CN111940531B - Cold extrusion die and preparation method thereof - Google Patents

Cold extrusion die and preparation method thereof Download PDF

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Publication number
CN111940531B
CN111940531B CN202010577674.3A CN202010577674A CN111940531B CN 111940531 B CN111940531 B CN 111940531B CN 202010577674 A CN202010577674 A CN 202010577674A CN 111940531 B CN111940531 B CN 111940531B
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cold extrusion
die
extrusion die
powder
temperature
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CN111940531A (en
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钟黎声
樊荣
曹保卫
梁淑华
卢正欣
邹军涛
朱建雷
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Xian University of Technology
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Xian University of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C25/00—Profiling tools for metal extruding
    • B21C25/02—Dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C25/00—Profiling tools for metal extruding
    • B21C25/02—Dies
    • B21C25/025—Selection of materials therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C25/00—Profiling tools for metal extruding
    • B21C25/10—Making tools by operations not covered by a single other subclass

Abstract

The invention discloses a cold extrusion die, which comprises a die body, wherein a die hole is formed in the die body, the die body consists of 70-85% of titanium carbide powder, 8.5-13.75% of hydroxyl iron powder, 0.5-1.25% of graphite powder and 6-15% of molybdenum wire according to mass percentage, the sum of the mass percentages of the components is 100%, the molybdenum wire is distributed in the cold extrusion die in a net shape, the wire diameter of the molybdenum wire is 0.2-0.8 mm, the granularity of the titanium carbide powder is 8-20 mu m, the granularity of the hydroxyl iron powder is 2-5 mu m, and the granularity of the graphite powder is 1-5 mu m; the invention also discloses a preparation method of the cold extrusion die, and the cold extrusion die prepared by the preparation method has higher toughness and hardness, and is suitable for various working conditions.

Description

Cold extrusion die and preparation method thereof
Technical Field
The invention belongs to the technical field of cold extrusion dies, and relates to a cold extrusion die and a preparation method thereof.
Background
The metal cold extrusion is a molding method that a metal blank is placed into a die cavity in a cold state, and metal is forced to be extruded out of the die cavity under the action of strong pressure and a certain speed, so that an extruded piece with a required shape, size and certain mechanical properties is obtained. The metal cold extrusion process has the characteristics of high quality, high efficiency, low consumption, low cost and the like, and is a novel non-cutting processing method. The cold extrusion die plays an important role in the extrusion process, and metal generates directional flow relative to the surface of the die during plastic deformation, so that friction and frictional force are generated on the interface of a deformation body and the die, and the die is abraded.
The materials which can be used for manufacturing the cold extrusion die mainly comprise cold-work die steel and hard alloy. Common cold-work die steel comprises Cr12, Cr12MoV and the like, and is formed by mechanical processing in an annealing state, then quenched and tempered, and the final hardness after heat treatment is HRC 55-65. When the hardness of the mold made of the materials is higher, the mold is usually very brittle and has large internal tissue stress; when the hardness is lower, although the toughness is better and the wear is not easy to be damaged, the wear is fast, the service life is short, and the replacement is needed frequently. The cold extrusion die with higher hardness requirement is usually made of tungsten-cobalt hard alloy, which is a high-hardness material prepared by sintering WC particles and metal Co or Ni at high temperature, and has very high hardness, wear resistance and insufficient toughness.
In order to overcome and solve the above-mentioned failure problem of the cold extrusion die, a great number of researchers have conducted a great deal of research with the goal of improving the toughness and wear resistance of the cold extrusion die. For example, patent No. CN102389970A discloses a powder metallurgy material for cold extrusion die and a method for forming the die. The invention uses tungsten carbide, vanadium carbide, cerium oxide and the like as raw materials and adopts a powder metallurgy method to prepare the cold extrusion die material. Compared with a die steel die, the wear resistance of the product is improved due to the addition of cerium oxide; due to the addition of tungsten carbide, vanadium carbide and chromium carbide, the sintered crystal grains are finer, and compared with a common hard alloy die, the fracture toughness and the breakage resistance are greatly improved.
For another example, patent No. CN110468385A discloses a process for sequentially depositing a micro-diamond coating and a nano-diamond coating on the surface of a matrix of a cemented carbide cold extrusion die such as tungsten carbide by a hot wire vapor deposition method. The wear resistance of the cold extrusion die is improved by two coatings with different quantity grades in the composite size, and the service life of the cold extrusion die is prolonged. In particular, the nano diamond coating is adopted to improve the impact resistance of the cold extrusion die.
