US2861908A - Alloy steel and method of making - Google Patents

Description

Nov. 25, 1958 c. G. MlcKELsoN ETAL 2,861,908

ALLOY STEEL AND METHOD 0E MAKING Filed Nov. 50, 1955 Nov. 25, 1958 c. G. MICKELSON ET AL 2,861,908

ALLOY STEEL AND METHOD oF MAKING 2 usw no" 8S a m M. 5 8 j@ Filed NOV. 30, 1955 Nov. 25, 1958 c. G; MlcKELsoN ET AL 2,861,908

y ALLOY STEEL AND METHOD oF MAKING Filed Nov. 30, 1955 8 Sheets-Sheet 3 RfzAr/a/vs/f/P afin/uw fmnmvsss No aw TEMPS/:Arana .muHA/sss )vo RARE EARTH Nov. 25, 1958 c. G. MlcKLsoN i-:TAL

ALLOY STEEL AND METHOD oF MAKING Filed Nov; so, 1955 8 Sheets-Sheet 4 Nov. `25, 1958 c. G. MIcKELsoN i-:T AL 2,861,908

ALLOY STEEL AND METHOD OF MAKING Filed NOV. 50, 1955 8 Sheets-Sheet 5 BY ecu'c @i m Nov. 25, 1958 c. G. MlcKl-:LsoN ET AL 2,861,908

ALLOY STEEL AND METHOD OF' MAKING Filed Nov. 30, 1955 8 Sheets-Sheet 6 u E lb U) 0 L z S u c lu E o "l 's u 'n 'n e E L n :a 2 g 'El v3 f g/Mee R/NELL HDNES# NUMBER HEAT No 777s /fNovEL mLoy HEAT No. 77/ No eoRo/v HEAT N0. 77/.9 No RA @E 5mm:

` zao Nov. 25, 1958 c. G. MICKELSON ET AL 2,861,908

ALLOY STEEL. AND METHOD oF MAKING 8 Sheets-Sheet 7 Filed Nov. 50, 1955 60 lloa .u m. MN w u wyfmn L D f c r P 6 l L u RN E ...0. M A 0 l L .n Y R LCE 0 0 0 D Fm* m m. w w w m 600 800 TEMPERING TEMPERATURE 'E Nov. 25, 1958 c.; G. MlcKELsoN ET AL 2,861,908 ALLOY STEEL AND METHOD OF' MAKING I 8 Sheets-Sheet 8 Filed NOV. 50, 1955 7' ENS/LE YIELD BRINELL Euc WDM 0F AREA CHARPY Evan/0N Patented Nov. 25, 1953 2,861,908 ALLY STEEL AND METHOD F MAKING Cedric G. Mickelson, Gary, Ind., and Gustaf A. Lillieqvist, deceased, late of Hammond, Ind., by Ellen S. Lillieqvist, administratrix, Lake County, Ind., assignors to American Steel Foundries, Chicago, Ill., a corporation of New Jersey Appiication November 30, 1955, Serial No. 549,910 Claims. (Cl. 148-31) This application is a continuation-inpart of our copending application, Serial No. 451,- 652, led on August 23, 1954, nowv abandoned.

There has been a long felt need for a tough steel alloy having great resistance to Wear without tendency to deform. For example, in the production of cast steel parts, such as clipper buckets or clipper teeth, which are subjected to frequent and severe abrasion as well as blows of substantial magnitude, Wear resistance and toughness, Without tendency to deform, are of extreme importance.

Ordinary steels used in the production of such parts have not only been inadequate to resist Wear but have in many cases tended to creep or deform from repeated use, as is normally encountered in service.

hardened,

by a quench, is astonishinglytough and resistant to wear, Without tendency to deform in service.

It has been found that the novel steel alloy after heat treatment is characterized by a tine grain microthe form of tough interlocked Component Percent by Weight MM HRM Carbon about .20 to .50%.

Manganese. about .15 to 2.5%. Silicon about .1 to 2.0%. Phosphorus nil to about .05%.

Sulphur Molybdenum, Chromium, Tungsten (singly or in Combination). Nickel nil to about .07%. nil to about 5.0%.

nil to about 4.0%

Boron. about .0005 to .005% added to the metal state.

Rare Earth Metals in the molten The residue from the treatment of the molten metal in the molten state with about 0.0015 to 0.5%.

alance with residual impurities in ordinary amounts.

Iron B It has also been discovered that an economical composition of the novel alloy limited to narrower ranges is particularly effective for certain applications, in which case the following concentrations of alloying elements Will produce an alloy having the desirable characteristic of wear resistance:

Component l Percent by Weight about .20 to .50%. about .70 to 1.70%. about .20 to 2.0%. nil tlo3 about .05%.

about .05 to .70%.

about 0.5 to 1.50%.

about .01 to 1.00%.

about .0005 to .0057 added to the metal in the molten state.

