Abstract: A process for providing abrasion and corrosion resistance in the borehole of a steel body comprising placing an alloying material of solid form within the borehole of the steel body, the alloying material having abrasion and corrosion resistance, and thereafter melting the alloying material in a gas heated protective gas oven to effect diffusion bonding of the alloying material with the steel body and the formation of an abrasion and corrosion resistant lining on the steel body. The borehole is of non-circular shape in cross-section and, particularly, of figure 8 shape as shown in FIG. 2.

Abstract: In order to improve the wear-resistance of highly stressed surfaces of a kneading disc in a helical extruding machine, the exposed tips of the kneading disc are provided with inserts of an extremely wear-resistant, hard material. In a variety of embodiments, the tips of the lenticular kneading disc are provided with bores and recesses for receiving the hard inserts. Advantageously, the recesses are cylindrical wells in which cylindrical inserts are soldered or cemented. The inserts may be made from hard metals or ceramics, for example tool steel or tungsten carbide or the like.

Abstract: Improved joining of tubes for plural-screw screw extruders is achieved by using solder to join the tubes and applying the heat in the vicinity of a saddle from the inside of the tubes and symmetrically with respect to the saddle.