US3798027A

US3798027A - Gray iron

Info

Publication number: US3798027A
Application number: US00208489A
Authority: US
Inventors: C Defranco; Eeghem J Van
Original assignee: RECH SCIENT L IND FABRICATIONS
Current assignee: CENTRE RECH SCIENTIFIQUES L IND FABRICATIONS METALLIQUES BE; RECH SCIENT L IND FABRICATIONS
Priority date: 1968-02-13
Filing date: 1971-12-15
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19
Also published as: DE1906008A1; BE710679A; DE1906008B2; GB1258824A; FR2001827B1; DE1906008C3; CH508729A; FR2001827A1

Abstract

High strength low hardness gray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1% silicon and the balance iron, said gray iron having been inoculated with a minimum of 0.3 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium.

Description

United States Patent [191 Defranco et a1.

GRAY IRON Inventors: Charles Defranco, Zele; Jan Van Eeghem, Deurle, both of Belgium Centre de Recherches Scientifiques et llndustrie des Fabrications Metalliques, en abrege, C.R.I.F., Brussels, Belgium Filed: Dec. 15, 1971 Appl. No.: 208,489

Related U.S. Application Data Continuation of Ser. No. 797,622, Feb. 7, 1969, abandoned.

Assignee:

Foreign Application Priority Data Kglmm [451 Mar. 19, 1974 [56] References Cited UNITED STATES PATENTS 2,793,114 5/1957 Moore 75/130 2,885,284 5/1959 Moore 75/124 1,515,244 11/1924 Early 75/130 R X 2,134,905 11/1938 Bampfylde 75/130 R X 2,950,187 8/1960 Ototani 75/124 X 3,433,685 3/1969 Albertzart 148/35 Primary ExaminerL. Dewayne Rutledge fifi ifllii miflf fila M; Pari V, Attorney, Agent, or F irm-Hubbell, Cohen & Stiefel; Sheldon Palmer [57] ABSTRACT High strength low hardness gray iron consisting essentially of about '1 3 percent aluminum, 2 4 percent 1 carbon, up to 1% silicon and the balance iron, said gray iron having been inoculated with a minimum of 0.3 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium.

12 Claims, 3 Drawing Figures as l f I 2a PATENTED MAR 1 9 I974 SHEU 1 [IF 2 Kg/mm FIG/i.

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INVEA/TDRS il/wuss Min/v60 .Tn/v ww means;

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SHEET 2 OF 2 Kg/mm so 55 s2 11: 48 o 0 FEG-3.

IIVUENTORJ mamas psrnwao .m/v vmv E56 HEM GRAY IRON CROSS-REFERENCE TO RELATED APPLICA- TIONS This application is a continuation of application, Ser. No. 797,622, filed Feb. 7, 1969, now abandoned.

The present invention relates to gray iron.

The gray irons actually known as high strength gray irons with lamellar graphite have relatively low carbon (2.6 to 3.2 percent) and silicon (l to 1.5 percent) contents.

The tensile strength of these known irons, measured on a 30mm standard test-bar rarely exceeds 45 kgf/mm whereas their Brinell hardness may be as high as 320 Brinell.

To attain this high strength, it is generally necessary to add costly alloying elements such as copper, nickel,

molybdenum and/or chromium, and to subsequently 1 inoculate the liquid iron.

Furthermore, as a result of their low carbon and silicon contents these known high strength cast irons also present the disadvantage of a rather high tendency to white chilling. The danger of unmachinable white iron formation thus increases with the decreasing wall thickness of the casting.

Furthermore due to their high hardness, the machin- V ability of the known high strength cast irons is rather poor.

The production of cast iron based on iron carbon and aluminum, with little or no silicon was proposed more than 30 years ago.

However, such ironswere cast in the non-inoculated state, and their properties were inferior to those of the classical silicon cast irons.

Present knowledge concerning the inoculation mechanism enables one to give a plausible explanation to this phenomenon.

Indeed, due to the high deoxidizing power of aluminum the oxygen content of high aluminum irons, whether it is dissolved as FeO particles or combined with silicon as SiO inclusions, is almost negligible. This means that silicon particles, which act as natural nuclei in normal gray silicon-bearing irons are absent in high aluminum cast irons, and thus, these known but non-inoculated cast irons have a high chilling tendency and tensile properties which are not superior to, and may even be inferior to those of silicon irons.

