US2823992A

US2823992A - Alloy steels

Info

Publication number: US2823992A
Application number: US621475A
Authority: US
Inventors: Wilbur T Bolkcom; William E Knapp
Original assignee: American Metallurgical Products Co
Current assignee: American Metallurgical Products Co
Priority date: 1956-11-09
Filing date: 1956-11-09
Publication date: 1958-02-18
Anticipated expiration: 1975-02-18

Description

, Feb. 18, 1958 w. r. BoLKAczoM Erm. 2,823,992

ALLOY STEEL-S Filed Nov. 9. 1956 2 Sheets-Sheet 1 Bri nel( E800 m0 2.900 @350 3000 Mola .Enering Temp. .I'

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ALLOY STEELS Filed Nov. 9, 1956 2 sheets-sheet 2 950 Temperature E a ha i w1 lq @u Q .laqzunlvugfng unal; ;og INVEN-roRs W|LBUR T. BoLKcoM 8..

WILLMMEKN PP United States Patent O ALLOY srEELs Wilbur T. Bolkcom, Allison Park, and William E. Knapp, Pittsburgh, Pa., assignors to American Metallurgical Products Company, Pittsburgh, Pa., a partnership of Pennsylvania Application November 9, 1956, Serial No. 621,475 17 Claims. (Cl. 75-123) This invention relates to alloy steels and a method of manufacturing them and particularly to alloy steel castings having improved impact properties, particularly at low temperatures, improved resistance to corrosion and unusual freedom from hot tears. This application is a continuation-impart of our application Serial No. 599,284, tiled June 22, 1956, which was in turn a continuation-in-part of our application Serial No. 280,226, tiled April 3, 1952, and entitled Alloy Steel.

There has long been a great need for a steel alloy having high impact properties at low temperatures and at the same time having the properties of toughness, corrosion resistance and welda'bility. For example, in the production of cast parts, such as railway car truck frames, holsters, friction shoes, armor plate and other castings which are subject to frequent and severe impacts, impact properties and particularly low temperature impact properties, are of extreme importance. Ordinary steels used in the production of cast armor do not have the necessary toughness andresistance to impact without the addition of expensive and hard-to-get alloying constituents. Even with the addition of these expensive constituents, the low temperature impact properties are available and are difficult to maintain at the desired level. @ne of the primary disadvantages of impact resistant steels which have `been heretofore used for the abovedescribed purposes, has been their tendency to develop hot tears in the mold as is this tendency has been a constant problem to the steel casting industry. The presence of crystalline inclusions has been found to accentuate hot tearing, although other factors are known to be pertinent.

We` have discovered a steel alloy treated in the molten state with rare earth metals which is suitable for the manufacture of castings as well as wroughtarticles having surprising impact resistance at and below room ternwell known in the art, and

peratures, improved toughness, corrosion resistance and weldability and is characterized by line grain microstructure with mostly round and very few or no crystalline inclusions. We have found that the allow steel of our invention has the additional characteristic of greater than normal fluidity and that the castings formed therefrom have unusual resistance to hot tearing. We have also found a method of manufacturing such a steel alloy which will produce these characteristics.

The alloy steel of this invention may comprise broadly the following composition:

Component: Percent by weight Carbon 0.1 to 1.8. Manganese 0.2 to 6. Phosphorus nil to 0.04. Sulphur nil to 0.04. Silicon 0.1 to 0.75. Molybdenum Singly or Chromium in com- Tungsten bination nil to 5. Nickel nil to 4.

2,823,992 Patented Feb. 18, 8

TCC

Component-Continued Percent by weight Rare earth metals Residue from the treatment with about 0.0015% to 0.5% in the molten state after reducing the total oxide level of the molten metal to below .007%.

Iron Balance with. residual impurities in ordinary amounts.

It may be desirable to limit the composition of the alloy to narrower ranges for certain particular applications in which case the following concentrations of alloying elements will produce an alloy having the desirable characteristics of impact resistance at and below room temperatures as well as resistance to hot tears.

Carbon 0.15 to 0.35. Manganese 1.1 to 2. Phosphorus nil to 0.04. Sulphur nil to 0.04. Silicon 0.1 to .75. Molybdenum Singly Chromium or in Tungsten combination 0.3 to 1. Nickel 0.2 to l.

