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Register a new userImprovement of Properties of Carbon Steel by Cyclic Heat Treatment
تحسين خواص الفولاذ الكربوني عن طريق المعالجة الحرارية الدورية
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في هذا العمل تم إخضاع الفولاذ الكربوني CK85 إلى عملية معالجة حرارية تكرارية. تتألف هذه العملية من التثبيت لفترات قصيرة متكررة(min 3.4) عند درجة الحرارة C° 800 ( فوق درجة الحرارة Ac3 ) متبوعة بالتبريد الهوائي القسري. و بعد 8 دورات (حوالي ساعة من التسخين و التبريد المتكررين) تبين أن البنية المجهرية تحتوي في معظمها على حبيبات من الفريت و السمنتيت المتكور. تمتلك هذه البنية مزيجا من مقاومة الشد و المطيلية. إن تفكك صفائح البرليت أثناء انحلال السمنتيت على حدود الصفائح خلال هذه المدة القصيرة المثبتة فوق درجة الحرارة Ac3 و نشوء العيوب في الصفائح أثناء التبريد القسري غير المتوازن بالهواء كانا السببين الرئيسيين في تسريع عملية التكور . في البداية زادت مقاومة الشد بشكل رئيسي بسبب وجود الدقائق الصغيرة الناعمة ( الفريت و السمنتيت ) و من ثم انخفضت بشكل طفيف مع انعدام وجود صفائح البرليت و ظهور السمنتيت المتكور في البنية .
In this work, Ck85 carbon steel was subjected to cyclic heat treatment. Process that consisted of cyclic short-duration (3.4 minutes) holding at 800 C (above Ac3 temperature) followed by forced air cooling. After 8 cycles (about a total 1 hour duration of heating and cooling cyclic), the microstructure mostly contained fine ferrite grains and spheroidzed cementite. This microstructure possessed an excellent combination of strength and ductility. The disintegration of lamellar pearlite through dissolution of cementite at boundaries lamellar during short-duration holding above Ac3 temperature, and the generation of lamellar defects during nonequilibrium forced air cooling were the main reasons of accelerated spheroidization. The strength initially increased mainly due to the presence of finer microconstituents (ferrite and pearlite) and then marginally decreased with the elimination of lamellar pearlite and appearance of spheroid cementite in the microstructure.
References used
Smoljan B, An analysis of combined cyclic heat treatment performance, Journal of Materials Processing Technology 155–156 (2004) 1704–1707
M Muhammadpour,A-Reza Kiani-Rashid, AN ACCELERATED SPHEROIDIZATION METHOD IN HIGH CHROMIUM TOOL STEEL, 21. - 22. 11. 2012, Plzeň, Czech Republic, EU
ASM International
H.E.Boyer,chapter 2, pratical heat treating 1St ed , American Society for Metals , 1984
H.N. Oppenheimer, Heat Treatment of Carbon Steels, Course 42, Lesson1, Practical Heat Treating, Materials Engineering Institute, ASMInternational, 1995
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