JP4406874B2 - Method for firing a green sheet for producing a porous metal sintered body - Google Patents
Method for firing a green sheet for producing a porous metal sintered body Download PDFInfo
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- JP4406874B2 JP4406874B2 JP2004170320A JP2004170320A JP4406874B2 JP 4406874 B2 JP4406874 B2 JP 4406874B2 JP 2004170320 A JP2004170320 A JP 2004170320A JP 2004170320 A JP2004170320 A JP 2004170320A JP 4406874 B2 JP4406874 B2 JP 4406874B2
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Ni等の金属粉末を多孔質状に焼結した焼結体になる製品は、今日の諸産業で広く用いられており、この発明はかかる焼結体製品をつくるための前駆体となるグリンシートの焼成方法、特にかかるグリンシートを炭素化焼成するための炉内雰囲気下での加熱方法にかかるものである。 Products that become sintered bodies in which metal powders such as Ni are sintered in a porous state are widely used in various industries today, and this invention is a green sheet that serves as a precursor for producing such sintered body products. , Especially a heating method in a furnace atmosphere for carbonizing and firing such a green sheet.
例えば、所望の金属粉末にその約1重量%のバインダーを加え、これを5Kg/cm2程度の圧力下でプレス成型してグリンシートをつくり、このグリンシート成型品を焼結する粉末焼結冶金法は古くから知られるところである。この場合のグリンシート成型品は、高圧でプレスされたものであるので、焼結前にバインダーをほぼ全て脱脂してもグリンシートの形状は比較的に容易に保持されうる。 For example, powder sintering metallurgy that adds about 1% by weight of the binder to the desired metal powder, press-molds it under a pressure of about 5 kg / cm 2 to form a green sheet, and sinters this green sheet molded product. The law has been known for a long time. Since the green sheet molded product in this case is pressed at high pressure, the shape of the green sheet can be maintained relatively easily even if the binder is almost completely degreased before sintering.
ところが、Ni等の金属粉末とフェノール樹脂等の有機質バインダーとをスラリー状にし、このスラリーを、成型時に骨材として一時的に働く発泡性樹脂の気泡中に含浸させ、その後に加熱炉内で加熱してこの発泡樹脂を分解、気化せしめると共に、気泡中にあったバインダーを炭化して、この炭素化されたバインダーと金属粉とからなる本発明の対象の種類のグリンシートでは、炭化されたバインダーのみによって金属粉末が担持され、グリンシートの形状が保持されることになる。 However, a metal powder such as Ni and an organic binder such as phenol resin are made into a slurry, and this slurry is impregnated in foamed resin bubbles that temporarily work as an aggregate during molding, and then heated in a heating furnace. Then, the foamed resin is decomposed and vaporized, and the binder in the bubbles is carbonized, and in the green sheet of the type of the object of the present invention comprising the carbonized binder and the metal powder, the carbonized binder Only by this, the metal powder is supported, and the shape of the green sheet is maintained.
この発明が対象とする金属になる多孔質の焼結体の製造用のグリンシートでは、上記の背景技術の欄で述べたように、金属粉末は炭素化された有機質バインダーによって担持され、分散化されて多孔質をつくらなければならない。このためには、炉内で加熱された時に、スラリー状で発泡性樹脂の気泡中に含浸された有機質バインダー、例えばフェノール樹脂は、発泡性樹脂、例えばウレタンフォームが分解、気化すると共に、それ自体も熱分解して、炭素化されねばならない。しかしながら、グリンシートの段階で、有機質バインダーが酸化、即ちグリンシートから燃焼,脱炭すると、金属粉はバインダーによって分散して担持されなくなり、ついにはグリンシートが焼結体へと最終焼結される前に多孔質性を失うばかりでなく、グリンシート全体が形状を成さずに崩れてしまう。また、グリンシートの焼成時には金属粉末の酸化をも防がなければならない。 In the green sheet for the production of a porous sintered body that becomes a metal to which the present invention is applied, as described in the background section above, the metal powder is supported by a carbonized organic binder and dispersed. Must be made porous. For this purpose, when heated in a furnace, an organic binder, such as a phenolic resin, impregnated in foamed foam bubbles in the form of a slurry decomposes and vaporizes the foamable resin, such as urethane foam, itself. Must also be pyrolyzed and carbonized. However, when the organic binder is oxidized, that is, burned and decarburized from the green sheet at the stage of the green sheet, the metal powder is not dispersed and supported by the binder, and finally the green sheet is finally sintered into a sintered body. Not only does it lose porosity before, but the whole green sheet collapses without forming a shape. In addition, oxidation of the metal powder must be prevented when firing the green sheet.