For example, patent No. CN102218647A discloses a texturing self-lubricating treatment method for a metal plastic forming mold, which comprises performing texturing micro-processing on the surface of the mold, and then performing forming bonding processing on the self-lubricating composite material. By carrying out texturing self-lubricating treatment on the surface of the metal plastic forming die, the optimal distribution of the lubricating property of the surface of the die is realized while the bearing capacity and the matching precision of the molded surface of the die are ensured, and the flowing of materials and the lubricating and anti-wear properties of the die are improved.
In summary, the introduction of hard phase can improve the wear resistance of the cold extrusion die of die steel, and the use of surface coating or surface modification can improve the wear resistance and toughness of the cold extrusion die of hard alloy. However, the cold extrusion die still has the following problems to be solved:
(1) the cold extrusion die of die steel can not meet the gradually harsh requirement of extrusion conditions any more, and can not meet the requirement of large deformation fatigue stress action even if a hard phase is added under the condition of larger extrusion force.
(2) The hard alloy cold extrusion die still has the advantages of no need of adding noble metal Co, high hardness, poor toughness and greatly reduced service life under the repeated action of large deformation and strong extrusion force.
(3) The surface-modified hard alloy cold extrusion die has complex control on the bonding strength of the surface layer and the matrix, the thickness of the surface modification layer and the like. In addition, after the modified layer fails, the die wear and deformation failure are accelerated.
Disclosure of Invention
The invention aims to provide a cold extrusion die, which solves the problem of low toughness of the existing cold extrusion die.
Another object of the present invention is to provide a method for preparing a cold extrusion die.
The first technical scheme adopted by the invention is that the cold extrusion die comprises a die body, a die hole is formed in the die body, the die body is composed of, by mass, 70% -85% of titanium carbide powder, 8.5% -13.75% of hydroxyl iron powder, 0.5% -1.25% of graphite powder and 6% -15% of molybdenum wires, the sum of the mass percentages of the components is 100%, the molybdenum wires are distributed in the cold extrusion die in a net shape, and the wire diameter of the molybdenum wires is 0.2mm-0.8 mm.
The present invention is also technically characterized in that,
the granularity of the titanium carbide powder is 8-20 mu m, the granularity of the hydroxyl iron powder is 2-5 mu m, and the granularity of the graphite powder is 1-5 mu m.
The second technical scheme adopted by the invention is a preparation method of a cold extrusion die, which comprises the following steps:
step 1, respectively weighing 70-85% of titanium carbide powder, 8.5-13.75% of hydroxyl iron powder, 0.5-1.25% of graphite powder and 6-15% of molybdenum wire according to mass percent, wherein the sum of the mass percent of the components is 100%;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to be uniformly mixed to form mixed powder; putting the mixed powder and the plasticizer into a mixing roll for mixing to form a mixed material;
step 3, weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton, wherein the three-dimensional molybdenum skeleton has the same shape as the cold extrusion die;
step 4, placing the braided three-dimensional molybdenum skeleton into an injection molding die, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixed material into the die with the three-dimensional molybdenum skeleton through an injection molding machine to fill the gap of the three-dimensional molybdenum skeleton with the mixed material, and after injection, jacking and maintaining the pressure for a period of time to perform demolding to obtain a prefabricated part of a cold extrusion die;
and 5, high-temperature sintering, namely placing the prefabricated part into a high-temperature mold, inserting a corresponding mold core into a central hole of the prefabricated part, then placing the prefabricated part with the high-temperature mold into a high-temperature sintering furnace, performing multi-stage degreasing treatment on the prefabricated part under vacuum or inert protective atmosphere, then performing high-temperature sintering on the prefabricated part at 1200-1400 ℃, finally cooling to room temperature along with the furnace, taking out and demolding to obtain the cold extrusion mold.
In the step 2, in the material mixing process, the rotating speed of a material mixer is 65 r/min-75 r/min, and the material mixing time is 3 h-8 h; in the mixing process, the rotating speed of the mixer is 88 r/min-92 r/min, and the mixing time is 1 h-2 h.
In the step 2, the mass percentage of the mixed powder and the plasticizer is 99.2-99.5 wt.%: 0.5-0.8 wt.%.
And 4, injecting the mixed material into a mold with a three-dimensional molybdenum skeleton through an injection molding machine, wherein the injection temperature is 180-280 ℃, the injection pressure is 50-130 MPa, and after the injection is finished, the pressure is maintained for 1-5 min in a jacking manner, and demolding is carried out after natural cooling.
