US1492567A - Process of making high-speed steel tools - Google Patents

Description

Patented is, e, 1924.

UNIT 1I ERICK Q. LANGENBEBG, OF CAMBRIDGE, IASSACHUSETTS.

PROCESS F ING HIGH-SPEED STEEL TOOLS.

Ito Drawing.

' To all whom it may camera:

. in actual practice,

. originally Be it known that I, Fnnnnniox 0. LAN- GENBERG, a citizen of the United States, residing at Cambridge, county of Middlesex, Commonwealth of Massachusetts, have invented a certain new and useful Improvement in Processes of Making High-Speed Steel Tools, of which the following is a specification.

My invention relates to a novel method of making a high speed steel tool. The novel steel tool produced by the method embodying my invention is characterized chiefly by the fact that the final product contains a high percentage of molybdenum, this being the result of the peculiar process by which the steel and the tools made therefrom are produced.

I am aware that molybdenum used in very small quantities in the manufacture of machine and structural steels, as for instance, .as s own in the patents to James Churchward No. 1,251,341, dated December 25, 1917, and No. 1,261,7 i2, dated April 2, 1918, but in the formulae for such steels, molybdenum has not exceeded 3.0 per cent, and in Ethe steels themselves as made the percentage of molybdenum has probably been much less owing to the loss of the molybdenum oxide during the processes of manufacture.

My present invention is based on observation of the fact that in forging a steel rich in molybdenum red shortness is observed, and my discovery that this is due in part to the oxidation of the molybdenum. Since this oxide is volatile, there is a large loss of that element during the forging and to a lesser extent during that the final product contains molybdenum in quantities less than the amount which was introduced. As a result of this I have been able to produce tools containing a uniformly distributed molybdenum content far in excess- .of, that contained in any tools heretofore produced and having qualities which render them altogether superior to any high speed tools previously known to me.

Comparative cordance with the method embodying my invention and the best high speed steeltools obtainable in the market show that the presence of molybdenum in the large quantities mentioned'herein has a marvelous effect on the endurance of the steel, and that tools discovery,

has been the heat treatment, so

tests of tools made in -ac- Application filed January 17, 1921. Serial No. 437,992.

made in accordance with my invention have an efiiciency which is from two and onehalf to five or more times greater than those made of the best tool steel heretofore known, and that this is true whether the com arison is made on the basis of length of endurance or of. amount of metal removed.

In practicin my invention, I prefer to employ -molyb enum in combination with vanadium and chromium in about the proportions in which these elements are commonly'employed in the manufacture of tool steels, since this combination of elements produces the best final product which I have so far been able to produce, but I do not limit myself to these combinations since the method embodying my invention isapplicable to other combinations of elements. In particular, it will be understood that tungsten may be substituted in part for the mol bdenum in the mixture which will now be escribed, due consideration being given to the difference in molecular weights of the two substances, and it will be understood that the qualities of the final product will be varied accordingly.

In practicing my invention, I employ the elements mentioned in the followin proportions which are stated in terms of percentages throughout dlum 0.50 to 3.0, chromium 1.0 to 4.5, molybdenum 5.0 to 12.0, the remainder being steel containing carbon from 0.55 to 0.80, and including such other elements or im urities as manganese, silicon, sulphur and p osphorus.

The following is a more exact formula for the heat, this being the composition which I have employed with the best results z-Vanadium 1.10, chromium 3.70, molybdenum this specification z-Vana- 6.80, and steel containing carbon 0.71 to complete the mixture.

In making hi h speed steel and tools, I proceed as fol ows:-The materials are charged into a crucible or electric furnace and melted therein, being poured at a temperature of about molds are made to approximate the final form of the tool or other article desired closely enough so that forging will not be necessary. The molds may either be sand or metallic or combinations of the two, as for instance, a chill mold with a refractory lin ing of varying thickness to regulate the cooling of t e iflerent parts of the casting. In casting, care is taken to exclude the air as much as possible to prevent loss of the 1600 centigrade. The

- the use of such as molasses or core compound which on molybdenum through oxidation and conseuent volatilization of the molybdenum. This can be accomplished conveniently b some carbonaceous compoun contact with the molten metal gives 'ofl inert gases and thus surrounds the castin with an inert atmosphere which excludes t e am After castin the article is cooled to a temperature below the critical range of this steel and removed from the mold. It is then normalized by heating to from 900 to 1050 centigrade for one hour, after which it is removed from the furnace and cooled in still air at atmospheric temperature to below a black heat.

Next, the article is reheated to a temperature between 725 and 850 centigrade and held there for a relatively long eriod, for instance, four hours, after which it is cooled to 500 or below. The reheating just described has the effect of distributing the molybdenum carbides uniformly throughout the entire mass, and is important in producing the best results. This heatin as well as the first, is preferably performe in an inert atmosphere or vacuum so that there will be no loss of molybdenum through the formation of volatile oxides.

If the tool has been cast closely to sha e, it may then be rough ground and given t e final heat treatment which is the same as for ordinary high speed steel, i. e. heat slowly to 800 centigrade and then rapidly to about l300 centigrade, then quench in oil, then heat to 400 to 650 centigrade, hold at that temperature for one hour and cool in still air.

It the piece has not been cast closely to shape and machining is necessary, it will be annealed before rinding by heating to from 500 to 700, he d at that temperature for twelve hours and then cooled in the furnace.

From the foregoing, it will be seen that the production of the tool or other article directly by casting without the intervention of a forging step is an important feature contributing largely to the success of my invention, since it makes possible the production of a tool or other article havingthe remarkable properties which have been explained herein.

Although the tools made as described are meets? so much more valuable for the purposes for which they are designed than tools as heretofore made that I consider the invention on that account alone to be of a revolutionary character, nevertheless, tools can be made as described herein at much less cost than the present high speed steel tools. This is due in part to the fact that the expense for alloying elements is less than heretofore and in part to the elimination of the forging step.

What I claim is l. The hereindescribed method of making a high speed steel tool, which consists in melting to ether steel, vanadium, chromium and molybdenum, then casting to such sha e that no forging will be required, and finally subjecting the piece to suitable heat treatment, oxygen being excluded during the process suiiicientl to prevent formation of volatile compoun s of molybdenum.

2. The hereindescribed method of making a high speed steel tool which consists in melting together steel, vanadium, chromium and molybdenum, then casting, and finally subjecting to a heat treatment in an inert atmosphere.

.3. The hereindescribed method of making a high speed steel tool rich in molybdenum which consists in casting the molten metal at about 1600 centigrade, cooling to below 500, heating to between 900 and 1050 for about an hour, cooling to below black heat, and reheating to between 725 to 850 for a much longer period to distribute the molybdenum carbides uniformly through the mass, and then subjecting the piece to suitable heat treatment.

4. The hereindescribed method of making a high speed steel tool rich in molybdenum which consists in casting the molten metal at about 1600 centigrade, cooling tobelow 500, heating to between 900 and l050 for about an hour, cooling to below black heat, and reheating to between 725 and 850 for a much longer period to distribute the molybdenum carbides uniformly through the mass, the process being performed under conditions which prevent the formation of volatile compounds of molybdenum.

In testimony whereof I afiix my signature.

FREDERICK c. LANGENBERG.