بررسي تاثير ريز ساختار و اندازه‌دانه فولاد AISI1045 بر زبري سطح در فرايند سنگ‌زني

A STUDY OF THE ROLE OF MICROSTRUCTURE AND GRAIN SIZE IN SURFACE ROUGHNESS OF AISI1045 WITHIN GRINDING

هدف اين پژوهش بررسي تاثير ريزساختاري فولاد و اندازه‌دانه روي زبري سطح به دست آمده پس از فرايند سنگ‌زني است. براي اين كار نمونه‌هايي با ريزساختارهاي مختلف و با اندازه‌دانه‌هاي مختلف طي فرايندهاي مختلف عمليات حرارتي آماده‌سازي شده‌اند. عمليات سنگ‌زني با شرايط ثابت و مشخص روي قطعات اعمال شده است. پس از اتمام فرايند، زبري سطح كل قطعات اندازه گيري شد. مشاهده شد زبري با ريزساختار نمونه‌ها و سختي مربوط به آنها رابطه دارد، به‌طوري كه با افزايش سختي مربوط به هر ريزساختار، زبري سطح كاهش مي‌يابد. اين روند تا يك حد بحراني ادامه يافته و پس از آن زبري رو به افزايش مي گذارد. در اين بين صافي سطح نمونه‌هاي ريز دانه وضعيت بهتري نسبت به نمونه‌هاي درشت دانه دارند. همچنين سنگ‌زني روي نمونه‌هاي نورد شده نيز انجام گرفت. مشاهده شد سنگ‌زني در جهت عمود بر دانه‌هاي كشيده شده صافي سطح بهتري را به دنبال دارد.

This work outlines the effects of microstructure and grain size on surface roughness during the grinding process of carbon steel AISI 1045. According to this study, it is evinced that the obtained surface roughness after the grinding process is concerned with the microstructure and hardness of the initial surface. Different samples with different microstructures and three various levels of grain size (fine, median and coarse) have been prepared through specific heat treatment. After finishing the grinding operation, the surface roughness (Ra and Rz) was measured. A considerable relationship was found between the surface roughness and microstructures of samples. Furthermore, there was a relation between surface roughness and initial hardness. An increase in initial surface hardness of the material led to a decrease in surface roughness, but this relation in super hard materials was different. Surface roughness decreased after a critical initial hardness. In fact, surface roughness rose by increasing initial hardness, and, after that, there was a drastic reduction. Meanwhile, surface roughness was investigated for fine, median and coarse grain materials. The amount of surface roughness in fine grain materials was more than coarse grain materials. The surface roughness was improved by an increase in the grain size of microstructures. Another factor, which is focused upon in this paper, is an investigation of the relationship between the direction of the grinding operation and the orientation of grains in rolled materials. It was found that grinding in the same direction as elongated grains resulted in improved surface roughness, and grinding perpendicular to the elongated grains led to a decrease in surface roughness. As a result, it can be achievable to acquire a desired surface roughness by identifying microstructure type, initial hardness and grain size of materials correctly. Furthermore, it is important to note the grain direction of rolled material during the grinding process. Finally, one must be careful to observe that achieving ideal surface roughness does not result in a serious change in microstructure.