US2778742A - Method of impregnating a porous ferrous part with copper - Google Patents

Description

United States Patent M METHOD OF IMPREGNATING A POROUS FERROUS PART WITH COPPER Paul I. Shipe, Xenia, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware No Drawing. Application May 25, 1953, Serial No. 357,338

6 Claims. (Cl. 117-37) This invention relates to impregnation processes and is particularly directed to the impregnation of porous ferrous parts with a cupreous material.

. It is one of the objects of the invention to provide a method for impregnating porous ferrous parts with copper or other cupreous metals wherein the impregnated ferrous part is free from channels, pits or other surface imperfections due to the impregnation process.

In carrying out this object, it is a further object to supply suflicient ferrous metal with the cupreous metal used as the impregnant to satisfy the dissolving action of copper for iron prior to the time that said cupreous metal infiltrates the porous iron part and to also include suflicient non-metals in the impregnant material to prevent adhesion of excess ferrous metal to the surface of the ferrous part.

This object is accomplished by utilizing iron in the form of cast iron powder, which cast iron includes graphitic carbon that acts as the non-metal and in mixed form with the cupreous metal acts as a retardenttoward flow of molten cupreous metal from the mixture until such time that full distribution of ferrous metal in the impregnant has occurred. In this manner, when the cupreous metal actually infiltrates the ferrous part, cupreous metal has had its dissolving action fully satisfied whereby no further erosion occurs.

Numerous methods have been proposed for preventing erosion of porous ferrous materials by copper and copper alloys when said ferrous metals are infiltrated with copper. This infiltration process is one of high utility since a copper or copper alloy impregnated into a porous ferrous part adds strength to the part, reduces its porosity and thereby generally improves the physical characteristics of the part. metals are infiltrated into porous ferrous parts, there is a tendency toward erosion at the surface due to the dissolving tendencies of copper on iron. Past processes for controlling this tendency are disclosed in Bourne Patent No. 2,401,221, assigned to the assignee here, wherein iron powder is added directly to the copper impregnant, which procedure reduces the erosion tendency considerably. However, when large quantities of copper or copper alloys are desired to be impregnated into a selected area of a porous ferrous part, there is still some erosive tendency due to the concentration of copper at the point of entry.

The major portion of the erosive tendency can be controlled but in production processes, it is desirable to utilize a broad range of impregnation temperatures whereby the erosive tendencies are often aggravated. Another factor which causes difiiculty, is the tendency of copper to dissolve more iron at the impregnating temperature than will remain in combination therewith at the freezing point. In other words, as the temperature rises, the erosive tendency of copper on iron increases. This condition obviously suggests that the most desirable infiltrating conditions can be promoted by actually dissolving iron in the cupreous metal at the impregnating tem- As previously explained, when cupreous 2,778,742 Patented Jan. 22, 1957 perature and prior to the time that the cupreous metal is drawn into the porous ferrous part. In order to accomplish this end, Shigley applications, Serial Nos. 357,181 and 357,182, filed concurrently herewith (MP-157 and MP-2l3) and assigned to the assignee of the present invention suggest the use of compacts of cupreous metal, ferrous metal and a non-metallic material, such as magnesium oxide, which mixture with an excess of ferrous metal therein is briquetted into a compact of the shape and size desired and is placed on the porous ferrous part and heated therewith. When the temperature exceeds the melting point of the cupreous metal, melting occurs and simultaneously the molten cupreous metal commences to dissolve the associated ferrous material. This condition continues until the dissolving action of copper for iron'is fully satisfied. The magnesium oxide acts in this instance as a sponge to maintain this molten impregnant therein until such time that equilibrium temperature conditions are obtained between the impregnant and the ferrous part being impregnated, whereupon the molten impregnating metal is drawn into the porous fer rous part by capillarity.

This invention attacks the same problem in a slightly different manner. I have found that a similar result can be obtained by mixing the cupreous impregnant with cast iron powder. This cast iron powder not only supplies the ferrous metal which is to be dissolved by the cupreous impregnant prior to infiltration thereof into the porous ferrous part, but likewise, supplies the nonmetallics required to act as. a sponge for holding the molten impregnant until equilibrium temperature conditions are obtained between the impregnant andthe part to be impregnated. These non-metallic materials normally found in cast iron are mainly graphitic carbon, silicon and its derivatives, etc.