The present invention is a new and improved alloy, having properties which are not present in irons where aluminum is used with medium or high silicon contents (which are normal in classical silicon irons) nor in irons where high silicon contents are used without aluminum even when inoculated with an alloy containing calcium, barium or strontium. For this purpose, the cast iron according to the invention is characterized by the fact, that on the one hand it contains aluminum as a graphitizing element, and on the other hand it is inoculated.

The tensile strength of the irons according to the invention varies, for irons with lamellar graphite, be tween 35 and 70 kgf/mm as a function of wallthickness and carbon and aluminum contents; their tendency to chilling is almost non-existent.

Belgian patent 563,443 of Dec. 12, I957 discloses a ferrous alloy which is obtained by simultaneous addition of manganese and aluminum in order to improve the wear and heat'resistance of the iron. The properties of this known iron are considerably different from those of the iron according to the present invention, as

will appear below from a more detailed description of the present iron.

US. Pat. No. 2,662,820 of June 30, 1950 suggests the addition of aluminum in the course of elaboration of a gray iron. It must be pointed out however, that this patent concerns the production of a classical gray iron with spheroidal graphite, the purpose of the aluminum being to extend the duration of the effect of the nodulizing agent.

According to an advantageous embodiment of the present invention the useful and economical range of the aluminum content lies between 1 and 3 percent.

The silicon content of the cast irons according to the present invention should preferably and advantageously be lower than 1 percent.

In a particular embodiment of the invention, the silicon content is zero. Indeed, as a further advantage of the present invention, the selected from the group consisting of barium and strontium is incorporated in the molten iron by an aluminum containing bearer.

Other details and particularities of the present invention will be apparent from the description given below, by way of non-limitative example, of several embodiments of the invention, with reference to the drawings which show comparative graphs of the physical properties of the cast iron according to this invention, wherein FIG. 1 shows tensile strength plotted against carbon content, FIG. 2 shows tensile strength plotted against silicon content, and FIG. 3 shows tensile strength plotted against Brinell hardness.

The graph of FIG. 1 shows the variation of tensile strength in 30 mm -diameter test bars (ordinate), determined as a function of carbon content (abscissa) on irons containing respectively an average aluminium content of 1.8 percent (curve 1) or 2.5 percent (curve 2) and inoculated by addition of 1% SiCa.

The straight dotted line, 3, in FIG. 1, represents the theoretical tensile strength of classical irons containing 1.5 percent silicon.

It is seen therefrom that at the same level of carbon content, the strengths of the aluminum irons inoculated with l% SiCa, exceed by 10 to 15 kgf/mm the strengths of the classical irons containing 1.5 percent silicon.

According to an advantageous embodiment of the present invention, the useful and economical range of the aluminum contents lies between I and 3 percent.

FIG. 2 shows the influence of increasing silicon contents (abscissa) on the tensile strength (ordinate) of inoeula ted aluminum bearing iron cast intest-bars of 3 different diameters.

Curve 4 relates to 30 mm -diameter test bars, curve 5 to 20 ram-diameter test bars and curve 6 to 12 m ndiameter test bars.

It can be seen that the influence of silicon is slight between 0.4 and 0.8 percent, that the optimum value is about 0.75 percent and that in amounts over 0.9 percent silicon the tensile strength drops very quickly.

The silicon content of the irons according to the present invention should therefore preferably be lower than 1 percent.

According to a particular embodiment of the present invention, the silicon content of the iron as graphitizing element may even be zero, in which case the silicon is replaced totally by aluminum.

The influence of increasing manganese, sulfur and phosphorus contents on the properties of a base iron TAELE 1 Curve 7 of HG. 3 shows the relationship between tensile strength (ordinate) and Brinell hardness (ablnfluence of Mn, S and P on the mechanical properties of aluminum cast iron Cast Chill R kgllmm Impact depth modulus iron in mm 45 30 mm 46 mm 12 mm HB d: mm kgfcm/cm -cwflc. isw W W c- -W o .025 1 48.6 52 256 12.2 .038 2 46.5 51.2 51.8 2 2 4 lg l B .051 4 49.2 51.2 53.5 249 10.9 .079 5 43.6 48 50 252 11.6

These results show that manganese increases the chifi depth and decreases both the tensile strength and the impact modulus, particularly when the manganese content exceeds 0.6 percent.

