SE447126B - FORMAT FOREMAL INCLUDING A BASKET OF NON-RESPONSIBLE METAL PARTICLES AND AN INFILTRATED CONTINUOUS METAL PHASE AS WELL AS MANUFACTURING THIS - Google Patents

Description

15 20 25 30 35 447 126 2 25 ° Kelvin lower than the lowest melting point of the most low-melting, non-digestible spherical metal powder.

The resulting shaped monolithic metal article of the invention is a homogeneously infiltrated article comprising, for the most part, a first continuous phase of spherical, non-digestible metal particles which are metallurgically in one piece at their adjacent contact points in the form of a skeleton of interconnected spheres with appreciable waist formation. - when observed under a light microscope - between the largest adjacent particles and a second continuous metal phase, having a melting point of at least 25 'Kelvin lower than the lowest melting point of the lowest melting spherical non-melting particles, occupying the volume of the object , which is not absorbed by the skeleton of spherical particles, the object thereby comprising two matrixes and is substantially free of cavities.

Unless otherwise indicated in the context, the term "homogeneous" means that when a representative cross-section of either an inner or peripheral portion of the shaped infiltrated object is examined with a light microscope at a magnification at which the two phases are distinguishable, e.g. no significant deviation in the number of spherical, non-digestible particles in a given area, and that the infiltrating agent is evenly dispersed around and between the non-digestible spherical particles, and that there is no unique axis or densification in the spherical particle in any part of the object (especially in the peripheral part, i.e. the part adjacent to the surface of the object) which indicates the use of pressure for introducing coherence into the non-indigestible, spherical metal particles. These homogeneous objects are substantially free of internal defects and surface defects and therefore exhibit uniform physical, chemical, electrical and mechanical properties. In addition, the two mixed homogeneous matrixes have further desirable properties, for example resistance to abrasion and impact.

JF ».I .l 10 15 20 25 30 447 126 3 Some shrinkage occurs in the method according to the invention. Exactly how much shrinkage occurs depends on the selected process parameters, in particular the material used to produce a mold of the model, and the temperature at which light sintering takes place.

Once you have determined the magnitude of the shrinkage in the process for given process parameters, you can compensate for this shrinkage, for example by manufacturing too large a model. If you compensate for the shrinkage during the process, you can achieve a precision tolerance, ie the percentage deviation of the finished infiltrated object from the specification, which is better than about 0.2%, eg É 0.1.

Homogeneity and precision tolerance for the non-indigestible metal objects according to the invention means that these objects are particularly well suited for use in areas where small dimensional tolerances are required, such as objects with intricate or complex shapes and surfaces with fine details, eg dentures and nozzles for injection molding. .

In the accompanying drawings, Fig. 1 is a flow chart showing the manufacture of a shaped object according to the invention, Fig. 2 is a sketch of a microphotogram of an infiltrated non-digestible skeleton of a shaped object according to the invention.

In carrying out the invention, a metal powder composed of spherical particles of non-molten metal is used to produce a monolithic skeleton or matrix. "Non-difficult to melt" in this context refers to metals with melting temperatures between about] 000 ° C and 1800 ° C. "Spherical" in this context means substantially spherical and includes spheroids, spheres with flattened poles and spheres which are extended in the direction of the longitudinal axis.

Minor deviation from exact spherical shape does not adversely affect the use of the powder in the present invention.

Suitable non-refractory metals that can be used in accordance with the invention are iron, cobalt and nickel and alloys thereof. Typical alloying elements for such alloys are chromium, molybdenum, tungsten, carbon, silicon and boron, and combinations thereof. Unless otherwise stated, "metal" in this context refers to elemental metal and alloys. The preparation of spherical metal particles which can be used in the practice of the invention is described in, for example, U.S. Pat. Nos. 3,988,524, 3,258,817 and 3,041,672. Commercially available non-digestible spherical particles or powders which can be used according to the invention include alloys No. 1, 21 and 157 from Cabot Corp under the designation Stellitec), Special Metals Corporation's Co-6 alloy, sold under the name "Vertx (>, and stainless steel type 410 (American Iron and Steel Institute specification). These commercially available powders usually has a monomodal size distribution curve and comprises a mixture of small size particle fractions and larger particle size fractions.Because they are commercially available, these monomodal powders are preferred in the practice of the invention and the properties of the shaped articles of the invention can be achieved without using multimodal powders. Mixtures of these commercially available powders may a used in the practice of the invention. The size of the spherical metal powders used in the invention is a wide distribution of particles with diameters between about 1 and 200 Pm, with those with diameters below 44 Pm being preferred for optimal finished surface. Commercially available metal particles may contain small amounts of particles with diameters below 1 μm; such small particles do not adversely affect the invention as long as the content of such particles is not sufficient to prevent contact between the larger particles present and therefore interfere with efficient packing. The calculated outer surface area of the spherical particles, which falls within the size range preferred in the practice of the invention, is about 1.8x10 -2 m2 / g to 1.4.2x10 -2 m2 / g.

Dmömhæymæm fl mhædai fiflfl uweßmæ de object is a major factor in determining the particle size and size distribution of the spherical particles used in the manufacture of these objects. If you want an intricate detail surface or a high surface finish, the selected particle size distribution has a larger content of particles with a small diameter strip, but if you require small details or a raw surface finish, you can use a distribution with a larger content of spherical diameters with a large diameter.

The use of spherical metal particles offers a number of important advantages over the use of irregularly shaped metal particles. Irregularly shaped granules tend to form mechanical bridges between the particles due to the possibility of many particle contacts between two given particles, which negatively affects their flow properties. Two spherical particles, on the other hand, can only provide a contact between the particles and therefore do not form mechanical bridges. Consequently, the irregularly shaped particles do not flow as easily or fill these intricate shape details as completely as spherical particles even when the particles are vibrated. Stone filling in the organic binder is possible with spherical particles. "Filling" refers to the particle mass that can be included in a given amount of softened organic binder. Spherical particles are packed more efficiently than irregularly shaped particles and therefore less binder is required for a given mass of spherical particles. Better packing also provides metal skeletons with more even porosity before infiltration. By "porosity" in this context is meant gap passages between the slightly sintered spherical metal particles, of which the skeleton (or a first continuous phase) is composed.