The term rare earth metal as used herein is intended to mean the elements bearing numbers 57 through 71 of the periodic table either singly or in combination and particularly: cerium, lanthanum, neodymiurn, praseodymium, samarium, illiniurn, europium, gadolinium, dysprosium, ytterbium, their alloys and compounds. These rare earth metals may be in the form commonly known as misch metal. A mixture of rare earth metals which has proved particularly effective contains about 31.5 percent lanthanum, about 44.5 percent cerium, about 11 percent praseodymium, about 7 percent neodyrnium, and about 6 percent of the other rare earth metals above mentioned.

The presence of rare earth metals is critical and must be maintained substantially within the range set out above. The alloy must have had at least 0.0015% of rare earth metals added to the molten metal in order to produce the desirable characteristics of high impact resistance at and below room temperatures, resistance to hot tearing and tluidity. While a minimum of 0.0015% of rare earth addition must be maintained, we prefer to use a somewhat higher minimum under most conditions, and preferably we add not less than about 0.0025 of rare earth metals to the alloy. Greater additions of rare earth metals than 0.5 have proven deleterious to the alloy. p

We have found that, in manufacturing the alloy steel of this invention, themolten steel is preferably killed in the furnace as, for example, by adding a deoxidizer such as silicomanganese, and the steel is then tapped. We prefer to maintain the final silicon content of the steel below 0.75. However, this is not critical and iron higher silicon contents may be desirable in some applications and our silicon content.

invention contemplates such higher When the ladle is partly full, the steel `is preferably further deoxidized by adding, for example,

ihowever, be made before deleteriously affecting the alloy), whereupon aluminum is preferably added in an Vamount of the order of l to pounds per ton of charge,

and then'preferably a final addition of calcium silicon Vis made in an amount of the order of 11/2 pounds per ton of charge before the ladle is completely filled.

It has been further discovered that within the range above specified the rare earth metals are effective only if the addition-is made to molten steel in a basic condition and either after the total oxide level has been .reduced to below about 0.007% or deoxidizers are added .which will reduce the total oxide level to below about 0.007% before the rare earth metals have been dissolved in thebath. Attempts to add the rare earth metals within the stated proportions to acid steel have consisently failed, probably due to loss of the rare earth metals in the slag.

If extra hardenability characteristics are desired, boron may be added 'to thepmetal in the molten state without detrimentally affecting the rare earth effects. Preferably such boron additions should be in the area of 0.0005 to 0.005%. f

It will be noted that the novel process may be carried out by adding the rare earth metals to the ladle, as basic steel is poured from the furnace; or if an acid lined furnace is used the molten steel and slag may be poured into a first ladle wherein the slag may be converted to basic condition, and the steel and slag may then be poured into a second ladle wherein the additions are made as above described.

The unusual properties of the alloy of this invention are best demonstrated by referring to tests which were made on alloyshaving compositions within the above ranges. The results of these tests are set forth in the tables which appear hereafter and in the accompanying drawings in which:

Figure 1 is a graph comparing the impact characteristics of the novel steel with those of substantially identical steel produced in the same manner but lacking the rare earth elements;

Figure 2 is a graph comparing the hot tear susceptibility of the novel steel with that of substantially identical steel produced in the same manner but lacking the rare earth metals; and

` Figure 3 is a graph comparing the fluidity of the novel steel with that of substantially identical steel produced 1n the same manner but lacking the rare earth metals.

` Specic examples are described as follows:

EXAMPLE NO. l

In heat No. l the molten steel was killed in a basic lined induction furnace in the usual manner by adding 2% pounds of aluminum and 3 pounds of calcium-manganese-silicon per ton of charge.

In heat No. 2 the molten steel was killed in the basic lined induction furnace in the following manner: After the usual ferrosilicon and ferromanganese additions, the steel was killed with 11/2 pounds of aluminum, 2 pounds of the above-described rare earth metal mixture, and.y

nally with 3 pounds of calcium-mangagnese-silicon per ton of charge.

