Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
  • B01J3/06—Processes using ultra-high pressure, e.g. for the formation of diamonds; Apparatus therefor, e.g. moulds or dies
  • B01J3/08—Application of shock waves for chemical reactions or for modifying the crystal structure of substances
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/02—Compacting only
  • B22F3/087—Compacting only using high energy impulses, e.g. magnetic field impulses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

• the field of application of the present invention lies essentially in the production of components made of metal, alloys, ceramic-metal composites or hard materials, in which the commodity is solidified starting from powder and consists of several layers of different composition, thickness and properties.
• Many examples of triplex plates are known in which a plate with certain properties is enclosed between two resistant plates.
• insulation material between two metal plates, a uranium alloy between two plates with an aluminum or zirconium alloy, a honeycomb structure between two metal plates can be mentioned.
• the outer plates isolate and protect an active core, in other cases the component has improved properties due to the connection, for example the moment of inertia for the honeycomb structure.
• the outer plates can either have the same or a different thickness.
• the plates that are exposed to mechanical stresses or shocks can be stronger.
• One could say that the plates intended for the inside of a container are made of metal or an alloy with good corrosion resistance or are food-safe, while the outer plate is made of an alloy that is more mechanically resistant.
• One side could be copper to ensure good cooling, and the other AG5 to provide high resistance and good behavior in a marine atmosphere.
• AG5 is a classic . Alloy made of aluminum and 5 percent by weight magnesium.
• the core which can represent any of the different layers, is an initially non-preformed powder which can be consolidated and clad with the capsule material during the same method. According to the procedure, the capsule mentioned is actually firmly attached to the core or can split off entirely if it only has a temporary function.
• the basis of the manufacturing technology of powder metallurgical parts can be summarized using the example of a steel gear.
• the tools consist of a die, a lower and an upper punch.
• the powder is poured into a die.
• the upper punch goes down and acts on the powder with a pressure of 50 kg / mm 2 .
• the upper punch goes up again and ejects the compact, which is sufficiently solidified so that the preform can be processed. Its relative density is approximately 85%.
• the compact is sintered in a hydrogen furnace, with a reducing atmosphere or under vacuum. As a result, it reaches a density of more than 95%.
• the gearbox is pressed into a die, which calibrates it and compresses and smoothes the outer layer.
• Mainly hot pressing and hot isostatic pressing HIP
• the American patent US 5,397,050 from Tosoh SMD Inc. contains an improvement in which a diffusion bond on a plate is to be achieved simultaneously with the consolidation of the powder.
• the titanium plate is placed on the bottom of a vessel, the powder is poured onto it, compressed with a press and the vessel is closed.
• the container is then placed in a hot isostatic press and a pressure of 1000 bar is applied at a temperature of approx. 1000 ° C.
• the course of the hot isostatic pressing process can be as follows: 1 hour temperature and pressure rise, 4 hours holding time and 4 hours cooling and decompression.
• the bond between the solidified powder and the plate is achieved by solid-solid diffusion.
• the American patent US.6.248.291 B1 of Asahi Glass Cy Ltd specifies an order of magnitude with regard to the temperatures which are necessary for achieving a relative density of 95% for a powder mixture.
• the component with the lowest melting point is aluminum, which melts at 660 ° C
• the target temperature during pressing is at least 50 ° C lower than the melting point, which corresponds to approx. 95% of the temperature in ° C.
• a variant that is used for newer materials is in the Metals. Handbook by ASM, 8th edition Vol. 14 on pages 188 and following.
• the method is called powder forging (P / F).
• powder is pressed to produce a preform, as in the basic production method, but then calibrated or compacted by means of an impact.
• the preform is placed in a die between two punches when hot and is pressed into the mold by the action of the impact, so that it forms the fills all the free space in the die.
• This variant works with a shock wave, but does not offer the possibility of plating.
• European patent EP 0243995 B1 describes a way of producing target materials in two stages, in which a powder mixture is first cold-pressed to a shaped body of approximately 90% of its theoretical density and then, with or without a protective cover, by repeated forming, preferably in hydraulic Forging presses, is compacted. This method is cost-intensive due to the required production of a preform body and the repeated shaping and likewise does not provide for the possibility of plating.
• Hydraulic press 0.01 to 0.05 m / sec. Mechanical press 0.2 to 0.6 m / sec.
