Patent EA-004363-B1 (EA)
Title: Iron-base alloy containing chromium-tungsten carbide and a method of producing it
Inventor: ANDERSSON CARL-HAKAN
IPC: B22D1/00
Filed: 2001-05-15
Abstract: 1. Method for producing an alloy with high wear resistance comprising the melting an existing known base alloy of cast iron with known composition and definite content of iron (A) and carbon (C), characterized by the following steps: - adding the carbon in form of pieces of wolfram carbide (E) to the base melt of cast iron to dissolve in it and thereby to increase carbon content in base alloy melt, wherein the ratio of wolfram and carbon is definite; - adding chromium (D) to the said base alloy to control the solubility of the wolfram carbide in the melt of the base alloy and to provide the material for forming the carbide; - casting the melt and thereby forming an alloy with structure of a further settled carbide comprising on chromium and carbon, added in form of wolfram carbide (D), wherein the wolfram is substitutionally dissolved in the lattice structure of said chromium carbide structure. 2. The method according to claim 1, characterized in that said piece is added to the melt in the form of a worn-out cemented carbide product comprising wolfram carbide (E). 3. The method according to claim 2, characterized in that said piece is a worn-out cemented carbide cutting tool insert. 4. The method according to claim 1, characterized in that said cemented carbide is added to the melt in the form of a waste or rest product from the manufacture of a cemented carbide product, wherein the waste or rest product comprises wolfram carbide (E). 5. The method according to any of the previous claims, characterized in that said cemented carbide is added in pieces with a size of < 40 mm, in which the wolfram carbide (E) has a grain size of <= 10 mum. 6. The method according to any of the previous claims, characterized in that non-dissolved grains of wolfram carbide (E), after the solidification of the melt, has a grain size of <= 10 mum. 7. The method according to any of the previous claims, characterized in that the wolfram carbide (E), prior to dissolution in the melt, is bonded with a metallic material, which gives melting at a lower melting point than the base metal. 8. The method according to claim 7, characterized in that said metallic material in which the wolfram carbide (E) is bonded, is cobalt. 9. The method according to claim 1, characterized in that said chromium (D) gives the final alloys an increased corrosion resistance. 10. The method according to claim 1, characterized in that the chromium (D) in molten state lowers the melting point of the melt and decreases the surface tension of the melt. 11. The method according to any of the previous claims, characterized in that said base metal comprises stabilizing and supplementing alloying components Si and Mn. 12. The method according to any of the previous claims, characterized in that said base alloy is white cast iron. 13. The method according to any of the previous claims, characterized in that the wolfram carbide (E), to a part which comprises > 5 weight-% of the final material, is added to and dissolved in the melt in a melting furnace. 14. The method according to any of the previous claims, characterized in that the wolfram carbide (E), to a part which comprises < 15 weight-% of the final material, is added to the molten alloy immediately prior to casting by a super inoculation process. 15. The method according to any of the previous claims, characterized in that the wolfram is included in the final material to a part of 5 - 40 weight-%. 16. The method according to any of the previous claims, characterized in that an additional alloying component (F) is added to the melt, which additional alloying component (F) facilitates the dissolution of the wolfram carbide (E) in the melt. 17. The method according to claim 16, characterized in that said additional alloying component (F) decreases the carbon affinity. 18. The method according to claim 17, characterized in that said additional alloying component (F) is easily dissolved in the molten alloy and does not affect the final application properties of the final material. 19. The method according to claim 17, characterized in that said additional alloying component (F) contributes to an increased hardenability of the final material by mete-stable states after casting. 20. The method according to claims 16-19, characterized in that said additional alloying component (F) comprises cobalt or nickel. 21. The method according to any of the previous claims, characterized in that the final material is used for the manufacture of compound materials as by die casting or on casting on a core material. 22. The method according to claim 21, characterized in that during on casting, a protective or active gas is added in order to achieve a solution hardening effect. 23. The method according to claim 21, characterized in that the steps of: - induction heating of the core material prior to on casting, - carrying out on casting in a shell mould. 24. The method according to any of the previous claims, characterized in that a product manufactured of the final material is used in a re-cycling process, and is thereby added and dissolved in a melt of a base alloy. 25. A wear resistant cast iron based alloy, prepared according to claim 1, characterized in that, it includes, in weight-%: Carbon  1-5%, Wolfram  2-40%, Chromium  40%. and the balance iron and other components. 26. The wear resistant alloy according to claim 25, wherein said other components, in weight-% includes: Silicon  0.5-2%, Manganese  0.3-10%, Nickel  0- Titanium  0-2.5%, Molybdenum  0-5%, Cobalt  0.1-1 27. The wear resistant alloy according to claim 25, in weight-% including: Carbon  2-3.5%, Wolfram -20%, Chromium  20-30%. the balance iron and otheralloying components. 28. The wear resistant alloy according to claim 25, wherein said other components, in weight-%, includes: Silicon  0.8-1.2%, Mangnese  0.4-2%, Nickel  0.8-2%, Titanium  0.2-0.5%, ybdenum  0-1%, Cobalt  0.5-5%. 29. The wear resistt alloy according to claim 25, wherein said other components, in weight-%, amounts to 0-5%. 30. The wear resistant alloy according to claim 25, wherein said other components includes any of the components silicon, manganese, nickel, titanium, molybdenum or cobalt. 31. A wear resistant cast iron based alloy including, in weight -%, Carbon  2.5-3.5%,Wolfram  8-12%, Chromium  20-28%. the balance ironnd other alloying component. 32. Use of an alloy according to any of the previous claims 25-31 for the manufacture of a cutting tool (40). 33. The use according to claim 32, wherein said cutting tool is a granulator knife (40). 34. Use of an alloy according to any of the previous claims 25-31 in a re-use procedure, with the re-melting of the alloy in a cast iron melt and casting of the melt.