Classifications

• • 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
  • B22F3/10—Sintering only
• • 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
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
  • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
• • 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
  • B22F3/10—Sintering only
  • B22F3/1017—Multiple heating or additional steps
• • 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
  • B22F3/10—Sintering only
  • B22F3/1017—Multiple heating or additional steps
  • B22F3/1021—Removal of binder or filler
• • 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
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
• • 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
  • B22F2201/00—Treatment under specific atmosphere
  • B22F2201/10—Inert gases
• • 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
  • B22F2201/00—Treatment under specific atmosphere
  • B22F2201/20—Use of vacuum
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the present invention relates to a method for producing a cemented carbide or a cermet alloy, and particularly to an organic binder after molding a cemented carbide powder or a cermet alloy powder into a predetermined shape by an injection molding method.
• the present invention relates to a method for producing a cemented carbide or a cermet alloy for removing and sintering.
• Cemented carbide and cermet alloys are high melting point materials. Therefore, when obtaining a cemented carbide or a cermet alloy sintered body, the powder metallurgy method of sintering after pressing or CIP forming the powder raw material has been conventionally used. . However, this method has many restrictions on the shapes that can be manufactured. In order to obtain a complicated final shape, it is necessary to grind the sintered body with a diamond grindstone after sintering, resulting in a very high cost.
• Japanese Patent Publication No. Sho 62-33232 discloses a method of kneading a metal powder or a ceramic powder with an organic binder and molding the mixture into an article having a complicated shape by injection molding. ing.
• cemented carbide powders and cermet alloy powders are fine powders with a particle size of about ⁇ . Furthermore, these alloys have a high specific gravity. Furthermore, the allowable amount of carbon concentration in the alloy is small. Due to the material properties of such cemented carbides and cermet alloys, deformation and defects are likely to occur during binder removal processing. In addition, high quality alloys cannot be obtained due to the effect of residual carbon due to the decomposition of organic binders. In order to avoid such problems, it is necessary to perform the binder removal process for a very long time. Due to the above problems, injection molding technology for cemented carbide and cermet alloy has hardly been put to practical use yet.
• Another object of the present invention is to provide a method that does not cause deformation or defects of a molded article during binder removal processing.
• Still another object of the present invention is to provide a method capable of performing binder removal processing in a short time.
• the method for producing a cemented carbide or cermet alloy which is a prerequisite for the present invention includes a step of mixing and kneading cemented carbide powder or cermet alloy powder with an organic binder;
• the method includes a step of molding the powder into a predetermined shape by an injection molding method, and a step of thereafter removing the organic binder from the molded body and sintering the molded body.
• the organic binder is first removed in an inert gas atmosphere as the first removal step, and subsequently, the second binder removal step is performed at 1 T0 rr or less. It is performed in a vacuum.
• the organic binder includes a plurality of types of binders divided into a group that can be removed at a low temperature and a group that can be removed at a high temperature.
• the composition of each binder in the organic binder is such that when the low-temperature removal group loses 30% of the total weight in the inert gas atmospheric pressure heating weight loss test (TG) using only the organic binder, the weight loss rate of the high-temperature removal group decreases. It is selected to satisfy the condition of within 5%.
• the ratio of the binder belonging to the low-temperature removal group to the entire organic binder is 30% to 90%.
• the temperature at which the transition from the first removal step to the second removal step is selected so as to satisfy the following condition.
• the condition is that the removed amount of the binder belonging to the low-temperature removal group is 30% or more of the whole organic binder, and the remaining ratio of the binder belonging to the high-temperature removal group is the whole organic binder. Is 5% or more.
• a binder that is a main component of the low-temperature removal group a box having a hydrophilic polar group and a melting point of 80 ° C. or less is preferable.
• a sintering process may be subsequently performed.
• the organic binder may be cooled once after removing the organic binder, and then sintered.
• the injection molded body is composed of a powder and a binder, and has almost no voids.
• the binder first flows out due to the expansion of the binder, and then the binder is removed due to evaporation from the surface.
• 30% of the binder is removed by such a process, pores communicating with the surface are formed inside the molded body.
• the gas generated inside the compact is removed through the pores, and the binder removal proceeds further.
• gas is generated inside the molded body when the binder removal is less than 30%, the molded body will crack or swell.
• the binder removal process requires a long time.
• waxes as a plasticizer and polymer resins as a binder are required. Since waxes evaporate without decomposition at low temperatures, binder removal can be performed relatively easily.