The volume of the infiltrated object to be taken up by the skeleton of spherical metal particles is also determined by the particle size and size distribution of the selected particles. The infiltrated article generally contains slightly sintered spherical net metal particles preferably at least 60% by volume (and preferably at least 10% by volume) and not more than about 80% by volume of spherical metal particles. The volume percentage of the object which is taken up by spherical metal particles is regulated by the degree of filling of organic binder. Variation of particle size and size distribution for regulating the filling is previously known, see t Soc. 44, 513-22 (1961).

Organic binders which are suitable for use according to the invention are those which melt or soften at low temperature, for example less than 180 °, preferably less than 120 ° C, whereby a mixture of metal powder and organic binder with good liquid properties is obtained. properties when heated and yet the mixture of powder and binder solidifies at room temperature so that an unsintered object formed therefrom can be easily handled without collapsing or deforming. The binders used according to the invention are those which are volatile in heat, i.e. which burn off or volatilize, when the unsintered object is heated without any internal pressure being obtained on the obtained non-difficult-to-digest skeleton object due to evaporation and without leaving any significant adhesive residue on the skeletal object as a result of such a heating step.

Organic thermoplastics, or mixtures or organic thermoplastics with organic thermosets are mixed with non-digestible spherical metal powders to form a moldable paste-like or plastic mass, when the resulting binder-powder mixture is heated. Examples of thermoplastic binders are paraffin, eg "Gulf Wax" (purified household grade paraffin), a combination of low molecular weight polyethylene paraffin, mixtures containing oleic acid or stearic acid or lower alkyl esters thereof, eg "Emerest 2642 "(polyethylene glycol distearate, average molecular weight 400) as well as other waxy and paraffinic substances having the softening and flowing properties of paraffin. Representative thermosetting materials which can be used in combination with thermoplastics as binders are epoxy resins, for example diglycidyl ethers of bisphenol A, such as 2,2-bis [p- (2,3-epoxypropoxy) phenyl] - propane, which can be used with suitable curing catalysts. Care must be taken not to produce crosslinking during the mixing and forming steps by the action of heat, as mixtures of thermoplastic thermosets are used as binders. Once the adhesive mixture of thermoplastic thermosetting plastic and the spherical metal particles have been placed in the heated mold and vibrated, curing can be initiated by further keeping the mold warm. Mixtures of thermoplastic-thermosetting plastics tend to give unsintered articles which have greater raw strength and are thus more manageable than unsintered articles which are made with only thermoplastic as binder.

The spherical metal powder and the inorganic binder are preferably mixed in a heated mixing device, for example a sigma mixer, whereby the temperature may be high enough to soften the organic binder and thereby allow the powder and the binder to be mixed homogeneously. The particular amount of binder used depends on the particle size and size distribution of the spherical metal particles used. Sufficient binder should be used, eg 2 to 10 parts by weight, if 100 parts of metal powder are used, so that the spherical particles are allowed to flow into and optimally take up space in the mold, thereby eliminating variations in bulk density and surface density in the molded article. The mixture of powder and binder can be heated to form a plastic mass and directly transferred to a flexible mold. Alternatively, the hot mixture of metal powder and organic binder can be cooled and the resulting solid ground to a granular, free-flowing form (such as a granular material, termed "pill dust"), and later heated and poured into the mold. 10 15 20 25 30 35 447 126 8 To obtain a mold for forming a "pill dust" or hot plastic mass into the desired shape, a pattern or a copy of a model is made. A molding material is poured around the model in a suitable container, the molding material is cured and the model is removed to form a mold which can reproduce substantially identical copies of the model, including fine details and cross-sections according to the invention.

The metal objects made according to the invention may have a working surface (ie working part) which comes into contact with and effects a deformation in a material to be machined and a supporting part which holds the working surface in the correct position for give the desired deformation. For example, a core made according to the invention can be used to form a hole in a syringe-shaped plastic part. The working surface of the core is the part which comes into actual contact with the plastic material to be formed, and the supporting part holds the core in position so that the desired hole is formed.

The desired model has a work surface part mounted on a bottom part, from which the work surface and the supporting part extend or away. The working and supporting part can consist of the remainder of the material from which the working surface - the supporting part is made, or the working surface - the supporting part can be mounted on a special bottom part after production. A mold of the model is produced by placing the model in a special container, molding material is poured around the model and the molding material is cured. If a suitable model is used, in the later stage with light sintering, a porous metal skeleton will be obtained in one piece with a working surface - supporting part mounted on a bottom part. This is desirable because the metal skeleton formed in this way can be infiltrated by passing the infiltrating metal through the bottom part before it penetrates the body of the porous metal skeleton below the supporting part - the working surface. . .ÉIfv-w w, - ~ 10 15 20 25 30 35 447 126 9 Infiltration of the metal skeleton through the bottom part enables the infiltrating agent to be solubilized, ie enriched with the metal of which the working surface - the supporting part is composed before the infiltration of the skeletal body below the working surface - the supporting part.

Such enrichment of infiltrating metal reduces dimensional changes that would occur if the skeletal body were infiltrated with unreacted infiltrating metal and the skeletal metal would be significantly solubilized by this unreacted infiltration. After infiltration in this way, the bottom part is completely removed or machined to the desired design for use as a supporting part for the work surface. In this latter case, the bottom part functions both as a supporting part and the bottom part and therefore the work surface can be mounted directly on the bottom part.