In step 5, the prefabricated member is first subjected to multi-stage degreasing treatment, wherein the degreasing temperature is 550-650 ℃, and the degreasing time is 3-10 h.
In step 5, the prefabricated part is sintered at high temperature of 1200-1400 ℃, and the high-temperature sintering time is 0.05-0.5 h.
In step 5, after the prefabricated member is sintered at high temperature, the furnace temperature is firstly reduced to 900-plus-1100 ℃ and is kept for 1-8h, then the temperature is reduced to 800 +/-10 ℃ and is kept for 30-60min, and finally the prefabricated member is cooled to room temperature along with the furnace.
And 5, cooling to room temperature along with the furnace at a cooling rate of 5-10 ℃/min.
The invention has the beneficial effects that the cold extrusion die is prepared by adopting the molybdenum skeleton woven by molybdenum wires, so that the toughness of the cold extrusion die can be improved, and the cold extrusion die has higher hardness and toughness; the structural distribution of the molybdenum skeleton can be flexibly adjusted according to the stress characteristics of the die, so that the preparation method has wide application range; TiC is added and Mo generated in situ2The multi-scale matching between C improves the wear resistance and toughness of the die; the use of noble metal Co is avoided, the manufacturing cost of the die is reduced, and the application field of the die is increased.
Drawings
FIG. 1 is a schematic structural view of a cold extrusion die for a monolithic cylindrical member in example 1 of the present invention;
FIG. 2 is a schematic structural diagram of a molybdenum skeleton in a cold extrusion die for an integral cylindrical part in example 1 of the present invention;
FIG. 3 is a schematic structural view of a cold extrusion die for a solid conical member in example 2 of the present invention;
FIG. 4 is a schematic structural view of a cold extrusion die for a stepped shaft member in example 3 of the present invention;
FIG. 5 is a schematic structural diagram of a cold extrusion die for a straight-hole-free member in example 4 of the present invention.
In the figure, 1, an integral cylindrical part cold extrusion die prefabricated part, 2, an integral conical part cold extrusion die prefabricated part, 3, a stepped shaft part cold extrusion die prefabricated part, 4, a blocked straight hole part cold extrusion die prefabricated part and 5, a molybdenum skeleton.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention relates to a cold extrusion die which comprises a die body, wherein a die hole is formed in the die body, the die body comprises, by mass, 70% -85% of titanium carbide powder, 8.5% -13.75% of hydroxyl iron powder, 0.5% -1.25% of graphite powder and 6% -15% of molybdenum wires, the sum of the mass percentages of the components is 100%, the molybdenum wires are distributed in the cold extrusion die in a net shape, and the wire diameter of the molybdenum wires is 0.2mm-0.8 mm. The granularity of the titanium carbide powder is 8-20 mu m, the granularity of the hydroxyl iron powder is 2-5 mu m, and the granularity of the graphite powder is 1-5 mu m.
The invention relates to a preparation method of a cold extrusion die, which comprises the following steps:
step 1, respectively weighing 70-85% of titanium carbide powder, 8.5-13.75% of hydroxyl iron powder, 0.5-1.25% of graphite powder and 6-15% of molybdenum wire according to mass percent, wherein the sum of the mass percent of the components is 100%;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to mix uniformly, wherein in the mixing process, the rotating speed of the mixer is 65-75 r/min, and the mixing time is 3-8 h to form mixed powder; mixing the mixed powder and the plasticizer in a mixing mill, wherein the mass percentage of the mixed powder to the plasticizer is 99.2-99.5 wt.%: 0.5-0.8 wt.%, and in the mixing process, the rotating speed of the mixing roll is 88-92 r/min, and the mixing time is 1-2 h, so as to form a mixed material;
step 3, weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton, wherein the three-dimensional molybdenum skeleton has the same shape as the cold extrusion die;
step 4, placing the woven three-dimensional molybdenum skeleton into a mold for injection molding, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixed material into the mold with the three-dimensional molybdenum skeleton through an injection molding machine, wherein the injection temperature is 180-280 ℃, the injection pressure is 50-130 MPa, so that the gap of the three-dimensional molybdenum skeleton is filled with the mixed material, jacking and maintaining the pressure for 1-5 min after the injection is finished, and demolding after natural cooling to obtain a prefabricated member of the cold extrusion mold;
step 5, high-temperature sintering, namely placing the prefabricated part into a high-temperature mold, inserting a corresponding mold core into a central hole of the prefabricated part, then placing the prefabricated part with the high-temperature mold into a high-temperature sintering furnace, and under the vacuum or inert protective atmosphere, firstly, raising the temperature in the sintering furnace from room temperature to 550-650 ℃ for multi-stage degreasing treatment, wherein the degreasing time is 3-10 h; then the furnace temperature is raised to 1200-1400 ℃, the prefabricated part is sintered for 0.05-0.5h at high temperature, the furnace temperature is reduced to 900-1100 ℃ and is kept for 1-8h, then the furnace temperature is reduced to 800 +/-10 ℃ and is kept for 30-60min, finally the prefabricated part is cooled to room temperature along with the furnace at the cooling rate of 5-10 ℃/min, the prefabricated part is taken out and is demoulded, and the cold extrusion die is prepared, wherein the volume percentage of TiC tissues in the cold extrusion die is 78-90%, Mo in the cold extrusion die, is Mo2The volume percentage of the C structure is 2-6%, the volume percentage of the alpha-Fe phase is 5.5-10%, the volume percentage of the metal molybdenum is 2-5.5%, and the sum of the volume percentages of the structures is 100%.
