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Sinter shrinkage of strontium-ferrite and application in sinter joining
Nanocrystalline Fe oxide powders were prepared by inert gas condensation, in He, and consolidated by pulsed electric current sintering. Mean particle size varied from 8 to 18 nm. After sintering at 800°C the grain size was 33 nm. Densities and hardness are described. PRODUCTION OF NEODYMIUM-IRONBORON MAGNET POWDERS BY MODIFIED PROCESS K.Oki et al. (Kyushu University, Kasuga, Japan.) J Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999, 5156. (In Japanese.) The effect of an intermediate treatment in Ar, after hydrogenation, on NdFe-B and Nd-Fe-Co-B-Zr-Ga powders, processed by hydrogenation-decomposition-desorption-recombination to give anisotropic powders, was investigated. Ar treatment is shown to improve anisotropy but to reduce coercivity. Magnetic properties are described. Changes in microstructures were detected: growth of a(Fe,Co), matrix decomposition of (Fe,Co),B and formation of a new phase. COMPACTION OF ANISOTROPIC MAGNETIC POWDER IN A MAGNETIC FIELD SMino et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999,57-61. (In Japanese.) Magnetically anisotropic Nd-Fe-B powder, with a binder, was compacted in a magnetic field to make bonded magnets with high maximum energy products. Effects of magnetic field strength and duration of application on magnetic orientation in the magnet were studied. The degree of magnetic orientation is shown to depend on bulk density of the powder in the mould. THERMAL STABILITY OF COMPRESSION MOULDED NEODYMIUM-IRONBORON ANISOTROPIC MAGNETS N.Ishigaki et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999,62-66. (In Japanese.) It is reported that compression moulded bonded Nd-Fe-B magnets, with various binders, had been investigated with regard to effects of the binder on thermal stability and mechanical properties. Thermo-setting components resins with volatile reduced thermal stability. The magnets had a solids content of 77% and 96%. magnetic orientation of Mechanical properties were influenced by alterations in processing in the mixing stage. 34
MPR June 2000
SINTER SHRINKAGE OF STRONTIUMFERRITE AND APPLICATION IN SINTER JOINING SHosokawa et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999, 57-61. (In Japanese.) The feasibility of using sinter-joining to make a Sr-ferrite part, comprising a disc and an outer ring, with differing orientations of the crystallites was investigated. The disc was compacted in a magnetic field and the ring was not. The combined part was sintered at 1150°C. Shrinkage in the disc caused dimensional anisotropy which affected joining. Shrinkage and strength of the joint between disc and ring were investigated with regard to powder and process parameters. EFFECT OF MOULDING CONDITIONS ON MAGNETIC PROPERTIES OF BONDED STRONTIUM-FERRITE MAGNETS
Solid state sintering of WC-Co, with and without an axial applied load, was investigated by dilatometry. Increase in the load resulted in increased volumctric shrinkage. Decrease in shrinkage rate during isothermal treatment is the result of increased compact rigidity. STUDIES OF GRADED CEMENTED CARBIDE COMPONENTS M.Rosso et al. (Politecnico di Torino, Torino, Italy.) Int. J. Refractory Metals Hard Mater., Vol 17, No l-3, 1999, 187. 192. Graded WC structures were produced from different WC grades, some with (Ta,Nb)C, and a Co binder, by vacuum sintering at 1450°C. Hardnesses and shrinkages were determined. The observed microstructures correlated well with the coupled grades and the presence of a diffusion zone. It is shown that it is possible to make a multi-layer cutting tool with a tough core and a hard surface. TRANSFORMATION OF METAL SURFACE TO CERMET BY PLASMA PROCESSING
SHosokawa et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999,72-76. (In Japanese.) Effects of moulding pressure, 30 or 50 MPa, and temperature, 100 to 250°C on the magnetic properties of bonded Srferrite magnets were investigated. Above 200°C coercivity was not affected by moulding temperature. This is attributed to quasi-isostatic pressure exerted by the binder on the Sr-ferrite powder. Cold isostatic pressing and epoxy resins were used to study this. Coercivity was correlated with torque in the blending machine.
M.Nunogaki. (Osaka University, Ibarakishi, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 12, 1998, 1220-1223. (In Japanese.) Conversion of the surface of metallic substrates of Ti or Zr to cermets by plasma carburizing or nitriding, at less than 1300°C for less than 3 hours, was investigated. Hardness and depth of penetration of the chemically altered layers were determined. Effects of pre-irradiation on nitriding of pure Al were also investigated.
Hard materials steels
PROPERTIES OF PULSE CURRENT SINTERED ATOMIZED CAST IRONDIAMOND COMPOSITES
and tool
SOLID STATE SINTERING OF CEMENTED CARBIDES et al. (Royal Inst. of S.Haglund Technology, Stockholm, Sweden.) Z. Metallkd, Vol89, No 5, 1998,316-322. Solid state sintering of cemented carbides was investigated by dilatometry and scanning electron microscopy. Powder surfaces were analysed. It is reported that the major part of densification is in the solid state and that higher heating rates give greater densification rates. Presence of TiC resulted in a in sintering rate. reduction large Melting of the binder had only a minor effect on densification.
