US2295706A - Alloy for treatment of steel - Google Patents

Description

Sept. 15, 1942. G. F. cams'rocx ALLOY FOR TREATMENT OF STEEL Filed June 17, 1941 XXN,

...... .-llv'lHll/lll l. .lll. 5.115..: '2l-ll ln/ lll 'l i!!! j .h All .l v.. Il N x f A Y d nur lvl v l 1 m f fr f l f, .u l .f Il .JV/ l1l|||| ...hl a l' d x X IVENTOR i @M5/'ack ATT Patented Sept. 15, 1942 v UNITED STATES PATENT OFFICE l mesme George F. Comstock, Niagara Falls, N. Y., assignor to The Titanium Alloy Manufacturing'company, New York, N. Y., a corporation ot Maine Application June 11, 1941., Serial No. 398,425 4 calms. (o1. 'z5-ss) This is 'a continuation-impart of my copending application Serial No. 353,918, flled August 23, 1940.

This invention relates to alloys for use in deoxidizing steel or cast iron, and more particularly to such alloys containing titanium, boron. and aluminum, and at least one element of the group manganese, silicon, ironzirconium and calcium.

Structural or forging steel of fine grain-size, or so treated in manufacture that its grain structure remains fine even though heated to such temperatures as would cause other steel. to become coarse-grained, has well recognized advantages that make it desirable for many uses. Some of these advantages, which'may occur separately or simultaneously, are superior ductility in a given condition of heat-treatment, a better combination of strength and ductility, higher elastic limit or yield point, and greater resistance to impact or shock. 'I'he hardenability of such :ne-grained steel, however, is generally lower than that of similar steel of coarser grainsize. For many, uses high hardenability is desirable, since steel having that property does not require such rapid cooling to develop a given hardness, that is, it permits the treated steel to become hard under moderate quenching treatments. As drastic quenching treatments may be harmful to other desired characteristics of treated steel, and are difficult to accomplish with large pieces of steel, it is seen that the ability to harden without requiring such drastic quenchings is very desirable. Thus, it is much easier to harden thicker and heavier parts of such steel which will not cool very rapidly, even though quenched in a rapid and voluminous stream of cold water. l

The treatment of molten steel shortly befor casting with such deoxidizing agents as aluminum, titanium and zirconium, either separately or in combination, is well known to be an effective means of producing fine-grain characteristics in the steel. This treatment, however, does not generally improve the hardenability of the steel. The addition of small amounts of boron has been found to definitely increase the hardenability of a given steel, but its addition as ferroboron, even when accompanied by a grain-reilning amount of aluminum, separately added, tends to coarsen the grain size.

In accordance with the present invention, it has been foundthat both fine-grain characteristics and high hardenability may be conferred on the same steel by adding thereto a deoxidizing and aluminum, and preferably also containing.

manganese, silicon and iron. Theuse of such an alloy has been found to confer many of the beneilcial. characteristics not obtainable when the l as separate ferro-alloys. Of especial importance,

as pointed out above, is the fact that fine grainsize and improved hardenabllity cannot be obtained in thersame piece of steel by separately adding aluminum (the element normally used to secure'iine grain size) and boron (the'element used to secure improved hardenability) In previous practice, in fact, it wasV not thought possible to secure both these characteristics in high degree in the same piece of steel. i

Alloys suitable for use in the practice of this invention may contain from about 0.25 to 5% boron,.5 to 25% each of titanium and aluminum, and the balance iron with up to 10% zirconium, up to 30% manganese, up to 40% silicon, up to 5% calcium, up to 3% carbon, and small amounts oi phosphorus, sulfur, copper and other impurities. The titanium and aluminum contents should each be at least two or three times the boron content. 'I'he presence of manganese, silicon and calcium in the alloy is benecial but not essential for the purpose of simultaneously improving the hardenability and securing fine grain characteristics in -the steel. Preferably, the