Sulfur increases the chill depth and decreases both the tensile strength and the impact modulus.

Phosphorus has no influence on chill depth but considerably decreases the impact modulus.

It is thus advantageous to limit the manganese, sulfur and phosphorus contents respectively to the following maximum values: 0.7 percent for Mn; 0.05 percent for S and 0.1 percent for P.

Due to the absence of natural nuclei and in spite of the graphitizing effect of the aluminum, the tendency to ledeburitic solidification of the non-inoculated castirons according to the invention is very important.

The chill depth of the non-inoculated cast irons varies generally between 20 mm and total chill, although it becomes almost non-ex'istant (O2 mm) after inoculation.

However, to obtain this result, the amount of inoculating alloy added to the cast iron according to the invention must be more greater than that used for the inoculation of conventional silicon cast irons.

Indeed, while the conventional cast irons are generally inoculated with 0.1 to 0.3 percent of an inoculant, for instance SiCa, the cast irons according to the invention must be inoculated with at least 0.3% SiCa.

Although the properties increase with the amount of added inoculant, it is not justified economically to use more than 2% SiCa. I

It must be mentioned that it is not indispensable that the inoculant contain silicon as the bearer of the active inoculating element. On the contrary, in order to avoid the introduction of silicon in the iron, and the accumu-- lation of this element by using foundry returns, it is advantageous to inoculate with alloys of the Fe-Al-Ca type. which do not contain silicon, and which have been specially developed for this purpose.

scissa) of 5655156553011. The Ffikifr'cie are the results obtained with irons containing 1.8 percent aluminum, whereas the crosses represent the results obtained on irons containing 2.5 percent aluminum, all tests having been performed on cast irons inoculated with 1% SiCa and cast in 30 mm-diameter bars.

For comparison purposes with conventional silicon cast irons, the straight dotted line 8 gives the theoretical relation according to the formula HB 4.3 R,, where HE is the Brinell Hardness, and

R, is the Tensile Strength.

The black circles represent the scarce quantitative data given in the literature for conventional high strength gray irons.

As seen from FIG. 3, with the same level of tensile strength, the Brinell hardness of the aluminum cast iron is on the average 50 to 60 Brinell units lower than that of the conventional silicon cast irons.

In spite of the high strengths, the hardness of the cast irons according to the invention is relatively low, which results in machinability which is comparable to, or even betterthan that of the silicon cast irons.

The cast irons according to the present invention also have the advantage of being made from inexpensive raw materials.

The new cast irons are particularly suited to produce high strength castings and thin-walled castings which have to be machined.

The aluminum contained in these cast irons prevents any mold-metal reactions so that sand adherence is almost unexisting.

The skin of the castings of aluminum cast iron is smoother than the skin of the usual castings of silicon cast iron, which allows a considerable reduction of cleaning costs. 7

A particularly interesting area of application of the new cast irons is in casting in metal molds.

The castings in conventional silicon irons, cast in metal molds must generally be heat-treated to decompose the carbides which are formed during the rapid cooling in the metal mold.

It has been shown experimentally that due to the very low tendency to chilling of the irons according to the present invention, the castings made in metal molds with these irons, do not have to be heat-treated afterwards.

Two non-limitative examples of the composition of cast irons according to the invention, untreated for nodulizing and cast in bars are given below.

The hardness and strength tables of in Example 1 give the comparative results of tests for an iron according to the invention which has been inoculated, the silicon content being the sum of the silicon content of the base materials and the silicon content added to the iron as a component of the inoculant, and for the noninoculated base iron, the silicon content of the latter being the silicon content of the base n at et ials.

i i M lli- Chemical composition:

l. A high strength low hardness gray iron consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been innoculated with l to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being preseltia P'EfiUQljEEF! emqqn s ivs, F L 3 b? non-inoculated base iron 2.90% C; 0.09% Si; 1.85% Al inoculated iron 2.70% C; 0.35% Si; 1.85% Al inoculation with SiCa: 1%

Tensile strength in kgf/mm 30mm 20mm 12mm non-inoculinoculnon-inoculinoculnoninocu1- inoculated ated ated ated ated ated 24.7 50.2 38.9 52.6 white iron 57.9

non-inoculated inoculated chill depth in mm: 40 2 impact modulus: kgfcm/cm: (da mm) 5.6 13.5

Brinell Hardness 4530mm 20mm 12mm non-inoculinoculnon-inoculinoculnon-inoculinoculated ated ated ated ated ated 246 234 295 256 white iron 280 EXAMPLE 2 Brinell Hardness of the as cast alloy by about 50 Brinell In this example an iron inoculated with 1% Fe-Al- Ca has been added flor comparison.

units.

