E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
22/185, 255/69
E21B 10/08 (2006.01) B22D 15/00 (2006.01) B22D 27/20 (2006.01) E21B 10/46 (2006.01) E21B 10/56 (2006.01)
Patent
CA 1256423
S P E C I F I C A T I O N "Improvements in or relating to rotary drill bits and methods of manufacture thereof" ABSTRACT OF THE DISCLOSURE A method of manufacturing a rotary drill bit at least partly from cast iron comprises forming a hollow mould in the configuration of at least a portion of the bit body, and casting said portion of the bit body in the mould by a casting process which includes the steps of pouring molten cast iron into the mould and then cooling in the mould so that the cast iron solidifies to form said portion of the bit body. The method includes the further step of subjecting the cast iron to treatment, during the casting process, which results in at least one surface portion of the cast iron bit body becoming hardened. The hardening treatment may comprise adding an iron carbide forming additive, such as boron or tellurium, to the cast iron before it is poured, or by chill hardening during solidification, or by coating the interior of the mould, before pouring, with a wash of iron carbide forming material, such as tellurium, or by controlling the rate of cooling after solidification so as to effect the formation of martensite.
505588
Mccarthy Tetrault Llp
Nl Petroleum Products Limited
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