as indicated in the legend of Fig. 1, contained steel approximately 65% to,80%, siliconapproxi- 'mately 1.20% to 1.90% and total carbon approximately .98% to 1.89%. The distribution of the plotted points Il shows that in most cases an iron having a constitutional carbide wedge value above lhi will have a tensile strengthv above 50,000#

p. s. i. and this is represented in the diagram by the fact that the malority of the. plottedpoints lie within the area deilned by the angular line AB. It isfimportant to note,however, that the plottedpoints lying within this area are scattered and do not conform to any definite pattern. This shows that tensile strenlths above 50,000# p. s. i. are consistently obtainable when the physical constitution of the base iron is controlled.

The diagram of Fig. 2 illustrates the lack of uniformity in the physical properties if iron castings when the iron from which they are obtained is controlled on the basis of the total carbon and silicon analyses in the resultant castings or test bars. In this diagram ytensile strength values expressed in 1000# p. s. i. are plotted against the total carbon and silicon content of the test bars expressed as a percentage. The tensile a total carbon and silicon analysis ranging from about 4.30% to about 4.85% and which charges,-

as indicated in the legend of Fig. 2, `contained steel approximately 65% to 80%, silicon approximately'1.20%to 1.90% and total carbon approxivmately .98% to 1.80%. The wide dispersion of 40 the plotted points Il shows that there is no cor-- relation between the tensile strength of an iron and the percentage. value of its total carbon and silicon content.

' Previous to ,this invention consideration has been given only to the total carbon content in the making' up of the furnacewcharge. Under lthat practice it has generallyA been assumed that when the various charges all have the sametotal carbon content. `the physical constitution of the castings obtained "wond be me same providing mambo recarburiiation value remains the same for all of the melts and that the cupola is operated in a stantially the same total carbon content is clearly indicated by the following examples designated 1 and 2.

:sample 1 00 Steel, .1303#.=61%

Auto cast. 383#=18% Returns, 317#-4.=16%% Spelgel s5#=.45%` Total carbon charged==l.52%

35 Total carbon of me1t=3.02% v Example 2 Steel, 1050#=l0% 1 Pig iron ss0#=2s.33%

strength values corresponding with certain per- 7 Silvery, #:=6.07%

Total carbon.charged=1.53%

Total carbon of melt=8.00%

Constitutional carbide wedge values varied from 10 /n to M. l

The result given above in Example 1 were obtained over a period of a months operation of the cupola during which a large number of tests were made and the results of Example 2 were obtained from a corresponding number of tests performed during a like period of time. From the tabulations given in these two examples it will be seen that the total carbon content of the charges are almost identical in value but that the constitutional carbide wedge values of the irons diifer widely which shows denitely that the physical constitutions of the melts are not the same and that the control of the total carbon content of the charge did not provide an accurate control for the physical constitution of the melt.

The reason for the variance in the constitutional carbide wedge Values obtained in Examples 1 and 2 was found to bedue to the inclusion of various types of steels in the materials constituting the charge. These examples demonstrate that the total carbon content of the charged materials is not the controlling element in sey` jcuring a desired predetermined physical constitution in the iron.

In analyzing the relationship of the graphitic carbon content to the physical constitution of a base iron numerous tests were made and the results set out in the following tabulation, designated Example 3, are illustrative thereof.

Example 3 Graphitic Carbon Constitutional Carbide Wedge Values in lfm Content of Charges,

percent The foregoing tabulation of Example 3 lists the constitutional carbide Wedge values ygiven by base irons obtained from charges having the percentages of graphitic carbon which are indicated in the example. The wide variation in the graphitic carbon content for charges which produced base irons having the same constitutional Example 4 Charge consisting of:

Pounds Pig iron 100 Silvery 80 Spiegel 20 Returns 195 Rail steel 500 Misc. steel 305 Total 1200 Calc. combined carbon .61% calc. .76% silicon 1.43%.

graphitic carbon Calc. combined carbon 80%; calc. graphitic carbon 1.20% :silicon 1.64%.

In Example 4 the charge consisted-of the ferrous materials listed in this example which aggregated 1200# and had a calculated combinedA carbon content of approximately .61%, a calculated graphitic carbon content of approximately .75% and a silicon content of approximately 1.43%. In Example 5 the charge consisted of. the same kinds of ferrous materials having the same aggregate weight but with the weights of the individual materials differing considerably from the weights of the corresponding individual materials in Example 4. The materials constituting the charge of Example 5 had a calculated combined carbon content of approximately .60%, a calculated graphiticcarbon content of approximately 1.20% and a silicon content of approximately 1.64%.

An important factor to be noted in Examples 4 and 5 is the fact that the materials have been so selected that the combined carbon content is substantially the same in both exampleseven though the other percentages and the amounts of the individual materials vary widely. Charges as represented by Example 4 yielded regularly a base iron with a constitutional carbide wedge value of 19/32 and charges corresponding with Example 5 yielded regularly a base iron with a constitutional carbide Wedge value of 16/s:. The results 'represented in these examples therefore clearly show that Iby controlling the combined carbon content of the materials of the charge a desired calculated percentages of approximately .30% to l .60% for the combined carbon content of the materials charged in the furnace when using in the charge approximately 35% to 50% of steel, approximately 1.50% to 2.00% of silicon, and ap'- proximately 1.60% to 2.65% for the total carbon content.

The diagram of Fig. 4 illustrates the use of typical calculated percentages of approximately .35% to .65% for the combined carbon content of the materials charged in the furnace and the resulting constitutional carbide wedge values as represented by the plotted points I 3 when using in lthe charged materials approximately 50% to 65% steel, approximately 1.40% to 2.00% of silicon, and a total carbon content of approximately 1.10% to 1.90%.