以上の課題、即ち(1)有機質バインダーが酸化し、グリンシートから脱炭することなしに高い炭化収率で炭素化して、金属粉をよく担持して、グリンシートの燒成後の多孔性が保証されること、(2)金属粉がグリンシートの焼成時にも酸化されないようにすることは、今まで余りに問題視されなかった。しかしながら、本発明の対象である金属の多孔質の焼結体を製造するためのグリンシートの焼成のためには、重大な課題である。良質なグリンシートを焼成し得ることは、良質な焼結体を焼結し得るための基であるが、上記した特許文献1を含めグリンシートの焼成そのものについてのめぼしい発明、考案は今までにない。 The above problems, that is, (1) the organic binder is oxidized and carbonized with a high carbonization yield without decarburizing from the green sheet, the metal powder is well supported, and the porosity after the green sheet is formed is Assured, (2) preventing the metal powder from being oxidized even when the green sheet is fired has not been regarded as a problem so far. However, it is a serious problem for firing a green sheet for producing a porous sintered body of a metal that is an object of the present invention. The ability to fire a good quality green sheet is a basis for sintering a good quality sintered body. Absent.
上記した課題(1)を解決するために、グリンシートをつくる有機バインダーの加熱が、常にCOの酸化還元平衡線よりも低い酸素圧下で行なわれるようにし、と同時に上記した課題(2)が解決されるために、金属粉末がその酸化還元平衡線よりも低い酸素圧下で行われるようにした。 In order to solve the above problem (1), heating of the organic binder forming the green sheet is always performed under an oxygen pressure lower than the redox equilibrium line of CO, and at the same time, the above problem (2) is solved. In order to achieve this, the metal powder was made under an oxygen pressure lower than its redox equilibrium line.
かかる課題(1)と課題(2)とを同時に、かつ容易に解決するためには、有機質バインダーの炭素化が始まる温度である約300℃における金属または金属合金粉末の酸化還元平行線よりも低い酸素分圧の雰囲気ガス下で、グリンシート材の焼成を完了すればよいことを、全くの新しい知見として本願発明者は得た。 In order to solve the problem (1) and the problem (2) simultaneously and easily, it is lower than the redox parallel line of the metal or metal alloy powder at about 300 ° C., which is the temperature at which the carbonization of the organic binder starts. The inventor of the present application has obtained as a completely new finding that the firing of the green sheet material should be completed under an atmospheric gas having an oxygen partial pressure.
