Diffusion alloyed iron powder

Abstract

A diffusion alloyed iron powder is provided wherein tungsten W is bonded to the surfaces of the particles of an iron or iron-based powder, and wherein the diffusion alloyed iron powder comprises by weight-%: 30-60 W, with the balance being essentially only iron and unavoidable impurities.

1 . A diffusion alloyed iron powder wherein tungsten W is bonded to the surfaces of the particles of an iron or iron-based powder, the diffusion alloyed iron powder comprising by weight-%:
 30-60 W, and the   balance essentially only iron and unavoidable impurities.   
   
   
       2 . The diffusion alloyed iron powder according to  claim 1  wherein the iron or iron-based powder is a water atomised powder. 
   
   
       3 . The diffusion alloyed iron powder according to  claim 1  wherein the iron or iron-based powder is a sponge iron powder. 
   
   
       4 . A metallurgical powder composition comprising at least 90 percent by weight of a diffusion alloyed iron powder and about 0.05 to about 2 percent by weight of a lubricant and optionally about 0.05 to about 2 percent by weight of a binder, the weights based on the total weight of the metallurgical powder composition wherein the diffusion alloyed iron powder is an iron or an iron-based powder having tungsten W bonded to the surfaces of the iron or iron-based powder particles, the diffusion alloyed iron powder comprising by weight-%:
 30-60 W, with the   balance being essentially only iron and unavoidable impurities.   
   
   
       5 . The powder composition according to  claim 4 , wherein the composition comprises 1-4 wt % carbon C in the firm of Graphite. 
   
   
       6 . The process for producing a diffusion alloyed iron powder which comprises in weight-%:
 30-60 W with the   balance being essentially only iron and unavoidable impurities,   said process comprising:   a) mixing a tungsten oxide and an atomized iron powder, and   b) annealing the mix of step a) under a reducing atmosphere whereby the tungsten oxide is reduced and tungsten is bonded to the surfaces of the iron powder particles of the iron powder.   
   
   
       7 . The process according to  claim 6  wherein in step b) the annealing is performed for at least 30 minutes. 
   
   
       8 . The process according to  claim 6  wherein in step b) the annealing is performed at a temperature of at least 800° C. and at a temperature below 1500° C. 
   
   
       9 . The process according to  claim 6  wherein in step b) the reducing atmosphere comprises essentially hydrogen. 
   
   
       10 . A method for producing a bullet comprising:
 a) providing a powder metallurgical composition including 1) a lubricant, 2) a diffusion alloyed iron powder comprising 30-60 wt % W and at least 40 wt % Fe, and 3) 1-4 wt % C in the form of graphite,   b) forming a green body from the powder metallurgical composition; and   c) sintering the green body in a reducing or neutral atmosphere, at an atmospheric pressure or below, and at a temperature above 1100° C.   
   
   
       11 . The method according to  claim 10  wherein in b) the green body is formed by cold compaction of the mixture, where the compaction pressure is within the range of 500-1500 MPa, and where the temperature during compaction is below 100° C. 
   
   
       12 . The method according to  claim 10  wherein in b) the green body is formed by warm compaction of the mixture, where the compaction pressure is within the range of 500-1500 MPa, and where the temperature during compaction is within the range of 100-200° C. 
   
   
       13 . The method according to  claim 10  wherein in c) the sintering temperature is in the range of above 1100° C. to 1400° C. 
   
   
       14 . A powder metallurgically manufactured bullet, wherein the bullet comprises by weight-%:30-60 W, 1-4 wt % C, and the balance is essentially only iron and unavoidable impurities. 
   
   
       15 . The bullet according to  claim 14  wherein the sintered density of the bullet is at least 10 g/cm 3 . 
   
   
       16 . The bullet according to  claim 14  wherein the bullet is coated with a jacket selected from the group consisting of tin, zinc, copper, brass and plastic. 
   
   
       17 . The bullet according to  claim 14  wherein the bullet is a shot gun bullet. 
   
   
       18 . The bullet according to  claim 14  wherein the bullet is a hunting bullet. 
   
   
       19 . The diffusion alloyed iron powder according to  claim 2  wherein the iron or iron-based powder is a sponge iron powder. 
   
   
       20 . The process according to  claim 7  wherein in step b) the annealing is performed at a temperature of at least 900° C. and at a temperature below 1200° C. 
   
   
       21 . The method according to  claim 11  wherein the compaction pressure is at least 800 MPa. 
   
   
       22 . The method according to  claim 12  wherein the compaction pressure is at least 800 MPa. 
   
   
       23 . The method according to  claim 11  wherein in c) the sintering temperature is in the range of above 1100° C. to 1400° C. 
   
   
       24 . The method according to  claim 12  wherein in c) the sintering temperature is in the range of above 1100° C. to 1400° C. 
   
   
       25 . The bullet according to  claim 14  wherein the sintered density of the bullet is at least 11 g/cm 3 . 
   
   
       26 . The bullet according to  claim 15  wherein the bullet is coated with a jacket selected from the group consisting of tin, zinc, copper, brass and plastic.