The residue from the treatment of the molten metal in the molten state with about 0.0015 to 0.5

B ance with residual impurities in ordinary amoun It may also be noted that titanium in an amount of the order of nil to 5 pounds per ton of charge may be added to the alloy in the molten state prior to addition of the boron and rare earths; Titanium is preferably added in the form of ferrotitanium although other forms thereof may be used. Under certain melting conditions it has been found that the addition of'titanium is critical as, for example, when the steel is cast .at a very high temperature or has been subjected to a long hold after having been killed in the furnace. Under these conditions nitrogen absorption by the steel may be very high. Also a heat having a poor boil may tend to have a high soluble vnitrogen content. Under any one of these conditions tltanium must be added to change the soluble mtrogen to the extent that the titanium combines with soluble nitrogen. The effective range of titanium for the purpose is from about .0005 to about .02% by weight.

It has been found that a low carbo-n alloy steel such as above described having the desired characteristic of Wear resistance and presenting minimum diculties from centrations of alloying elements:

Percent by Weight about .26 to .30%.

about 1.35 to about 1.55%. about .30 to .46%.

Component Carbon A higher carbon alloy having even'greater resistance to wear, but presenting certain difficulties from a viewpoint of the heat treatment, has been foundrto contain the following concentrations of alloying elements:

Percent by Weight about .33 to .37%. about 1.35 to 1.55%. about .30 to .46%. nil to about .020%

Do, about .47 to .53%. about .52 to .68%. residual Component Nickel Rare Earth Metals The residue from the treatment of the molten metal in the molten state with about 0.0015 to 0.5%. Boron... about .0020 to .005% added to the metal in the molten state. l Balance with residual impurities in ordinary amounts.

Iron

According to the invention, the novel steel alloy, after casting thereof, is heat treated in the following manner to achieve maximum wear resistance and toughness. The castings are first normalized by heating them, for example, to about 1600-1900" F. After a hold of any desired duration, the castings are then air cooled so that they may be conveniently worked in lthe shop. This treatment is followed by a hardening heat treatment in which the castings formed of the lower carbon steel alloy above mentioned are heated, for example, to about 1500# 1700" F., and the higher carbon alloy steel castings are heated, for example, to about 1450-1650" F. ln either case the castings are preferably held at the hardening temperature for about an hour or more, depending upon the section and are then quenched, preferably in water.

The castings are then heated to a tempering ternperature of the order of 100 F. or more up to but less than 600 F., although unusually excellent results have been attained within `a range of about 250 to 450 F. The castings are held at the tempering temperature, preferably for a period of about two hours or more depending upon the size of the castings and are then quenched, preferably in water, or possibly inair.

It will be understood that the hold time for the various heat treatments may vary considerably depending v upon the type of furnace equipment and the size of material being produced. The shortest possible time at temperature is preferred, and it may be noted that excellent results have been achieved by the foregoing practice. If desired, in addition to the above described heat treatment, the castings may be tempered before hardenlng to reduce machining costs.

rare earth elements are then added,

The term rare earth metals as used herein is intended to mean the following elements either singly or in combination: cerium, lanthanum, neodymium, praseodymium, samarium, illinium, europium, gadolinium, dysprosium, ytterbium, their alloys and compounds.

These rare earth metals may be in the form of a mixture commonly known as misch metal. A mixture of rare earth metals which has proved particularly effective contains about 31.5% lanthanum, about 44.5% ceriurn, about 11% praseodymium, about 7% neodymium and about 6% of the other rare earth metals above mentioned.

The percentage of rare earth metals and boron additions is critical and must be maintained substantially within the ranges set out above.

It is also noted that the tempering temperature is critical inasmuch as it has been discovered that brittleness of the castings is caused by tempering at a temperature of about 700 F., and wear resistance of the castings is inadequate if they are tempered at a temperature in excess of 700 F. Under certain conditions, the tempering step may be eliminated entirely, although this is not ordinarily desirable.

It has been found that in manufacturing the steel alloy of this invention, the molten steel is preferably killed in the furnace as, for example, by adding a deoxidizer such as aluminum, ferromanganese, ferrochrome, silicomanganese and/ or ferrosil-icon. When the ladle is partly full, the steel is preferably further deoxidized, and then aluminum and titanium (if any) are preferably added, the aluminum being in an amount of the order of The boron and irrespective of sequence; and finally an addition of calcium silicon is made, preferably in an amount of the order of three pounds per ton of charge before the ladle is completely lled.

If the steel is produced in small quantities, as, for example, in an induction furnace, the additions may be made in the furnace prior to pouring of the heat.

It has been further discovered that, within the ranges above specified, the alloying elements are effective only if the addition is made to molten steel in a basic condition, and it may be noted that the alloying elements may be added to the ladle as the 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 a basic condition, and the steel and slag may then be poured into a second ladle wherein the alloying additions are made.

The unusual properties of steel castings produced in the foregoing manner are best demonstrated by referring to tests of castings which were composed and heat treated within the specified ranges. The results of these tests are set forth in the tables which appear hereafter and in the accompanying drawings, wherein:

Figure 1 lis a graph illustrating the eiect of tempering temperatures on the toughness of the novel steel alloy casting (about .25% carbon) at room temperature;

Figure 2 is a graph illustrating the effect of tempering temperatures on the toughness of the same steel alloy one to five pounds per ton of charge.