The steel from both heats was poured into test block molds to form test plates which were identified by theirv heat number plus alphabetical symbols for the respective plates and were heat treated as follows:

Plates 1-A, B, C and plates 2-A, B, C:

0 F.-2 hr.-air cooled l575 F.-4O min-water quenched Plates 1-A and 2-A:

1010 F.1 hr.-water quenched Plates l-B and 2-B:

1055" F.-1 hr.-water quenched Plates l-C and 2-C:

1110 F .-1 hr.-water quenched Results of the Charpy specimens taken from the plates and tested at 40 F. were as follows:

Table I [Heat No. 1 (1 x 6 X 10 plates) Specimen No. A (332) B (322) C (300) [Heat No. 2 (1 x 6" x 10 plates) .1

Specimen No. A (332) B (322) i C (290) The numbers in parentheses are hardnesses taken in Rockwell C and converted to Brinell.

inclusions of the specimens of heat No. 1 were crystalline while those of heat No. 2 were round. The microstructure of the specimens from both heats was a uniform tempered martensite.

'The results of these impact tests can be compared by reference to Figure l of the drawings which graphically compares the impact resistance of the specimens from the two heats. It will be readily apparent by reference to the figure that the impact resistance values of the castings poured from heat No. 2 were consistently and greatly higher than the corresponding impact values of the castings poured from heat No. 1 to which the rare earth metals were not added.

1t will be noted that the susceptibility to hot tearing of the steel poured from heat No. 2 was considerably less than that of the steel poured from heat No. 1 to which the rare earth metals were not added; however, this characteristic of the novel steel is more fully discussed under Example No. 3.

EXAMPLE NO. 2 Two heats were poured with the following analyses:

Heat N0. C M11 P S Si asesinas? then 3 pounds of Graphidox per ton of charge were added, and finally 2 pounds of the above-described rare earth metal mixture per ton of charge were added;

We have discovered that the presence of soluble nitrogen is critical in our alloy. We have found that the soluble nitrogen content should not exceed about 0.006%. This limit can be obtainedY by titanium additions preceding the rare earth addition. We have also found that the hydrogen content should not exceed about four parts per million. We have successfully reduced the hydrogen to this level by having a high rate of carbon boil--at least 30 points per hour. Any other means of removing hydrogen would of course be satisfactory.

Runners were removed from standard test blocks poured lfrom these heats and the runners were normalized at 1650 F. for 20 minutes. All runners were tempered at 950 F. for two hours and air cooled. Pull bars were aged at 550 P. for three hours4 after machining.

The individual results obtained on the pull bar and Charpy specimens identified by heat number plus alphabetical symbols are tabulated in Table II below.

The inclusions of heat No. 3 were crystalline, and the structure was uniform ferrite and pearlite. Heat No. 4 with the rare earth metal addition had mostly round duplex inclusions. There were a few of the pink crystalline inclusions present normally found in titanium treated steels, because the Graphidox addition contains some titanium. It was interesting to note that the rare earth metals were able to transform the nonnal crystalline in clusions to the round type but had no effect on the pink crystalline inclusions associated with titanium treated steels.

Summary of the average physical properties were as follows:

Table III Charpy Ft. Yield, Tensile, Elong., Red. of Lbs. HeatNo. p.s.i. p.s.i. percent Area,

percent Rt. -40 F.

Again it was noted that the hot tear susceptibility of the steel produced by heat 4 was considerably less than that produced by heat 3 to which the rare earth metals were not added. However, the following Example No. 3 discloses a series of heats and tests to determine accurately the eiect of the rare earth metals upon the hot tear susceptibility of this type of steel.

EXAMPLE NO. 3

3 pounds of Ca-Si-Mn per ton of charge were added.

Heat No C Mn P S Si F5 31 1 67 015 031 38 29 1 54 017 .032 38 .30 1 61 016 030 41 3l 1 59 015 030 42 32 l 61 015 033 46 .32 1 62 O16 032 36 30 1 64 017 031 47 3l l 54 016 027 45 31 1 57 014 031 50 The following heats were also poured with the specified analyses, and the procedure was identical with that of the above-mentioned heats cited in this example, except that 2 pounds of the rare earth metal mixture per ton of charge were added.

Heat No. I C Mn l P I S S1 .30 1 62 015 .030 47 .30 l 63 015 .032 44 .31 1 33 .015 .028 48 .32 1 34 .016 .022 49 .32 l 67 O15 .02B 42 .31 1 62 015 .036 49 .33 1 67 016 .034 48 .3l 1 59 014 .033 43 .34 1 72 O17 .033 36 .30 1 72 018 .032 46 .25 l 72 017 .031 45 The hot tearing susceptibilities of castings poured from these heats was tested by pouring a -so-called 1.4 inch wall thickness hot spot cylinder casting from each heat. The same melting procedure was used in all heats, and all critical cores were made in exactly the same way and from the same mixture.