図1で示される通りに、有機質バインダーの炭素化が始まる上記した温度におけるNiOのLOGPO2(酸素分圧の対数)は約1×10-35(対応するPH2:PH2O比では約1×10-3:1,また対応するPCO:PCO2比では約1×10-5:1)であり、MoO2のLOGPO2は約1×10-44(対応するPH2:PH2O比では約2×102:1,また対応するPCO:PCO2比では約10:1)であり、CoOのLOGPO2は約1×10-36(対応するPH2:PH2O比では約1×10-3:1、また対応するPCO:PCO2比では約1×10-4:1)であり、FeOのLOGPO2は約1×10-41(対応するPH2:PH2O比では約6:1、また対応するPCO:PCO2比では約1×10-1:1)である。 As shown in FIG. 1, the LOGPO 2 (logarithm of oxygen partial pressure) of NiO at the above-described temperature at which carbonization of the organic binder begins is about 1 × 10 −35 (corresponding PH 2 : PH 2 O ratio is about 1). × 10 -3: 1, also the corresponding PCO: about the PCO 2 ratio 1 × 10 -5: 1) a is, the MoO 2 LOGPO 2 is about 1 × 10 -44 (corresponding PH 2: PH 2 O ratio Is about 2 × 10 2 : 1, and the corresponding PCO: PCO 2 ratio is about 10: 1), and the LOGPO 2 of CoO is about 1 × 10 −36 (the corresponding PH 2 : PH 2 O ratio is about 1). × 10 −3 : 1 and corresponding PCO: PCO 2 ratio is about 1 × 10 −4 : 1), and FeO LOGPO 2 is about 1 × 10 −41 (corresponding PH 2 : PH 2 O ratio). About 6: 1, and the corresponding PCO: PCO 2 ratio is about 1 × 10 −1 : 1).
なお、この発明では、炭化水素系ガスと空気とを混合し、その完全燃焼比の70〜98%でこれを燃焼して得られた発熱型変性ガスを、炉内雰囲気として用い、そのLOGPO2またはPH2:PH2O比またはPCO:PCO2比によって、所望の低い酸素分圧の雰囲気ガスを得た。 In the present invention, an exothermic denatured gas obtained by mixing hydrocarbon gas and air and combusting it at 70 to 98% of its complete combustion ratio is used as the furnace atmosphere, and the LOGPO 2 Alternatively, an atmospheric gas having a desired low oxygen partial pressure was obtained according to the PH 2 : PH 2 O ratio or the PCO: PCO 2 ratio.
グリンシート中に高い炭化収率で有機質バインダーが残って、金属粉を分散して担持して、グリンシートの型が良好に保たれ、しかも金属粉が酸化されることがなかった。有機質バインダーの炭化収率が高いので、バインダーの使用量を減じることができて、経済的であり省エネルギーの効果も伴って認められた。 The organic binder remained in the green sheet with a high carbonization yield, and the metal powder was dispersed and supported, so that the mold of the green sheet was kept good and the metal powder was not oxidized. Since the carbonization yield of the organic binder was high, the amount of the binder used could be reduced, and it was recognized that it was economical and energy-saving.
実施例1
幅200mmx長さ300mmの発泡ウレタン樹脂に、30重量%のフェノール樹脂を含み粘度が500CpのNi粉末(平均の粒径が1〜15μm)のスラリーを含浸させた。これをバッチ炉に入れ、毎分5℃の昇温速度で600℃に加熱して焼成した。炉内雰囲気にLPGと空気を混合、燃焼した発熱型変成ガスを用い、そのPCO:PCO2比を1×10-5:1とした。
ウレタン樹脂は消失し、炭素化したフェノール樹脂にて担持されたニッケルのグリンシートが得られた。
Example 1
A foamed urethane resin having a width of 200 mm and a length of 300 mm was impregnated with a slurry of Ni powder (average particle size: 1 to 15 μm) containing 30 wt% phenol resin and having a viscosity of 500 Cp. This was put into a batch furnace and heated to 600 ° C. at a temperature rising rate of 5 ° C. per minute and baked. An exothermic modified gas obtained by mixing and burning LPG and air in the furnace atmosphere was used, and the PCO: PCO 2 ratio was set to 1 × 10 −5 : 1.
The urethane resin disappeared, and a nickel green sheet supported by a carbonized phenol resin was obtained.
