US2438221A

US2438221A - Method of making a hard facing alloy

Info

Publication number: US2438221A
Application number: US454672A
Authority: US
Inventors: Kurtz Jacob; Zampieri Enrico
Original assignee: CALLITE TUNGSTEN CORP
Current assignee: CALLITE TUNGSTEN Corp
Priority date: 1942-08-13
Filing date: 1942-08-13
Publication date: 1948-03-23
Anticipated expiration: 1965-03-23

Description

wear"resisting alloyparticularly suitable" excessive wear, excessive oxidation and xcessive Patented Mar. 23, 1948 Jacob -Kurtz, Tcaneck, and Efii-ico i'zampieri,

Union'City, N. J., assignorsito Callite Tungsten x; Corporatiom-Union City, N. 1.;- ai'corpdration of Delaware No'Drawin'g. Application Aiugust' 13,1942, -Srial N0. 454,672

l Cla-im.

"Ihelpres'ent invention-relates 'to aiiw 'hard h'ere abrasion are encountered. "The alloy of the invention is particularly useful for dies, cutting tools, sand blast nozzles, and similar devices.

Various alloys "have been u'se'd heretofore for 1 such hard facing but most of'these alloys develop an abnormal amount of pitting and blow holes, particularly when the facing is done by an oxy-acetylene torch. Blow holes and pits usually result from oxidation of carbon or other impurities in the alloy or from an incomplete fusion of the alloy ingredients. These pits and blow holes usually show up upon grinding the hard faced piece of the device and the facing in which the material is used becomes so pitted and full of blow holes that it will not function properly. The new improved alloy of the present invention by reason of the composition thereof and the method of manufacture employed is a homogeneous alloy which, on being cast into molds, forms sound castings and subsequently, even though fused by an oxy-acetylene torch, vproduces a hard facing that is substantially free from blow holes and pits when ground.

According to the present invention, the alloy is made in the following manner:

First, a mixture of iron powder and carbon black or lamp black is made; the iron powder preferably about 200 mesh constitutes 80% to 94% of the total weight and the carbon black or lamp black 20% to 6%. There is preferably a small excess of free carbon remaining. When this mixture is subjected to a heat treatment under controlled conditions, an iron carbide is formed. Tunsten carbide powder is then mixed with this iron carbide powder in the proportions of 95% by weight of tungsten carbide and by weight of iron carbide.

When these powders are thoroughly mixed, they are pressed into convenient pellets :by hydraulic pressure, the pellets being about two inches in diameter by one inch in height. The pellets are heat-treated in a dry hydrogen or other neutral atmosphere in order to pre-alloy the mixture and cause a partial sintering thereof. The sintering of the alloy may be carried out in a magnesia crucible, in a high frequency furnace or in any suitable furnace under dry hydrogen or a neutral atmosphere, conditions being such as to prevent excessive oxidation and decarburization.

Chromium and cobalt in proper proportions are then put into a crucible and melted, whereupcn tne: sintered' tun-gsten iron carbide pellets are eused. "When athoroug-h fusion of these thater-i-alshas' ta-ken place; certain grain refiners or' deox idizei's are added-to the melt. These "deoxid'izirig a'ddi'ti'ons, and gr'ain refiners may be -one or more of siich metals as calci-um, ss'ilicon, manganese, :bor'on or a n alloy of silicon, aluin'inum -aiid zirconi'um -or ierrous 'a'll'oys of the metals of the IV, V and VI periodic groups such as ferrotitanium, ferrovanadium, ferrochromium, etc., in an amount sufficient to leave a metallic residue not in excess of 5% of the total weight of the melt.

The melt is then cast into suitable molds to form a cast ingot of approximately to of an inch in diameter by 14 to 16 inches long. On cooling, these ingots are trimmed and dressed and they are then ready for use as a hard facing material. The resulting alloys have a hardness on the Rockwell A scale of the order of -88 and they are highly resistant to oxidation and abrasion. Thepreferred composition of the alloy is as follows:

Per cent Tungsten 31.00 Iron 2.00 Carbon 2.25 Chromium 24.50 Deoxidizers 2.50 Cobalt Balance The proportions of the ingredients may be varied within certain limits without materially afiecting the desirable characteristics of the alloy. The following ranges have been found suitable:

The carbon, of course, is added mainly as carbide in combination with tungsten and iron. It is possible, however, that during the fusion of the ingredients, some carbon is taken up by the chromium so that some chromium carbide is formed. Tungsten carbide may be replaced in whole or in part by molybdenum carbide, the proportions of molybdenum carbide or tungstenmolybdenum can-bide content remaining substantially the same as in the examples given for tungsten.

amount, perform the function oi. removing :gen and perhaps nitrogen from the alloy :efiecting a general scavenging thereof. This ti permits a finer grain formation and adds 3. The deoxidizing additions, though small in oxyand

to the strength and toughness of the alloy. There is, accordingly, in the final product apractical absence of pits and blow holes that ordinarily characterize alloys of this type.

The alloy may be cast in a mold to form any desired predetermined shape, such as rings, dies, cylinders, and the like, and then ground to finished size. By heating the alloy after casting at a temperature of about 1000 C. fora period of 6-10 hours, added strength and hardness are imparted to the piece.

Having thus described our invention, what we claim is:

Process of making a hard facing alloy which comprises pressing into pellets and sintering about 95% by weight of tungsten carbide powder and about by weight of iron carbide powder;

, preparing a melt of chromium and cobalt and adding thereto and fusing therewith said tungsten iron carbide pellets; then adding deoxidizing and grain refining material of the group consisting of calcium, silicon, manganese, boron, alloys of silicon, aluminum, and zirconium, and ferrous alloys of titanium, .vanadium and chro- 4. mium; and casting the same into ingots; the proportions of the ingredients forming said alloy being about 24% to of tungsten, 1% to 5% of iron, 2% to 5% of carbon, 20% to 25% of chromium, 0.5% to 5% of deoxidizing and grain refining metal and the balance cobalt.

, JACOB KURTZ.

ENRICO ZAMPIERI.

REFERENCES CITED UNITED STATES PATENT Number Name Date 1,602,995 Wissler Oct. 12, 1926 1,698,934 Chesterfield Jan. 15, 1929 1,698,935 Chesterfield Jan. 15, 1929 1,946,130 Comstock Feb. 6, 1934 2,030,343 Wissler Feb. 11, 1936 2,048,707 P-fanstiehl July 28, 1936 2,050,266 Boyer Aug. 11, 1936 2,088,825 Welch Aug. 3, 1937 2,253,476. Wirth Aug. 19, 1941 FOREIGN PATENTS Number Country Date 373,711 Great Britain, June 2, 19.32 427,074