Vcastings at low temperatures of the-order of 40 F.;

Yorder of 1000" F. or more;

Figure 7 is a graph comparing the toughness of the 'i Y' novel steel alloy castings (about .26% carbon) with those of substantially identical steel castings produced and heat Block No. (ontreated in the same manner but lacking either boron or Vrrtilello rare earth metals;

Figure 8 is a graph showing the effect of tempering 7816 47 5 48 47 47u5 472 temperatures on the physlcalcharacteristics of the novel 7815l gng-g. eel alloy castings containing about .30% carbon; ggg 47;? 7h48-5jjjjjjjjj 472 Figure 9 is a graph showing the effect of tempering 7816 temperatures on the physical characteristics of the novel steel alloy castings containing about .25% carbon and about 1.0% -chromium and nickel.

Specific examples are disclosed as follows:

Example No. 1

Two heats were poured with the following analyses:

Heat No. C Mn Si P S Cr Mo Ni B Heat No. 7816 of the molten steel was killed in a basic lined induction furnace by adding 11/2 pounds of aluminum per ton of charge, then .0024% boron, then 2 pounds of the above descr' 19-18-18-19-.. 18. f 472 per ton of c l1a1ge, and 22 21 21 21 21o 46:5 manganese-slllcon per ton of charge. The boron was ggg ggg 251m 713 added in the form of a composition known as Borosil 816 411 21 20 22*22I 21 458 95 7 whlch` 1s a mixture made up prlmarily of about 3% ggg 5 1820*19 19- jf boron, about silicon, and the remainder iron, al- 781s 7 17.5 415 though other types of boron containing materials may 7816 23`22`2321- 22 385 781s 32-26-32-32 30.5 se be used 1f deslred. 7816 40-40-39-30 39.5 838 The molten steel of HeatNo. 7817 was killed in a ggg 5 basic lined induction furnace by adding 21/2 pounds of 40 7815 13 59 222 aluminum per ton of charge, then .0024% boron, added im 5 gg as BorosiL and nally 3 pounds of calcium-manganese- 7817 2,- 16 45s f srllcon per t0n of charge. ggg 4- 215 Both heats were poured into standard block test run- 7817 5 18.5 1go ners which were normalized and cut into sections 21/2 gg; s g1g g inches long. 7817 8--- 16.5 880 All sections were normalized by heating to 1750 F., ggg lo g' at which temperature value the sections were held for 7817 11 39 2 78 two hours. The sections were then air cooled and were ggg gli: hardened by heating to 1650 P., at which temperature value the sections were held for one hour followed by a Charpy results at *40 F. were as follows; water quench. The tempering heat treatment tor these y sections was as follows: Blnell Average R(F om oe. yel HCH) 7815 AQ 1.8 472 Heat and Block No. Temperature, Hold, Cooling 7816/7817 AQ F. hrs. 7816 3 22.5 472 m M 7815 4 21 458 100 2 Water quench. 20o 2 Do. t 300 2 D0 7816 7 14.5 415 400 2 DO- 7816 8 18.5 385 500 2 DO- 7810 9.- 19.5 855 600 2 Do- 7816 10 26.5 838 700 2 DO- 7815 11- 51.5 282 200 2 Do- 65 7816 12 08.5 24.4 900 2 Do. 5 1, 000 2 Do. 15' 4.58 1,100 2 Do. 15 4:8 1, 200 2 Do. l@ 5 s 11300 2 D0' 7817 15. 5 152 7817 12 440 7817 11 421 7817 12 405 7817 11.5 380 7817 1s 851 After heat treatment the sections were machined into gg; 34-37 3S 5 ggg four Charpy specimens. Hardness readings taken on 7817 12- 40-34 36-88 55.5 238 the tested Charpy specimens were as follows: 7817 13' 29`22`3Fr35 30' 220 The graphs shown in Figures 1-4 were derived from the foregoing data and illustrate relationships found to exist with respect to tempering temperatures, toughness, hardness and addition practice.

Referring to Figure 1, it will be seen that a brittle zone resulted from a tempering temperature of the order of 700 F., in the case of the novel steel alloy containing rare earth elements and boron (Heat No. 7816) as illustrated by the top line in this graph. The sections heat treated at temperature values above 700 F. were found to have inadequate resistance to wear due to the low hardness values shown in Figure 4. Referring again to Figure l, it will be seen that the best results with respect to toughness were achieved by tempering temperatures between 300 and 400 FL, although very good results in this regard were attained by tempering temperatures below 600 F.

Referring to Figure 2, it will be seen that a low temperature brittle zone resulted from a tempering .temperature of 700 F. in the case of the novel steel alloy containing rare earth elements and boron (Heat No. 7816) illustrated by the upper line of the graph. The best results in this regard resulted from tempering temperatures between 3,00 and 400 F., although good results were attained at temperatures below 600 F.

As illustrated by both graphs of Figures 1 and 2, the novel steel alloy (Heat No. 7816) Was greatly superior from a viewpoint of toughness than that to which the rare earth elements were not added (Heat No. 7817).

