The development of a binder system and process for the manufacture of large diameter tungsten carbide drill blanks

[摘要] A novel extrusion binder system was developed to enable the manufacture of tungsten carbide drill blanks greater than I 4 mm in sintered cross-sectional diameter at Sandvik Hard Materials Coventry. The binder system comprised primarily of methyl cellulose and water, which was capable of being removed from the extrudate with no adverse effects on extrudate quality or increases in drying and de-binding times. The tungsten carbide feedstock was prepared by z-blade mixing on laboratory, pilot and production plant scales. Extrudates were manufactured either as solid cylindrical rods or as rods formed with internal coolant channels following a helical rotation up to 20 mm sintered diameter. Extrusion tooling was modified to aid the forming process and maintain the desired tolerances of internal properties of the drill blanks. Such properties included coolant hole diameter, coolant hole relative concentricity and the distance between the coolant hole centres (pitch circle diameter). Controlled stress rheometry and oscillatory rheometry techniques were used in the selection of the methyl cellulose and water based binder for further analysis. Contro lled stress and oscillatory rheological techniques were a lso used to determine how modifications to the binder systems could be used to improve the extrus ion feedstock behaviour.

[发布机构] University:University of Birmingham;Department:School of Chemical Engineering

[关键词] T Technology;TP Chemical technology