Thus if cast iron turnings or powder for example, are properly graded, preferably to a -l00 mesh powder, this powder will contain sufficient of the so called nonmetallics to create the desired condition. This cast iron powder is then thoroughly mixed with copper powder, or copper alloy powder in a desired quantity to provide suflicient cupreous metal to impregnate the porous ferrous part as desired. Preferably, the mixture of the cast iron powder and the cupreous metal powder is briquetted into a self-sustaining mass.

I have found that the cast iron powder should be in quantities ranging from 1 to 5% by weight of the total impregnant used which may be copper or copper alloy or may be copper, for example, with some zinc, tin or other alloying ingredient. In any case, the cast iron powder supplies, sufiicient iron to satisfy the dissolving action of copper or iron and simultaneously, due to the nonmetallics, acts as a retardent toward the immediate flow of the molten constituent. After the porous ferrous part has been impregnated, the residue of the impregnant material may be brushed 01f the surface of the part due to the fact that the graphitic carbon, silicon, etc., prevents any firm adhesion of the residue to the surface of the porous ferrous part. In this manner,-an excess of cast iron powder maybe utilized with no deleterious results such as sticking to the surface of said part and thereby marring said surface due to the removal of the adhered parts.

In practice, it is desirable to briquet the impregnant material into a shape and size approximating the shape of the surface of the part to be impregnated particularly where selective impregnation is required. Sufiicient metal is supplied to the compact to provide the adequate and desired quantities of the cupreous metal in the porous part.

impregnation is carried out at temperatures above the melting point of copper and below the melting point of iron and preferably within the range of 2000 F. and 2150 'F. The -heating may be carried out by induction if selective impregnation is comprehended, but preferably is carried out by standard furnace heating. Usual non-oxidizing atmospheres should be .used n all cases to facilitate the impregnation.

It is to be understood that cast iron powder as referred to herein may be powder from white cast iron, gray cast iron or any of the conventional cast irons as known commercially.

While the embodiments of the present invention as herein disclosed, constitute preferred foims, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a method for impregnating a porous ferrous part with a cupreous metal wherein the ferrous part, after impregnation, is substantially free from pits, channels and .the like, the steps comprising; mixing a desired quan .tity of cupreous metal with from 1 to 5% by weight thereof of cast iron powder, placing said mixture upon said ferrous part to be impregnated in a desired position relative thereto, heating the ferrous part with the mixture .of cupreous metal and cast iron powder thereon toa temperature above the melting point of .the cupreous metal. and below the melting point of iron fora time sufficient to obtain equilibrium temperature conditions in said mixture and said part whereupon sa-id cupreous metal dissolves a desired portion .of the iron in lthe cast ,iron and then infiltrates said ferrous part, and finally removing any .residueof said mixture from-said infiltrated part.

2. In .a method for impregnating a porous ferrous part with a cupreous metal wherein the ferrous part, after impregnationjis substantially .free from pits, channels and the like, .the steps comprising; mixi gfi desired quantity of .cupreous metal with :from 1 to 5% by weight thereof of .castiron powder, briquetting said mixture into aselfsustainingcompact of ,a .desired shape, placing said compact upon the ferrous part .to .be impregnated and in a desired position relative thereto, .heatingdhe ferrous part and the compact 'to a temperature above the meltingpoint of the cupreous metal and below the melting pointof iron .for a .time sufficient to obtain equilibrium temperature .conditions betweensaidco-mpactrand said part whereupon said .cupreousmetal dissolves .a portion of the iron in the cast iron and lthen'infiltrates said ferrous part, and finally removing anyresiduetof saidcompactfromsaid infiltrated :part.

3. In a method for impregnating aporous ferrous part with acupreousmetal wherein the ferrous ,part,,after impregnation, is substantially free from pits, channels .and .the like, the st pscomprising; mixinga cupreous metal .in a predetermined quantity with cast iron powder in- ..cluding sufficient iron to.fully satisfy the dissolving action of copper or ironatthe impregnating temperature, placing said :mixtureupon ,thesferrouspart .in proxirnityto the area thereof to be impregnated, dissolving at .least aportion .of ,the iron in :said cast, iron into said ,cupreous metal by heating the mixture and .the -part simultaneously to a temperature above the .melting point of the cupreous .metal-and'below-t-he melting point of iron fora time suf- .ficient .to obtain equilibrium temperature conditions between the mixture and the part, causing said 'cupreous metal to then infiltrate-said part only after said equilibrium is obtained by drawing said molten impregnant by capillarity into the pores of said part and finally removing any residue of said mixture from said part.