1A h en t 10W a ness re rs sensistin Chemical composition non-inoculated 3.18 0.15 0.45 0.042 0.040 2.53 inoculated with SiCa 3.02 0.77 0.44 0.042 0.030 2.53 inoculated with Fe-Al-Ca 3.10 0.12 0.45 0.041 0.031 2.85 (Fe: Al: 40%; Ca: 20%) Properties 30 mm 4b 20 mm d) 12 mm nqn-ino- SiCa FeAl non-ino- SiCa FeAl non-ino- SiCa FeAl culated Ca culated Ca culated Ca Tensile strength 40.1 47.6 49.8 42 51.8 53.5 43.2 53.3 55.1 kgf/mm Brinell Hardness 239 241 245 272 285 278 288 302 302 non-inoculated SiCa FeAlCa Chill depth in mm: 20 0.5 0.5

essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

3. A high strength low hardness gray iron consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1 percent phosphorus, and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

4. A high strength low hardness gray iron having a flake graphite structure and consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

5. A high strength low hardness gray iron consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, upto 1 percent silicon and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and percent calcium.

6. A high strength low hardness gray iron consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese and the balance iron, said gray iron having been inoculated with l to 2 percent ofan inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.

7. A high strength low hardness gray iron consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to l percent silicon, up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1 percent phosphorus and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.

8. A high strength low hardness gray iron having a flake graphite structure and consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.

9. In a cast gray iron article having a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about I 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

10. In a cast gray iron article having a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, and the balance iron, said gray iron having been inoculated with 1 to 2 perce of an inocu- Ent alloy, the active inoculant brivifihi elected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

11. In a cast gray iron article having a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1 percent phosphorus, and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

12. In a cast gray iron article having a flake graphite structure and a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to l percent silicon and the balance iron, said gray iron having been inoculated with l to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.

Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,798,027 Dated March 19, 1974 Charles Defrancq et a1. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page, left side alongside the word "inventorsz' "Charles Defranco" should read Charles Defrancq alongside the word "Assignee"; "Centre de Recherches Scientifiques et l'lndustrie des Fabrications Metalliques,

en abrege', C.R.I.F.," should read Centre de Recherches Scientifiques et Techniques d l'Industrie des Fabrications metalliques, en abrege, C.R.I.F., Column 2, line l8, "the selected" should read the active inoculating element selected Column 2, line 19, "of barium and strontium" should read of calcium, barium and strontium Column 5,

line 13, "tables of in" should read tables in Column 5 v Example 2, "Tensile strength kgf/mm" should read Tensile 2 strength kgf/mm Column 6, line 2, "beside" should read besides Column 6, line 19, claim 1: "innoculated" should read inoculated Signed and' sealed this 17th day of September 1974.-

(SEAL) Attest: I v

C. MARSHALL DANN MCCOY GIBSON Commissioner of Patents Att sting Officer

Claims

2. A high strength low hardness gray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.
3. A high strength low hardness gray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1 percent phosphorus, and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.
4. A high strength low hardness gray iron having a flake graphite structure and consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.
5. A high strength low hardness gray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.
6. A high strength low hardness gray iron consIsting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.
7. A high strength low hardness gray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1 percent phosphorus and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.
8. A high strength low hardness gray iron having a flake graphite structure and consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy selected from the group consisting of SiCa consisting essentially of about 33 percent calcium and the balance being silicon and FeAlCa consisting essentially of about 40 percent iron, 40 percent aluminum and 20 percent calcium.
9. In a cast gray iron article having a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.
10. In a cast gray iron article having a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.
11. In a cast gray iron article having a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1 percent phosphorus, and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.
12. In a cast gray iron article having a flake graphite structure and a chill depth in mm. of between about 0.5 and 2, said article consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 perceNt silicon and the balance iron, said gray iron having been inoculated with 1 to 2 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium, said active inoculant being present in the alloy in an amount effective to reduce the Brinell Hardness of the as cast alloy by about 50 Brinell units.