Powder metallurgy method for producing an extruded profile

Abstract

The invention relates to a method for producing a profile by extruding powdered metal and/or powdered metal alloys. According to said method, a powder feedstock is heated to an extrusion temperature below the melting temperature of the powder and is expelled under pressure through an opening in a die to form the section. At least one metal or a metal alloy of the powder is a reactive metal that spontaneously forms a natural oxide layer on a free surface and/or the powder contains fibre-type particles that are distributed homogeneously in the powder feedstock and that absorb microwave radiation. The powder feedstock is heated to an extrusion temperature by microwave irradiation. The method permits rapid, uniform heating in all regions of the powder feedstock.

1 . Method for producing a profile by extruding powdered metal and/or powdered metal alloys, in which method a bulk powder material is heated to an extrusion temperature below the melting temperature of the powder and pressed under pressure through an opening of a die to form the profile, wherein at least one metal or a metal alloy of the powder is a reactive metal spontaneously forming a natural oxide protective layer on a free surface and in that the bulk powder material is heated by microwave irradiation to extrusion temperature. 
   
   
       2 . Method according to  claim 1 , wherein the density of the bulk powder material or the dimension of the hollow spaces between the powder particles including the oxide layers, is matched to the wavelength of the microwave radiation. 
   
   
       3 . Method according to  claim 1  wherein the reactive metal spontaneously forming a natural oxide protective layer on a free surface is aluminium, magnesium, titanium, tantalum or zirconium. 
   
   
       4 . Method according to  claim 15 , wherein the length of the fibre-like particles is matched to the wavelength of the microwave radiation. 
   
   
       5 . Method according to  claim 15  wherein the fibre-like particles are at least partially integrated in the metallic powder particles. 
   
   
       6 . Method according to  claim 1 , wherein the bulk powder material contains carbon nanotubes (CNTs) in a homogeneous distribution. 
   
   
       7 . Method according to  claim 1 , wherein the bulk powder material on heating to extrusion temperature firstly has low microwave energy radiated through it at a changing frequency, the absorbed energy is measured as a function of the frequency and on occurrence of a maximum of the absorbed energy, the resonance frequency is determined and in that the bulk powder material then has high microwave energy radiated through it at the resonance frequency. 
   
   
       8 . Method according to  claim 7 , wherein the determination of the resonance frequency of the bulk powder material and the following radiation with high microwave energy at the resonance frequency to heat the bulk powder material to extrusion temperature are carried out fully automatically by means of control electronics. 
   
   
       9 . Method according to  claim 7  wherein the bulk powder material is pre-compacted in an intermediate container, the pre-compacted bulk powder material is radiated through in the intermediate container at the resonance frequency and heated to extrusion temperature and then pressed from the intermediate container through the die opening by means of a ram. 
   
   
       10 . Method according to  claim 9 , wherein the pre-compaction of the bulk powder material in the intermediate container is carried out with a screw conveyor. 
   
   
       11 . Method according to  claim 1 , wherein the powder contains fibre-like particles distributed homogeneously in the bulk powder material and absorbing microwave radiation. 
   
   
       12 . Method according to  claim 11 , wherein the length of the fibre-like particles is matched to the wavelength of the microwave radiation. 
   
   
       13 . Method according to  claim 11 , wherein the fibre-like particles are at least partially integrated in the metallic powder particles. 
   
   
       14 . Method according to  claim 11 , wherein the bulk powder material contains carbon nanotubes (CNTs) in a homogeneous distribution. 
   
   
       15 . Method for producing a profile by extruding powdered metal and/or powdered metal alloys, in which method a bulk powder material is heated to an extrusion temperature below the melting temperature of the powder and pressed under pressure through an opening of a die to form the profile, wherein the powder contains fibre-like particles distributed homogeneously in the bulk powder material and absorbing microwave radiation, and in that the bulk powder material is heated by microwave irradiation to extrusion temperature. 
   
   
       16 . Method according to  claim 15 , wherein the bulk powder material on heating to extrusion temperature firstly has low microwave energy radiated through it at a changing frequency, the absorbed energy is measured as a function of the frequency and on occurrence of a maximum of the absorbed energy, the resonance frequency is determined and in that the bulk powder material then has high microwave energy radiated through it at the resonance frequency. 
   
   
       17 . Method according to  claim 16 , wherein the determination of the resonance frequency of the bulk powder material and the following radiation with high microwave energy at the resonance frequency to heat the bulk powder material to extrusion temperature are carried out fully automatically by means of control electronics. 
   
   
       18 . Method according to  claim 16 , wherein the bulk powder material is pre-compacted in an intermediate container, the pre-compacted bulk powder material is radiated through in the intermediate container at the resonance frequency and heated to extrusion temperature and then pressed from the intermediate container through the die opening by means of a ram. 
   
   
       19 . Method according to  claim 18 , wherein the pre-compaction of the bulk powder material in the intermediate container is carried out with a screw conveyor. 
   
   
       20 . Method according to  claim 15 , wherein the bulk powder material contains carbon nanotubes (CNTs) in a homogeneous distribution.