Example 1
Preparing a cold extrusion die for a monolithic cylindrical piece, with reference to fig. 1 and 2, comprises the following steps:
step 1, respectively weighing the following components, by mass, 70% of titanium carbide powder with the particle size of 8 microns, 13.75% of hydroxyl iron powder with the particle size of 2 microns, 1.25% of graphite powder with the particle size of 1 micron and 15% of molybdenum wire, wherein the sum of the mass percentages of the components is 100%, and the wire diameter of the molybdenum wire is 0.2-0.3 microns;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to be uniformly mixed, wherein the rotating speed of the mixer is 70r/min and the mixing time is 3h in the mixing process to form mixed powder; mixing the mixed powder and the plasticizer in a mixing mill, wherein the mass percentage of the mixed powder to the plasticizer is 99.5 wt.%: 0.5 wt.%, and in the mixing process, the rotating speed of the mixing roll is 90r/min, and the mixing time is 1h, so as to form a mixed material;
and 3, weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton 5 according to the shape and size of the integral cylindrical piece cold extrusion die and the principle of 'density combination and key arrangement', wherein the Mo wires with the diameter of 0.2mm are used at the inlet part (accounting for 40% of the total height of the die) at the top of the cold extrusion die in the molybdenum skeleton 5 and are arranged at the interval of 1 layer/4 mm along the extrusion direction, one circle of radial Mo wires is arranged at intervals of 3mm in the radius direction between layers, one radial Mo wire is arranged at intervals of 20 degrees, and the Mo wires are arranged at intervals of 5 degrees in a staggered manner of rotating between layers.
The extrusion force on the outlet part (accounting for 60 percent of the total height of the die) at the bottom of the cold extrusion die in the molybdenum skeleton is relatively small, so that the molybdenum wires are arranged sparsely, the distance between the molybdenum wires is relatively large, from the last layer at the inlet side, Mo wires with the diameter of 0.2mm are used to weave a loose structure at the layer distance of 1 layer/10 mm, a circle of radial Mo wires are arranged between layers at intervals of 5mm along the radius direction, one radial Mo wire is arranged at intervals of 40 degrees, and the Mo wires rotate 10 degrees and are arranged in a staggered manner between layers;
meanwhile, Mo wires with the diameter of 0.3mm are used for connecting Mo wire frameworks of all layers along the extrusion direction, a three-dimensional Mo wire framework structure is constructed, and the stability of the frameworks is improved.
Step 4, placing the braided three-dimensional molybdenum skeleton into a mold for injection molding, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixed material into the mold with the three-dimensional molybdenum skeleton through an injection molding machine, wherein the injection temperature is 180 ℃, the injection pressure is 50MPa, so that the gap of the three-dimensional molybdenum skeleton is filled with the mixed material, jacking and maintaining the pressure for 1min after the injection is finished, and demolding after natural cooling to obtain an integral cylindrical part cold extrusion mold prefabricated part 1;
step 5, placing the integral cylindrical member cold extrusion mold prefabricated part 1 into a high-temperature mold, inserting a corresponding mold core into a central hole of the integral cylindrical member cold extrusion mold prefabricated part 1, then placing the prefabricated part with the high-temperature mold into a high-temperature sintering furnace, and under the vacuum or inert protective atmosphere, firstly, raising the temperature in the sintering furnace from room temperature to 550 ℃ for multi-stage degreasing treatment, wherein the degreasing time is 3 hours; and then, heating the furnace to 1200 ℃, sintering the prefabricated part at high temperature for 0.05h, cooling the furnace to 900 ℃, preserving heat for 1h, then cooling to 790 ℃, preserving heat for 30min, cooling to room temperature along with the furnace at a cooling rate of 7 ℃/min, taking out, and demolding to obtain the integral cylindrical part cold extrusion mold.
