US2754193A - Process for making copper-iron powder - Google Patents

Description

PROCESS FOR MAKENG COPPER-IRON POWDER Marion Ernest Graham, Parma, and William A. Reed,

West Richiield, ()liio, assignors to Republic Steel Corporation, Cleveland, ()hio, a corporation of New Jersey No Drawing. Application December 29, 1953, Serial No. 401,063

5 Claims. (Cl. 75-05) This invention relates to a process for making articles consisting essentially of copper and iron, having a high tensile strength and high density and more particularly to a process for making copper-iron powder from which such articles may be fabricated by powder metallurgy methods.

This case is related to the co pending application of Marion Ernest Graham and William A. Reed entitled Process for Making Copper-Iron Powder, Serial No. 401,064, filed December 29, 1953. This co-pending application discloses a method for making copper-iron powder by the reduction of iron oxide in the presence of certain reducible copper compounds or metallic copper and particularly in the presence of gaseous hydrogen chloride which must be supplied from an external source.

The line of division between the invention of that application and the present invention resides in the fact that the present invention'relates to the reduction of certain iron and/or copper compounds by hydrogen. The supplying of gaseous hydrogen chloride from a separate source during reduction is not a necessary feature of the present invention. Said co-pending application relates to the production of copper-iron powder by a reduction step effective on iron oxide plus a source of copper by hydrogen wherein HCl gas must be supplied from an external or separate source during the reduction.

High strength and high density articles consisting essentially of copper and iron have found numerous industrial applications, notably in the manufacture of turbine blades and other parts subjected to wear and requiring quite high strength. In the past, such parts have been produced by such methods as infiltration of molten copper into iron parts previously prepared by powder metallurgy methods and the coining of parts made from mixtures of copper and iron powders. While such methods may be ettective in producing articles having a high tensile strength, they are objectionable in that they involve substantially more complexity and expense of operation than do powder metallurgy processes.

it is an object of this invention, therefore, to provide a process for making articles of high tensile strength consisting essentially of copper and iron that utilizes the relatively simple methods of powder metallurgy.

It is a further object of the invention to provide a process for making copper-iron powder, which is capable of being formed into articles having a high tensile strength and high density by pressing and sintering and without the necessity of infiltration, coining or similar operations.

ther objects of the invention will be in part apparent and in part pointed out by the subsequent description.

The process of the invention may be carried out by reducing one of the hydrogen-reducible oxides of copper such as CuO or 0120 or one of the hydrogen-reducible chlorides of copper such as CuClz or CuCl in intimate admixture with iron powder of either one or both of two special types, i. e. iron powder that has been made either nited rates Patent by the hydrogen reduction of iron chloride or by the reduction of iron oxide by a mixture of hydrogen and hydrogen chloride. This reduction is carried out by hydrogen or by a reducing gas containing hydrogen as its essential active ingredient. It has been found that in order to produce a copper-iron product having the desired physical properties in accordance with the present invention, an actual chemical reduction of the copper compound must take place while it is in intimate contact with the special type iron powder as aforesaid. Furthermore, the metallic iron ingredient of the starting material must have been made either by the reduction of iron chloride by hydrogen or by the reduction of iron oxide by a mixture of hydrogen and hydrogen'chloride. cases, it may be desirable to produce a metal powder having some predetermined carbon content. To this end it may be necessary to add a small amount of carbon (e. g. about 1%) to the starting mixture.