The diagram of Fig. 5 illustra-tes the use o! typical calculated percentages 0f approximately wcm .50% to .80% for thev combined carbon content resulting constitutionalcarbide wedge values as represented by the plotted points l5 when using in the charged materials approximately 60% to 80% steel. approximately .80% to 1.20% of silicon. and a total carbon content of approximately .96% to 1.58%.

Obviously. if the total carbon content of a charge of metal is a fixed value, any decrease in the graphitic carbon centen-t results in an 'increase in the combined carbon content,` with a resultant increase in the constitutional carbide value as shown in Figures 3-6. This can be illustrated, by referring to Figure 5, using a iixed total carbon content of the metal charge of 1.25%

` Per cent Total carbon n 1.25 lGraphitic carbon .60

Combined carbon Constitutional carbide wedge value="/n.l

.'15 Constitutional carbide wedge valu`e=/as.

In the diagrams of 'Figa 3 to 6 inclusive the -plotted points have a definite pattern in which 'substantially all of the points lie between a Pair of parallel sloping lines I6 and I1 which show that the physical constitution of the base iron is directly related to and dependent upon the combined carbon content ofthe materials 0f the charge. The upper line i8 corresponds with a j low steel-high silicon value for the percentages specified for the materials of the charges in Figs. 3 to 6 inclusive and the lower line II corresponds with a high steel-low silicon value for the speci-` ned percentages. The slope of the lines Il and Il can be varied by altering the silicon content or the steel percentages of the charge but the principle of the invention will remain the sarne.

From the drawing 'and .the foregoing specincation it will now be understood that this invention provides a practical and workable method by which a predetermined physical constitution can be readily and uniformly obtained in a base iron, and hence, iron castings having desired physical properties can be uniformly produced when the bese iron is processed. v i

The Iterm cast iron as used herein is intende'd to mean iron products as distinguished from steel products, that is, iron products containing 1.8% to 4.5% carbon and more than .25% silicon.

and which include all of the commonly known cast irons such as gray cast iron, white cast iron, air furnace iron, chilled iron, alloy iron. mottled iron, semi-steel and the various trade name irons.r

Although the invention has been disclosed herein in a detailed way it should not be regarded as being correspondingly limited since it is intended to include all changes and modifications coming within the scope ofthe appended claims.

. y 8l Iclaimasmyinvention: 1. Themethod of producing cast iron trolled physical properties which comprises chargwedge values being related as shown in Figure I of the drawing, the relationship of the steel and silicon charges being shown by lines Il and Il of saidilgure withline llbeinglowsteelandhigh silicon velue and line I'I being high steel and lo' silicon value, melting said charge, and casting' the' molten iron.

2. The method of producing cast iron of controlled physical properties which comprhes charging into a cupalo 1|.v mixture of ferrous materials which will provide a predetermined approximate percentage of 50 to 65 percent for the steel content of the materials charged, 1.40 to 2.00 percent forthe silicon `content and 1.10 to 1.90 percent for the total carbon content, and said selected ferrous materials also providing a predetermined approximate percentage oi' .35 to .65 percent for the combined carbon content of the materials charged such that said mixture will substantially uniformly give corresponding approximate constitutlona1 carbide wedge values of '/:z to zuha, the steel charge. the silicon charge, the combined carbon, and constitutional carbide wedge values being related as shown in Figure 4 of the drawing, the relationship of the steel and silicon charges being shown by lines I8 and Il of said ligure with line I 6 being low steel and high silicon and line il beinghigh steel and low silicon, melting said charge, and `casting the molten iron.

8. The method of producing cast iron of controlled physical properties which comprises charginginto a cupola a mixture of ferrousm terials which will provide a predtermined approximate percentage of 65 to 80 percent for the steel content of the materials charged, 1.20 to 1.90 percent for the silicon content and .98 to 1.89 percent for the total carbon content, and said selected ferrous materials also providing a predetermined approximate percentage of .50 to .80 percent for the combined carbon` content of the materials charged such that said mixture will substantially uniformly give corresponding approximate constitutional carbide wedge values of^192 to 2%2, the steel charge, the silicon charge, the combined carbon, and constitutional carbide wedge values being related as shown in Figure 5 of the drawing. the. relationship of the steel and silicon charges being shown by lines I6 and Il of said gure with line i8 being low steel and high silicon and line Il being high steel and low silicon, melting said charge, and casting the molten iron.

4. The method of producing cast iron of controlled physical properties which comprises charging into a cupola a mixture oi' ferrous materials which will provide a predetermined approximatepercentageof35toiiopercentforthe` Near..

steel content of the materials charged, .80 to 2.00 percent for the silicon content and .96 to 2.65 percent for the total carbon content, and said selected ferrous materials also providing a predetermined approximate percentage of .30 to .90 percent for the combined carbon content of the materials charged such that said mixture will substantially uniformly give corresponding approximate constitutional carbide wedge values 0i 5&2 to 4%2, the steel charge, the silicon charge, the combined carbon, and constitutional carbide wedge values being related as shown in Figures 3 to 6 of the drawing, the relationship of the steel and silicon charges being shown by lines I6 and I1 of said figures with line I6 being low steel and high silicon and line I1 being high steel and low silicon, melting said charge, and casting the molten iron.

5. The method of producing cast iron .of con- 10 trolled physical properties in which the base molten iron of the character described in claim 4 is treated by dissolving a. graphitizing material therein.

6. The method of producing cast iron of controlled physical properties in which the base iron of the character described in claim 4 is treated by dissolving a hardening material therein.

HERBERT A.v REECE.

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

UNITED STATES PATENTS Number Name Date 2,371,654 Smalley et al. Mar. 20, 1945

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