• Screw press 0.5 to 1 m / sec.
• the Petroforge hammer and similar machines achieve a tool speed of a maximum of 20 m / sec.
• An explosive substance is used in the American patent US 5,779,852 of the Korean Institute for Machines & Materials, the Explosion is triggered by an igniter which exposes the powder-sleeve combination to a shock wave at a speed of 2000 to 3000 m / sec., Under a pressure of 1 to 30 GPa, which corresponds to 100 to 3000 kg / mm 2 .
• the most common examples are known under the name 'AI-clad'.
• the middle plate is sandwiched between two plates, which results in a better appearance and / or a higher resistance.
• the classic method is to stack three aluminum or aluminum alloy blocks on top of one another, to join them by stapling or welding on the sides, and to roll them together at a high temperature. The rolling mill compresses them, pulls them apart and reduces their strength. The plating is carried out separately from the solidification.
• the shock wave is due to one blow.
• the present invention makes it possible to manufacture parts, which can consist of several materials of different material thicknesses, to use them in this state, to forge them or even to roll them.
• the principle is to create a connection of the elements to be joined in the form of superimposed or concentric layers.
• These layers can be made from a first plate that acts as the outer Plating layers serve spll, a second plate for the core, a third plate as an intermediate layer and a fourth plate for the second plating layer.
• - Figure 1 shows a container made of these layers and which is ready for the shock wave generated by the shock. These layers are used in such a way that they can have very different thicknesses and mechanical properties.
• a shock is applied at a high speed to one or both sides at the same time, so that a shock wave is generated in the composite.
• the speed can be between 7 m / sec. and 100 m / sec. be. Ideally, it is between 20 m / sec. and 60 m / sec.
• This shock wave propagates in the material at a speed that corresponds approximately to the speed of sound in said material.
• the shaft With the penetration of the individual materials, the shaft changes its speed every time. It is deflected in soft material and reflected again in solid material.
• Figure 2 shows some possibilities of elementary behavior of a shock wave at the interface between two materials with different hardness. In the connection areas, there is an addition of the shock waves, which multiplies the energy and thereby achieves a consolidation and connection which are far higher than those which are achieved by the already known forging, rolling or explosion welding. ,
• the wave that propagates in the composite is displaced by the penetration of the powder, the plastic layer and the hard layer.
• the wave changes its speed every time.
• the method thus leads to a superposition of the waves.
• This principle of overlay has significant effects that can be calculated or at least predictable.
• each function F (t) of a real variable can be broken down into a sum of harmonic functions of the variable f, which means one of the following function sums:
• Each elementary function, or Fourier component, is characterized by its degree of development in relation to t. This sum indicates the superposition of the harmonic waves as shown in Figure 3.
• shock waves are superimposed from a single shock is due to the different speeds of sound in the materials, depending on their structure and mechanical properties.
• the speed of sound in water is approx. 1570 m / s, in most solids it is approx. 3000 m / s, but can vary between 1000 and 6000 m / s.
• the speed of sound in steel is approximately 5000 m / s. In solid copper, it can be around 1000 m / s.
• the materials themselves, their condition and their temperature one can thus move within a sufficient scope so that the application of the method within the scope of the invention can be implemented on an industrial basis. >.
• the reduction in the intensity of a spherical wave can be calculated with the distance from its source. In reality they correspond actual measurements never the results of the calculation. This loss of intensity even takes place when the wave propagates in a homogeneous medium. This loss of intensity is due to absorption and conversion to heat. , One cause is the internal 5 friction in the material. This friction mainly occurs at the interface between two materials, powder grains versus powder grains, plate grains, plate-plate ... There are temperature peaks at the maximum compression levels. This temperature is transferred to the adjacent levels. On the microscopic scale, the energy of the wave not only serves to increase the translational speed of the atoms or molecules, but part of it is lost due to collisions in the form of vibrations.
• the speed of the shock wave increases with frequency. It is therefore of interest to apply shock wave generation by impact to a solid and thin layer in which the speed of sound is increased, for example steel, inconel, titanium.
• the powder, the granulate or the plastic layers, such as copper or aluminum at elevated temperatures, must be arranged behind the hard layer 20.
• the reflective layer must also be hard in order to prevent the shaft from being absorbed and thus the conditions of a simple forging are restored.