After the ingredients of the starting material, selected in accordance with the principle outlined above, have been mixed together in the proportions that will result in the desired ratio of iron to copper in the reduced prod uct, the starting material is introduced into a reaction zone and there contacted with a reducing gas containing hydrogen. The solid starting material and the reducing gas are both maintained at an elevated temperature in the range of about 1000 F. to about 1800 F. and contact between them is continued until the reduction of the hydrogen-reducible copper compound has been substantially completed. The resultant material is then cooled and, in the event that it be in a massive or semi-sintered condition, is comminuted to powder. This copper-iron powder may then be pressed to a self-sustaining mass of predetermined size and shape, which is subsequently sintered in a suitable non-oxidizing atmosphere usually at a temperature of about 2000 F. The physical properties of the resulting article will be in part dependent upon the ratio of iron to copper contained therein, the pressure at which it was molded, the sintering temperature and other factors, but in all cases the product of the present invention will have a higher tensile strength than conventional copper-iron parts of the same chemical composition which have been pressed and sintered under similar conditions respectively. In many instances, the tensile strength of articles made in accordance with the process of the present invention will exceed 100,000 pounds per square inch.

Summarizing the present invention, copper-iron powder suitable for use in powder metallurgy for forming articles having high tensile strength and high density is produced by introducing into a reaction zone a starting material, the essential active ingredients of which consist of: metallic iron powder, in at least one form selected from the group consisting of (a) metallic iron which has been reduced from iron oxide by a reducing gas containing hydrogen chloride, and (b) metallic iron which has been reduced from iron chloride by hydrogen, and copper, in at least one form selected from the group consisting of (a) the chlorides of copper, and (b) the oxides of copper; and then contacting said starting material with a reducing gas containing hydrogen as an essential active reducing ingredient under such conditions of temperature and for such a time as to reduce the hydrogen-reducible copper compound to metallic copper.

Since it is an object of the present invention to produce a copper-iron powder, the ingredients of the starting ma terial are preferably provided in finely-divided form. This further facilitates thorough mixing of the ingredients of the starting material, which is necessary to insure the production of a chemically uniform and homogeneous material.

The ingredients used for the starting material must in- In some elude at least one copper-containing ingredient and at least one iron-containing ingredient. The eo pefleentainin ingredient is one or more materials selected from the group consisting of the hydrogen-reducible oxides of copper, i. e., CuO and CuzO and the hydrogen reducible chlorides of copper, i. e., CuClz and CuCl. All that is required is that the copper compound shall have a particle size sufficiently small to insure the, production, of; a substantially homogeneous mixture as the starting material. The same consideration is controlling with regard to the particle size of the other ingredient of the starting material. a a 7 It is immaterial, insofar as the operation ofthepresent invention is concerned, whether the copper compound ingredient be in thecupric or cuprous state or a: mixture ofboth. It is believed thatwhen cupric oxid'e for example, is reacted with a suitable reducing agent, it is initially converted to cuprous oxide as an intermediate stage in the reduction to metallic copper. It is believed that an analogous process takes placefinthe reduction of.

cupric chloride, i. e., that cuprous chloriide is formed as an intermediate product. Whether these theoriesbe accurate or not, it has been found that the cupric and cuprous forms of both the oxide and; the chloride, are equally effective and as such are the equivalents of one another for the purposes of the present invention. They are both intended to be included in the terms icopperoxide and copper chloride, respectively, as those terms are used herein and in the appendediclaims,

It is a), be further understood that the terms copperv oxide? and copper chloride as used herein, are meant to include those copper compounds which decompose easily under the influence of heat to form oxides or chlorides. alates, formates and similar organic salts, which quickly form oxides when heated, and are so converted in the reaction zone before reduction actually begins. These compounds may, therefore, be considered the chemical equivalent of copper oxide for the purposes of the present invention. Similarly, hydrated chlorides of copper such as CuC12-2H2O which lose their water of hydration at elevated temperatures may be used as the copper-containing ingredient. I a p The one or more iron-containing ingredient ort ingretdients of the starting material is .or are selected from a groupsomewhat more circumscribed than that from which the copper-containing material is chosen. For want of a better term, this iron may be referred to a s chloride iron because its process of production involves. the pres ence of a chloride, and in theory it is believed to be derived, either directly or indirectly, from or to involve the reduction of iron chloride. Thus, iron powder made by the hydrogen reduction thereof of iron chlorideis among the iron containing.materials that may be used as a start-Y he ing material in practicing the present inv ntiOn. other possible iron-supplying ingredient is metallic iron thathasj been made by the reduction of. iron oxide with a mixture of hydrogen and a substantial amount oil hydrogen chloride as taught, for example, in the Crowley application, Serial No..375,927, filed August 24,. 1953.

