(19)
(11)EP 0 312 032 A3

(12)EUROPEAN PATENT APPLICATION

(88)Date of publication A3:
23.08.1989 Bulletin 1989/34

(43)Date of publication A2:
19.04.1989 Bulletin 1989/16

(21)Application number: 88116965.0

(22)Date of filing:  12.10.1988
(51)International Patent Classification (IPC)4C01B 31/30
(84)Designated Contracting States:
DE FR GB

(30)Priority: 13.10.1987 JP 258986/87

(71)Applicant: DAIKIN INDUSTRIES, LIMITED
Osaka-shi, Osaka-fu (JP)

(72)Inventors:
  • Kitamura, Ikuo
    Kyoto-shi Kyoto-fu (JP)
  • Shibuya, Yoshiyuki
    Osaka-shi Osaka-fu (JP)
  • Shibanuma, Takashi
    Kadoma-shi Osaka-fu (JP)
  • Daimon, Shigeo
    Osaka-shi Osaka-fu (JP)

(74)Representative: Barz, Peter, Dr. et al
Patentanwälte Dr. V. Schmied-Kowarzik Dipl.-Ing. G. Dannenberg Dr. P. Weinhold Dr. D. Gudel Dipl.-Ing. S. Schubert Dr. P. Barz Siegfriedstrasse 8
80803 München
80803 München (DE)


(56)References cited: : 
  
      


    (54)Iron carbide fine particles and process for preparing the same


    (57) Iron carbide fine particles consisting essentially of iron carbide, which are characterized in that, in the step of the variation of the weight under the condition of combustion, the increase of the weight in the equilibrium after arrival at the maximum weight is 22% or less, on the basis of the weight before combustion. In which (a) after fine particles of iron oxyhydroxide or iron oxide have been or have not been contacted with a reducing gas containing no carbon atom, (b) the particles are contacted with a carburizing gas or a mixture of a carburizing gas and a reducing gas containing no carbon atom at a temperature of from 250 to 395°C to prepare iron carbide fine particles, and (c) the resulting iron carbide fine particles are contacted with a carburizing gas at a temperature higher than the said temperature by 5 to 20°C for 0.5 to 5 hours.





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