Contrastive Study On Cutting Performance Of One Quenched And Tempered Steel With One Non-quenched And Tempered Steel

The situation of energy shortage and environmental deterioration encourages people to develop new products that have high energy-saving and low-pollution effect. Compared with quenched and tempered steel, non-quenched and tempered steel is characterized with energy-saving and low-cost and it has been widely used. Nowadays, some brands of quenched and tempered steel, which have equal mechanical properties to non quenched and tempered steel, have been successfully developed. On the other hand, the materials’machinability has a major impact on the products’performance and economical efficiency. Therefore, it is imperative to carry out a comparative study on cutting performance between them. In this dissertation, the cutting performances of a domestic non quenched and tempered steel and a quenched and tempered steel, which have similar mechanical properties, were compared. The experiments were conducted by using the orthogonal cutting test method and the test results were analyzed theoretically.First of all, the dynamic cutting forces were measured by piezoelectric cutting dynamometer during the turning process. The results of cutting-force experiment show that cutting force goes down with the increase of cutting speed, and goes up with the increase of feed rate and cutting depth. The three-direction cutting forces of non-quenched and tempered steel are smaller than that of the quenched and tempered steel. In the dissertation, a analytical model that predicts the two kinds of steel’s cutting force was presented. The empirical formulas had been proven to be significant through F test.Second, the workpiece surface roughness was measured by surface roughometer. The orthogonal experiment results show that the surface roughnesses of non-quenched and tempered steel are slightly lower than or equivalent to that of quenched and tempered steel, except for the first group. According to the analysis results, the surface roughnesses of the two steels obviously increase with the rise of feed rate, slightly increase with the rise of cutting depth, and slightly decrease with the rise of cutting speed.At last, tool wear was observed by scanning electron microscopy (SEM). The reasons for tool wear mainly include adhesion wear, mechanical wear, oxidation wear and diffusion wear. Compared with quenched and tempered steel, the tool flank wear of non-quenched and tempered steel is smaller, but the boundary wear is more serious. The results also show that cutting speed and workpiece hardness have a significant effect on tool wear. In addition, screw diameter of chip was measured by tool microscope. The results show that non-quenched and tempered steel has a better chip-breaking performance and chip compact degree. Chip screw diameter of the non-quenched and tempered steel is smaller than that of quenched and tempered steel. By observing the chip’s color, it can be concluded that cutting temperature of the non-quenched and tempered steel is lower than that of the quenched and tempered steel.