Referring now to Figure 3, it will be seen that a brittle zone was discovered in the novel steel alloy (Heat No. 7816) at a Brinell hardness of approximately 415. At greater hardness values than 415, toughness increased, with the best results from this viewpoint at a Brinell hardness of 440 or greater.

Referring now to Figures 5 and 6, it will be seen that Figure 5 illustrates the microstructure of a casting composed of the novel steel alloy magnified 600 times. The steel alloy casting of Figure 5 is composed of Heat No. 7816 normalized and hardened as above described, and tempered at 375 F. It will be noted, as seen in Figure 5, that the microstructure is fine, predominately in the form of tough interlocked martensitic needles. 'Ihe steel alloy casting shown in Figure 6 is also magnified 600 times7 and it will be seen that the martensitic needles are no longer plainly visible in the microstructure of Figure 6 due to the fact that this casting was tempered at about l000 F. or more. As a result the wear resistance of the steel alloy casting shown in Figure 6 is quite inferior to that of Figure 5.

Example No. 2

Heat No. 7773 was' treated in the molten state in accordance with the above described practice with 11/2 pounds `of aluminum per ton of charge, then 2 pounds of the rare earth metal mixture per t0n of charge, then .002.4% boron added in the form of Borosil, and

finally 3 pounds of calcium-manganese-silicon per ton of charge.

Heat No. 7719 was treated in the molten state by adding 21/2 pounds of aluminum per ton of charge, then .0024% boron addedA as BorosiL and finally 3 pounds of calcium-manganese-silicon per ton of charge.

Heat No. 7718 was treated in the molten state by adding 11/2 pounds of aluminum per ton of charge, then 2 pounds of the rare earth metal mixture per ton of charge, and finally 3 pounds of calcium-manganese-silicon per ton of charge.

All three of these vheats were produced in basic lined induction furnaces, and the addition practice was identical except for the fact that the rare earth metal mixture was eliminated from Heat No. 7719 and boron was eliminated from Heat No. 7718.

Steel from these heats1was poured into test runners from ll x 6" x 10 Charpy blocks. All runners and the Charpy blocks were normalized at 1750 F. for 2 hours. The runners were machined into plugs and inserted into 5" Charpy blocks. All blocks were then hardened by .heating to 1650u F., holding one hour and water quench- Heat and Block No. Tempera- Hold, Cooling ture, F. hours 7773-10, 7719-IC 7718-IC 1,000 2 water quench. 7773-IX, 7719-Dix, 7718-1X 1, 050 2 Do. 7773-IA, 7719IA, 7718-IA.. 1, 2 D0. 7773-20, 7719-20, 7718- 1, 100 2 D0. 7773-2X, 7719-2X, 77l8-2X l, 165 2 Do. 7773-2A, 7719-2A, 7718-2A 1, 210 2 D0. 7773-50, 7719-5C 7718-5C. 1, 120 2 Do. 7773-5X, 7719-5x, 7718-5X 1,185 2 D0. 7773-5A, 7719-5A, 7718-5A-. 1, 250 2 D0. 7773-8() 1, 120 2 D0. 7 773-8X- 1, 185 2 D0. 7 773-8A.. 1, 250 2 Do. 7719-8C-- 1,120v 2 Do. 7719-8 1,185 2 Do.

After iinal heat taken from slices of Heat and Rockwell C Readings Center to Surface Block No.

Charpy specimens were machined from the plugs and fromV the 5 inch Charpy blocks, and the results when tested at 40 F. were as follows:

Heat and Location of Notch Foot Pounds Avg. Average Block No. -40 F. Brinell 7773-5C l from surface 50-51-5454 from s11rfaee g--ii 53'4 287 rom sur ace 6 -60-65- l g4 g2gg4 6 62.9 261 9- y 7-7 7719-5o i inzqig 70.3 241 i2%ffromsurrace.... 3s-4o-4339 i 38'5 279 7719-5X 1" from surface 37-40-40-40 41 2 25S 2% from surace 43-43-43-43 7719-5A {V' from surface 44-444345 44 0 23S 2% from surfaee. 44--44-45-44 7718-5C {V from surface... 22-23-23-25 20 0 272 2%" from surface 18-19-16-14 7718-5X {1 from surface. 36-38--40-33 l 33 2 2K5 2% from surfe 30-33-28-27 l 7718-5A l1 from surface 39-48-49-44 42 6 229 2% from surfaee 37-42-41-41 Example No. 3

A basic lined inductionr furnace heat was produced in accordance with the following table:

1650 F. followed by a water quench after one hour hold at temperature and were then tempered for two hours by heating to various temperatures followed by a water quench. The tempering temperatures used were vselected to give a hard ess range from 250 to 500 Brinell in increments of approximately 50 points Brinell. All pull bar specimens were aged for 24 hours at 250 F. Th following table lists the mechanical properties of boron in the form of that tests at 40 F. disclosed a brittle zone for the samples tempered at 700 F., and the samples'V tempered at 550 F. or less were much tougher atV -40 F. than those tempered at temperatures between 600 and 800 F. Furthermore the Brinell hardness of samples tempered above 700 F. indicate unsatisfactory resistance to wear'.