The molding materials that can be used in the practice of the invention are those which cure to elastic or flexible rubber mold and usually have a durometer value (Shore A) of about 25-60 and reproduce fine details of the model part without significant dimensional change, i.e. without more than 1% linear change from the model. The forming materials should not decompose as they are heated to the forming temperature, eg 180 °, and should have a low curing temperature, such as room temperature.

A molding material that cures at low temperature forms a mold that maintains a close dimensional control from model to mold. A forming material with a high cure temperature usually gives a shape of dimensions which differ significantly from the dimensions of the model. In order to maintain dimensional stability, it is suitable that the molding material has a low moisture sensitivity. Examples of molding materials are curable silicone "RTV" 08-347, January 1969 from Dow Corning Co., and low exothermic ureas, such as those described in Bulletin Tan Resins. Such molding materials cure to elastomeric or rubber molds with low shrinkage after curing. ____._....._..._.._._.._..._., _. The amount of molding material used to shape a mold of the model may vary depending on the particular molding material used and the shape of the model. It has been found that about 10-14 cm 3 of molding material for each cubic centimeter model provides a mold which retains the desired flexible properties and also has sufficient strength to withstand the small hydrostatic pressure drop produced by the plastic mass of the powder. binder in the mold before the solidification of the binder. The molding conditions for molding articles according to the invention discussed below allow the use of a cheap, soft, elastic or rubbery mold, since the only applied pressure is the hydrostatic pressure from the plastic mixture of powder binder in the mold. , which pressure is very low and gives rise to negligible distortion. The mild shaping conditions thus help to ensure a precisely shaped unsintered object even if a highly deformable shape is used. In addition, the forming technique results in a shaped unsintered object with an even density due to the advantageous flow properties of the spherical powder.

The mixture of powder binder heated to 10-20 ° C or more above the softening point of the binder component can be fed to the vibrating elastic mold preheated to approximately the same temperature as the mixture of powder and binder, and the mold and its components can then be evacuated.

By selecting the appropriate size distribution for the spherical non-digestible particles and a suitable organic binder, the consistency of the powder binder mixture is such that upon heating above the melting point of the binder in vacuo, the mixture can be formed with only slight vibration in purpose of ensuring the removal of air pockets or gas bubbles.

When the heated, evacuated mold is filled, the vibration of the mold is stopped and the mold is kept isothermal, for example at a constant temperature of 10 to 30 ° C above the breaking point of the binder for a sufficient period, e.g. to 24 hours, to ensure even complete filling of the mold. The mold and its contents are vibrated for a short period before cooling.

Cooling of the mold and its contents at room temperature causes the organic binder to solidify and form the unsintered molded article. If the binder melts at a rather low temperature, for example 35 - 40 ° C, it becomes common to cool, for example to 0 to 5 ° C, the mold and its contents to the point where the binder is relatively rigid, preferably in a desiccator to lower the moisture condensation. The solid unsintered article can be easily removed from the mold by applying a vacuum to the outer part of the flexible mold. Removal of molds in vacuum is easy when it comes to molds with bevelled lower edges. The resulting, removed from the mold, unsintered object is a faithful copy of the model. This shaped article has good raw strength due to the hardened matrix of organic binder, which supports the non-digestible spherical metal particles. The non-digestible powder is homogeneously dispersed in the matrix of organic binder and contributes to the formation of a sintered object of even density (due to the even distribution of the powder within the binder) and to the formation of a skeleton thereof with corresponding even porosity when the binder is removed.

The even density of the unsintered article is important in the subsequent heating and infiltration steps. An even density minimizes or prevents mold distortions as the sintered molded article is heated and infiltrated. Furthermore, an even density will minimize or prevent the emergence of local pockets of infiltrating material, which would otherwise cause the final finished non-digestible object to exhibit unstable and uneven electrical or physical properties.

In order to form the skeletal matrix, the unsintered shaped object is preferably packed in a weakly vibrating bed of non-reaction-difficult hard-to-digest powder, e.g. alumina or silica, to prevent settling and dimensional loss when heated in a programmed oven to a temperature of about 900 to 1400 ° C. Upon heating the shaped unsintered article, the organic binder is removed and the non-refractory particles sinter easily or become tacky to form a one-piece metallurgical, manageable, porous, non-digestible, monolithic article or skeleton. The term "metallurgical in one piece" in this context means that there is interatomic diffusion in the solid state, ie that bond is formed in the solid state between adjacent spherical metal particles. This heating step entails, in addition to removing the binder, a first stage of sintering of the spherical particles, ie the formation of interparticle waist formations, whereby a monolithic object is obtained. Programmed heating is preferably used to provide only minimal sintering or to provide tack for the spherical particles at adjacent contact points. Programmed heating avoids the significant shrinkage that would occur if heating and sintering were continued past the first stage, thereby giving an undesired skeletal shrinkage and increase in density as the volume between the pores would decrease and the particles would unite through larger neck portions.

Programmed heating also avoids the occurrence of internal and external cracks, which otherwise occur if a gaseous binder develops rapidly if the unsintered shaped object were to be heated quickly to a light sintering temperature. Small unsintered shaped objects can usually heat up faster than larger objects. A heating scheme suitable for objects as large as 5 cubic cubes when, for example, polyethylene glycol distearate is used as the organic binder is as follows: ..-.._._.-....- ~.-.-_._. . .... ._ ._ ... W.

U1 10 15 20 25 30 35 447 126 13 Step 1 from room temperature to 200 ° C (approx. 43 ° C / h) Step 2 from 250 to 400 ° C (approx. 7.5 “C / h) Step 3 from 400 ° C to a light sintering temperature (about 100 ° C / h) This programmed heating is carried out in a protective atmosphere, for example hydrogen-argon, nitrogen, hydrogen-nitrogen, hydrogen, dissociated ammonia, and other neutral or reducing atmospheres, which are known in powder metallurgy to prevent oxidation of the metal particles.

