| 摘要 |
An extruder screw is made by layerwise build-up of a screw profile of one or more alloy materials by a thermal deposition process (esp. plasma powder deposition welding) on a rotationally symmetrical metal body. Pref. the layers consist of an initial base layer (2) of alloy A deposited by plasma powder deposition welding onto a steel body, one or more profile bottom layers of alloy A, several profile layers of alloy B, and a profile tip layer of wear resistant material C. For extrusion of chlorine-contg. plastics e.g. PVC, alloy A is pref. an 18/4 Cr/Ni steel and alloys B and C are pref. 29/9 Cr/Ni steel. For extrusion of sulphur-exuding plastic materials (e.g. rigid rubber-like materials such as ebonite) and nitrogen-contg. plastics (e.g. polyamides), alloys A,B,C pref. consist of 0.8-1.2% C, 28-33% Cr, less than 3% Ni, less than 1% Si, less than 3% Fe, 3-6% W, less than 1% Mn, and Co. USE/ADVANTAGE - The screw is useful for plastics xtrusion. It has a long service life and reduced material and prodn. costs.
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