US2334245A - Cutting tool - Google Patents

Description

Patented Nov. 16, 1943 CUTTING TOOL Charles 0. Burgess and William D. Forgeng,

Niagara Falls, N. Y., assignors to Haynes Stellite Company, a corporation of Indiana No Drawing.

Original application July 30, 1940,

Serial No. 348,445, now Patent No. 2,297,687,

dated October 6, 1942. Divided and this application November 15, 1941, Serial No. 419,287

2 Claims.

This invention relates to abrasion resistant alloys of the type composed principally of chromium and iron, and to new and useful cutting tools made therefrom. This application is a division of our. copending application, Serial No.

as is required of a metal-cutting tool has heretofore been accompanied by an undue degree of brittleness. Cutting tool "high speed steels have been basically tungsten-iron compositions rather than chromium-iron, and have typically contained 18% tungsten, 4% chromium, and 1% vanadium (so-called 18-4-1) sometines modified by the addition of one or more of the metals, cobalt, nickel, and molybdenum.

It is a primary object Of the invention to provide an abrasion resistant chromium iron alloy which, in the form of a cutting tool, will cut metals at high speeds at least as well as 184-1 high speed steel.

We have discovered that a hard chromium-iron alloy containing between 45% and 65% chromium is considerably toughened by the addition of carbon in a percentage between 1% and 3%. For some purposes the carbon content may be somewhat above or below that range. We have further found that the general suitability of such an alloy for use as a cutting tool and other abrasionresisting articles is enhanced by the addition of the elements cobalt, nickel, silicon and one or more of the following elements: tungsten; molybdenum; columbium; tantalum; titanium; vanadium; and zirconium in certain proportions hereinafter described.

More specifically, according to the invention, chromium alloys and cutting tools comprise compositions substantially within the following percentage limits:

With one or more of the elements tungsten,

molybdenum, columbium, tantalum, titanium, vanadium, and zirconium, in individual percentages not exceeding 5% and in a total aggregate percentage, including the silicon percentage, under 10%, the remainder iron, the iron being maintained above 15%. I On occasion it will be desirable to add manganese up to about 10%. The normal impurities of steels, such as phosphorus, sulfur, and nitrogen, may be present in small fractional percentages without departing from the invention.

The alloy tools of thi invention may be used in the as-cast condition (after casting in sand or carbon molds for instance) or when heat treated. A suitable heat treatment consists in holding-the alloy tools at a temperature between about 550 C. and about 850 C. for a time between about five minutes at the higher temperatures to about twenty hours at the lower temperatures. The alloys are hot forgeable to a limited extent. If the alloys are to be forged, it is best to begin that operation before they have cooled from the casting step to below 900 C. .Some cold deformation of the forged alloy can be effected, preferably after quenching from above 900 C.

Depending chiefly upon the composition and heat treatment, the hardness of the alloy of the invention varies between the approxiate limits of to 70 Rockwell C. The best cutting tool quality is usually attained in tools having a hardness in the neighborhood of Rockwell C. The transverse strength of the as-cast alloy is upwards of 1000 pounds (loading applied centrally to a section 0.5 inch by 0.5 inch square, supported in a 4 inch span) and in the preferred range of. compositions attains 3000 to 4000 pounds and sometimes more.

Cutting tests indicate that the alloy tool of the invention compares favorably with standard high speed steel tools of the 18-4-1 type. In accelerated life tests, cutting steel billets and semi-steel billets, and using surface speeds, feeds, and cuts considerably greater than normal, tools of this invention cut from two to eight times as far as standard Rex AAA, a widely steel of high quality.

Although the use of the alloy of this invention as a cutting tool has been emphasized in the foregoing description, the alloy is capable of many other uses which are within the invention, for instance as a hard-facing material for tool and machinery wear-resisting parts.

We claim:

1. A heat-treated, high speed, metal-cutting used high speed tool having substantially the composition: between 50% and 65% chromium, between 5% and 20% cobalt, between 4% and 20% nickel, between 0.05% and 5% silicon, between 1.5% and 3% carbon, a substantial amount of at least one of the elements from the group consisting of tungsten, molybdenum, columbium, tantalum, titanium, vanadium, and zirconium, in individual percentages not exceeding 5% and in an aggregate percentage, including the silicon percentage, under- 10%, remainder iron; and being in the condition resulting from being heated at a temperature within the range 550 C. t0'850" C. for a time between five minutes and twenty hours.

2. A heat-treated, high speed, metal-cutting tool having substantially the composition: 50% to.

56% chromium, 7% to 15% cobalt, 6% to 15% nickel, 0.2% to 2% silicon, 1.5% to 2.25% carbon, a substantial amount of at least one of the elements from the group consisting of tungsten, molybdenum, columbium, tantalum, titanium, vanadium and zirconium, in individual percentages not exceeding 5% and in an aggregate percentage, including the silicon percentage, under 10%, remainder iron, the iron content being more than 15%; and being in the condition resulting from being heated at a temperature within the range 550 C. to 850 C. for a time between five minutes and twenty hours.

CHARLES O. BURGESS. WILLIAM D. FORGENG.