Through detection, TiC group in integral cylindrical part cold extrusion die prepared in example 1The volume percentage of the weave is 78.9 percent, Mo2The volume percentage of the C structure is 5.9 percent, the volume percentage of the alpha-Fe phase is 9.8 percent, the volume percentage of the metal molybdenum is 5.4 percent, and the sum of the volume percentages of the above structures is 100 percent.
Example 2
The preparation method of the integral conical piece cold extrusion die comprises the following steps:
step 1, respectively weighing 80 mass percent of titanium carbide powder with the granularity of 15 mu m, 10.25 mass percent of hydroxyl iron powder with the granularity of 4 mu m, 0.75 mass percent of graphite powder with the granularity of 3 mu m and 9 mass percent of molybdenum wire, wherein the sum of the mass percent of the components is 100 percent, and the wire diameter of the molybdenum wire is 0.45-0.55 mu m;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to be uniformly mixed, wherein the rotating speed of the mixer is 65r/min and the mixing time is 4h in the mixing process to form mixed powder; mixing the mixed powder and the plasticizer in a mixing mill, wherein the mass percentage of the mixed powder to the plasticizer is 99.35 wt.%: 0.65 wt.%, and in the mixing process, the rotating speed of the mixing roll is 90r/min, and the mixing time is 1.5h, so as to form a mixed material;
step 3, weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton 5 according to the shape and size of the integral conical part cold extrusion female die and the principle of 'density combination and key arrangement', wherein because each part of the inner surface of the female die is subjected to extrusion force at the same angle, a uniform Mo wire skeleton is required to be arranged in the whole extrusion direction to provide sufficient deformation resistance;
mo wires with the diameter of 0.45mm are arranged at a layer interval of 1 layer/5 mm along the extrusion direction, the layers are arranged in a circle at intervals of 3mm along the radius direction, the radial Mo wires are arranged at intervals of 15 degrees, and the Mo wires are arranged in a staggered manner at intervals of 5 degrees in a layer-to-layer rotating manner. Meanwhile, Mo wires with the diameter of 0.55mm are used for connecting Mo wire frameworks of all layers along the extrusion direction, a three-dimensional Mo wire framework structure is constructed, and the stability of the frameworks is improved.
Step 4, placing the braided three-dimensional molybdenum skeleton 5 in a mold for injection molding, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixture into the mold with the three-dimensional molybdenum skeleton through an injection molding machine, wherein the injection temperature is 240 ℃, the injection pressure is 80MPa, so that the gap of the three-dimensional molybdenum skeleton is filled with the mixture, pressing and maintaining the pressure for 3min after the injection is finished, and demolding after natural cooling to obtain an integral conical piece cold extrusion mold prefabricated part 2 (shown in figure 3);
step 5, placing the integral conical piece cold extrusion die prefabricated part 2 into a high-temperature die, inserting a corresponding core into a central hole of the integral conical piece cold extrusion die prefabricated part 2, then placing the prefabricated part with the high-temperature die into a high-temperature sintering furnace, and under the vacuum or inert protective atmosphere, firstly, raising the temperature in the sintering furnace from room temperature to 590 ℃ for multi-stage degreasing treatment, wherein the degreasing time is 6 hours; and then, heating the furnace to 1300 ℃, sintering the prefabricated part at high temperature for 0.2h, cooling the furnace to 1000 ℃, preserving the heat for 5h, then cooling to 800 ℃, preserving the heat for 45min, cooling to room temperature along with the furnace at the cooling rate of 8 ℃/min, taking out and demoulding to obtain the integral conical part cold extrusion die.
Through detection, the volume percentage of TiC tissues in the integral conical piece cold extrusion die prepared in the embodiment 2 is 86.9%, and Mo2The volume percentage of the C structure is 2.9 percent, the volume percentage of the alpha-Fe phase is 7 percent, the volume percentage of the metal molybdenum is 3.2 percent, and the sum of the volume percentages of the above structures is 100 percent.