T.Tojo et al. (Toy0 Tanso Co Ltd, Mitoyogun, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 2, 1999, 120-124. (In English.) Development of a cast iron bonded diamond cutting material, made from atomized cast iron powder, is reported. Effects of porosity on mechanical properties were investigated. Decreased porosity increased Young’s modulus and bend strength. Diamond particle size influenced strength. Young’s modulus was increased by increase in diamond powder content.
Metal injection
moulding
SINTERING OF TUNGSTEN CARBIDECOBALT UNDER AXL4L LOAD
APPLICATION OF COPPER BASED POWDERS FOR INJECTION MOULDING
SHaglund et al. (Royal Inst. Technology, Stockholm, Sweden.) Metallkd, Vol89, No 5, 1998,323-326.
l?Sejc, A.Havalda. (STU, Bratislava, Czech Republic.) Pokroky Praskove Metal., Vol 37, No 1,1999,20-31. (In Czech.)
of Z.
MPR June 2000
SINTER SHRINKAGE OF STRONTIUMFERRITE AND APPLICATION IN SINTER JOINING SHosokawa et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999, 57-61. (In Japanese.) The feasibility of using sinter-joining to make a Sr-ferrite part, comprising a disc and an outer ring, with differing orientations of the crystallites was investigated. The disc was compacted in a magnetic field and the ring was not. The combined part was sintered at 1150°C. Shrinkage in the disc caused dimensional anisotropy which affected joining. Shrinkage and strength of the joint between disc and ring were investigated with regard to powder and process parameters. EFFECT OF MOULDING CONDITIONS ON MAGNETIC PROPERTIES OF BONDED STRONTIUM-FERRITE MAGNETS
Solid state sintering of WC-Co, with and without an axial applied load, was investigated by dilatometry. Increase in the load resulted in increased volumctric shrinkage. Decrease in shrinkage rate during isothermal treatment is the result of increased compact rigidity. STUDIES OF GRADED CEMENTED CARBIDE COMPONENTS M.Rosso et al. (Politecnico di Torino, Torino, Italy.) Int. J. Refractory Metals Hard Mater., Vol 17, No l-3, 1999, 187. 192. Graded WC structures were produced from different WC grades, some with (Ta,Nb)C, and a Co binder, by vacuum sintering at 1450°C. Hardnesses and shrinkages were determined. The observed microstructures correlated well with the coupled grades and the presence of a diffusion zone. It is shown that it is possible to make a multi-layer cutting tool with a tough core and a hard surface. TRANSFORMATION OF METAL SURFACE TO CERMET BY PLASMA PROCESSING
SHosokawa et al. (Sumitomo Special Metals Co Ltd, Osaka, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 1, 1999,72-76. (In Japanese.) Effects of moulding pressure, 30 or 50 MPa, and temperature, 100 to 250°C on the magnetic properties of bonded Srferrite magnets were investigated. Above 200°C coercivity was not affected by moulding temperature. This is attributed to quasi-isostatic pressure exerted by the binder on the Sr-ferrite powder. Cold isostatic pressing and epoxy resins were used to study this. Coercivity was correlated with torque in the blending machine.
M.Nunogaki. (Osaka University, Ibarakishi, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 12, 1998, 1220-1223. (In Japanese.) Conversion of the surface of metallic substrates of Ti or Zr to cermets by plasma carburizing or nitriding, at less than 1300°C for less than 3 hours, was investigated. Hardness and depth of penetration of the chemically altered layers were determined. Effects of pre-irradiation on nitriding of pure Al were also investigated.
Hard materials steels
PROPERTIES OF PULSE CURRENT SINTERED ATOMIZED CAST IRONDIAMOND COMPOSITES
and tool
SOLID STATE SINTERING OF CEMENTED CARBIDES et al. (Royal Inst. of S.Haglund Technology, Stockholm, Sweden.) Z. Metallkd, Vol89, No 5, 1998,316-322. Solid state sintering of cemented carbides was investigated by dilatometry and scanning electron microscopy. Powder surfaces were analysed. It is reported that the major part of densification is in the solid state and that higher heating rates give greater densification rates. Presence of TiC resulted in a in sintering rate. reduction large Melting of the binder had only a minor effect on densification.
T.Tojo et al. (Toy0 Tanso Co Ltd, Mitoyogun, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 46, No 2, 1999, 120-124. (In English.) Development of a cast iron bonded diamond cutting material, made from atomized cast iron powder, is reported. Effects of porosity on mechanical properties were investigated. Decreased porosity increased Young’s modulus and bend strength. Diamond particle size influenced strength. Young’s modulus was increased by increase in diamond powder content.
Metal injection
moulding
SINTERING OF TUNGSTEN CARBIDECOBALT UNDER AXL4L LOAD
APPLICATION OF COPPER BASED POWDERS FOR INJECTION MOULDING
SHaglund et al. (Royal Inst. Technology, Stockholm, Sweden.) Metallkd, Vol89, No 5, 1998,323-326.
l?Sejc, A.Havalda. (STU, Bratislava, Czech Republic.) Pokroky Praskove Metal., Vol 37, No 1,1999,20-31. (In Czech.)
of Z.