Example N0. 4 A 200 pound basic induction furnace heatof the novel 10 steel alloy having the composition shown inl the following table was produced in the usual manner:

The heat was deoXidized by adding 11/2 pounds of aluminum per ton. Following the deoxidization, 2 pounds of the rare earth metal mixture per ton and .0027% Borosil were added. Finally 3 pounds of calcium-manganese-silicon per ton were added.

Runners cast from this heat were normalized by heating to 1750 F. After atwo hour hold at temperature, the runners were softened at 1250 F. for two hours and were then air cooled. The runners were then water quenched from 1650or F. after a one hour hold at temperature aridwere then tempered by holding for two hours at various temperatures followed by a water quench. The` tempering temperatures used were selected to give castings obtained from this heat: hardness range from approx1mately 250 to 450 Brinell Charpy Impact, Heat Tempering Yield Tensile Elonga- Red. of Ft. Lbs. N o. Serial N o. Tempera- Strength Strength tion, Per- Area, Per- BHN ture, F. (p. s. i.) (p. s. i.) cent cent Rm. T. F.

1 250 198, 750 24S, 500 10. 0 31. 5 18-17 13-16 514 2 250 219, 000 246, 000 9. 5 29. 8 17-17 15-15 514 Average 250 208, 875 247, 250 9 75 30. 7 17. 25 14. 75 514 3 350 195, 000 239, 500 9. 5 31. 2 17-16 16-17 495 4 350 195, 000 235, 500 9. 0 30. 2 18-19 16-16 495 Average 350 195,000 237, 500 9. 25 30. 7 17. 25 16. 25 495 5 550 195, 000 224, 000 9. 5 31. 8 12-13 13-9 444 6 550 195, 000 224, 500 10. O 29. 8 11-12 13-13 444 Average 550 195, 000 224, 250 9. 75 30. 8 12. 00 l2. 00 444 l 7 750 188, 000 204, 500 11.0 33. 8 14-14 10-10 429 9203 8 750 189, 000 204, 500 10. `5 33. 8 15-13 7-10 429 Average 750 188, 500 204, 500 10. 75 33. 8 14. 00 9. 25 429 9 950 164, 000 177, 500 13. O 37. 0 26-26 16-17 388 l0 950 167, 500 178, 00D 13. 0 35. 7 26-27 16-16 375 Average 950 165, 750 177, 750 13. 0 36. 4 26. 25 16. 25 382 11 1, 050 1,50, 000 161, 500 15. O 44. 9 35-35 30-31 352 12 1, 050 149, 500 161., 500 15. 5 47. 5 36-36 29-27 352 Average l, O 149, 750 161, 500 15. 3 46. 2 35. 50 29. 25 352 13 1, 250 99, 000 117, 000 2l. 0 58. l 63-65 57-59 248 14 1, 250 100, 000 119, G00 21. 5 57. 0 6965 65H36 255 Average 1, 250 99, 500 118, 000 21. 3 57. 6 65. 50 61. 75 252 The data of the foregoing table in connection with Heat No.` 9203 is presented graphically in Figure 8, which emphasizes the effect of tempering temperature on the mechanical properties of the steel alloy. lt may be noted Temperng Temperature, F.

Serial No.

4 Average 1 5 800 Averag; 800

8 Average 9 10 Average l l 12 Average 1, 250 95,-500 115, 250 76. 8 71. 8

1 Detective bar. Not included in average data for Figure 9.

ing table lists the mechanical properties obtained from this heat:

Charpy Im pact, Yield Tensile Elonga- Red. of Ft. Lbs. Strength Strength tion, Per- Area, Per- (p. s. i.) (p. s. i.) cent cent Rm. T 40 F 181, 500 228, 000 9.0 32. l 27-22 23-20 183, 000 230, 500 9. 0 33. 4 24-24 22-25 182, 250 229, 250 9. 0 32. 8 24. 3 22. 5 No Bar No Bar No Bar N o Bar 27-26 27-23 186, 500 228, 000 11. 5 35. 0 20-27 22-24 186, 500 228, 000 11. 5 35. O 25. 0 24. 0 180, 000 188, 000 l1. 5 35. 7 l9-21 17-16 182, 500 190, 000 9. 5 27. 8 21-20 13-12 180, 000 188, 000 11. 5 35. 7 20. 3 14. 5 161,000 167, 500 13. 5 43. 1 3836 22-22 157, 000 168, 000 13. 5 4l. 6 39-39 22-23 159, 000 167, 750 13. 5 42. 4 38. 0 22. 3 109, 000 126, 500 19. 0 56. 0 64-67 (5460 110, 000 126, 500 2l. 5 57. 5 66-64 58-60 109, 500 126, 500 20. 3 56. 8 65. 8 60. 5

The effect of the tempering temperatures on the physical properties of the novel steel alloy is graphically depicted in Figure 9, wherein it will be seen that tempering ternperatures below 700 F. resulted in specimens having a Brinell hardness of 400 or more and having Charpy values of 20 or more foot pounds at room temperature and 15 or more foot pounds at -40 F. Tempering temperatures substantially above 700 F. resulted in inadequate resistance to abrasion because of the low Brinell hardness values shown in Figure 9. At 40 F. a brittle zone resulted from tempering temperatures above 700 F. and below 900 F. The brittle zone at room temperature was not so pronounced in the case of this heat; however, it is noted that the lowest Charpy values at room tempera- .ture occurred for specimens tempered at temperatures between 600 and 750 F. As above noted, tempering .temperatures below 700 F. resulted in satsifactory Charpy values at room temperature and at -40 F. and also resulted in satisfactory Brinell hardness of 400 or more.