The results are shown in the following table and are compared in Figure 2 of the drawings with standard heats of the same steel without the rare earth metals.

Table I V Temp. of Percent p Steel Contrac` Hot Tear Heat N o Entering tion of Rating Mold Internal No. F.) Diameter 5 2, 985 o. sa 1% 2, 885 0. 85 5 2, 910 0. 78 2 2, 720 D. 80 2 2, 925 (l. 78 3 2, 985 0. 67 4 2, 840 4 3, 010 0 2, 810 0. 56 1% 2, 930 0.86 1 2, 855 0. 76 2 2, 795 0. 70 1 2, 775 0. 70 M 2, 910 0. 66 0 2, 945 0. 67 21/2 2, 745 O. 63 2% 2, 985 0. 60 2 2, s55 o. 53 le 2, 900 0.25 5% 2, 765 0. 65 1` The tests upon which the hot tear ratings were established are conducted as follows:

Steel from each heat is poured into a mold to form a cylinder having an external protuberance extending from end to end thereof. After the cylinder casting has cooled at room temperature, the casting is removed from the mold and any hot tearing in the protuberance is visually compared with standard cylinder casting samples which have been formed in the same manner. The standard samples have been numerically designated in direct proportion to the severity of hot tearing therein. Thus a rating of 0 indicates no hot tearing, and a rating of 1 indicates slight tearing, whereas a rating of 5 indicates severe tearing.

EXAMPLE No. 4 l

The following 66,000 pound heat of steel was produced in a basic open hearthfurnace with the following analysis:

HeatNo. lo Mu P s si N1 or M0 25 Q .27 1.20 .016 1.05 .87 .sv

*.F. -for 1.4/2 hours, plugs were then machined out of the runners and were secured to 4 and 2 Charpy blocks, whereupon This heat was killed in the furnace by adding Si-Mn and was then tapped. When the ladle was approximately `one-fourth full, 11/2 pounds of Cav-Si per ton of charge :were added,v followed by ferrosilicon and rferromanga- 4nese'for adjustment. When the ladle was approximately one-third full, 2 pounds of the above described rare `earth metal mixture per tone of charge were plunged below the level of the bath, and then after the ladle was ap .proximately half full, 2 pounds of aluminum per ton of charge were added. Finally, when the ladle was approxi- .mately tive-eighths full, 11/2 pounds of Ca-Si per ton of i' l charge were added.

,The molten steel was poured into molds to form test 'bar blocks having runners which were softened at 1250 the plugs were given the following heat treatments:

1700 F.-l0 hrs-air cooled 1575 F.2 hrs.-water quenched Tempered- 2 hrs.-water quenched The tempering temperatures for the various blocks were as follows:

Temperature, Section Block No. F. Size,

v inches l 1, 165 4- 1, 100 4 1, 230 4 l, 165 2 l, 165 4 1, 230 4 1, 165 t 2 After the iinal heat treatment, the plugs were removed ffrom the blocks and hardness readings were taken by the standard method' using Rockwell C and Brinell readings.v Results were as follows:

Charpy specimens were then removed from the center section of each plug. Results were as follows:

Table VI Block No. Average Charpy Ft. Lb., -40 F.

Brinell The average results of these tests, and a comparison of the results with standard requirements for steels of substantially identical analyses to whichv rare earth metals haveY not been added, are` disclosed by the following tables from which it will be readily apparent .that the impact resistance valuesmof thesteel produced by this 'heat were astonishingly great in View of values normally EXAMPLE NO. 5

The heats Adiscussed under this example were made to determine the effect of the rare earth metal addition upon the uidity of the molten steel, inasmuch as prior art efforts to obtainriine grained steel with very few or no elongated inclusions have resulted in greatly reduced fluidity, an undesirable characteristic for the production of satisfactory castings.

-The following heats were prepared in a basic induction fur-nace, wherein the molten steel was killed by first adding 21/2 pounds of aluminum per ton of charge and ,then 3 pounds of Ca-Si--Mn per ton of charge. The

steel from each heat was poured into a mold containing a spiral passage connected to the gate, and the following table shows the uidity of the steel and its entering temperature. The fluidity was tested by measuring the Y number of inches the molten steel owed through the spiral passage.

Table VIII Mold Spiral Heat No. C Mn P S Si Additions Entering Fluidity Temp (in.)