The heating of the sintered molded article to a temperature above about 1020 ° C can when alumina is used as a difficult-to-digest non-reactive carrier material lead to some alumina adhering to the sintered molded article. For this reason, then, a final light sintering temperature above 1020 ° C can be meant, the light sintering process can be stopped at 1020 ° C, and the resulting coherent, manageable shaped article can be cooled and removed from the alumina bed. Alumina, which adheres to the surface of the article, is carefully removed, and the article is heated to the desired temperature at which light sintering occurs, without the need for carriers in the non-reactive, difficult-to-digest powder. When temperatures for light sintering below 120 ° C are used, surface adhesive carrier material can be removed by gentle brushing with a camel hair brush.

To ensure complete filling of the volume between the pores, if a mass of infiltrating metal exceeding the calculated volume between the pores is used, too much wetting of the skeleton and accumulation or accumulation of infiltrating metal on the outer surface of the object or "flowering" is often obtained. If excessive wetting of the skeleton is minimized by using slightly less infiltrating metal than is necessary to completely fill the hollow gels in the net metal skeleton, this leads to unfiltered cavities in the finished composite material and thereby lowers the material's mechanical strength and the the uniformity of electrical and physical properties. The surface bloom can be reduced or prevented according to the invention if the outer surface of the lightly sintered metal skeleton is covered with a thin layer of zirconia powder, for example by lightly spraying the outer part of the metal skeleton with a suspension of zirconia powder in a readily evaporable or volatile carrier, such as acetone. The zirconia powder coating reduces the accumulation of infiltrating metal on the surface and allows the use of excess infiltrating metal to what is necessary to accurately fill the gaps in the metal skeleton without the appearance of flowers (or non-infiltrated cavities). Contact between these outer surfaces of the skeleton, where infiltration is to occur, eg the bottom part, and the zirconia powder must be avoided with care, for example by: covering such areas with Haskering tape. The step of coating zirconia can be used selectively or eliminated if a certain amount of surface flowering is desired, for example for the production of a shaped object which looks as if it were made of only infiltrating metal, for example a decorative object with a metal skeleton of cobalt alloy infiltrated with silver or silver alloy.

The porous metal skeleton (preferably zirconia treated is infused with metal or alloy which melts at a temperature below the melting point of the spherical metal particles of which the metal skeleton is composed of ozdethar as described) or preferably the properties discussed below. It has surprisingly been found that infiltration can take place without significant dimensional change by using as infiltrating agent a metal which melts at a temperature as low as 25 ° K lower than the melting point of the most low-melting skeletal particles. Then the melting point of the infiltrating agent, Mpi, and the melting point of the metal of which the spherical particles are composed, msp, ratios MP1 / MPSP values of 0.95 or less. When this ratio decreases both are expressed in degrees Kelvin, one can use as high as 0.98 and one also prefers the dimensional changes, which means that the lower limit of the melting point ratio of infiltrating metal to melting point for skeletal metal is determined by the desired properties of the finished infiltrated objects.

Infiltrating agents with the desired properties discussed below usually have melting points above about 7000 Kelvin and therefore the lower limit of the melting point ratio is about 0.5 and the limit 0.6 is preferred.

The infiltration of the metal skeleton takes place uniformly by the action of the capillary force without pressure being applied to the infiltrating agent and without the formation of local accumulations of infiltrating material in the non-digestible skeleton. The non-digestible metal backbone can be supported by a bed of heavy melt, non-reactive powder. The bed is arranged so that the solid infiltrating material, which may be in the form of powder, balls or rods, is not in direct contact with the metal skeleton. When the infiltrating agent melts, it flows under the influence of gravity towards the area of the metal skeleton through which infiltration is to take place, for example the bottom part, comes into contact with the skeleton, while it is liquid, and penetrates into the skeleton by the action of capillary force. Direct contact between solid infiltrating material and metallic skeleton can give rise to bonds between them during heating. In addition, differences in coefficients of thermal expansion or sintering rate between the infiltrating agent and the skeleton give rise to stresses and possible cracking in the skeleton "No contact between the solid infiltrating material and the metal skeleton is therefore desired. Distributed throughout the non-difficult-to-melt skeletal body. acceptable electrical properties with minimal shape distortion of the finished infiltrated article due to thermal expansion. Since the infiltrating material is evenly the coefficient differences discussed above, the infiltrating metal used is selected with respect to When an electrode for electrical discharge is desired, infiltrating metals with good electrical conductivity are used, such as copper, silver and alloys of these materials.

When a harder or stronger finished particle is desired, for example for building parts, molds or nozzles, the infiltrating material like the spherical metal particles can be composed of hardenable alloys, which can be further treated in order to increase the hardness and strength of the object. Still other metals and alloys having melting points below the non-melting skeleton can be used as infiltrating agents.

The infiltrating metal is preferably such a metal in which the metal skeleton is substantially insoluble. Large dimensional changes and large distortion would occur if the infiltrating material was significantly dissolved in the metal skeleton. High solubilization of the metal skeleton in the infiltrating material can be minimized by using an infiltrating metal saturated with the metal from which the skeletal particles are made. As discussed above, solubilization can also be minimized by infiltrating the metal skeleton through a bottom portion. In addition, the molten infiltrating metal should wet the forged metal skeleton to achieve capillary infiltration. An excess of infiltrating metal, for example up to a volume of about 25% greater than the calculated volume between the pores, can be used if the exterior of the metal skeleton has been covered with zirconia powder before infiltration.

The time period at the infiltration temperature and the infiltration temperature used is a function of the size, wetting properties and volume of the non-digestible metal skeleton. At a temperature slightly above the melting point of the infiltrating material, 30 minutes is enough to infiltrate a knot-shaped skeleton with a volume as large as 130 cm3.

After infiltration, the article is cooled and the outer zirconia coating is removed, for example, by peeling with a glass bead stripper (Empire Abrasive Equipment Corp. Model No. S-20) at a pressure of 1.4 to 2.8 kp / cm 2 with an 8 mm opening diameter.

