US2097176A - Alloy - Google Patents

Description

Patented Get. 26, 19 3? anemic or Anthony G. de Golyer, New York, N. Y.

No Drawing. Application August 18,1936, Serial No. 96,597

3 Claims. (Cl. 148-421) f The present invention relates. to a new and useful alloy and relates particularly to an alloy containing boron, tungsten and cobalt, which is characterized by being responsive to thermal 5 treatment for the improvement of physical properties.

r An object of the present'invention is to provide an alloy especially adapted for use as metal Cutting tools, the cutting efiiciency of which is l superior to that of present known high speed steels and other alloys- A further object is to provide an alloy which is free from, or substantially free from carbon and which is readily amenable to thermal treatment, by means of which the hardness, tensile strength, cutting efficiency and other physical properties and characteristics may be accurately controlled over a comparatively wide range.

I have found through experiment that by alloymg or otherwise intimately combining boron,

tungsten and cobalt within the range of boron 0.50% to 2.75%, tungsten 5% to and cobalt substantially the balance, that I obtain metallic compositions which possess in combination mate- 25 rially improved physical properties compared to those of heretofore known alloys or compositions intended for the cutting or working of metals.

Alloys of this invention may be used in the cast condition but approximate maximum values of hardness, resistance to impact and certain other. important physical properties can be developed only through thermal treatment, or through mechanical working and subsequent thermal treatment. Bodies of the alloys which have been subjected to such treatment are particularly valuable for use as tools, dies and the like for the cutting or mechanical working of metals.

Numerous metallic compositions have heretofore been proposed as improvement on the gen- 40 erally known'18-41 type of tungsten-chromium-vanadium high speed tool steel, and while many of such compositions possess greater hardness than such steel, all of them have disadvantages which render them unsuitablefor general ,application as metal cuttingor forming tools. Compositions containing principally carbides of tungsten, molybdenum or tantalum bonded with a relatively soft matrix metal have a high'degree of hardness, but are extremely brittle. Cast 0 compositions of the type heretofore proposed'require the presence ofv at 'least 1.50% carbon to qualify as metal'cutting tools and, as is well known, such alloys are not only brittle, but are so sensitive to various operating conditions as to 55 greatly restrict the scope of usefulness. One of the greatest disadvantages of the heretofore proposed compositions is that none of them are re-' sponsive to thermal treatment for regulation of physical properties, and consequently physical properties and characteristics are governed en- 5 tirely by the chemical composition of the sintered or cast material. w I

My alloy may be used in the as-cast condition, or it may beiorged and rolled or otherwise mechanically worked. I have found that both the 10 cast and forged material are amenable to thermal treatment.

For example, cast bodies of this alloy may have a hardness of from to 60 on the Rockwell C. scale and by subjecting the material to suitable thermal treatment, such as 15 quenching from a temperature higher than approximately 1000 0., the hardness may-be lowered to an approximate range of from 40 to 47 Rockwell C. In this condition the bodies may be ground,- shaped or formed, as desired.- The 20 alloy may subsequently be submitted to a second thermal treatment, such as heating to a temperature of less than 1000 C. fora period of one hour or more, by which the hardness may be. increased to from approximately 60 to '70 Rockwell 5 C. In the lattercondition the alloy is especial- I ly valuable for the cutting or mechanical working of a large number of metals and alloys, as well as numerous non-metallic materials. An important property of the alloy is that virtually 30 all of the maximum hardness, developed by thermal treatment, is" retained when the alloy is subjected to elevated temperatures, e. g. such as are generated in the tip of a tool cutting metal at high speed. Although the alloy has a highde- 35 gree of hardness and resistance to abrasion by hot metal chips, especially after thermal treatment, it is remarkably resistant to failure from sudden or repeated shock. Therefore, tools made of the present alloy retain an eificient cutting 40 edge for longer periods than other tools;

The more important distinctiveand valuable advantages are, apparently, due to the presence of appreciable amounts of boron in the composition, in conjunction with the other essential '45 component elements within the percentages specifled herein.

I have found that molybdenum may be used to supplant all or a portion of the tungsten of the present alloy. Likewise, uranium may be used 0 in place or either tungsten or molybdenum.

Specific examples of compositions within the scope of the present invention which I have found welladapted for metal cutting tools,,.dies and the 'like' are the following: boron 1.20%, tungsten 14%, cobalt balance; boron 2.10%, tungsten 19.50%, cobalt balance; boron 1.65%, molybdenum 13%, cobalt balance; boron 1.70%, tungsten 5%, molybdenum cobalt balance..

An objective of the present invention is to provide alloys having high hardness, advantageous metal cutting properties, etc., which are free or' substantially free from carbon, and thus eliminate all of the serious disadvaritages'associated with carbon containing alloys or compositions intended for metal cutting tools. Although I prefer to have the alloys of this invention entirely free from carbon, in many instances I have found carbon present in the nature of animpurity incidental to manufacture. It is important to restrict the amount of carbon so present to a maximum .of about 0.15%, as I have found that the presence ing the essential components of thealloy of the present invention invariably are contaminated with other elements when produced in commercial quantities, the alloys of my invention usually contain insignificant amounts of one or more elements in the nature of impurities incidental to manufacture. The amount of such impurities should be restricted to percentages which are not efiective on thephysical properties or characteristics of the alloy, nor on the thermal reactions during thermal treatment. I have found that the amount of any one of such incidental impurities should be restricted to percentages not exceeding 1%, and in many instances to materially lower percentages. The presence of larger amounts of such impurities particularly silicon and aluminum not only lowers the tensile strength and impact value of the alloy, but inhibits the desired physical reactions during thermaltreatment.

My investigations indicate that the preferred structure of a body of the present alloy, particularly after thermal treatment, comprises at least two principal constituents: one, a relatively hard intermetallic compound of boron with one or more of the other essential components; and, SGOOIidyQ. solid solution of two or more of the essential components which has a lower degree of hardness and functions as a matrix. In some instances the structure'will contain a third con- -stituent-in the nature of an eutectoid. The ratio of the constituents and the ratio of particle size in. any particular body ofthe alloy may be accurately controlled and fixed over a wide range by means of thermal treatment, or mechanical working and subsequent thermal treatment.

' By reason of the combined advantageous physical properties possessed by the alloy of the present invention, tools and other articles composed of thisalloy may be operated efiiciently and economically under conditions which areimpossible or uneconomical with tools or articles composed of heretofore known alloys or metalliccompositions. I

By the term the balance substantially cobalt in the foregoing andin the following claims, I intend that the alloy of the present invention comprises boron and metal of the group tungsten, vmolybdenum and urani within the percentage limits specified, with the remainder cobalt except for ineffective amounts of impurities which may be present incidental to manufacture.

I claim:

1. An age hardened alloy containing boron 0.50% to 2.75%, metal from thegroup tungsten, molybdenum and uranium 5% to. 25%, the balance substantially cobalt.

2. Ah age hardened alloy containing boron 0.50% to 2.75%, tungsten 5% to 25%, the balance substantially cobalt.

3. An age hardened alloy containing boron 0.50% to 2.75%, molybdenum 5% to 25%, the balance substantially cobalt.

ANTHONY G. DE GOLYER.