Process for production of a screw for an extruder, and screw

Abstract

At least one section of the screw (11) has a wear-protection layer (13) and at least one other section of the screw preferably has an anti-friction layer (18). In a solid rod (11'), a bed (12) for the wear-protection layer (13) is first formed, and in this the wear-protection layer (13) is then applied, and finally the interstices (14) between the screw flights (15) are formed. According to the invention, the wear-protection layer (13), for example composed of tungsten carbide, is applied by build-up welding, and the interstices (14) are formed with lateral separation (16, 16') with respect to the wear-protection layer (13). For production of the anti-friction layer, the dimension of that / those section(s) of the screw (11) where the anti-friction layer, e.g. composed of molybdenum, is to be applied is reduced below specification, while providing lateral separation (19) with respect to the wear-protection layer. The anti-friction layer is then applied in the under-dimensioned region (17). Finally, the screw (11) is brought to the specified dimension.

Description

technical field [0001] The invention relates to a method for producing a screw for an extruder, wherein the screw is provided with a wear protection layer at least in one section, wherein first a base for the wear protection layer is formed in the complete shaft bed, the wear protection layer is then applied in the bed and finally an intermediate space is formed between the flight ribs. The invention also relates in particular to a method for producing a screw which is additionally provided with a sliding layer in at least one further section. Finally, the invention also relates to such a screw. Background technique [0002] From EP 1614502 A it is known to cover the housing of an extruder with a particularly wear-resistant material in areas subject to high wear. The region can be defined both axially and radially. According to EP1614502A, in a counter-running twin-screw extruder, in the radial direction, especially the zones corresponding to 10 o'clock and 2 o'clock are ...

AI Technical Summary

Problems solved by technology

However, tungsten carbide is so hard that it is almost impossible to achieve this by machining with material removal, because the cutting tool becomes dull in a very short time

[0010] In addition, for screws with different coatings in different sections, the known method also has the disadvantage that the coatings must have the same thickness, which is also not optimal: as The molybdenum of the sliding layer is usually applied in a smaller thickness (eg 0.4mm) than the tungsten carbide as wear protection layer (eg 1mm)

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