3() 1. 66 018 030 47 2, 790 17% 30 1. 63 018 032 46 2, 790 20% 31 1. 67 018 032 46 2%# Al-i- 2, 830 23 30 1. 66- 014 032 4 3# CIL-Mn* 2, S70 v27 32 1. 62 015 .O31 40 Si. 2, 89() 28% 31 1. 63 -.015 033 42 2, 895 29 f 3 0 l, 62 .01,8 032 40 ,2, 910 i 31 The following heats were made in a basic, induction `furnace wherein the steel was first killed by adding 11/2 pounds of aluminum per ton of charge; then 2 pounds of the above-described rare earth metal mixture per ton of charge were added; and then 3 pounds of Ca-Si-Mn per ton of charge were added. The fluidity of the steel alloys, heretofore used `for the manufacture of cast armor and the like. The tables also show that the reduction of area is improved a minimum of It is also apparent that the improvement which results from the use of our alloys permits significant reductions in the amounts of those elements ordinarily added to steel to was tested as above described, and the results are shown improve their toughness. on the'following table: We believe that the unusual properties of our alloy Table IX n Mold Spiral Heat C M n P S Si Additlons Entering Fluidity No. Temp., (in.)

33----- .29 1. 59 .016 .033 .47 2, 785 2115, 34- .2s 1.60 .016 .033 .46 2,800 24 35.---. .31 1.62 .016 .031 .46 1%#A1+3#Ca-Mns1+2# 2,815 26 36.---- .26 1.59 .016 .033 .45 Rare Earth metal mix- 2, s55 2s 37-.--- .31 1.62 .016 .032 .47 ture. 2.390 301/6 38----- .31 1.62 .016 .033 .43 2, 900 31 39----- .28 1.62 .016 .033 .45 2,920 l 30 It will be understood that the molds used in testing the various heats were identical, and the average results are shown in Figure 3 of the drawings wherein it will be seen that the fluidity of steel to which the rare earth metals were added greatly exceeded that of substantially identical steels made in exactly the same manner but lacking the rare earth metals.

EXAMPLE NO. 6

The test data outlined in Tables X-XII were obtained on a quenched and tempered high tensile plate steel containing several alloys and .15 carbon, .017 sulphur. The treated results were obtained from a large ingot treated with 1% lbs. per ton of rare earth metals added in the form of 3%1. oz. balls after deoxidation to a level below 0.007% of total oxides. The untreated ingot was a sister one from the same heat processed in the identical manner except for the rare earth treatment. There was no sulphur reduction from the rare earth treatment. All tests were conducted on a 1 plate.

Table X.-V notch charpy [In foot; lha-Averages] Charpy `V used for transition temperature in accordance with method given in transactions of ASM, vol. 47, 1955, pp. 13S-153, Tensile and impact properties of low carbon martensites, C. C. Busby, M. F. Hawks, and H. S. Paxton.

Careful consideration of the above tables shows that the alloy of this invention has low temperature impact properties which are far superior at 40 F. than the `to about 0.04% sulphur, about 0.2 to 0.5%

steel and the castings made therefrom are derived from the eifect of the rare earth metals upon other elements in the alloy. Our researches have not indicated what the nature or character of that effect may be, however, we believe that there is a tying up and suppression of certain elements and an accentuation of the desirable properties of others. While this theory seems to be consistent with what We have observed we do not wish to bind ourselves to any theory. The fact is that the alloy steels of this invention have a surprising resistance to impact at and below room temperature and at the same time an increased resistance to hot tearing and au increased fluidity, a combination of characteristics heretofore regarded as impossible in the art.

While we have described and disclosed a preferred embodiment and practice of our invention it will be understood that it may be otherwise embodied and practiced within the scope of the following claims.

We claim:

l. An impact resisting steel alloy comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about 5% of one or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel, the residue from the treatment of themolten metal with about 0.0015 to 0.5% rare earth metals after reducing the total oxide to below 0.007% and the balance substantially iron with residual impurities in ordinary amounts.

2. An impact resisting steel alloy 0.1 to 1.8% carbon, about 0.2 to 6% manganese, 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, the residue from the treatment of the molten metal with about 0.0015 to 0.5% rare earth metals after reducing the total oxide to below 0.007% and the balance substantially iron with residual impurities in ordinary amounts.