amount of manganese is 5 to 30%, and of silicon 10 to 40%. The relative proportions of titanium and aluminum are also important, as the presence of too much aluminum in excess of the titanium causes the steel to be dirty due to the inclusion of aluminum oxide; and the presence of too much titanium in excess of the aluminum causes the steel tobe coarse-grained, unless excessive amounts of the alloy, such as will give comparatively large residual titanium contents in the steel, are used. Accordingly. the amount of titanium preferably does not exceed twice the amount of aluminum, and preferably should not 'be more than half again as much. Likewise, the

amount of aluminum preferably does not exceed twice the amount of titanium, and preferably alloy containing,l in combination, titanium, boron should not be more than half again as much.

' Veryvsmall amounts of boron are sufficient to produce a significant eifect on the hardenability of quality, so that the amount of boron should be less than Finally, iron usually comprises a substantial percentage of the alloy,` and may be varied considerably, depending upon the concentration of 5 age, but is kept as low as conveniently possible,

and is preferably less than 3 In the preparation of these alloys, aluminum is usually added as such. The silicon and manganese may be added as Silico-manganese, and

the titanium as ferro-titanium. The boron is conveniently added `as borax to the slag formed in the manufacture of .the alloy, as the aluminum in the alloy reduces boron from such a slag. The calcium, if present, may be incorporated into these alloys either by direct reduction from a slag of high lime content, or preferably by adding the metal or one of its metallic compounds, `such as calcium-silicide, toa previously formed melt containing the other ingredients. The invention is not limited to any particular method of manufacture, however.

In the use of these alloys, they are added to molten steel in well known fashion. Generally, the amount of boron which should be added to steel by the usevvof the present alloys should be 0.001 to 0.01%, the amount of titanium 0.01 to 0.1%, and the amount of aluminum also 0.01- to 0.1%. Additional aluminum may also be added as a separate alloy addition, sufllcient to bring the total aluminum addition to 0.05 to 0.15%, but to secure the necessary` fine grain characteristics at least one quarter of the added aluminum must come from the titanium-boron-aluminum alloy of the present invention.

. The following table illustrates typical compo- 4* sitions of alloys in accordance with the present invention:

Tanz.: I

Example number 2. 19 l. Zi 8. 28 9. 00 10. 18 l1 14 15 20 l9 41. 6 42. 5

The eect of these alloys on the hardenability of steel may be demonstrated by Jominys method. This method involves quenching the test specimen at one end only, according .to a definite procedure, and then measuring the hardness at different distances from the quenched end. For this demonstration a series of steels containing about 0.4% carbon and 1.8% manganese was prepared as follows: vThe basic charge for each heat was 10 pounds Armco iron and 6 pounds of clean low=l carbon sheet steel scrap. When melted, this charge was deoxidized with 15 grams of 50% ferrosilicon and about 500 grams of pig iron was .then added to give the desired carbon content. In the rst two heats all this pig iron was the regular foundry grade, rather high in phosphorus and silicon'. When it was foundthat heat No. 2 contained 0.042% phosphorus and 0.028% sulphur, half the pig iron addition in subsequent heats was made in the form of a lower phosphorus iron, and in heat No. 3 the phosphorus content was down to 0.032%. This same charge was used for all the other heats. After the pig iron was dissolved, additions of ferrosilicon and 80% high-carbon ferromanganese were made to provide the proper amounts of those elements, and aluminum was added two minutes later. One minute later a special deoxidizer was added .to each heat, the composition of the special deoxidizers used being shown in Table II below. Two minutes later the steel was poured into the ingot mold. The ingots were rolled into 78 inch rounds,\which were cut into suitable lengths for test specimens before heat-treatment.