If an age-curable infiltrating material is used, for example copper alloyed with nickel (15%) and tin (7%), or if the metal skeleton is curable, the infiltrated object may be subjected to an aging cycle at low temperature in order to increase the hardness and / or abrasion resistance. Finally, excess infiltrating material or excess bottom part is removed from the molded composite or the work surface which gives the finished infiltrated molded metal article.

A list of suitable systems of spherical metal particles and infiltrating materials is shown in Table 1.

The melting points are given in O Kelvin and the melting point conditions are given.

Table 2 contains the compositions of the metals, which are given in Table 1. 447 126 18 .muwm fl xmunmn mxmwumwm mv mmm nmußøumu fl msm muwmm fi suv: oo uw fi m fi uwum fi wwcmuwuu fl wuu fi umw www uuw mmNo num m «n n« acw »N oß 1 ammmom mmo fi N om | == «u N oß» Hm fl mom ßm.o «~ .o N ~ .o wmm fi ~ ß.o ~ o ~ fi m @ .o nmn fl ~ wo nm ~ H o @ .o wmn fi o ~ .o Nmo fl n> .o «« H ~ ßm.o mmm fl ww.0 wmm fi K wwcq flfi mzuwwn w @ z \ @mz M0 .ms ummaom N NN I mdwum fi m N wß I w fl äw fl mæ 1: ON n I: EN m I mh N m I MZ uo > ~ mm ummmom N ww umnmox N Nß I um> ~ fl m ummmoxlën fififi mumm mcounuoumom umamom mmm fi mwumumä ww: muw »uH« w = HH AAwm ßoæ fl mow fl mmß fi nmm fi nova mom fl mona mw a mona mona mm mm H mma wa mona mona a mona wa mona a mona wa mona wa mona wa mona wa mona wa mona Nm: wu «fl Hwum: O fl w .HwH <fl wuw uu fi uwuwøm AN: wu« ~ Hvum: ßm fi: mu «fl Hmum: Aum fl ov mx flfi v mIOO: NUH0> ZH zmu fififl wuw: a: wu« ~ «wum: wiou: wiou: wiou: >: m | oo:% unm>: nh fi 447 126 19 ~ n, ~ H »N HN om mw Hmmmoxlësw flfl huwm mnounznowmom Nm zwuw fifi muwz OAQ .HmH <dwum u fl âuwumom HN: wu« HHwum: ßm fl: Hu ww: Hu mIOU ZMUHMP: m. fi .ämm ~ .o mo .ämm o. ~ m. ~ .ämm «. ~ m.« .ämm oH ~ .H .Hmm mo. «.Hmm ~ w ==« um m nu m 3 ou N Admmdh Nux «>. flfl duumwcmñëmm »Q um fi xmuumm fi dmu fl u mxw fl nmwm Pm mw fi ........_.-._-_._....._._..__.__ 7 10 15 20 25 30 447 126 20 The optical examination of the working surface of the finished object at the magnification 15OX reveals a continuous matrix of substantially spherical particles or connected spheres in contact with and surrounded by a continuous phase of infiltrating material.

No signs of cold working, eg disturbed surface metal as occurs with conventional machining methods, can be observed.

Fig. 2 shows a metallurgically polished inner cross section of infiltrated object according to the invention at the magnification 600X. A continuous matrix 3 of substantially spherical metal particles 4 with a size distribution is clearly seen.

The continuous phase of infiltrating metal 6 in contact with and mixed with the skeleton and spherical metal particles or spheres is seen with a neck formation 7 between the particles. At this magnification, deviations 8 from the spherical shape become clear. These deviations are the result of partial dissolution of the metal skeleton in the molten infiltrating agent and characterize the infiltrating metal objects according to the invention. Such dissolution gives rise to a slight loss of the spherical shape and gives the somewhat spherical, hollowed-out appearance to the spherical, connected non-heavy spherical metal particles.

The method according to the invention, described above, is shown in Fig. 1. A model 11, which has been machined to compensate for inherent shrinkage, is formed 12 with a flexible molding material, such as the silicone rubber "RTV". The molding material is suitably cured depending on the flexible molding compound used, and the machined model is removed 13 from the cured solid rubber mold 14. Non-digestible spherical metal powder 16, such as "Vertx" Co-6 cobalt-based powder of suitable size distribution; mixed with a thermoplastic binder 17, for example paraffin or a mixture of thermoplastic and thermosetting plastic binders, and heated 18. The mass formed may optionally be allowed to cool to a solid 21, and ground to "pill dust", 23, which requires heating 24 before the pulp 26 of powder binder is fed to the heated mold 27 or the heated pulp 26 of powder binder may pass from step 18 to the mold 27. The mold 14 is heated 28 in a suitable manner before being filled with the heated mass 26. The mold and its contents are evacuated while being vibrated 29 to remove air bubbles and completely pack the mold 30. The completely f the mold is kept at a constant temperature and vibrated 32 shortly before cooling 33. Removal of the mold in a vacuum 34 gives a rigidly manageable unsintered shaped object 35.

The resulting unsintered shaped article 35 is packed in a non-reactive hard-to-digest powder and is programmably heated 37 to drive off the thermoplastic adhesive and to cause the metal particles to sinter easily to form a porous metal article 38. The porous article is surface treated 39 and placed in a container suitable for infiltration 41 with, for example, copper 42. After cooling 43, the resulting infiltrated object 44 can be polished at the infiltration site for the purpose of removing irregularities 45.

Once the mold has been removed in vacuum from the sintered molded article 35, the flexible mold 14 can be returned 14 to make another article.

The infiltrated non-rigid net net articles of the invention have uniform density, are tough, impact resistant and substantially free of internal defects and surface effects.

They exhibit uniform physical, mechanical and electrical properties and a precision tolerance better than tO, 2% can be achieved. These objects are particularly useful in areas where tough hard-to-digest objects with small dimensional tolerances are required, such as objects with intricate or complex shapes and surfaces with fine details, such as dentures, dies for die casting of metals and nozzles for injection molding of plastics. The objects and advantages of the invention are illustrated in the following examples, which are not to be construed as limiting the scope of the invention. All parts are by weight unless otherwise indicated.

