﻿NEW 
  METALS 
  AND 
  NEW 
  METHODS 
  — 
  DESCH 
  215 
  

  

  new 
  branch 
  of 
  technology, 
  known 
  as 
  powder 
  metallurgy, 
  has 
  grown 
  up. 
  

   Not 
  only 
  the 
  metals 
  of 
  high 
  melting 
  point, 
  but 
  also 
  copper, 
  bronze, 
  

   and 
  even 
  the 
  low-melting 
  alloys 
  of 
  tin, 
  are 
  prepared 
  in 
  the 
  form 
  of 
  

   small 
  particles 
  and 
  made 
  to 
  cohere 
  by 
  heat 
  and 
  pressure. 
  

  

  The 
  method 
  has 
  several 
  advantages. 
  Small 
  objects 
  may 
  be 
  produced 
  

   of 
  accurate 
  shape, 
  requiring 
  no 
  machining, 
  by 
  pressing 
  in 
  dies, 
  while 
  

   the 
  mass 
  may 
  be 
  made 
  completely 
  solid 
  or 
  given 
  any 
  required 
  degree 
  

   of 
  porosity. 
  Such 
  porous 
  masses 
  are 
  particularly 
  useful 
  for 
  bearing 
  

   metals, 
  the 
  spongy 
  metal 
  holding 
  the 
  lubricant 
  better 
  than 
  by 
  any 
  ar- 
  

   rangement 
  of 
  grooves. 
  The 
  method 
  of 
  consolidating 
  a 
  powder 
  is 
  also 
  

   used 
  in 
  the 
  making 
  of 
  carbide 
  tools. 
  Certain 
  very 
  hard 
  compounds, 
  

   especially 
  the 
  carbides 
  of 
  tungsten 
  and 
  titanium, 
  which 
  for 
  many 
  pur- 
  

   poses 
  can 
  replace 
  diamonds, 
  are 
  brittle 
  in 
  the 
  mass, 
  but 
  if 
  crushed 
  and 
  

   mixed 
  with 
  a 
  metallic 
  powder, 
  mainly 
  cobalt, 
  and 
  then 
  heated 
  until 
  

   perfect 
  union 
  with 
  the 
  binding 
  material 
  is 
  brought 
  about, 
  yield 
  a 
  com- 
  

   posite 
  mass 
  which 
  is 
  excellent 
  for 
  tools 
  and 
  dies. 
  

  

  The 
  chief 
  obstacle 
  to 
  chemical 
  operations 
  at 
  very 
  high 
  temperatures, 
  

   1600° 
  C. 
  or 
  above, 
  lies 
  in 
  the 
  difficulty 
  of 
  finding 
  materials 
  for 
  furnace 
  

   construction 
  and 
  for 
  containing 
  vessels 
  which 
  are 
  both 
  strong 
  and 
  

   resistant 
  to 
  chemical 
  attack 
  at 
  such 
  temperatures. 
  The 
  ordinary 
  fire 
  

   clays 
  become 
  soft 
  and 
  are 
  attacked 
  by 
  slags. 
  A 
  few 
  oxides, 
  especially 
  

   alumina, 
  magnesia, 
  thoria, 
  and 
  beryllia, 
  meet 
  severe 
  requirements 
  in 
  

   this 
  field, 
  but 
  their 
  refractory 
  qualities 
  are 
  lessened 
  by 
  quite 
  small 
  

   proportions 
  of 
  impurity, 
  and 
  their 
  preparation 
  calls 
  for 
  special 
  tech- 
  

   nique, 
  which 
  has 
  been 
  developed 
  as 
  a 
  result 
  of 
  long 
  research 
  in 
  the 
  

   laboratory, 
  but 
  has 
  as 
  yet 
  been 
  little 
  applied 
  on 
  a 
  large 
  scale. 
  When 
  

   such 
  materials 
  become 
  available 
  in 
  quantity 
  — 
  and 
  there 
  is 
  no 
  difficulty 
  

   in 
  principle, 
  although 
  the 
  procedure 
  may 
  be 
  costly 
  — 
  we 
  shall 
  see 
  im- 
  

   portant 
  developments 
  in 
  chemistry 
  and 
  metallurgy 
  at 
  high 
  tempera- 
  

   tures. 
  It 
  is 
  interesting 
  to 
  note 
  that 
  it 
  is 
  the 
  oxides 
  of 
  some 
  of 
  the 
  rare 
  

   elements 
  — 
  thorium, 
  beryllium, 
  and 
  zirconium 
  — 
  which 
  have 
  the 
  highest 
  

   softening 
  points 
  among 
  the 
  refractory 
  materials, 
  so 
  that 
  their 
  impor- 
  

   tance 
  will 
  grow 
  with 
  the 
  extension 
  of 
  high-temperature 
  processes. 
  

  

  In 
  the 
  heating 
  of 
  metals 
  or 
  other 
  conductors, 
  it 
  is 
  not 
  necessary 
  

   that 
  the 
  heat 
  should 
  pass 
  through 
  the 
  walls 
  of 
  the 
  containing 
  vessel, 
  

   as 
  it 
  does 
  when 
  a 
  metal 
  is 
  melted 
  in 
  a 
  crucible 
  furnace. 
  Modern 
  

   heating 
  by 
  induced 
  currents 
  of 
  high 
  frequency 
  allows 
  the 
  heat 
  to 
  be 
  

   generated 
  where 
  it 
  is 
  required, 
  that 
  is, 
  within 
  the 
  mass 
  to 
  be 
  heated. 
  

   This 
  involves 
  a 
  less 
  severe 
  tax 
  on 
  the 
  refractory 
  materials, 
  and 
  also 
  

   makes 
  it 
  possible 
  to 
  enclose 
  the 
  charge 
  in 
  an 
  outer 
  closed 
  vessel 
  which 
  

   remains 
  cold, 
  so 
  that 
  the 
  operation 
  can 
  be 
  carried 
  out 
  in 
  a 
  high 
  

   vacuum 
  or 
  in 
  an 
  atmosphere 
  of 
  some 
  inert 
  gas. 
  This 
  is 
  not 
  merely 
  

   a 
  laboratory 
  device, 
  but 
  is 
  used 
  on 
  a 
  large 
  scale 
  in 
  a 
  number 
  of 
  manu- 
  

   facturing 
  operations, 
  which 
  will 
  become 
  more 
  numerous 
  in 
  the 
  future. 
  

  

  