US1975310A - Process of making ferrous alloys - Google Patents

Description

Patented Oct. 2, 1934 Gregory J. Comstock, Edgewood,

Firth-Sterling Steel Company,

Pa.,- assignor to McKeespoi-t,

Pa a corporation of Pennsylvania No Drawing.

Application December 5, 1932, Serial No. 645,754

This invention relates generally to ferrous al-- loys, and more particularly to alloy steels especially adapted formaking cutting or forming tools, dies, punches, and the-like, which combine 5 the desirable properties of exceptional cutting ability, extreme hardness, and great resistance to abrasion. I

In my application, Serial No. 551,547, filed July 17, 1931, there is disclosed a process of making ferrous alloys in which a hard metal carbide such for example as tungsten carbide is added to a ferrous alloy bath. When the alloy bath containing the tungsten carbide is cooled, a hard carbide constituent separates out and gives to the alloy its exceptional cutting ability, its extreme hardness after heat treatment, and its great resistance to abrasion. According to that application, the tungsten carbide or other carbide is added to a ferrous alloy bath after the bath has been formed, and preferably the addition of the carbide is made shortly before teeming, so that the carbide will not have the opportunity to thoroughly disseminate-throughout the bath, but I on the contrary, will have locally enriched carbide areas which act as nuclei for the reprecipitation of hard'carbid'es when the bath is cooled.

in accordance with the present invention, the .hard carbide is added with the other constituents which go to make up the charge and the charge containing the hard carbide is then melted. In the preferred manner of practicing the invention, all of the constituents which are used in the charge are in powdered form; In the case of relatively light carbides such as titanium carbide, it is sometimes desirable tocompact the carbide into billets and to make a charge of the billets, together with the remaining constituents of the ferrous alloy, it being preferred to have the reov maining constituents in powdered form and to place the billets at the bottom of the charge. In this way the billets are helddown by the heavier constituents until a bath is formed. I

The hard metal carbides which may be used as a part of the original charge for forming the alloys are tungsten carbide, chromium carbide, molybdenum carbide, vanadium carbide, titanium carbide. tantalum carbide, zirconiumcarbide,

- thorium carbide, uranium carbide, and colum- 5o bium carbide. One or more of these carbides may be mixed with the remaining constitilents required to form the particular ferrous alloy. The charge is then melted,'preferably under sub-, tantially non-oxidizing conditions, and then l5 cast either by pouring it into a mold or by allowcontaining tungsten, cobalt. A powdered mixture is'made containing ing it to solidify in the melting vessel. As the alloy cools, a carbide constituent separates out and this constituent differs from the ordinary carbides which are produced according to the usual steel making processes in which either a ferro alloy of the alloying metal or the alloying metal per se is added to the steel bath, and the alloying metal carbide is formed upon'cooling, In other words, where tungsten carbide, for example, forms a part of a charge which is then 66 melted and cast, the timgsten containing carbide which separates out upon cooling differs from the carbide which would separate out if the tungsten had been added to a steel bath in the form of metallic tungsten or ferro tungsten and the tung- 70 sten had combined with carbon supplied to the bath in some other form than as the carbide. The use of a hard metal carbide either as a part of the original charge, as in the present application, or as an addition to a bath of a ferrous alloy, as in my prior application above referred to, results in the precipitation of an unusual carbide when the alloy is cooled. J

The present process may be employed in the following manner to produce a high-speed steel l0 chromium, vanadium, and

by weight "about 10% tungsten carbide, 25% tungsten, 4% chromium, 1% vanadium, 20% cobalt, and 40% iron. Each of these materials is in powderedform. The tungstencarbide may be produced in powdered formby carburizing a mixture of tungstic oxide or tungsten in pow- .dered form and carbon. The metallic tungsten may be obtained by reducing. the oxide with hydrogen. The iron is used in the form of hydrogen reduced iron powder. The cobalt may be formed by powdering, metallic cobalt. The chromium;and vanadium are used in the form of powdered ferro chromium and. term vanadium.

This powdered mixture is then melted and then' either poured into molds or allowed to cool in the furnace. The melting may be done in any suit-- able furnace such as a crucible furnace or an 1011 electric furnace of the induction type which, due

t?) its construction, sets up a flow of the molten metal and eliminates the necessity f stirring.