• the container impacts a container or an ingot on a solid base with high inertia with a shock.
• the ingot consists of several layers of different materials, as shown in Figure 1.
• the layer which has a specific gravity of 3.0 less than 1, ie the second layer, can be reshaped to a thickness of 2 mm.
• the time to stop the moving mass is 1 / 10,000 seconds. This impulse creates a shock wave. If the moving Mass has a weight of 30 tons, the work done on the ingot can be calculated as follows:
• a forming machine with two counterblow dies of the same speed has the advantage that parts can be produced in which there is no difference between the top and bottom.
• Time of the impact does not primarily depend on the speed of the die, but only on the mass of the impact body and the flexibility of the impacted body, and thus on the density and the modulus of elasticity of the composite part.
• the modulus of elasticity of a copper-aluminum alloy at room temperature is 6500 kg / mm 2
• the modulus of steel is 22,000 kg / mm 2 .
• the time of the shock can be expressed as follows:
• M is the elastic modulus in kg / mm 2
• D is the density.
• Propagation of the shock wave " The propagation speed of the * shock wave practically corresponds to the speed of sound in the material.
• Load acting on the component is the first phase of the work, as is the case with the other methods and like this with a classic hammer, a hydraulic or mechanical press or even with one hot isostatic press can be applied. This work is overlaid by the work specially done by the shock wave.
• M is the elastic modulus in kg / m 2 d .
• density g 9.81 m / s 2 R is the specific load in kg / mm 2
• Shock load and wave The load alone has a known impact. It can be applied by a press or a classic forging machine. In the context of the invention, the load with which the material is compacted serves as the basis. Above a certain speed and if an exact arrangement of the composite part is observed, a shock wave is generated, which penetrates the material, is reflected, broken and thus concentrates on the selected interfaces. This speed together with the corresponding arrangement is part of the invention.
• the wave propagates at high speed in the hard layers and at low speed in the soft layers and is broken at certain hard points.
• Type of procedure according to the invention The type of procedure within the scope of the invention is the following. A piece of pipe is cut, cleaned and welded at one end. Then it is filled with metal powder and sealed at the other end under vacuum. This is the classic procedure. The tube is heated to a temperature which corresponds to approximately half the melting temperature of the powder. The pipe is placed on a block of high-carbon steel or a similar hard tool and an impact is generated which is produced by another block and which spreads at an adapted speed between 20 and 60 m / sec. The powder is consolidated, has a density of more than 96% and the connection to the pipe is of metallurgical quality.
• the procedure is further defined by the following conditions.
• the container tube is intended to represent the optional plating layer.
• the powder is not introduced into the container as a preform. It has been shown that the present method enables the realization of high-density materials without the additional production step of preform body production.
• the impact is carried out by mechanical means without explosion. No tools which comprise a die with a punch or a closed die are used for the method.
• the dies are flat and have a relative speed of 7 m / sec. up to 100 m / sec., ideally it is between 20 m / sec. and 60 m / sec.
• the speeds of sound in the various bodies, the cladding layer, the core and possibly other components are at least 1: 2 or higher in working conditions.
• the process is carried out at a temperature which is lower than the usual forging, sintering or rolling temperature, which corresponds to a temperature of 40% to 80% of the melting point in ° C., in contrast to normally 80% to 95%. In any case, the temperatures are below the melting temperature of the lowest melting component.
• the powder is a chrome metal powder, for example.
• the powder is a mixture of several metal powders, such as Ti and Al or Cr and Ni or Mo, Cr and Si (non-metal).
• the number is not fixed, only a sufficiently homogeneous mixture has to be achieved. In practice, the author has rarely exceeded more than 6 components with cobalt-based alloys.
• the powder is a mixture of metal and ceramic powders, such as Ti and TiB 2 ⁇ or Cr and Cr 2 O 3 .
• the tube is made of metal or another alloy, for example based on copper, titanium, Inconel or aluminum.
• the tube is not round, but rather ellipsoidal or rectangular.
• the required tube made of copper or aluminum, is too soft so that no controlled shape can be guaranteed after exposure. It is therefore placed in a stabilizing container or an outer tube made of, for example, stainless steel ( Figure 4).
• the raw dimension is so large and of such a nature that the work for simultaneous consolidation and connection is too small, ie a load of only 1 to 5 kg / mm 2 is applied.