Specimens cast from this heat and tempered at values between 250 to 500 F. were unusually excellent in that Charpy values at room temperature and at 40 F. were 20 or more foot pounds and Brinell hardness values were 430 or higher.

Example No. 5

Three 200 pound induction furnace heats were poured having the following analyses:

Serial Heat C Mn Si P S Cr M Ni B No. No.

The deoxidation practice and the additions of rare earth metals and boron, and calcium-manganese-silicon were substantially the same as those discussed in connection with previous heats.

- teeth indicating ductility Five dipper teeth castings were poured from these heats and were normalized by heating to 1750 F. and holding for two hours followed by air cooling. The hardening treatment consisted of heating the teeth to 1650 F. with a one hour hold at this temperature. This was followed by a water quench until the castings were at a temperature of about 200 F. riihe castings were then reheated to the tempering temperature of about 400 F. with a two hour hold, again followed by a water quench. Brinell hardness readings were taken on the cope side of each casting with the following results:

Casting, Serial No.: Brinell 25 534 26 534 27 540 28 534 30 534 These castings were utilized in conventional clipper buckets and were subjected to trial service in the mining of taconite ore, an unusually severe type of service in which prior art teeth were worn to a condition which required replacement loadings. The novel steel alloy teeth `did not require replacement prior to 533 truck loadings and were ultimately removed to prevent wearing on a new, wider tooth holder placed in service after the novel teeth had been submitted for tests. According to conservative estimates, approximately 100 additional truck loadings would have been possible if the novel steel alloy teeth had been in use for the full service life thereof.

After removal of these novel steel alloy teeth, visual examination thereof indicated no evidence of spalling, cracking, or bending, and a slight amount of metal flow after service of about 300 truck' was observed on the edges of both faces and on the edges of the holder sockets on the sides of the novel thereof, even at the high hardness values above described.

Microscopic examination of the teeth after removal from service disclosed a hard white layer of untempered martensitic structure created by heating the surface to its upper critical temperature of about l500 F. and subsequent rapid cooling, due to the service co-nditions to which the teeth were subjected. Beneath this layer the teeth were formed of the low tempered martensitic structure illustrated in Figure 5.

Example N o. 6

having the following composition:

The heat was killed in the furnace by adding ferromanganese in an amount sufficient to bring the manganese content about equal to that stated above. The following additions were then made in the ladle: ferrosilicon in an amount to increase the silicon content to about .28, then 3 pounds of aluminum per ton of charge, then l pound of high carbon ferrotitaniurn per ton of charge, then 11/2 pounds of the above described rare earth metal mixture per ton of charge, then .0035 percent by weight of boron in the form of Borosil and finally four pounds of calcium-manganese-silicon per ton of charge.

The castings were normalized by heating to about 1750 F. with a two hour hold at that temperature followed by air cooling to about room temperature. The castings were then hardened by heating them to about 1650 F. with a one hour hold at that temperature followed by a four minute hold in air at room temperature and then a water quench to about 15G-200 F. The castings were then immediately placed into a tempering furnace and heated to about 300 F. with a two hour hold at that temperature followed by a water quench to room temperature.

These teeth had a service life of about 913 truck loadings as compared with the average of 300 truck loadings for prior art teeth. Brinell hardness readings were taken on two of the teeth before and after removal from service with the following results:

It will be understood that certain of the following 4claims recite certain percentages of the rare earth metals; however, it will be understood that the exact amount of such metals in the casting cannot be accurately measured and the amounts stated in the claims refer to the residue from the treatment of the molten metal with the amounts of rare earth metals recited by the claims. It is also noted that the term iron in the claims includes residual impurities in ordinary amounts, such as, for example, aluminum, titanium, calcium, copper, lead,l tin and others.

We claim:

1. A steel alloy casting composed of: about .20 to .50% C, about .15 to 2.5% Mn, labout .1 to 2.00% Si, nil to about .025% P, nil to about .025% S, about .50 to 1.50% Cr, about .05 to .70% Mo, residual to 1.00% Ni, about .0005 to .005% B, about 0.0015 to 0.5%

Ten `steel alloy dipper teeth were cast from `a heat rare earth metals, the balance-iron, said casting having an internal structure produced by normalizing at 1600 to 1900 F. followed by air cooling, then heating to about 1500 to 1650" F. followed by a quench, then heating to about 200 to less than 600 F. followed by another quench, and said casting being characterized by the properties of a Brinell hardness value of at least 444, and a Charpy impact value of at least 12 foot pounds at 40 F.

