Modified high speed steel particle, powder metallurgy method using the same, and sintered part obtained therefrom

Abstract

Particles made from a High Speed Steel (HSS) that is modified to contain dispersed precipitations of manganese sulfide (MHSS), a Powder Metallurgy (PM) method using the same, and a part produced by the PM process using the modified HSS particles. By forming a melt of a HSS and 1) Mn or a Mn-containing compound and 2) S or an S-containing compound, followed by an atomization process, modified HSS particle can be obtained containing dispersed sulfide precipitations containing mainly manganese sulfide. The amount of Mn and S are chosen such that the weight ratio of Mn to S (Mn/S), in wt-% of the total weight of the particle, is in the range of 8.0-1.0. An article obtained by a PM manufacturing method using the particles has improved machinability as compared to a an article prepared from a corresponding non-modified HSS.

1 . A High Speed Steel (HSS) particle that is modified to contain dispersed precipitations of manganese sulfide, wherein the weight ratio of Mn to S (Mn/S), in wt-% of the total weight of the particle, is in the range of 8.0-1.0. 
     
     
         2 . The HSS particle that is modified to contain dispersed precipitations of manganese sulfide according to  claim 1 , having a composition consisting of, in weight %,
 C: 0.75-1.40   Mn: 0.41-2.00   Si: 0.10-0.45   Cr: 3.75-5.00   Ni: up to 0.20   Mo: 4.50-6.50   W: 5.50-7.50   V: 1.75-4.50   Cu: up to 0.20   S: 0.050-0.300   the balance being Fe and unavoidable impurities in an amount of up to 0.5% by weight.   
     
     
         3 . The HSS particle that is modified to contain dispersed precipitations of manganese sulfide according to  claim 1 , wherein the longest axis of the manganese sulfide precipitations is from 1 to 10 μm, as determined by SEM image analysis. 
     
     
         4 . The HSS particle that is modified to contain dispersed precipitations of manganese sulfide according to  claim 1 , wherein the total amount of Mn and S (Mn+S) is from 0.10-3.80% by weight. 
     
     
         5 . The HSS particle that is modified to contain dispersed precipitations of manganese sulfide according to  claim 1 , wherein the amount of Mn in the overall particle is 3.00% by weight or less. 
     
     
         6 . The HSS particle that is modified to contain dispersed precipitations of manganese sulfide according to  claim 1 , wherein the particle contains 4.00% by weight or more of at least one element selected from Mo, W, V and Cr. 
     
     
         7 . The HSS particle that is modified to contain dispersed precipitations of manganese sulfide according to  claim 1 , wherein the amount of S is 0.10% by weight or more, and the amount of Mn is 0.45% by weight or more. 
     
     
         8 . A multitude of HSS particles that are modified to contain dispersed precipitations of manganese sulfide as defined in  claim 1 , wherein 98% by weight or more of the particles have an particle size of 0 to 300 μm and wherein the a mount of particles bigger than 300 μm is 2% by weight or less, as determined by sieve analysis according to ISO4497:1983. 
     
     
         9 . A method for forming a powder metallurgy product, which comprises the steps of:
 providing a multitude of particles as defined in  claim 1 ;   compacting a composition comprising the particles to form a green part;   sintering the green part, and   optionally heat-treating the part obtained from step c; and   optionally machining the sintered part obtained from step c. or from step d.   
     
     
         10 . A method for forming a powder metallurgy product according to  claim 9 , wherein the step a. of providing the particles includes the steps of:
 a.1-1 adding Mn or an Mn-containing compound and S or an S-containing compound to HSS material, and melting the obtained mixture; or   a.1-2 adding Mn or an Mn-containing compound and S or an S-containing compound to a melt of HSS;   a.2. forming particles from the melt, preferably by water atomization or gas atomization.   a.3. optionally annealing the particles in vacuum, inert or reducing atmosphere.   
     
     
         11 . A sintered part, obtainable from the particles as defined by in  claim 1 . 
     
     
         12 . The sintered part according to  claim 11 , which is a part for a combustion engine. 
     
     
         13 . (canceled) 
     
     
         14 . (canceled)