• the connection achieved serves only as a raw material for consolidation and connection by rolling and replaced the welding or folding of the edges with the adhesion in the micro range, which should ensure a homogeneous speed between the layers in order to avoid shearing of the connections during the individual roll passes.
• a container consisting of a stainless steel tube with a length of one meter, a diameter of 140 mm and a thickness of 5 mm is provided with a copper layer on the inside.
• This layer represents an inner tube with an initial thickness of 10 mm
• the composite pipe is welded at one end and then filled with a mixture of titanium and aluminum powders, which does not have to be pressed or inserted in any other form, as is the case with a preform body used in powder forging.
• the composite body is heated up to a temperature which may be significantly lower, than the melting temperature of the body with the lowest melting temperature, in this case, the aluminum, that is more than 100 ° C lower, and is defined by two opposed flat body at a rate of hit approximately 28 m / s.
• the layer of stainless steel demonstrates. This temperature a modulus of elasticity of 17,000, loose powder and copper of approx., 2000 on. Due to the applied load, the powder is compressed to approx. 90%, which could be done with a moderate capacity hydraulic press.
• the shock wave penetrates the steel without reducing its initial properties change, penetrates the pressed powder with a considerable amount. Scatter and is broken in the copper. It is stopped and reflected by the second layer of steel.
• the shock wave concentrates on the part that is to be plated, where it does mechanical work and releases heat. According to this process, the powder mixture is consolidated and completely welded to the copper. A duplex plate is obtained by machining.
• the steel only serves as a carrier for the shock wave and as a protective cover.
• the mechanical payload which is only used for a short time, less than 1/10 sec., Can be estimated at a few kg / mm 2 .
• the powder is still fully consolidated and the plating is ensured by a real metallurgical connection.
• a container consisting of a stainless steel tube with a thickness of 4mm is filled with chrome powder and then closed at both ends under vacuum.
• the composite pipe is heated to a temperature as low as half
• Melting temperature of chromium may be, and then of two bodies that approach each other at a speed of approximately 25 m / s
• An ingot consists of two plates of an aluminum alloy, which are separated by a layer of a powder mixture based on an aluminum alloy. This does not have a particularly high relative density, it is sic. therefore no preform.
• the composite is held together by a welded aluminum alloy frame or, in another case, placed in a stainless steel container. The connection is closed under vacuum.
• the ingot is heated to a medium temperature, which is more than 200 ° C lower than the melting temperature of the aluminum, and is subjected to an impact of two bodies in motion at a speed of approximately 28 m / s.
• the powder is compressed to a density of approx. 85% by the effect of the load.
• the consolidation of the powder and the welding to the central part, which originally consisted of a powder, is carried out with the two side plates or via the sleeve through the refraction and addition of the shock wave.
• the core-sleeve is sufficiently welded that the billet can be rolled at the same time without the components shifting.
• chromium-copper despite the temperature of less than 1000 ° C and about 50% of the melting temperature of chrome in ° C, which is determined by the behavior of copper; Chrome inconel; Titanium-aluminum; Titanium-titanium diboride, the latter being a ceramic-stainless steel; Nickel chrome alloy steel and Inconel, zircon alloy-uranium alloy-zircon alloy, the same with an aluminum-based plating.
• the method is flexible in that a solid material can be introduced in powder form, which reduces the speed of propagation of the wave.
• a layer consists of at least one powder or a sublayer of the materials Al, C, Si, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Bi, Ce, V, Zr, Ta, W , AI2O3, ZnO, TiB 2 , MoS, TiC, SiAl and one or more layers of solid metal.
• the method can be used as described above, but there is also the possibility, if one or more of the sleeves should not be retained in the end product, to remove them by machining so as to use only the core and one or more layers of the sleeve. In the latter case, the sleeve has only a transitional function during the manufacturing process.
• a method can be used in which the removal of the sleeve does not have to be carried out by expensive processing.
• a size which acts as a diffusion barrier, is applied to one or more components, such as the inside of a stainless steel tube. This layer, which is a few micrometers thick, does not interact when the shock wave propagates and enables the casing to be removed easily, which would be endangered by diffusion. Different layers, mainly oxidic and non-oxide ceramics, were successfully tested.

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• Pressure Welding/Diffusion-Bonding (AREA)
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