3. An impact resisting steel alloy comprising about 0.1 to 1% carbon, about l to 2% manganese, abo-ut 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil chromium, about 0.5 to 1% molybdenum, about 0.5 to 1.5% nickel, the residue from the treatment of the molten metal with about 0.0025 to 0.5% rare earth metals after reducing the total oxide to below 0.007% and the balance substantially iron with residual impurities in ordinary amounts.

4. An impact resistant casting formed of a steel alloy comprising about 0.1 to 1.8% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about 5% of one or more of the groupmolybdenum, chromium and tungsten, nil to about 4% nickel, the

comprising about to about 0.04% sulphur, about 0.3 to 1% i of metal, about 1/z pound to residue from the treatment of the molten metal with about 0.0015 to 0.5% rare earth metals after reducing the total oxide to below 0.007% and the balance substantially iron with residual impurities in ordinary amounts, said casting being characterized by a line grain microstructure with predominantly round inclusions and by resistance to hot tearing.

5. An impact resistant casting formed of a steel alloy comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, the residue from the treatment of the molten metal with about 0.0015 to 0.5 rare earth metals after reducing the total oxide to below 0.007% and the balance substantially iron with residual impurities in ordinary amounts, said casting being characterized by a fine grain microstructure with predominantly round inclusions and by resistance to hot tearing.

6. An impact resistant casting,r formed of a steel alloy comprising about 0.1 to 1% carbon, about l to 2% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, about 0.2 to 0.5% chromium, about .5 to 1% molybdenum, about 0.5 to 1.5% nickel, the residue from the treatment of the molten. metal with about 0.0025 to 0.5 rare earth metals after reducing the total oxide to below 0.007% and the balance substantially iron with residual impurities in ordinary amounts, said casting being characterized by a ne grain microstructure with predominantly round inclusions and by resistance to hot tearing.

7. An impact resisting steel alloy comprising about 0.1 to 1% carbon, about 0.2 to about 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about of one or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel, the balance substantially iron with residual impurities in ordinary amounts, and having been treated in the molten state with about 0.0015 to about 0.5 by weight of rare earth metals after reducing the total oxide to below 0.007

8. An impact resisting7 steel alloy comprising about 0.15 to 0.35% carbon, about 1 to 2% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil of one of the chromium and tungsten, about 0.2 to 1% nickel, the balance substantially iron with residual irnpurities in ordinary amounts, and having been treated in the molten state with about 0.0025 to about 0.5% rare earth metals after reducing the total oxide to below 0.007%.

9. The method of producing impact resisting steel comprising the steps of pouring molten basic steel comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about 5% of onel or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel and the balance substantially iron with residual impurities in ordinary amounts into a ladle while adding rst a deoxidizer to reduce the total oxide level below 0.007% and then about 0.0015 to about 0.5% by weight of rare earth metals.

l0. The method of producing impact resisting steel comprising the steps of killing a bath of molten basic steel comprising about 0.1 to 1% carbon, manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about 5% of one or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel and the balance substantially. iron with residual impurities in ordinary amounts in a furnace, pouring the molten metal into a ladle and while pouring making the following additions in the order specified to reduce the total oxide level below about group molybdenum,

metals per ton of metal; about 1 to 5 pounds of aluminum about 0.2 to 6% I' comprising the steps 0.007%: about l1v toj2 pounds of calcium silicon per ton about 5 pounds of rare earthsteel comprising about about 5% chromium and tungsten,

' ordinary amounts in a -into a ladle and while pouring ditions to reduce 0.007%: about 2` to per ton of metal and about 1 to 2 pounds of calcium silicon per ton of metal.

ll. The method of producing impact resisting steel comprising the steps of producing a bath of molten steel, rendering said bath basic, deoxidizing said bath to a total oxide level 'below 0.007% and adding rare earth metals thereto.

12. The method of producing impact resisting steel comprising the steps of killing a bath of molten basic steel comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, Vnil to about 0.04% phosphorus, nil to about 0.4% sulphur, nil to about 5% of one or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel and the balance substantially iron with residual impurities in ordinary amounts in a furnace,pouring the moltenrmetal into a ladle and while pouring making the following additions to reduce the total oxide level belowabout 0.007%: about 2 to 4 pounds of calcium silicon per ton of metal about 1/2 pound to aboutrS pounds of rare earth metals per ton of metal; and about 1 to 5 pounds of aluminum per ton of metal.