The invention is applicable to theproduction of various ferrous alloys. In each case, however. irrespective of the particular type of alloy which it is desired to form, at least. one of the hard metal carbides above mentioned is present in/tliecharge, together with the remaining constituents required 'to form the alloy. A high-speed steel having the following approximate analysis may be made by the present process:

Balance iron with the usual impurities.

In this case the tungsten, chromium, vanadium, and iron are in the form of powders. At least one of the elements tungsten, chromium, and vanadium is in the charge as a carbide. That is, the charge may consist of;finely divided tungsten carbide, powdered ferro chromium, powdered ferro vanadium, and powdered iron, or it may consist of a mixture of more than one of the carbides of tungsten, chromium,'and vanadium, together with iron. powder. In all cases, however, at least one of the carbide forming elements is in the charge before melting in the form of a carbide, insteadof using all of the alloying elements in the form of the metals themselves or as ferro alloys. 7

Other ferrous alloys may be made ina similar manner by using in the charge'one or more of .the carbides of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, or columbium. Although it is preferred to 'have the remaining constituents of the charge which are; required to form the ferrous alloy present as powders, they may be in the forms. now commonly used in producing steel. As illustrativeof the types of ferrous alloys which may be made according to the present invention by the use of at least one hard metal carbide in the charge, the following examples are given:

EXAMPLE 2 A cobalt high-speed steel of the type which may be represented by the following analysis:

Per cent Carbon .75 Silicon -1. .25 1 Manganese .40

Sulphur .025 Phosphorus .040 Tungsten 18.00 Chromium 4.75 Vanadium 1.75 Molybdenum .75 Cobalt -2. 8.50

Balance iron with usual impurities.

EXAMPLE 3 Manganese steel of the type which may be represented by the following typical analysis:

Balance iron with usual impurities EXAMPLE 4 A high-carbon, high-chrome, steelof the typ Balance iron with usual impurities.

which maybe represented by the following typi cal analysis: i

Per cent Carbon 2.25 Silicon .30

Manganese .30 Sulphur .030 Phosphorus .030 Chromium 12.50 Balance iron with usual impurities.

EXAMPLE 5 7' A high-carbon, high-chrome, steel with molybdenum and vanadian present of 'the type which may be represented by the following typical analysis:

, Per cent Carbon 1.50 Silicon, .25 Manganese r .35 Sulphur .030

Phosphorus a .030 Chromium 12.50 Vanadium 1.00 Molybdenum 1.00 Balance iron with usual impurities.

' i EXAMPLE 6 So-called stainless steels and irons of the types which may be represented by the following typical analyses:

Type A Per cent Carbon .35 Silicon .20 Manganese .30 Chromium 13.50 Sulphur .030 Phosphorus .030 Balance iron with usual impurities.

yp B Per cent Carbon .65 Silicon --i .25 Manganese .35 Chromium 17.00 Sulphur .030 Phosphorus .030 Balance iron with usual impurities.

Type C Per cent Carbon .18 Silicon' .30 Manganese .40 Chromium -s 18.00 Sulphur .030 Phosphorus .030 Nickel 8.00 Balance iron with usual impurities. i

EXAMPLE 7 A chrome-vanadium steel of the type which may be represented by the following typical analysis:

. Per cent Carbon--- .40 5 Silicon .25 Manganese .25 Chromium -s 3.50 Vanadium .85

higher percentage of tungsten and Exulrts 8 An alloy having a composition between that of cast iron and a true steel:

Balance iron with usual impurities.

A portion of the exceptional cutting properties of high-speed steels is attributable to they presence of tungsten bearing carbides. In such alloys, tungsten bearing carbidesare formed only to a limited extent, the formation of this desirable constituent depending upon the amount of carbon and tungsten which can be added to the steel without seriously affecting the hot forging and forming properties of the alloy. As a general rule, a high-speed steel which contains more than 20% of tungsten and more than 1% of carbon cannot be hot-formed and shaped without producing a large percentage of defective material. 4

Heretofore this fact has limited the amounts of carbon and tungsten which could be added as such in the production of high-speed steel alloys. It would ordinarily be presumed that whether tungsten and carbon, as such, are added to a steel bath to form high-speed tool steel, or whether tungsten carbide is added, the amounts of tungsten and carbon which could be added without seriously aflecting the ability of the alloy to be hot shaped, would be the same. However, this is not the case for I have discovered that a much carbon can be used in the charge in the production of highspeed steels if the tungsten and carbon are added as tungsten '-carbide rather than in the form of ferro tungsten and carbon or metallic tungsten and carbon, and thcsteel will still be capable of being hot shaped. This condition, which would not be foreseen by one skilled in the art, enables me to produce high-speed steel which, because of the greater amounts or different character of tungsten bearing carbides which it contains, has properties which make it greatly superior to ordinary high-speed steels, withoutthe disadvantages which have previously been mentioned.