2. A steel alloy casting composed of: about .2O to .50% C, about .15 to 2.5% Mn, about .l to 2.00% Si, nil to about .025% P, nil to about .025% S, about .50 to 1.50% Cr, about .05 to .70% Mo, residual to 1.00% Ni, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, yabout .0005 to .02% Ti, the balance iron, said casting having an internal structure produced by normalizing at 1600 to 1900 F. followed by air cooling, then heating to about 1500 to 1650 F. followed by a quench, and then heating to about 200 to less than 600 F. followed by another quench, and said casting being characterized by the properties of a` Brinell hardness Value of at least 444, and a Charpy impact value of at least 12 foot pounds at 40 F.

3. A steel alloy casting composed of: about .20 to .50% C, about .15 to 2.5% Mn, about .1 to 2.00% Si, nil to about .05% P, nil to about .05% S, nil to about 5.00% of the group consisting of Cr, Mo, and W, nil to about 4.00% Ni, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, the balance iron, said casting having a Brinell hardness value of 444 or more and having a Charpy impact value of the order of at least 12 foot pounds at 40 F.

4. A steel alloy casting composed of: about .20 to .50% C, about .15 to 2.5% Mn, about .1 to 2.00% Si, nil to about .05% P, nil to about .05% S, nil to about 5.00% of the group consisting of Cr, Mo, and W, nil to about 4.00% Ni, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, `about .0005 to .02% Ti, the balanceimm said casting having a Brinell hardness value of 444 or more and having a Charpy impact value of the order of at least 12 foot pounds at 40 F.

5. A steel alloy casting composed of: about .20 to .50% C, about 1.35 to 1.55% Mn, about .1 to 2.00% Si, nil to abo-ut .020% P, nil to about .020% S, about .52 to .68% Cr, about .47 to .53% Mo, Ni in residual amount, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, the balance iron, said casting being characterized by an internal structure having plainly visible martensitic needles produced by a heat treatment at about 1600-1900 F., then air cooling, then another heat treatment at about l500-1700 F., followed by a quench, and then a tempering heat treatment at about 100-400C F. followed by another quench, and said casting being characterized by the properties of Brinell hardness of about 444 or more and a Charpy impact value of the order of 15 foot pounds or more at 40 F.

6. A steel alloy casting composed of: about .20 to .50% C, about 1.55 to 1.75% Mn, about .l to 2.00% Si, nil to about .020% P, nil to about .020% S, about .70 to .90% Cr, about .47 to .53% Mo, Ni in residual amount, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, the balancehom said casting being characterized by an internal structure having plainly visible martensitic needles produced by a heat treatment at about 1600- 1900 F., then air cooling, then another heat treatment at about 1450-1650" F., followed by a quench, and then a tempering heat treatment at about 20D-600 F., followed by a quench, and said casting being characterized by the properties of a Brinell hardness of about 444 or more and a Charpy impact value of the order of 12 or more foot pounds at 40 F.

7. A steel alloy casting composed of: about .20 to .50% C, about 1.25 to 2.5% Mn, about .1 to 2.00% Si, nil to about .020% P, nil to about .020% S, about .90

ld to 1.10% Cr, about .50 to .65% Mo, about .90 to 1.10% Ni, about .0005 to .005% B, abo-ut 0.0015 to 0.5% rare earth metals, the balance -:`ron, said casting having an internal structure produced by a hardening heat treatment at about 1500-1700" F. followed by a quench, and then a tempering heat treatment at about 20G-600 F. followed by another quench, and said casting having the properties of a Brinell hardness of about 444 or more and a Charpy value of about 15 foot pounds at 40 F.

8. A steel alloy casting composed of: about .20 to .50% C, about .l5 to 2.5% Mn', about .1 to 2.00% Si, nil to about .020% P, nil to about .020% S, about .l to 2.5% Cr, about .05 to 2.5% Mo, about 0 to 4.0 Ni, about .0005 to .005% B, about 0.0015 to 0.5 rare earth metals, about .0005 to .02% Ti, the balance-iron, said casting having an internal structure produced by a normalizing heat treatment atr about 1600-1900` F., followed by air cooling, then a hardening heat treatment at about 14501700 F., and then a tempering treatment at about 20G-600 F. followed by another quench and having the property of a Brinell hardness value greater than about 444.

9. A steel alloy casting composed of: about .35 to .50% C, about 1.35 to 2.5% Mn, about .1 to 2.00% Si, nil to about .020% P, nil to about .020% S, about .60 to 2.5% Cr, about .45 to 2.5% Mo, about 0 to about 4.0% Ni, about .0005 to .005% B, about `0.0015 to 0.5% rare earth metals, the balanceimm said casting having an internal structure produced by a normalizing heat treatment at about 1600-1900 F. followed by air cooling, then a hardening heat treatment at about 0-1700" F. followed by a quench, and then a tempering heat treatment at about 20D-600 F. followed by another quench, and said casting having a Brinell hardness value of at least about 500.