Example 3
The step shaft piece cold extrusion die comprises the following steps:
step 1, weighing 85% of titanium carbide powder with the particle size of 15 microns, 8.5% of hydroxyl iron powder with the particle size of 4 microns, 0.5% of graphite powder with the particle size of 4 microns and 6% of molybdenum wire according to mass percentage, wherein the sum of the mass percentages of the components is 100%, and the wire diameter of the molybdenum wire is 0.7-0.8 microns;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to be uniformly mixed, wherein the rotating speed of the mixer is 72r/min and the mixing time is 5 hours in the mixing process to form mixed powder; mixing the mixed powder and the plasticizer in a mixing mill, wherein the mass percentage of the mixed powder to the plasticizer is 99.3 wt.%: 0.7 wt.%, and in the mixing process, the rotating speed of the mixing roll is 91r/min, and the mixing time is 2h, so as to form a mixed material;
and 3, according to the shape and the size of the stepped shaft piece cold extrusion die and the principle of 'density combination and key arrangement', weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton 5, wherein the top inlet part (accounting for 20% of the total height of the die) of the cold extrusion die in the molybdenum skeleton is subjected to a large extrusion deformation force, so that Mo wires with the diameter of 0.7mm are arranged at a layer interval of 1 layer/3 mm along the extrusion direction in an encryption arrangement mode, one circle of Mo wires is arranged at intervals of 2mm in the radius direction between layers, one radial Mo wire is arranged at intervals of 15 degrees, and the Mo wires are arranged at intervals of 5 degrees in a staggered manner of rotating between layers.
At the stepped shaft (about 60% -70% of the die from the inlet side along the extrusion direction), the extrusion force born by the die is the largest, a Mo wire framework with the diameter of 0.7mm needs to be used for providing strong extrusion resistance, the Mo wires are arranged at the layer interval of 1 layer/2 mm along the extrusion direction, one circle is arranged at the interval of 1mm along the radius direction between layers, one radial Mo wire is arranged at the interval of 10 degrees, and the Mo wires are arranged at the interval of 2 degrees. Meanwhile, the inlet side needs to be densely arranged within 5 percent of the upper and lower ranges of the stepped shaft.
In other parts of the die, the received extrusion force is gentle, a sparse arrangement mode is adopted, Mo wires with the diameter of 0.7mm are arranged at the interval of 1 layer/5 mm along the extrusion direction, a circle is arranged at intervals of 3mm along the radius direction between layers, one radial Mo wire is arranged at intervals of 20 degrees, and the Mo wires are arranged at intervals of 5 degrees in a layer-to-layer rotation mode.
Meanwhile, Mo wires with the diameter of 0.8mm are used for connecting Mo wire frameworks of all layers along the extrusion direction, a three-dimensional Mo wire framework structure is constructed, and the stability of the frameworks is improved.
Step 4, placing the braided three-dimensional molybdenum skeleton into a mold for injection molding, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixed material into the mold with the three-dimensional molybdenum skeleton through an injection molding machine, wherein the injection temperature is 260 ℃, the injection pressure is 125MPa, so that the gap of the three-dimensional molybdenum skeleton is filled with the mixed material, jacking and maintaining the pressure for 4.5min after the injection is finished, and demolding after natural cooling to obtain a prefabricated member 3 (shown in figure 4) of the cold extrusion mold of the stepped shaft piece;
step 5, placing the stepped shaft cold extrusion die prefabricated part 3 into a high-temperature die, inserting a corresponding core into a central hole of the stepped shaft cold extrusion die prefabricated part 3, then placing the prefabricated part with the high-temperature die into a high-temperature sintering furnace, and under the vacuum or inert protective atmosphere, firstly, raising the temperature in the sintering furnace from room temperature to 605 ℃ for multi-stage degreasing treatment, wherein the degreasing time is 6 hours; and then, heating the furnace to 1375 ℃, sintering the prefabricated part at high temperature for 0.4h, cooling the furnace to 1000 ℃, preserving heat for 6h, then cooling to 805 ℃, preserving heat for 50min, cooling to room temperature along with the furnace at a cooling rate of 5 ℃/min, taking out, and demolding to obtain the stepped shaft piece cold extrusion mold.
