Barrel for a twin screw extruder with an abrasion resistant layer

摘要

A barrel for a twin screw extruder having a pair of helical screws has a barrel body provided with a pair of partly overlapping cylindrical bores, and the pair of helical screws are rotatably supported in the pair of cylindrical bores of the barrel to mix and extrude a molding material. An abrasion resistant layer is formed in at least portions of the surfaces of the pair of cylindrical bores extending in the vicinity of at least one of the two lines of intersection of the pair of partly overlapping cylindrical bores. The abrasion resistance of the abrasion resistant layer has a maximum in a portion thereof around the line of intersection of the pair of cylindrical bores and decreases gradually with distance from the line of intersection. The abrasion resistant layer is formed by depositing a material containing a hard substance by build-up welding, and the hard substance content of the material in the abrasion resistant layer is varied with distance from the line of intersection. The abrasion resistant layer is formed by depositing a material consisting of a corrosion resistant base alloy and a hard substance. The abrasion resistant layer may be formed on a corrosion resistant layer formed over the entire surfaces of the pair of cylindrical bores.