10. A steel alloy casting .5% C, about 1.25 to 1.40% nil to about .020% P, nil to about .020%/S, about .70 to 1.05% Cr, about .50 to .65% Mo, about .90 to 1.00% Ni. about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, the balance iron, said casting having an internal structure produced by a hardening heat treatment at about 1600l700 F. followed by a quench, and then a tempering heat treatment at abo-ut ZOU-600 F. followed by another quench, and said casting having a Brinell hardness of at least about 444.

11. A steel alloy casting composed of: about .20 to .5% C, about .15 to 2.5% Mn, about .1 to 2.00% Si, nil to about .020% P, nil to about .020% S, about .70 to 1.05% Cr, about .50 to .65% Mo, about .90 to 1.00% Ni, about .0005 to .002% B, about 0.0015 to 0.5% rare earth metals, about .0005 to .02% Ti, the balance-iron, said casting having an internal structure produced by a hardening heat treatment at about 1600-1700 F. followed by a quench, and then a tempering heat treatment at about ZOO-600 F. followed by another quench, and said casting having a Brinell hardness of at least about 444.

l2. A steel alloy casting composed of: about .20 to .5% C, about 1.30 to 1.60% Mn, about .l to 2.0% Si, nil to about .05% P, nil to about .07% S, about .50 to .70% Cr, about .40 to .60% Mo, Ni. in residual amount, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, the balance-iron, said casting being characterized by an internal structure having plainly visible martensitic needles produced by a heat treatment at about 1500-1700" F., followed by a quench, and then a tempering heat treatment at about 20G-600 F., followed by another quench, and said casting being characterized by the properties of a Brinell hardness value of about 444 or more and a Charpy impact value of the order of 15 or more foot pounds at 40 F.

13. A steel alloy casting composed of: about .20 to .5% C, about 1.30 to 1.60% Mn, about .1 to 2.0% Si, nil to about .05% P, nil to about .07% S, about .50

composed of: about .20 to Mn, about .1 to 2.00% Si,

l5 to .70% Cr, about .40 to .60% Mo, Ni in residual amount, about .0005 to .005% B, about 0.0015 to 0.5% rare earth metals, the balance-iron, said casting being characterized by an internal structure having plainly visible martensitic needles produced by a heat treatment at about l500-l700 F., followed by a quench, and then -a tempering heat treatment at about 200-600" F., followed by another quench, and said casting being characterized by the properties of a Brinell hardness value of about 444+ or more and a Charpy impact value of the order of 20 or more foot pounds at -40 F.

14. In a method of treating molten steel in a basic condition, the steps of rst deoxidizing the steel and reducing soluble nitrogen in the steel to a value not substantially greater than the order of about .008% by adding titanium in an amount of the order of .0005 to .02% and then, irrespective of sequence, adding boron in an amount of the order of .0005 to .005% and rare earth metals in an amount of the order of 0.0015 to 0.5%.

15. In a method of producing wear resisting steel, the steps of killing a bath of molten basic steel comprising: about .20 to .50% C, about .15 to 2.5% Mn, about 0.1 to 2% Si, nil to about .05% P, nil to about .07% S, nil

16 to about 5.00% of one or more of the group consisting of Cr, Mo, and W, nil to about 4% Ni, the balance-iron, pouring the metal into the ladle and while pouring, making the following additions in the order specified: ferromanganese and/ or ferrosilicon and about 1 to 5 pounds of aluminum per ton of charge, then adding titanium in an amount of about .0005 to .02% of the charge and then, irrespective of sequence, adding boron in an amount of the order of .0005 to .005% of the charge and rare 10 earth metals in an amount of the order of 0.0015 to 0.5% o-f the charge.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Transactions, American Society for Metals, vol. 28, page 618. Published in 1940 by the American Society for Metals, Cleveland, Ohio.

Claims (1)

1. A STEEL ALLOY CASTING COMPOSED OF: ABOUT 20 TO .50%C, ABOUT .15 TO 2.5% MN, ABOUT .1 TO 2.00% SI, NIL TO ABOUT .025% P, NIL TO ABOUT .025% S, ABOUT .50 TO 1.50% CR, ABOUT .05 TO .70% MO, RESIDUAL TO 1.00% NI, ABOUT .0005 TO .005% B, ABOUT 0.0015 TO 0.5% RARE EARTH METALS, THE BALANCE-IRON, SAID CASTING HAVING AN INTERNAL STRUCTURE PRODUCED BY NORMALIZING AT 1600 TO 1900*F. FOLLOWED BY AIR COOLING, THEN HEATING TO ABOUT 1500 TO 1650*F. FOLLOWED BY A QUENCH, THEN HEATING TO ABOUT 200 TO LESS THAN 600*F. FOLLOWED BY ANOTHER QUENCH, AND SAID CASTING BEING CHARACTERIZED BY THE PROPERTIES OF A BRINELL HARDNESS VALUE OF AT LEAST 444, AND A CHARPY IMPACT VALUE OF AT LEAST 12 FOOT POUNDS AT -40*F.

Images