Through detection, the volume percentage of TiC tissues in the stepped shaft part cold extrusion die prepared in the embodiment 3 is 90%, and Mo2The volume percentage of the C structure is 2.2 percent, the volume percentage of the alpha-Fe phase is 5.7 percent, the volume percentage of the metal molybdenum is 2.1 percent, and the sum of the volume percentages of the above structures is 100 percent.
Example 4
The preparation method of the cold extrusion die for the blind straight hole part comprises the following steps:
step 1, respectively weighing 75% of titanium carbide powder with the particle size of 12 microns, 12% of hydroxyl iron powder with the particle size of 3 microns, 1% of graphite powder with the particle size of 2 microns and 12% of molybdenum wire according to mass percentage, wherein the sum of the mass percentages of the components is 100%, and the wire diameter of the molybdenum wire is 0.3-0.4 microns;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to be uniformly mixed, wherein the rotating speed of the mixer is 75r/min and the mixing time is 3.5h in the mixing process to form mixed powder; mixing the mixed powder and the plasticizer in a mixing mill, wherein the mass percentage of the mixed powder to the plasticizer is 99.4 wt.%: 0.6 wt.%, and in the mixing process, the rotating speed of the mixing roll is 92r/min, and the mixing time is 1.2h, so as to form a mixed material;
and 3, according to the shape and the size of the blind cylindrical piece cold extrusion female die and the principle of 'density combination and key arrangement', weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton 5, wherein the top inlet part (accounting for 50% of the total height of the die) of the cold extrusion die in the molybdenum skeleton is subjected to a large extrusion deformation force, so that the molybdenum wires with the diameter of 0.3mm are arranged at the interval of 1 layer/3 mm along the extrusion direction in an encryption arrangement mode, one circle of the molybdenum wires is arranged at intervals of 2mm in the radius direction between layers, one radial molybdenum wire is arranged at intervals of 15 degrees, and the molybdenum wires are arranged at intervals of 5 degrees in a staggered manner of rotating.
The outlet side of the die (accounting for about 50% of the total height of the die) is relatively small in extrusion force, so that relatively loose arrangement is adopted, Mo wires with the diameter of 0.4mm are woven into a loose structure at the layer interval of 1 layer/5 mm from the last layer on the inlet side, a circle of Mo wires are arranged between layers at intervals of 5mm in the radius direction, a radial Mo wire is arranged at intervals of 30 degrees, and the Mo wires are staggered and arranged in a way of rotating for 10 degrees between layers;
meanwhile, Mo wires with the diameter of 0.4mm are used for connecting Mo wire frameworks of all layers along the extrusion direction, a three-dimensional Mo wire framework structure is constructed, and the stability of the frameworks is improved.
Step 4, placing the braided three-dimensional molybdenum skeleton 5 in a mold for injection molding, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixed material into the mold with the three-dimensional molybdenum skeleton through an injection molding machine, wherein the injection temperature is 200 ℃, the injection pressure is 60MPa, so that the gap of the three-dimensional molybdenum skeleton is filled with the mixed material, pressing and maintaining the pressure for 2min after the injection is finished, and demolding after natural cooling to obtain a cold extrusion mold prefabricated part 4 (shown in figure 5) of the blind straight hole part;
step 5, placing the cold extrusion die prefabricated part 4 of the blind straight hole part in a high-temperature die, inserting a corresponding core into the central hole of the cold extrusion die prefabricated part of the blind straight hole part, then placing the prefabricated part with the high-temperature die in a high-temperature sintering furnace, and under the vacuum or inert protective atmosphere, firstly, raising the temperature in the sintering furnace from room temperature to 575 ℃ for multi-stage degreasing treatment, wherein the degreasing time is 4 hours; and then, raising the temperature of the furnace to 1250 ℃, sintering the prefabricated part at high temperature for 0.1h, then reducing the temperature of the furnace to 950 ℃, preserving the heat for 3h, then reducing the temperature to 795 ℃, preserving the heat for 35min, finally cooling to room temperature along with the furnace at the cooling rate of 7.5 ℃/min, taking out and demoulding to obtain the blind straight hole part cold extrusion mould.
Through detection, the volume percentage of TiC tissues in the blind hole piece cold extrusion die prepared in the embodiment 4 is 82.7%, and Mo2The volume percentage of the C structure is 4.6 percent, the volume percentage of the alpha-Fe phase is 8.4 percent, the volume percentage of the metal molybdenum is 4.3 percent, and the sum of the volume percentages of the C structure and the alpha-Fe phase is 100 percent.