Experience and research tests have shown that iron powder of this type differs substantially as to its physical properties and metallurgical structure from iron powder made by the reductionof iron oxide with pure hydrogen or other reducing agent free of substantialamounts of the fact that during the reduction process; the iron; oxide is converted at least momentarily to ferrous: chloride,

which is then reduced to metallic iron. This theory tends;

Examples of such compounds are acetates, ox-

1-101. It is believed that this difference may be; duet-to,

4 established empirically regardless of the theoretical reasons therefor.

It is essential to the production of the high strength articles, which is an object of this invention, that the ingredients of the starting material be selected in such a way that at least one of them (a hydrogen-reducible copper compound) is reduced in the presence of the other or others (a special form of iron powder). Thus, metallic copper and metallic iron (even iron made in the presence (senor-or by reducing iron chloride) and when no hydrogndeducible material is present, the whole then treated in hydrogen, did not produce the desired material. Subsequentexamples willillustrate that copper-iron powder made in this way is definitely inferior as to its tensile strength to copper-iron powder made in accordance with the teachings of the invention. The fact that a chemical reduction reaction takes place while the ingredients are mixed together appears to be necessary for the production of the-novel copper-iron powder of thepresent invention, which iscapable of-pr'oducin'g sintered bodies of unusually. hightensile: strength. Thereason for this novel requirement'of; the present invention is not fully understood;v

After the ingredients of the starting material have been selected-in accordance with the principles outlined above, they;are proportionedso as to result ina reduced powder having thedesired ratio of copper to iron andare thoroughlyv mixed; In order that thorough mixing take place, it is;.desi rable;that the starting, ingredients be supplied in the form of powdenqand preferably, as finely divided as isiconvenient. In-practiceit hasbeen found that excellent is, obtained by the. use of mesh starting materials,

The. mixedingredients may then be placed in a suitable container, such as a, metal boat or pan, and introduced into; a: reaction zone, wherein" the hydrogen-reducible copper constituent of'the starting material isreduced. In.

order to insure, maximumyield based on the amount of raw; materialpsed, it. is. necessary: that the chemical reaction be carried to substantial, completion. By this it is meant thatthe; copper of the hydrogen-reducible copper compoundbe-reduced to an oxidation state of zero. This phrase; as; usedin this description, and the appended claims, isqmcantto embrace boththe production of either a physicalmixture of elementalmetallic powders or the production of; some alloy, of copper and iron alone: or which may bemixedtwith, a simple mixture of copper and iron. Irr-any case the; metallicconstituents-are pres.- entin anpxidation state of zeroas opposed to the positive xi ation tate n ch ppe rp y v ingredient wasintroduced in the starting material as copper chloride; etc.

The QQlldltlQllSgOf reduction are notcriticalto the succes of ithe -process exceptthat they mustbe-sufiicient as;

sinterdproduqt,.Which willbe difficult to grind. This" condition is to be avoided, since one .of the objects of-the presentv invention is the production'of pulverulent material whichmay be;used;in powder metallurgy processes. It has ,been'found thattemperatures up to. about1800 F.

will.res,ultvin: the production of materialwhich is quite frangible and: thus: may. be, comminuted to powder without unduje ,trouble or expense.

After -.the -reductionhas. been completed, the reduced powder is cooled1in-a non-oxidizing atmosphere toabout 200 F. tin-less; Theresultant:mass -is then comminuted to; powder; which; iS-;,th en use d. in various powder;- metallur'gpprogesses, according-to";standard-practice;

The process of the present invention is further illustrated by the following examples, which are not intended as narrowly limiting upon the scope of the present invention.

