Thesis Details

Thesis Title: A comparison of the performance of cryogenically-treated and untreated knitting elements
Thesis Author: Norman M. Parker, IV
Abstract: Open-end rotor spun yarn is widely used in the knitting industry. These yarns, however, have been shown to accelerate knitting element wear. Service life of needles and sinkers, when processing open-end yarn, has been reduced to as little as four weeks, compared to at least six months when processing ring-spun yarn. The purpose of this thesis was to compare the performance of cryogenically-treated and untreated knitting elements and to explain the effect of treatment on high-carbon steel parts. The work included a plant trial, wear simulation tests, and metallurgical tests. Samples of the plant trial knitting elements were measured for wear, analyzed microscopically, and photographed. Wear simulation testing was used to confirm the results of the plant trial. Metallurgical tests (microhardness and x-ray diffraction) were used to explain the effect of the treatment on the knitting elements. All results confirmed that the cryogenic treatment does impart enhanced wear characteristics to the knitting elements. The treated needles were less worn and more uniform compared to untreated needles in both the plant trial and in wear simulation. Treated sinkers were also less worn than untreated sinkers. But the sinker cams, at the end of the plant trial, did not show any differences in wear as a result of the treatment. The plant trial also revealed that mixing treated and untreated needles and sinkers deteriorated the wear performance. Best results were obtained when both the needles and sinkers were treated. Fabric samples taken from the plant trial revealed that treated needles produced a more attractive fabric with increased cover compared to fabric produced from untreated needles. This is attributed to an increasing greige wale count with treated needles and a decreasing greige wale count with untreated needles as a result of the wear characteristics of the needles. The course count for both fabrics remained constant. Metallurgical testing revealed that cryogenic treatment is most effective when treating parts with substantial levels of retained austenite. If a needle, sinker, or sinker cam has little or no retained austenite in the untreated state, very little improvement can be expected. This thesis proved that 9ryogenic treatment of certain knitting elements can be used to combat the accelerated wear caused by open-end rotor yarn.