• high molecular weight resins generate a large amount of gas by decomposition, and thus are likely to cause defects in the molded body in the early stage of binder removal.
• the inventor of the present application has focused on the points described above and has achieved the present invention. It has been reached. Specifically, a polymer resin that does not start decomposing even when it reaches a temperature at which waxes are removed by 30% or more of the total is selected, and this polymer resin and waxes are mixed. I do. In the initial state of the binder removal treatment, the binder is removed by 30% or more by evaporating only the waxes, and continuous pores are formed inside the compact. After the pores are formed, the decomposition of the polymer resin is started.
• the main components of the low-temperature removal group are Hexadex, Carnauba Wax, Montan Wax, Ozokei Light Wax, Polykiuri Wax, and Candelilla Wax. And microwax, microwax, microwax, etc.
• the binders for the high-temperature removal group include low-density polyethylene, low-molecular-weight polyethylene, ethylene-vinyl acetate, polypropylene, and acrylic resin.
• the atmospheric pressure is reduced or brought to a state close to vacuum, so that the gas evaporates from the surface of the gas and the gas generated inside the molded body. Promote withdrawal.
• the binder removal processing is performed in two stages of a first removal step and a second removal step.
• the first removing step is performed under an atmospheric pressure atmosphere
• the second removing step is performed under a vacuum atmosphere.
• the first removal step is desirably performed in an atmosphere of an inert gas such as N 2 or Ar. If the binder removal treatment is performed in an oxidizing atmosphere such as air, the surface oxidation of Co, i, and the like progresses during the progress of the binder removal. When such a surface oxide layer is present, the bonding force due to reduction in the second removal step is reduced. In addition, since the binder removal progresses and oxidation of only the portion exposed to the surrounding atmosphere progresses, the carbon concentration in the alloy increases. The degree of non-uniformity causes the liquid phase appearance temperature during sintering to become non-uniform, greatly reducing dimensional accuracy.
• an inert gas such as N 2 or Ar.
• Cemented carbide powder The surface of the met-alloy powder is hydrophilic.
• waxes such as n-paraffins are hydrophobic. Therefore, the wettability between the wax such as n-paraffin and the cemented carbide powder or cermet alloy powder is poor. Therefore, in order to obtain the viscosity required for injection molding, it is necessary to use more wax.
• the inventor of the present application has found that the amount of binder can be reduced by using a certain kind of natural wax having a hydrophilic polar group.
• the wax is brittle, so that the molded body is likely to get loom.
• a box having a hydrophilic polar group and a melting point of 80 ° C. or less the effect is the same whether it is synthetic or natural.
• stearic acid or the like may be used as a lubricant. Even so, the effect of the present invention does not change.
• the compact was placed in a furnace, and the furnace was maintained at 1 atm in an Ar atmosphere.
• the inside of the furnace was heated at a heating rate of 8 ° CZ up to 425 ° C at an Ar flow rate of 3H for 8 hours, and the binder was removed.
• the inside of the furnace was heated up to 700 ° C at a heating rate of 50 ° C for an hour and held at that temperature for 1 hour. After cooling. Thus, the binder removal processing has been completed.
• the inside of the furnace was evacuated to 0.05 Torr, the temperature was raised to 140 ° C. for 200 hours CZ, and the temperature was maintained for 1 hour, followed by cooling.
• the sintered body thus obtained had no defects and good alloy properties.
• the temperature was reduced to 425 ° C under a pressure of 1 atm of N ⁇ . Kuss lost 95%.
• the weight loss of low molecular weight polyethylene was 13%.
• the atmosphere in the furnace is 1 atm under an Ar atmosphere, and the initial binder removal treatment is performed by raising the temperature to 43 ° C at a rate of 10 ° CZ for a flow rate of 3 JL Z minutes. Was performed.
• the temperature was raised to 700 ° C at a heating rate of 50 ° C / hour while maintaining the inside of the furnace at 0.2 Torr or less with a vacuum pump, and the temperature was maintained for 1 hour. In this way, the binder removal processing has been completed. Thereafter, the inside of the furnace was heated up to 135 ° C. in a vacuum of 0.05 Torr over a period of 200 ° C.Z for 1 hour, kept at that temperature for 1 hour, and cooled.
• the sintered body thus obtained did not have any defects, and had good properties of the alloy.
• the carnauba wax was reduced by 92% to 43 ° C under the conditions of N 2 and 1 atm. . It also has low molecular weight at 430 ° C Weight loss of propylene was 8%.
• the temperature was raised to 38 ° C. at a rate of 13 ° C./hour under the condition of 1 Z, and the initial binder removal treatment was performed.