Example I Finely divided metallic iron, made by the hydrogen reduction of ferrous chloride, was mixed with cupric chloride (CuClz) and treated with hydrogen supplied at the rate of 2000 cubic centimeters per minute and a temperature of 1200 F. for 3 hours. This was done by blending the finely divided metallic iron in a dry state with the copper cloride, so as to obtain a reduced material including the metals iron and copper in the weight ratio of about 85% iron and about 15% copper. The mixture of iron and copper chloride was spread on a tray to a depth of about 4 inch and the tray placed in an electrically heated mufile furnace. Dry hydrogen Was passed through the furnace over the surface of the mixture at the rate of 2,000 cubic centimeters per minute throughout the reduction. The temperature of the contents of the furnace was maintained at about 1200 F. for 3 hours. The sealed inner tube of the furnace was then removed from the heating muffle and the contents allowed to cool to a temperature below 200 F. The completely reduced copper-iron product which had formed into a semi-sintered,

but easily frangible, cake was then ground to a particle size of about 100 mesh. The resulting powder was found by analysis to contain 15.83% copper and the ballance, principally iron. This powder was mixed with 1% zinc stearate as a lubricant, pressed at 50,000 p. s. i. to form a standard test bar, which was then sintered in hydrogen at 2000 F. for one hour. The resulting piece had a tensile strength of 113,000 p. s. i. In addition to copper and iron this powder also contained about 0.24% carbon. It is believed that the unusually high strength obtained in this instance may have been due, in part, to the presence of this small amount of carbon. This example thus also demonstrates that the presence of a small amount of carbon in the powder is not deleterious insofar as tensile strength is concerned.

Example II Copper-iron powder was prepared under the same conditions as those described in Example I, except that cuprous oxide was used instead of cuprous chloride. The powder thus prepared contained 14.92% copper and 0.074% carbon. A pressed and sintered test piece prepared from this powder by the standard procedure above set forth had a tensile strength of 82,400 p. s. i.

Example III Metallic iron prepared by the reduction of iron oxide with a mixture of hydrogen and hydrogen chloride may be used as a substitute for reduced ferrous chloride, although the tensile strengths obtainable under these circumstances are not as high as those resulting from the use of ferrous chloride or reduced ferrous chloride. For example -325 mesh iron powder prepared by the reduction of iron oxide (FezOa) at 1400 F. with a mixture of hydrogen and hydrogen chloride was mixed with cuprous oxide (CuzO) and treated with hydrogen at 1200 F. to reduce the copper oxide. The resulting copper-iron powder, containing 14.32% copper, was pressed and sintered according to the standard procedure above outlined and yielded a piece having a tensile strength of 62,200 p. s. i. While this powder does not yield pieces having as high a tensile strength as those set forth in the previous examples, its strength is still almost double that obtained using prior art practices and starting materials. Thus,

when copper oxide and commercial iron powder, made by the comminution of sponge iron and without the use of hydrogen chloride, were mixed in the same proportion given in the first portion of this example and reduced with hydrogen at 1200 F., and this powder pressed and sintered in accordance with the standard procedure, there was produced a piece having a tensile strength of only 32,000 p. s. i. A comparison of these two values illustrates the unexpected and valuable results obtained in accordance with the present invention by providing the iron in one of the forms set forth hereinabove. Merely reducing any copper compound in the presence of any metallic iron is ineffective to produce the product of the present invention.

Example IV Metallic iron reduced with a mixture of hydrogen and hydrogen chloride under the conditions described in Example III was reduced with cupn'c chloride by hydrogen at 1100 F. to a powder containing 15.25% copper. A piece pressed and sintered from this powder in accordance with the standard procedure above set forth had a tensile strength of 65,700 p. s. i.

