Abstract

The steel collar is an important part of textile machine, which not only requires good abrasion resistance, but also have more stringent requirements for ovality and irregularities, as shown in Figure 1. Generally low carbon steel collar is carburized (or carbonitrided) after quenching to increase its surface hardness. However, in some cases, steel ring can not meet the production requirements. The greatest feature of powder is metallurgy gap and low density. But poor hardenability, large deformation and brittle hair after heat treatment, makes it a key issue. Fig. 1 schematic ring Introduction The ring is an important part of the textile machine, wear resistance, deformation of the surface, with stringent requirements, the use of low carbon steel carbonitriding (or carburizing) quenching improve the surface hardness and wear resistance to meet. But the gap matrix steel, high-density, large deformation and can not meet the production requirements. According to the technical requirements of the ring, we have iron-based powder metallurgy test chemical heat treatment process, and achieved good results, and through the production have proved that the process is feasible. Heat Treatment Technology (1) Raw materials: raw test is to provide Brothers factory, the carbon content of the iron-based powder metallurgy materials 0.1%, density before heat treatment was 6.2g/cm 3 or so, the microstructure shown in Figure 2. (2) Carbonitriding Media: carburizing atmosphere of 50% methanol plus 50% acetone Walter cracking furnace at 920°C, and then Walter ammonia 1/3. The furnace pressure of 10 mm water column. (3) technology test: initially the gas carburizing and nitriding heat test, but the results were not satisfactory. The main reason is too large deformation after carburizing, easy shaping, waste up to 60%. Meanwhile hardness is not uniform, can not meet the performance and quality requirements. Deformed after nitriding is also large, extremely brittle, while the hardness is low, the same can not International Conference on Material Science and Application (ICMSA 2015) © 2015. The authors Published by Atlantis Press 134 meet the requirements. To solve this problem, has conducted a carbonitriding process after repeated trials, worked out at 740°C Penetrating oil cooling can be satisfied with the result after 20 minutes, microstructure shown in Figure 3. Carbon and nitrogen at different temperatures and time permeation results shown in Table 1. Fig.2 500×4%alcohol, nitric acid corrosion Carbonitriding organizations: martensite + graphite Fig.3 500×4%alcohol, nitric acid corrosion materials organizations: ferrite + graphite Tab. 1 carbonitriding temperature and time of cooling microstructure and deformation No. Carbonitriding temperature and time Cool down Gold phase tissue and deformation case 1

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