Analysis of Metallic Materials used for Manufacturing of Extruders Screws

Abstract

Received: 2019.05.21 Revised: 2019.06.05 Accepted: 2019.08.27 Available online: 2019.09.15 Abstract: The article presents a review of metallic materials used for manufacturing of extruders screws. The analysis is carried out for the NEWEX project, which aims to develop and test an innovative extruder [1-2]. The collected knowledge about the materials used to date to produce screws of extrusion machines and methods of increasing their service life will allow to design a new extruder consisting of materials of the highest quality and durability. Currently the screws are usually manufactured from steels for nitriding, heat resisting steels, tool steels and stainless steels. The study provides an analysis of the chemical composition and mechanical properties of the most commonly used material types. Among those, the following types of steels for nitriding, in accordance with the standard PN-EN 10085:2003 can be distinguished: 34CrAlNi7-10, 34CrAlMo5-10, 31CrMoV9. The type of heat resisting steel used for screws of extrusion machines is 14CrMoV6-9 according to the standard PN-H-84024:1975 (withdrawn without replacement). The most commonly used tool steels are X37CrMoV5-1 and X153CrMoV12 according to the standard PN-EN ISO 4957:2018-09. Among the stainless steels of the standard PN-EN 10088-1:2014-12 the steels X90CrMoV18 and X39CrMo17-1 are used in the production of screws. The study also presents methods of increasing the durability and strength of the screws of extrusion machines, including surface treatment processes. These processes include: hardening, surfacing and coating, as well as thermochemical treatment in the form of: carburising, nitriding and sintering.