EXAMPLE 1 100 parts of spherical metal powder of cobalt-based alloy (-100 mesh US Sieve "Vertx" Co-6 sold by Special Metals Corp (less than 149 μm mixed with 3.5 parts of polyethylene glycol distearate ("Emerest" 2642, mp 36 ° C) and the resulting mixture of metal powder and binder was heated to 6600. The resulting plastic mass was transferred to a cubic cavity (5.08 cm) in a flexible mold of hardened silicone rubber "RTV", which was heated to 66 ° C. The mold was evacuated to 399 Pa. and held at 66 ° C for 10 minutes while vibrating with a Model J 50A Jogger, which vibrated at a resistance setting of 80 to 90. The mold and its contents were depressurized and transferred to an oven to be maintained at 38 ° C. After the treatment at constant temperature, the mold was vibrated again (with a resistance setting of 40) for 5 minutes and then allowed to cool at room temperature for a period of 2 hours.The cooled mold and its contents were placed in a desiccator containing anhydrous calcium sulfate oc The cooled mold and its contents were removed from the desiccator and the unsintered article was immediately removed from the mold under vacuum. The resulting unsintered article was placed in a graphite vessel containing alumina powder ("Alcoa" Quality A-100) and vibrated slightly to easily pack the unreacted difficult-to-digest powder around the unsintered article. , comb-controlled Lindberg furnace and the retort were slowly evacuated so that the ahnum number spread through at about 67 Pa was sufficient to prevent the furnace.A vacuum reactive gases would be quickly filled with argon, which the majority of those removed and the furnace contained 5 % hydrogen 10 15 20 25 30 35. »w - w-en.- -. a .i 447 126 23 A dynamic gas atmosphere was maintained during the heating cycle at a flow rate of 85 liters / h.

The furnace was heated from room temperature to 250 ° C at a rate of 43 ° c / h, from z 50 to 30 ° C at a rate of 7.5 ° C / h, from 350 ° C to 100,000 at a rate of 100 ° C / h and kept at 100 ° C for 1/2 hour to break down and remove the binder and easily sinter the spherical metal particles. The heating was stopped and the ship and its contents were allowed to cool at room temperature down a dynamic gas atmosphere in the furnace. The lightly sintered article was removed from the alumina bed and carefully brushed with a camel hair brush to remove any surface adhesive alumina. The surface of the article was then sprayed with an aerosol suspension composed of 10 g of zirconia powder (diameter about 1 to 5 μm) in 100 ml of acetone. The object was cubic and about 0.5 cm of the part of the four surfaces that were located on the side or bottom was covered with masking tape while the exposed remainder of the five surfaces was sprayed with the aerosol suspension. The front or bottom was not covered with masking tape as it was directed away from the zirconia spray and therefore protection of this surface was unnecessary. After removing the masking tape, the unsintered object was placed on the bottom of a sloping alumina bed in a graphite vessel. A quantity of copper powder ("Gou1d" type R-64, -100 mesh) was placed on the alumina bed so that upon melting the liquid copper would, by the action of gravity, flow towards the part of the skeletal object which was not covered with zirconia powder. with the metal skeleton and infiltrate through the unsprayed outer surface.

The vessel and its contents were placed in a molybdenum-wound electric furnace and the furnace was evacuated to 6.7 Pa and backfilled with hydrogen. A dynamic hydrogen atmosphere was maintained at a flow rate of 141 liters / h while the temperature was raised from room temperature to 100 ° C for a 2 hour period and maintained at this temperature for 1/2 h. After 10 15 20 25 30 35 4-47 126 24 During the infiltration, the resulting infiltrated article was cooled and the outer zirconia coating was removed by passing a cold hammer with glass beads (less than 44 .mu.m) through an 8 mm opening at a pressure of 1.4 to 2.8 kp / cm @ 2.

The cold-hammered object was cut, metallographically polished and examined at SOX and 750X, the object being homogeneous with waist formations between adjacent sintered spherical particles and no internal cracks, large porosities or other discontinuities. Fig. 2 shows the appearance of the objects.

EXAMPLES 2-11 A number of experiments (Examples 2-17) were performed in the manner described in Example 1 to prepare other infiltrated articles of the invention and these additional experiments are summarized in Table 3. In each of these additional experiments 100 parts of spherical metal powder were used in the manufacture of infiltrated objects in the form of bars measuring 5.08 cm 3 for impact testing. When sintering temperatures in excess of 1020 ° C were used, the unsintered shaped article was programmed to about 1020 ° C in a programmed manner, cooled, removed from the non-reactive refractory support and then heated to the indicated light sintering temperature. The cut sheets of infiltrating material were commercially available metals, while cut plates with infiltrating agents consisted of laboratory-produced metals. The results of the Rockwell "C" and Rockwell "L" metallurgical hardness tests are given in Table 3 as well as Charpy tests with scored and non-scored samples. Hardness tests Rockwell "B" and "C" were performed according to ASTM Specification E18-74.

The tensile test was performed according to ASTM Specification E23 ~ 72.

