بررسي رفتار سايشي فولاد گرافيتي در فرآيند كوبش فراصوتي

Investigation of the Wear Behavior of Graphite Steel (GSH48) in Ultrasonic Peening Process

مقاومت به سايش جهت افزايش طول عمر غلتك­ ها بسيار حائز اهميت است لذا در اين تحقيق براي تعيين سايش غلتك هاي نورد از جنس فولاد گرافيتي، از روش تست سايش و تعيين ضريب اصطكاك استفاده شد. در فناوري كوبش فراصوتي، ايجاد كار سختي و فشردگي در لايه هاي سطحي قطعه كار باعث بهبود برخي خواص مكانيكي از جمله صافي سطح، سختي و استحكام مي شود. با شبيه سازي و ساخت ابزار ارتعاشي فراصوتي و نصب آن بر روي دستگاه تراش، عمليات كوبش فراصوتي بر روي نمونه هاي آماده شده از غلتك هاي نورد انجام گرفت. در آزمايش سايش، مقاومت به سايش در نمونه بعد از عمليات بهبود يافت. همچنين نتايج مبين كاهش ضريب اصطكاك در حدود 50 درصد بعد از عمليات مي باشد. با تهيه گراف پروفيل سطح از سطح سايش مشخص شد بعد از عمليات عرض و عمق سايش كمتر مي باشد. تصاوير ميكروسكوپ الكتروني از سطح سايش نمونه هاي قبل و بعد از عمليات تهيه شد و مكانيزم سايش مورد بررسي قرار گرفت كه مكانيزم چسبان و خستگي سطحي قبل از عمليات و مكانيزم خراشان بعد از عمليات مشاهده شد . با انجام فرآيند بر روي سطح غلتك هاي مقاومت به سايش، استحكام، صافي سطح و طول عمر آنها افزايش مي يابد.

Rolling mill rolls are an essential component of the rolling stand and an important factor in the efficiency and quality of rolling products. The wear durability is very significant for optimizing operation and rolls life so wear test method and coefficient friction determination were utilized in order to determine the wear of rolling mill rolls made of graphite steel (GSH48). The amount of wear was determined on samples before and after conducting ultrasonic peening technology. In ultrasonic peening technology process, making work hardening and compression on surface layers of workpiece contribute to the improvement of some mechanical properties like surface roughness, hardness, and strength. After the simulation and manufacturing of ultrasonic vibratory tool and installing it on lathe machine, ultrasonic peening technology process was performed on the specimens prepared from rolling mill rolls. In the wear test, wear durability improved in the sample after ultrasonic peening technology process. In addition, the results suggested that the coefficient friction has been reduced around 50% after the process. By preparing surface profile graph from the surface, it is perceived that the atitude and depth of wear have decreased after ultrasonic peening technology process. Scanning electron microscopy images were taken from the wear surface of the samples before and after ultrasonic peening technology process and wear mechanism was investigated that adhesive wear and surface fatigue wear mechanism before and abrasive wear mechanism after the process were observed. By performing ultrasonic peening technology process on the surface of the rolling mill rolls resistance to wear, strength, surface roughness, and their life have increased.