得られたグリンシート中のNiは還元され、酸化は認められず、フェノール樹脂バインダーの残炭率は熱重量分析によれば600℃85%であり、フェノール樹脂を炭化したときの通常の残炭率の600℃で70%を15%も超えた。なお、このフェノール樹脂バインダーの炭素化は約300℃で始まり、約600℃で完了した。その他の有機物の炭化も同様に約300〜400℃で起こり、約600℃で終わる。 Ni in the obtained green sheet was reduced, no oxidation was observed, and the residual carbon ratio of the phenol resin binder was 600 ° C. and 85% according to thermogravimetric analysis. At a rate of 600 ° C., 70% exceeded 15%. The carbonization of the phenol resin binder started at about 300 ° C. and completed at about 600 ° C. Carbonization of other organic substances also occurs at about 300 to 400 ° C and ends at about 600 ° C.
なお、この実施例において、フェノール樹脂バインダーの炭素化が始まる300℃でのNiOの酸化還元平衡線はLOGPO2で前述した通りの約1×10-35(対応するPCO:PCO2比では上述の約1×10-5:1)にあり、炉内雰囲気がこの酸素分圧下もしくはこれよりも低ければ、この温度下でNiは酸化されずに還元下に保たれる。フェノール樹脂バインダー(CO)のこの温度における酸化還元平行線は、図1で示される通りにそれよりも高いので、該有機物バインダーの炭素化は酸化、脱炭することなしに始まる。焼成温度が高くなると、より高い酸素分圧下へとNiとフェノール樹脂バインダーの酸化還元平行線はもたらされるが、焼成中に焼成温度に対応して炉内の雰囲気の酸素圧を逐次に変えることは必ずしも容易なことでなく、得策でもないので、この実施例では雰囲気の酸素分圧を終始最低の1×10-35として、グリンシートを焼成した。 In this example, the oxidation-reduction equilibrium line of NiO at 300 ° C. at which the carbonization of the phenol resin binder begins is about 1 × 10 −35 as described above for LOGPO 2 (the corresponding PCO: PCO 2 ratio is about 1 × 10 -5: located 1), the furnace atmosphere is lower the oxygen partial pressure or than this, Ni at this temperature is kept under reduced without being oxidized. Since the redox parallel line at this temperature of the phenolic resin binder (CO) is higher as shown in FIG. 1, carbonization of the organic binder begins without oxidation and decarburization. When the firing temperature is increased, the redox parallel lines of Ni and phenolic resin binder are brought to a higher oxygen partial pressure, but it is not possible to sequentially change the oxygen pressure in the furnace atmosphere corresponding to the firing temperature during firing. In this example, the green sheet was fired with the oxygen partial pressure of the atmosphere set to the lowest 1 × 10 −35 throughout.
実施例2
上記実施例1では、上記実施例1ではNi粉のグリンシートの焼成について述べたが、Mo粉、Co粉、Fe粉についてもこの発明を実施した。即ち、グリンシート材中のフェノール樹脂の炭素化が始まる温度である約300℃におけるこれら金属粉のそれぞれの酸化還元平行線よりも低い酸素分圧の雰囲気ガス下で、グリンシート材の焼成を実施した。かかる雰囲気ガスの低い酸素分圧(LOGPO2)ならびにそれに対応するPH2:PH2O比の値とPCO:PCO2比の値は、上記の「0009」欄にて記載した通りである。
いずれの金属の場合にも、酸化が生じることがなかった。また、フェノール樹脂バインダーの残炭率は、600℃で平均約82%であった。
Example 2
In Example 1 described above, firing of the Ni powder green sheet was described in Example 1, but the present invention was also implemented for Mo powder, Co powder, and Fe powder. That is, the green sheet material is fired in an atmosphere gas having an oxygen partial pressure lower than the respective redox parallel lines of these metal powders at about 300 ° C., which is the temperature at which the carbonization of the phenol resin in the green sheet material starts. did. The low oxygen partial pressure (LOGPO 2 ) of the atmospheric gas and the corresponding PH 2 : PH 2 O ratio value and PCO: PCO 2 ratio value are as described in the column “0009” above.
In any case, oxidation did not occur. The residual carbon ratio of the phenol resin binder was about 82% on average at 600 ° C.
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