Samples of smooth test rods type A, for Charpy testing were used but modified so that the cross-sectional dimensions 0.01 cm É 0.008 cm were used. Samples showing "uncut" impact strength were not scored. -_..-. ...- w-v-.W -... Wv-. .., - .., ........._..._....._..-_- ~ --__--- »447 126 25 In table 3 there were no internal blisters on fracture surfaces or metallographically polished sections of the 131 cm knobs in Examples 9 and 10. This is partly due to the even density of the finished infiltrated objects. 4-47 126 26 muu flfl m N oH1Nz ~ «@ ~ øfco II Hm mßOH wmuu fl üw N O fl l fi w OQHA ßw. # Zumwnwüm: QQ: KuHw>: w Nmßlnu quuw fl ß NN law NNQN @ | ° u I nNWuw Om OO Om OO ßm.w: umwHwEm: QQ. ¥ uHw>: ß Nmn | = ud> «Mm N N.OlOO Nwww wl0O II mN OOHH wmuumßm N m.alwm Ooa fl ßo.« zumwwmëm: wc: NuHm>: m Nw »| = u m fi ä N m6- .H S3 oLö II wm Oo fl a wmuuwdm N H. fl ImZ Oø flfl ßw. #: umuhwämz we% uHw>: m _ Nwmw o | 0U mm I am WNHH Hm> HDm SO Omu fl ßw.w zuwwnwäm: ev: NuH @>: w Nwwm mI0O N fi N.N Nw.O ow Ou fifl Hw> fl Dm UU O «NH mM: um0umEW: mw fi: Nuhm>: m Nwow olou A NO.N #mO dm Om flfl H0> fi9 w: U OONA mm : ummHmEH: med: XuhU>: N uoc umumxmo umumxm uwnwnms oo Enom m H uo um fi mu mæß EN V mhß H% luom Ewa> o »m | mmumnu: o: .mäwu .mëmu xu fi Smsxuom nwøo fl .àm wx fi u Louw. L fifi N "ENS: NÉÃ> wuw> oua mos umamxwcmwm Hmwnmumä ww: mumuuH« u: H Hævmëmwc fl m H fl muwë xm fl nmwm m AAmm 447 126 ^ .m »~ o« vm 4 @ mm @ | oU .fw Zumuhwb: .NQ | fl UUW => w um fi ww Nwom mx flfi> m ww I Nm OOHH um> fl: m nu ow flfi ~ ww zummuwêmz .cvum fi m Nwum ~: muw fl m 1 o ~ .o mm m ~ H H wnmum w <oøo fi ~ @. «=» W @ ~ waw = qq | H ~ »w = muum fi m N - | w <~« @N ~ = @ - H wn 1 mw www wmuu fl nw N wN | øo om flfl fl w. «: UwwumEm:« «u fi wum: _ / Mum» 2 lmmum fi hu Inn “Hou | mmh fl mumx m flfl m olou m II | o flflfl um> ~ fl m so oø flfl o. fl www: øomm: ce .Ruuw>: onøo m I | | OOHH uw> fi sm su ßw. «Øwwwmumm we: xunm>: uoa umwmxmo umumxw uwswum: Uo Euom mN% oo um fi ww mN% mmïl fl l. MNNI | ~ om em *> o ~ @ 1 »@Hm; u = u = .QEQU .mama ßw fl H fi wäxuom um fi omu amwc fi u | uouw lmuu | uc« m l fi wx .à fi c fi »än: Üpmm> mum> onm mon uwmwxmuwwu ~. «McH fi mwmñmwcwm fifi muwä Mwmuwww mä NH aa OH. .._... ~.-...._..._-....._......_. ~, _ _________ ._ __ ~ .__.....-. . ABU al UXM flfl mume umuud f m ABU fi nm fifl Wa N Nm.O ma wøwdmüæum .m, fl mëwuæw uwmmmum umawuu fi wmdw nuo ABU fi wxw fifl muuñ umuunww uum fl f m flfl Me n m ~ .o ma WNW fi mñmum .q .fl wmëmxm muuwu m MWW fifl mumämum max Eu al etc. 4 .m Hmñwuæw ummwmum uwnwuu fi wmøm Soc Hmëmuww umëuow uwnuu fi mo al w flfl Me n mm.H mm mu «ußE> HM .N Hmëmumw ummwwum umnmuu fifi wc fl: oo fi mämuwm umenow uwuuc fl mo cm flfl æu N« mo ma wuwun fi æuz .N nuwuouuom Nm N52 »S2 .. ._33 w HN.o | mw om umuu fi cw N omlcm ooo fi Nm.m: ummumEm: wc I fl wumz NN Hun Iso muum fi m N N law Nwww we H zwuw fl æm. fl | o «m fifl wmuu fl cw N m fl n fl z o« HH Ho.e: umoumEm: l fi uuwz w fi Hmn I no N m az ßm fifl äÉ N m å NÉN ._33 | I mm oo flfl wmuuwnm N m fi z oo flfl Nø. «Zuwwnuëm: we | Hmuw = ma o? 99 .H.m.H. <Qw Hmum Ncwu uu fl uu H.H | ww oo fifi um> N: m: U ONOH mm.m. : mha luø fi m l fl wz | H «udH uuwu l fl uumm> mum> o» a wo: ummmxwøwmm Hm fi nwuma wwøwumuu flfi mc fl Hmnwämwc fl m fifi wumê xw fl nmwm ^ .wu »o« vn 25 en qem 15 15 rod-shaped core, which was suitable for extrusion is produced. The core had a diameter of about 0.32 cm and was used to make a cylindrical hole which ran along the axis of a cylindrical plastic part which was about 0.27 cm long and had an outer diameter of 0.813 cm.

A spherical metal powder (Stellite No. 1, less than 44 microns) was mixed with 4.61 parts of a thermoplastic organic binder "Emerest" 2642. Weak sintering of the unsintered shaped core was continued at 111 DEG C. for 45 minutes. Copper alloy containing nickel (15%) and tin (7%) was carried out for 45 minutes at a temperature of 120 ° C.

The infiltrated core was machined for press fit on the moving part of a two-part injection mold. The fit of the rod-shaped core on the stationary part of the mold was secured by grinding the tip of the rod. After the installation of the core in the movable mold part, the whole mold was installed in a machine (58 000 kg)) with an injection molding capacity of 156 g of polymeric material with the same density as polystyrene. 120 injection molded plastic injection molds (VanDorn 75 ton parts are made of polystyrene. Each plastic part was removed from the core and discarded when the moving part of the mold was opened. A cylinder temperature of l93 ° C was used together with a spray force of l4, lx106 kp / cm2.