• the temperature was raised to 700 ° C at a heating rate of 50 ° C / hour, and the temperature was maintained for 1 hour. Later cooled. Thus, the binder removal processing has been completed.
• the inside of the furnace was evacuated to 0.05 Torr, the temperature was raised to 135 ° C. in 200 ° C. for Z hours, and the temperature was maintained for 1 hour, followed by cooling.
• the sintered body thus obtained did not have any defects and had good alloy properties.
• the furnace was heated to 1 atm in an Ar atmosphere, heated to 350 ° C at a rate of 10 ° CZ for a flow rate of 3 it for an initial binder removal process.
• the inside of the furnace kept at 0.5 T 0 rr or less using a vacuum pump, the temperature was raised to 65 ° C at a heating rate of 50 ° C for 50 hours, and the temperature was maintained for 1 hour. Binder processing has been completed.
• the inside of the furnace was evacuated to 0.05 Torr, the temperature was raised to 140 ° C. over 200 ° C. for 1 hour, maintained for 1 hour, and cooled.
• the sintered body obtained in this way had no defects and good alloy properties.
• the loss of the Montax was 93% and 3% at 350 ° C under the conditions of N 2 and 1 atm. Reduction of low-density polyethylene at 50 ° C The amount was determined to be 0%.
• the atmosphere in the furnace was 1 atmosphere in an Ar atmosphere, and the temperature was raised to 350 ° C at a heating rate of 10 ° CZ for 3 minutes at a flow rate of 3 minutes to perform an initial debinding process.
• the temperature inside the furnace was kept at 0.5 T 0 rr or less with a vacuum pump, and the temperature was raised to 65 ° C over a period of 50 hours at a heating rate of 50 hours.
• the binder removal processing has been completed.
• the inside of the furnace was evacuated to a temperature of 0.05 T 0 rr, heated to 140 ° C. in 200 ° C. for Z hours, held for 1 hour, cooled, and then cooled to 135 ° C. HIP processing was performed.
• the sintered body thus obtained did not have any defects and had good alloy properties.
• a heating loss test was performed on the binder used in this example, the temperature of the Montawan wax was reduced to 350 ° C under the conditions of N 2 and 1 atm. The weight loss was 93%, the weight loss of n-paraffin was 100%, and the weight loss of low-density polypropylene at 350 ° C was 0% as measured.
• Example 2 Under the same conditions as in Example 1, a plurality of raw material grain compacts were produced. With respect to these compacts, the state after the binder removal was examined by changing the heating rate in the first removal step of the binder removal treatment and the transition temperature to the second removal step. Table 2 shows the results. Table 1 shows the results of heat loss test of Bewax and low molecular weight polyethylene (PE). As is clear from the results in Tables 1 and 2, according to the method of the present invention, the state after the binder removal is good, and the binder removal time can be shortened.
• PE low molecular weight polyethylene
• Heating rate N 2 latm, 10. C / min heating
• Binder composition is percentage of alloy powder 100%
• a binder removal test was performed using the same alloy powder as in Example 3 while changing the type and composition of the binder. Table 4 shows the results.
• the binder removal conditions were the same as in Example 3.
• Test Nos. 18 to 20 allowed good injection and debinding. However, in the test using II-paraffin No. 21, good injection could not be achieved unless the amount of n-paraffin was increased.
• Test No. 22 was deformed in the binder removal processing.
• Test No. 23 in which Biwax and n-paraffin were mixed at 1Z1 required a slight addition of binder amount, but no deformation was observed during binder removal.
• Binder composition is percentage of alloy powder 100%
• the present invention provides a method for manufacturing a cemented carbide or a cermet alloy in which a cemented carbide powder or a cermet alloy powder is formed into a predetermined shape by an injection molding method, and then an organic binder is removed and sintered. Used effectively in the method.

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• 1990
  • 1990-09-12 EP EP90913553A patent/EP0443048B1/en not_active Expired - Lifetime
  • 1990-09-12 WO PCT/JP1990/001171 patent/WO1991004119A1/ja not_active Ceased
  • 1990-09-12 CA CA002041668A patent/CA2041668C/en not_active Expired - Fee Related
  • 1990-09-12 DE DE69015150T patent/DE69015150T2/de not_active Expired - Lifetime
  • 1990-09-12 KR KR1019910700490A patent/KR940009337B1/ko not_active Expired - Lifetime
  • 1990-09-13 TW TW079107703A patent/TW225493B/zh active

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