US779171A - Manufacture of tool-steel. - Google Patents

Description

IINTTED STATES Patented January 3, 1905.

PATENT EETcE.

JOHN ALEXANDER MATHEWS, OF SYRACUSE, NEW YORK, ASSIGNOR TO ORUCIBLE STEEL COMPANY OF AMERICA, A CORPORATION OF NEW JERSEY.

MANUFACTURE OF TOOL-STEEL.

SPECIFICATION forming part of Letters Patent No. 779,171, dated January 3, 1905.

Application filed September 6,1904. Serial No. 223,409.

To all whom, it may concern.-

Be it known that I, JOHN ALEXANDER MA- THEWS, a citizen of the United States, residing at Syracuse, in the county of Onondaga and State of New York, have invented or discovered a certain new and useful Improvement in the Manufacture of Tool-Steel, of which improvement the following is a specification.

My invention relates to the manufacture of tool-steel, and particularlj tool-steel of the class generally known as high-speed steel or air-hardening steel. These terms have been indifferently employed to characterize a steel which differs from the ordinary carbon tool-steel in three respects-namely, in composition, in'method of hardening, and in physicalproperties and characteristics. In composition it differs from the ordinary carbonsteel in that it contains in addition to carbon one or more alloying metals which act as hardeners supplementary to or partially in substitution for the carbon. The metallic hardeners ordinarily employed for this purpose have been chromium, molybdenum, and tungsten. Of these metals the steel usually contains either molybdenum or tungsten, either alone or in combination with chromium, although molybdenum and tungsten may both be contained in the steel and in some cases all three of these metals. The quantities employed vary widely, from four per cent. to thirty per cent. of tungsten or in the alternative from two per cent. to fifteen per cent. of molybdenum, according to the particular purpose for which the steel is made, it having frequently been demonstrated in practice that the hardening effect of molybdenum is approximately double that of tungsten. Chromium has usually been employed in quantities ranging from one per cent. to seven per cent. In respect of the method of hardening this steel difiers from ordinary carbon-steel .in that while the latter requires immersion in water or oil to harden it air-hardening steel, as its name applies, is hardened by exposure merely to a blast of air or in the case of some compositions by simply cooling in the open atmosphere, in which latter instance it is known as self-hardening steel. As regards the third point of distinction above mentioned, it is Well known that tools made of ordinary carbon-steel are incapable of withstanding without material deterioration even a moderately high temperature, and consequently where tools of ordinary carbon-steel are subjected to severe usage, as in cutting or dressing cast iron or steel, they can be operated only at a very low speed. Otherwise the frictionally-generated heat at the point or working face of the tool will quickly render it useless. High-speed or air-hardening steel, on the other hand,does not depend entirely upon carbon for its hardness, but partially, and in some instances to a great extent, upon the hardening effect of the metals above specified, and it has been demonstrated that the hardness of steel containing these metals is not as easily destroyed by exposure to the high temperature incidental to severe usage at high speed. Steel containing these metals has therefore largely replaced the ordinary carbon-steel in tools intended for Work of the character above referred to and has thus obtained the name of high-speed steel. It has been made both high and low in carbon, varying from less than .25 per cent. to two per cent. or over, and I herein employ the terms high-speed steel and air-hardening steel indifferently and synonymously to designate the class of toolsteel to the manufacture of which my present invention relates, containing one or more of the metals above specified in about the quantities stated and either high or low in carbon and possessing to a greater or less degree the qualities mentioned.

Generally stated, my invention consists in the addition to such high-speed or air-hardening steel of a quantity of vanadium in amount such as will leave in the ingot when cast not less than .10 per cent. of that metal and preferably not more than about one per cent. I add the vanadium to the steel while it is still molten, and as the vanadium oxidizes quite rapidly I have found that in the crucible process now ordinarily employed for the manufacture of tool-steel it is more economical to add it about twenty or thirty minutes before pouring. The loss is then about twenty per cent; but the precise time at which the addition is made is not material, providing the quantity added be suflicient to leave in the ingot not less than .10 per cent. of vanadium.

The benefits attained by my invention are both chemical and mechanical. The vanadium acts chemically upon the moltenmixture by virtue of its great aflinity for oxygen and nitrogen, purifying the molten steel of dissolved gases and oxids of iron, molybdenum, tungsten, &c., and resulting in the production of sound ingots free from small blow-holes. One of the faults in the high-speed steels now on the market has been the presence of seams and other small defects, which cause the tools to split or crack off in service. These defects are usually the result of small blow-holes in the ingot. In the finished tool the vanadium acts as a hardener, supplementing and intensifying the hardening effects of the molybdenum, tungsten, &c. It also imparts to the tool the quality of toughness to a marked degree, greatly increasing its capacity to withstand sudden shocks, which are frequent in severe service.

I prefer that the quantity of vanadium in the tool should not materially exceed one per cent., having determined by experiment that this is ordinarily sufiicient; but higher percentages may be'desirable in particular cases, and hence my invention is not limited to any maximum addition. The precise quantity to be added will, however, depend somewhat upon the composition of the steel and its intended use. Very eflicient high-speed steels now on the market are made to contain from six per cent. to ten per cent. of molybdenum (or in the alternative from twelve per cent. to twenty per cent. of tungsten) and from .50 per cent. to one per cent. of carbon. To such steel I have added about .50 per cent. of vanadium and have found that the efficiency and endurance of the tool were more than doubled. There was also a great increase in the resisting power of the tool as against the sudden cross sectional strains and shocks which are not infrequent in severe usage; but whatever be the precise quantity of vanadium added to the steel my experiments have convinced me that so long as the quantity in the product is not less than .10 per cent. im-

proved results will be attained, and I intend to include within the scope of the present invention all such additions to steel of the class hereinbefore described and defined indifferently as i high-speed steel and air-hardening steel.

I am aware that experiments have heretofore been made in the addition of vanadium to ordinary carbon-steel and that it has been represented that such additions have proven beneficial for some purposes. My invention, however, is essentially different in .that it comprises only the addition of vanadium to the above-specified class of tool-steel known as high-speed steel, and by the practice of my invention I have attained in the manufacture of such steel benefits and improved results not attained in such prior experiments with ordinary carbon steel. Moreover, I have found by experiments that the addition of vanadium to ordinary carbon-steel will not convert it into a high-speed steel, nor will it impart to ordinary carbon-steel to any appreciable extent any of the properties essential to high-speed work.

What I claim, and desire to secure by Letters Patent, is-

1. High-speed steel containing not less than .10 per cent. of vanadium.

2. Steel containing metallic hardening material in about the proportions hereinbefore specified, and not less than .10 per cent. of vanadium.

3. Steel containing metallic hardening material in about the proportions hereinbefore specified, and from .10 per cent. to one per cent. of vanadium.

4. Steel containing more than six per cent. of molybdenum, and from .10 per cent. to one per cent. of vanadium.

5. Steel containing less than one per cent. of carbon, more than six per cent. of molybdenum, and from .10 per cent. to one per cent. of vanadium.

In testimony whereof I have hereunto set my hand.

JOHN ALEXANDER MATHEWS.

Witnesses:

H. A. PARDEE, RAYMOND L. SKINNER.