Claims (10)

1. A cold extrusion die is characterized by comprising a die body, wherein a die hole is formed in the die body, the die body comprises, by mass, 70% -85% of titanium carbide powder, 8.5% -13.75% of hydroxyl iron powder, 0.5% -1.25% of graphite powder and 6% -15% of molybdenum wires, the sum of the mass percentages of the components is 100%, the molybdenum wires are distributed in the cold extrusion die in a net shape, and the wire diameter of the molybdenum wires is 0.2mm-0.8 mm.
2. A cold extrusion die according to claim 1, wherein the titanium carbide powder has a particle size of 8 μm to 20 μm, the iron hydroxy powder has a particle size of 2 μm to 5 μm, and the graphite powder has a particle size of 1 μm to 5 μm.
3. The preparation method of the cold extrusion die is characterized by comprising the following steps of:
step 1, respectively weighing 70-85% of titanium carbide powder, 8.5-13.75% of hydroxyl iron powder, 0.5-1.25% of graphite powder and 6-15% of molybdenum wire according to mass percent, wherein the sum of the mass percent of the components is 100%;
step 2, sequentially putting the powder weighed in the step 1 into a mixer according to the density from high to low to be uniformly mixed to form mixed powder; putting the mixed powder and the plasticizer into a mixing roll for mixing to form a mixed material;
step 3, weaving the molybdenum wires weighed in the step 1 into a three-dimensional molybdenum skeleton, wherein the three-dimensional molybdenum skeleton has the same shape as the cold extrusion die;
step 4, placing the braided three-dimensional molybdenum skeleton into an injection molding die, inserting a mold core in the middle of the three-dimensional molybdenum skeleton, injecting the mixed material into the die with the three-dimensional molybdenum skeleton through an injection molding machine to fill the gap of the three-dimensional molybdenum skeleton with the mixed material, and after injection, jacking and maintaining the pressure for a period of time to perform demolding to obtain a prefabricated part of a cold extrusion die;
and 5, high-temperature sintering, namely placing the prefabricated part into a high-temperature mold, inserting a corresponding mold core into a central hole of the prefabricated part, then placing the prefabricated part with the high-temperature mold into a high-temperature sintering furnace, performing multi-stage degreasing treatment on the prefabricated part under vacuum or inert protective atmosphere, then performing high-temperature sintering on the prefabricated part at 1200-1400 ℃, finally cooling to room temperature along with the furnace, taking out and demolding to obtain the cold extrusion mold.
4. The method for preparing a cold extrusion die according to claim 3, wherein in the step 2, in the mixing process, the rotating speed of a mixer is 65 r/min-75 r/min, and the mixing time is 3 h-8 h; in the mixing process, the rotating speed of the mixer is 88 r/min-92 r/min, and the mixing time is 1 h-2 h.
5. A method for preparing a cold extrusion die according to claim 3, wherein in the step 2, the mass percentage of the mixed powder and the plasticizer is 99.2-99.5 wt.%: 0.5-0.8 wt.%.
6. The method for preparing a cold extrusion mold as claimed in claim 3, wherein in the step 4, the mixture is injected into the mold with the three-dimensional molybdenum skeleton by an injection molding machine, the injection temperature is 180-280 ℃, the injection pressure is 50-130 MPa, and the pressure is maintained for 1-5 min after the injection, and the mold is removed after natural cooling.
7. The method as claimed in claim 3, wherein in the step 5, the preform is first subjected to a multi-stage degreasing treatment at a degreasing temperature of 550 ℃ and 650 ℃ for a degreasing time of 3h to 10 h.
8. The method as claimed in claim 7, wherein in step 5, the preform is sintered at 1200-1400 ℃ for 0.05-0.5 h.
9. The method as claimed in claim 8, wherein in the step 5, after the preform is sintered at high temperature, the furnace temperature is first reduced to 900-.
10. The method for preparing a cold extrusion die as claimed in claim 9, wherein in the step 5, the die is cooled to room temperature with a furnace at a cooling rate of 5 ℃/min to 10 ℃/min.
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JPS63195236A (en) * 1987-02-10 1988-08-12 Agency Of Ind Science & Technol Manufacture of powdered ti/ti alloy-long fiber composite material having superior surface characteristic
EP1696046A1 (en) * 2003-12-18 2006-08-30 Shimane Prefectual Government Metal base carbon fiber composite material and process for producing the same
CN101743080A (en) * 2007-07-13 2010-06-16 艾尔坎技术及管理有限公司 Powder metallurgical method for producing an extruded section
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