4. In a method for impregnating a porous ferrous part with a cupreous metal wherein the ferrous part, after impregnation, is substantially free from pits, channels and the like, the steps comprising; mixing a predetermined quant y o upr ous m ta Po de w th cas iron powder in amounts to provide suflieient iron to fully satisfy the dissolving action of copper for iron at the imp es s pera ur hr que t n sa d ix u e into a compact, placing said compact upon said part and in proximity to the area thereof to be impregnated, dissolving at least a portion of the iron in said cast iron powder into said cupreous metal by heating the mixture and the part simultaneously to a temperature above the melting point of the cuprcous metal and below the melting point of iron for a time sulficient to obtain eguilibrium temperature conditions between the part and the compact, then causing said cupreous metal to infiltrate the ports of said porous ferrous part only after said equilibrium is obtained by drawing the molten impregnant by capillarity into the pores of the part and finally removing any residue of said compact from said part.

5. In a method for selectively impregnating predetermined portions of a porous ferrous part witha cuprctous metal while maintaining the ferrous part substantially free from pits, channels and the like .at the surface thereof, the steps comprising; providing a compact including a predetermined quantity of cupreous metal together with from 1 to 5% by weight thereof of cast iron powder having a particle size of at least minus mesh said compact having a shape substantially similar to the shape of the area to be impregnated of said ferrous part, pla ng he compa urea h e o pa ti the e r d Pos t n nd o tiguou o t a ea t b mp gna selectively heating the ferrous part at that portion only .to be impregnated to a temperature above the vmelting point f he unre u m ta an be t m l n po n of iron While simu a e u y he tin d mpa t e ntinu ng said heat fo u a t me tha qui riumtemperature eonditions are obtained between the part and the compact while progressively dissolving sufiicient iron from said cast iron by said cupreous metal to fully satisfy h dis o v n act o coppe on iron an the when equilibrium temperature conditions have been obtained, causing said cupreous metal to infiltrate the selected heated portion of said porous ferrous part for imp e at n e sa e and fin y m ng ny r sidue of said compact framsa dpar The me hod as c ai e in .c aim 5, whe e the s l ct ve heating is ac omp ishe y i du v y h ting a partion only of theferrous part.

References Cited in the file of thispatent UNI ED TATE E 1? 2,401,221 {Bourne May '28, 19.46 2,422,439 Schwarzkopf June 117, :1947 2,481,962 Whitfield Sept. :13, .1949 2,561,579 Lenel July '24, 1951 2715589 Smith Aug. :16, 1:955

Claims (1)

1. IN A METHOD FOR IMPREGNATING A POROUS FERROUS PART WITH A CUPREOUS METAL WHEREIN THE FERROUS PART, AFTER IMPREGNATION, IS SUBSTANTIALLY FREE FROM PITS, CHANNELS AND THE LIKE, THE STEPS COMPRISNING; MIXING A DESIRED QUANTITY OF CUPREOUS METAL WITH FROM 1 TO 5% BY WEIGHT THEREOF OF CAST IRON POWDER, PLACING SAID MIXTURE UPON SAID FERROUS PART TO BE IMPREGNATED IN A DESIRED POSITION RELATIVE THERTO, HEATING THE FERROUS PART WITH THE MIXTURE OF CUPREOUS METAL AND CAST IRON POWDER THEREON TO A TEMPERATURE ABOVE THE MELTING POINT OF THE CUPREOUS METAL AND BELOW THE MELTING POINT OF IRON FOR A TIME SUFFICIENT TO OBTAIN EQUILIBRIUM TEMPERATURE CONDITIONS IN SAID MIXTURE AND SAID PART WHEREUPON SAID CUPREOUS METLA DISSOLVES A DESIRED PORTION OF THE IRON IN THE CAST IRON AND THEN INFILTRATES SAID FERROUS PART, AND FINALLY REMOVING ANY RESIDUE OF SAID MIXTURE FROM SAID INFILTRATED PART.