The percentage of hard metal carbide used in the charge may be varied within wide limits, depending upon the type of alloy which it is desired to produce. Some alloys will dissolve a greater percentage of tungsten carbide or other carbide than-will be dissolved by other alloys. It ordinarily is desirable touse as large a percenta'geof carbide as can be d lved or the ultimate desired composition will permit and which will still produce an alloy capable of being hot shaped or worked inaccordance with usual practice. In cases where the alloy is cast in substantially finished shape, and for this reason does not require hot working, an amount of carbide even beyond the point of saturation may be used in the charge.

In the production of many alloys, one part of Q molybdenum is considered the equivalent of two parts of tungste One type of high-speed steel contains about 18% of tungsten and, although it has been attempted repeatedly to substitute about 9% of molybdenum for the 18% of tungsten, the results have not been satisfactory. The substitution of 9% of molybdenum for 1% of tungsten is advantageous from an economic standpoint, ff but up to the present time, ithas not been found I practical to use more molybdenum, since when this amount is exceeded, the structure of the steel is bad and this leads to a high -percentage rejectionof the steel'in the process of working or forging it to shape. Furtherniore, when more than about 5% or 6% of molybdenum is used, there is a high loss of molybthe sub- .stitution of molybdenum for tungsten in highdenum during forging. For this-reason,

speed steels has not been satisfactory up to the present time. Molybdenum may,- however, be substituted for tungsten if the molybdenum is used in the form of molybdenum carbide in the charge. The carbides formed according to the present invention differ from those produced in the usual steel-making processes, as has been described previously. Not all of the tungsten need be replaced by retain a small amount, say 3% or 4% of tungsten, and to substitute molybdenum for the remainder molybdenum, it being preferable to than about 5%.o1 6% OI v of the tungsten. This results in a material decrease in the cost of the alloy steel.

It has been proposed heretofore to add tanta lum to high-speed steel with the idea of improving the red hardness properties of such alloys and also with the idea of increasing their capacity for cutting metals, since it was believed that the addition of tantalum would increase the formation of tantalum bearing carbides. The addition of tantalum, however, has not proved entirely satisfactory, for the reason, it is believed, that sumcient quantities of tantalum bearing .carbides have not been formed. The amount of tantalum in carbide form may be increased, however, if the tantalum is used in the form of tantalum carbide in the charge.

The amount of any of the carbides which should be used in the charge depends upon the type of alloy which it is desired to produce. Where it is desired to produce an alloy which can be hot shaped, it is advisable not to use more than 50% of the carbide-and generally not more than 30%. An addition of even of carbide has-a noticeable beneflcial affect in some cases, although the amount generally used is between 5% and 20%.

I have given certain examples of the types of ferrous alloys which may be made according to 1. The process of making high-speed steel, comprising providing a powdered 'charge containing a carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, and columbium, and the remaining constituents including a ferrous constituent required to form high-speed steel, and melting the charge.

2. The process of -making high-speed steel, comprising providing a powdered charge, containing a'carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, and columbium, and the remaining constituents including a ferrous constituent required to form high-speed steel, and melting the powdered charge.

3. The process of making h-speed steel,

' comprising providing a powdered charge containtungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, and columbium, and the remaining constituents including a ferrous constituent required to form the high-speed. steel, and melting the charge under substantially non-oxidizing conditions.

4. The process of making ferrous alloys, comprising compressing into billets a powdered carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, and columbium, forming a charge containing the billets and the remaining constituents required to form the ferrous alloy, and melting the charge.

' 5. The process of making ferrous alloys, comprising compressing into billets a powdered carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, and columbium, forming a charge containing the billets and the remaining constituents required to form the ferrous alloy, melting the charge under substantially non-oxidizing conditions and casting the melt.

6. The process of making ferrous alloys, comprising compressing into billets a powdered carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium, and columbium, forming a charge containing the billets and the remaining constituents in powdered form required to form the ferrous alloy, and melting the charge.

GREGORY J. COMSTOCK.