13. Themethod of producing impact resisting steel comprising the steps of killing a bath of molten basic steel comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, ynil to about 0.4% sulphur, nil to about 5% of one or morer of the group molybdenum, chromium and tungsten, nil to about 4% nickel and the balance substantially iron with residual impurities in ordinary amounts in a furnace, pouring the molten metal into a ladle and while pouring making the following additions to reduce the total oxide level below about 0.007%: about 2 to 4 pounds per ton of metal of a material selected from the .group consisting of ferromanganese and ferrosilicon, about 1/2 pound to 5 pounds of rare earth metals per ton of metal, and about l to 5 pounds of calcium, manganese silicon per ton of metal.

14. The method of producing impact resisting steel comprising the steps of killing a bath of molten basic steel comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about 5% of one or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel and the balance substantially iron with residual impurities in ordinary amounts in a furnace, pouring the molten metal into a ladle and while Vpouring making the following additions to reduce the total oxide level below about 0.007%: about 2 to 4 pounds of silicon alloy per ton of metal, about 0.03 pound to 5 pounds of rare earth metals per ton of metal; and about l to 5 pounds of aluminum per ton of metal. v

15. The method of producing impact resisting steel comprising the steps of killing a bath of molten basic 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75 silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to of one or more of the group molybdenum, nil to about 4% nickel and the balance substantially viron with residual impurities in furnace, pouring the molten metal making the following adthe total oxide levelbelow about 4 pounds per ton of metal of a material selected from the group consisting of ferromanganese and ferrosilicon, about 0.03 poundto 5 pounds of rare' vearth metals per ton of metal, and about l to 5 pounds of calcium manganese silicon per ton of metal.

v16. The method of' producing impact resisting steel of killing a bath of molten basic steel comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nilto about 5% of one or more of the group molybdenum,

chromium and tungsten, nil to about 4% nickel and the balance substantially iron with residual impurities in ordinary amounts in a furnace, pouring the molten metal into a ladle and while pouring making the following additions to reduce the total oxide level below about 0.007%: about 1 to 5 pounds of aluminum per ton of metal, about 0.03 pound to 5 pounds of rare earth metals per ton of metal, and about 1 to 5 pounds of calcium silicon per ton of metal.

17. The method of producing impact resisting steel comprising the steps of killing a bath of molten basic steel comprising about 0.1 to 1% carbon, about 0.2 to 6% manganese, about 0.1 to 0.75% silicon, nil to about 0.04% phosphorus, nil to about 0.04% sulphur, nil to about 5% of one or more of the group molybdenum, chromium and tungsten, nil to about 4% nickel and the balance substantially iron with residual impurities in ordinary amounts in a furnace, pouring the molten metal into a ladle and while pouring ditions in the order specied level below about 0.007%: minum per ton of metal pounds of rare earth metals making the following adto reduce the total oxide about 1 to 5 pounds of aluand about 0.03 pound to 5 per ton of metal.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES The American Foundryman, and 46.

December 1951, pages 45 U S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 2,823,992 February 18, 1958 Wilbur T., Bolkcom et alo It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let ters Patent should read as corrected 'below Column 1 line 38, for uavailable" read 1f-variablen; line 5dr, for uallowm read @eilloy-m-0 Signed and sealed this 15th day of' April 1958.,

(SEAL) Attest:

Ho AXLINE ROBERT C WATSON Atts'bing Officer Conmissioner of Patents

Claims

1. AN IMPACT RESISTING STEEL ALLOY COMPRISING ABOUT 0.1 TO 1% CARBON, ABOUT 0.2 TO 6% MANGANESE, ABOUT 0.1 TO 0.75% SILICON, NIL TO ABOUT 0.04% PHOSPHORUS, NIL TO ABOUT 0.04% SULPHUR, NIL TO ABOUT 5% OF ONE OR MORE OF THE GROUP MOLYBDENUM, CHROMIUM AND TUNGSTEN, NIL TO ABOUT 4% NICKEL, THE RESIDUE FROM THE TREATMENT OF THE MOLTEN METAL WITH ABOUT 0.0015 TO 0.5% RARE EARTH METALS AFTER REDUCING THE TOTAL OXIDE TO BELOW 0.007% AND THE BALANCE SUBSTANTIALLY IRON WITH RESIDUAL IMPURITIES IN ORDINARY AMOUNTS.