The plastic parts did not show any foreign plastic material, which indicates that the hole was completely closed with the inserted core evenly attached to the stationary molded part. No cold hammering, cracking or abrasion occurred on the core, which showed the homogeneous physical properties of the core.

EXAMPLE 19 A spherical metal powder ("Stellite" 21, less than 53 microns) was used to make a fitting piece, using the method of Example 1. After slight sintering (157 V) 447 126 V) at 100 ° C, the skeleton was sprayed with zirconia powder dispersed in acetone. The covered fitting piece was placed in contact with a dental insert B of cast gold with the composition gold (76%), silver (l4.3%), copper (7.5%), palladium_ (2%) and indium (the rest) . Heating to 100 DEG C. for 1/2 hour in a hydrogen atmosphere resulted in infiltration of the gold insert into the skeleton of spherical metal powder.

No distortion of the skeleton occurred and the pass bit shrinkage from the model averaged 0.79%. The mean value of Rockwell "B" hardness was 96.

EXAMPLE 20 200 g of cobalt-based spherical metal powder (less than 44 Fm, "Vertx" Co-6) was mixed with 2.0 g of thermoset "Epon" 828 for 5 minutes. Half a gram of epoxy curing catalyst (Shell Oil Co., Type F1). ) was added and mixed for about 2 minutes Finally, 8.0 g of butyl stearate were added to give an even putty-like consistency after another 5 minutes of mixing, this mixture was fed into a vibrating mold preheated to 66 ° C , vented in vacuo (133 Pa) and then re-pressurized to ambient pressure, the object was then held at 66 ° C for 1/2 hour to cure the thermosetting plastic so that the molded article became rigid.The article was removed from the mold, packed in an alumina bed and heated to 1010 ° C in an argon atmosphere containing 5% hydrogen as in Example 1. The lightly sintered article in the form of a cube (5.08 cm) was covered with an aerosol suspension of zirconia and infiltrated with copper at 111 ° C for 45 min.

EXAMPLE 21 A cavity in a die casting in the form of a sawtooth button having a diameter of about 1.27 cm and a length of 1.27 cm was prepared according to the procedure of Example 1. A male model of the sawtooth button was used and a female mold was made with a two-component molding material sold under the "Carbalon" 122G brand. The individual components of the surface material were cooled to 10 ° C and vented for 10 minutes to approximately pump vacuum (approximately 4 kPa).

Equal parts of the two components were mixed and poured over the male model, which was placed in a suitable container to contain the casting material. The casting material, which covered the pump vacuum and was cured for 1 hour at about 10 ° C. Male model male model was deaerated for about 1 minute at the kid was then removed from the mold from the cured female copy and the copy was allowed to cure for an additional 24 hours at room temperature. The copy of the cavity in the casting is a female pattern of the original male model.

The female copy of the cavity of the casting was copied according to the procedure of Example 1, using a cobalt-based alloy ("Stellite" 1, less than -44 .mu.m) and 4.61 parts of "Emerest" 2642. The sintered shaped copy of the cavity was easily sintered at 130 ° C and the resulting metal skeleton was infiltrated with a copper alloy containing nickel (15%) and tin (7%), the infiltration was carried out in a hydrogen atmosphere for a 45 minute infiltration period and an infiltration temperature of 111 ° C.

Zinc, which was heated to a temperature of 500 ° C in an air oven, was poured into the infiltrating mold cavity.

The zinc was allowed to solidify and the casting was removed from the cavity. No reaction appeared to occur between the zinc and the wall of the cavity.

Various modifications and alterations to the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention, and it is to be understood that the present invention is not to be limited to the illustrative embodiments and examples set forth above.

Claims (5)

A format, homogeneous, monolithic metal article comprising as a main part a first continuous phase of metal particles, which by bonding in solid state I are metallurgically bonded to a piece in the form of a skeleton, and a second continuous phase of metal occupying the volume of the object not occupied by the skeleton, characterized in that the first "continuous phase has spherical, non-meltable metal particles with a diameter distribution of 1-200 Fm, that upon observation in a light microscope one can observe a noticeable waist formation between the largest adjacent particles in the first phase and that the second continuous phase has a melting point which is at least 25 ° Kelvin lower than the melting point of the most low melting of the spherical, difficult-to-digest particles, with the lower limit of the melting point ratio being 0.5. 2. An article according to claim 1, characterized in that the non-digestible spherical metal particles have a diameter of less than 45 Pm. 3. An article according to claim 1, characterized in that the first continuous phase comprises metal selected from the group consisting of cobalt, iron, nickel and alloys containing one or more of the substances cobalt, iron and nickel, An article according to claim 1, characterized in that the second continuous phase contains metal selected from the group consisting of copper, silver, gold and alloys containing one or more of the substances copper, silver and gold. A method of forming a monolithic, infiltrated non-molten object from a mold, comprising a mixture of non-molten spherical metal particles which, by solid state bonding, are metallurgically bonded to a piece in the form of a skeleton and a second continuous metal phase, characterized by the new combination of steps: heating a mixture of non-digestible spherical metal powder with a diameter distribution of 1-200 μm and volatile organic binder, comprising a thermoplastic material, above the bending temperature of the adhesive, the formed plastic mass is formed into a heated flexible mold to form an unsintered shaped article, which is substantially free of cavities and which has the shape and size of the mold, it is supported the unsintered shaped article is obtained in a non-reactive difficult-to-digest powder, the unsintered shaped article is heated to volatilize the organic binder and for easy sintering of the non-digestible spherical metal powder to form a coherent monolithic metal skeleton, the formed monolithic metal skeleton is cooled, which is infiltrated with a second metal having a melting point at least 25oK lower than the melting point, the lower limit of melting point the ratio is 0.5 for the lowest melting point of the spherical metal powder to form an infiltrated shaped metal object.