TABLE II Composition and deozidatzon of the steels used Chemical analy- Alumi- Speciaideoxidizer added a s1s, percent num p proximate composition C Heat No' agg??? Gms'. omitted unless over 1 per- C Mn Si cent and Fe omitted) .4o 1.75 .27 3 16 mgty'r,i 114% A11, 24% Mn, .414 1.84 .27 3 16 3.7% A1,'24.6% Mn,

1. .464 1.82 .26 3 25 9% Ti-11% .41, 14% Mn, 42 175 26 3. 20% s1,1.5% 06,15%13. 25 1o?8 T1, 5.722%' AC1, 13.6% Mn,

. l, .404 1.79 .14 3 12 15.5% "111, 9% 141.25% V. .396 1.86 .16 s 16 35.6% zr, 24.3% A1,4.8% s1. .398 1.74 .16 5 16 26.7% mi, 11S1.2% A1, 38.5%

n, l. 1o 26.7% Ti, 16.2% A1, 88.3% .394 1.84 16 3 10 14MB' 117 S- o .364 1.78 .27 6 16 37.317 zr, 117 11,3737 si. .396 1.80 .22 6 16 2O.7%T1,32.1%S1,25.4'% cr. .402 1.80 .24 12 19.3767g rk/115.8% A1, .5% si,

. 0 0. 1o 10.67 '1159.117 M6. .364 1.84 24 3 1o msyy'i, 21.1%7 A1, 2.7% si, .464 1.87 25 3 '12 15.570'11'97 .41,2517 v. .402 1.87 26 3 16 35.6% zrI243% A1,.s% si.

per net ton.

, tests were made on strips ground ilat about lf3 inch wide on-opposite sides ot the 1% inch diameter test specimens. Hardness tests were made on both sides of each bar, and the results were averaged to obtain the values reported in Table III below, and plotted in. the accompanying graph. Tenu.' DI

Rockwell C. Hardness of specimens quenched from 1550 F. at one end only, according to Jominys method y Ht Inchesfrom quenched end tolocation oihardness test 54534942343027252423222120 545246342826242i222lm1019 56545344332826242i21 2l 21212) 56545245383l2825232221m19 54655260443835302625232221 5453524838343230292827262626 5663524942353331292827262625 55556351474136323028272726 5453604645403430282624232221 Some of the results of Table III are shown graphically in the drawing, in which the curve numbers refer tothe respective heat numbers of Table III.

' Heat Nos. 1 and 3 were deoxidized with alloys corresponding approximately to vExamples 1 and 3, respectively. The deoxidizers used in heats 2 and 4 were approximately the same as the deoxidizers of heats 1 and 3, respectively, except 4 that the boron was .omitted from heat 2, and was substituted by an equal amount of calcium in heat 4.

As many modiiications are possible within the scope oi.' this invention, it is not intended to be limited except as defined by the appended claims.

I claim:A

1. An alloy for deoxidizing steel and-iron, said4 alloy containing 0.25 to 5% boron, 5 to 25% titanium, 5 to 25% aluminum, 5 to 30% manganese, 10 to 40% silicon, andl the remainder being principally iron with a small amount of carbon and 'other impurities.

2. An alloy for deoxidizing steel and iron, said alloy containing r0.25 to 5% boron, 5 to 25% titanium, 5 to 25% aluminum, 5 to 30% manganse, 10 to 40% silicon, an appreciable amount up to 5% calcium, and the remainder being principally iron with a small amount of carbon and other impurities.

3. The method of treating forging steel to improve hardenability while maintaining line grain size and the superior physical properties produced thereby, comprising adding to the molten steel a small amount of an alloy containing0.25 to 5% boron, 5 to 25% titanium, 5 to 25% aluminum, 5 to 30% manganese, 10 to 40% silicon, and the remainder being principaly iron with a small amount of carbon and other impurities.

4. The method of treating forging steel toI improve hardenability while maintaining fine grain size and the superior physical properties produced thereby, comprising adding to the molten steel a small amount of an alloy containing 0.25 to5% boron, 5 to 25% titanium, 5 to GEORGE F. COMSTOCK.

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