Example V Example III illustrated that the mere reduction of a copper compound in the presence of metallic iron not derived in some manner from a chloride source and/or in the presence of HCl does not produce the desired copperiron powder of the present invention. This example illustrates that the mere presence of metallic iron of the proper type according to the present invention but without the presence of a hydrogen-reducible copper compound is similarly undesirable and is not to be considered as included in the present invention.

Thus, when a reduced metallic iron made by the hydrogen reduction of ferrous chloride is mixed with metallic copper, both metals when mixed being in finely divided form, and mixed in the proportions of 15% copper and iron, then pressed and sintered according to the standard procedure above set forth, a piece having a tensile strength of only 48,200 p. s. i. was obtained. This clearly indicates that an actual chemical reduction must take place while the ingredients of the starting material are in contact with one another in order that the novel and desirable results of the present invention shall be attained.

While there have been disclosed herein several specific processes and certain variants thereof, other alternatives and equivalents will occur to those skilled in the art from the foregoing disclosure. We do not wish to be limited, therefore, except by the scope of the appended claims, which are to be construed validly, as broadly as the state of the prior art permits.

What is claimed is:

1. The process of making copper-iron powder suitable for use in powder metallurgy for forming articles having high tensile strength and high density, comprising the steps of introducing into a reaction zone a starting material the ingredients of which consist essentially of: metallic iron, in at least one form selected from the group consisting of (a) iron powder which has been reduced from iron oxide by a reducing gas containing a substantial amount of hydrogen chloride and (b) iron powder which has been reduced from iron chloride by hydrogen; and a hydrogen-reducible compound of copper, in at least one form selected from the group consisting of (a) the chlorides of copper, and (b) the oxides of copper; and contacting said starting material in said reaction zone and at an elevated temperature with a reducing gas containing hydrogen as its essential active reducing ingredient for a time and under conditions sufficient to reduce the copper of said hydrogen-reducible compound of copper to an oxidation state of zero.

2. The process according to claim 1, wherein the ironcontaining ingredient of said starting material is metallic iron which was reduced from iron oxide by a reducing gas containing hydrogen chloride; and the copper-containing ingredient of said starting material is copper chloride.

3. The process according to claim 1, wherein the ironcontaining ingredient of said starting material is metallic iron, which was reduced from iron oxide by a reduc-

Claims (1)

1. THE PROCESS OF MAKING COPPER-IRON POWDER SUITABLE FOR USE IN POWDER METALLURGY FOR FORMING ARTICLES HAVING HIGH TENSILE STRENGTH AND HIGH DENSITY, COMPRISING THE STEPS OF INTRODUCING INTO A REACTION ZONE A STARTING MATERIAL THE INGREDIENTS OF WHICH CONSIST ESSENTIALLY OF: METALLIC IORN, IN AT LEAST ONE FROM SELECTED FROM THE GROUP CONSISTING OF (A) IRON POWDER WHICH HAS BEEN REDUCED FROM IRON OXIDE BY A REDUCING GAS CONTAINING A SUBSTANTIAL AMOUNT OF HYDROGEN CHLORIDE AND (B) IRON POWDER WHICH HAS BEEN REDUCED FROM IRON CHLORIDE BY HYDROGEN; AND A HYDROGEN-REDUCIBLE COMPOUND OF COPPER, IN AT LEAST ONE FORM SELECTED FROM THE GROUP CONSISTING OF (A) THE CHLORIDES OF COPPER AND (B) THE OXIDES OF COPPER; AND CONTACTING SAID STARTING MATERIAL IN SAID REACTION ZONE AND AT AN ELEVATED TEMPERATURE WITH A REDUCING GAS CONTAINING HYDROGEN AS ITS ESSENTIAL ACTIVE REDUCING INGREDIENT FOR A TIME AND UNDER CONDITIONS SUFFICIENT TO REDUCE THE COPPER OF SAID HYDROGEN-REDUCIBLE COMPOUND OF COPPER TO AN OXIDATION STATE OF ZERO.