INVESTIGATING THE EFFECT OF HEAT TREATMENT ON THE COLD FORGING OF 27MNB4 STEEL VIA CALPHAD METHODOLOGY AND FEM

Abstract

As a material forming method, cold forging is preferred due to the reasons like absence of a heating step and high surface quality. Recently, the finite element method (FEM) has received growing attention for controlling and predicting final material properties for cold forging applications. FEM combines microstructure evolution models with failure criteria, thus providing solutions to complicated problems in the modern cold forging industry. The fastener industry extensively utilizes cold forging, in which manganese and boron-containing steels like 27MnB4 can be formed to obtain high mechanical properties. The current study investigates the effect of two different heat treatments, namely softening and spheroidizing annealing, on the formability of 27MnB4 bolts. Softwares such as Thermo-Calc 2022a and Forge NxT 3.2 were used to predict the microstructure of the wire rod and evaluate the cold forming process of the same rod under two different heat treatment conditions. Therefore, the current study also provides a relationship between microstructural features and the cold formability of 27MnB4 steel. The microstructure of 27MnB4 is predicted by CCT diagrams. The predicted microstructure corresponds to the microstructure of 27MnB4 samples taken from the production line. In addition, temperature, von Mises stress, and equivalent strain distributions for 27MnB4 steel in the hot rolled state were calculated higher than in annealed states due to the differences in the microstructure. These results demonstrate that computational material engineering methods and simulation techniques could be practical tools for cold forming processes.

Keywords

• 27MnB4
• Cold forming
• Finite element method
• Forging simulation
• Computational materials Engineering

27MnB4 Çeliğinin Soğuk Dövülmesinde Isıl İşlem Etkisinin Calphad ve Sonlu Elemanlar Yöntemi ile İncelenmesi

Abstract

Malzeme şekillendirme yöntemi olarak soğuk dövme, ısıtma adımının olmaması ve yüksek yüzey kalitesi bakımından tercih edilir. Sonlu elemenlar metodolojisi ise son zamanlarda soğuk dövme prosesinde malzeme özelliklerinin kontrolü ve tahmin edilmesi noktalarında popüler olmuştur. Sonlu elemanlar yöntemi, mikroyapı ve hata kriteri modellerini birleştirerek dövme endüstrisindeki karmaşık sorunlara çözüm sunabilmektedir. Bağlantı elemanları sektörü soğuk dövmenin en sık kullanıldığı alanlardandır. 27MnB4 borlu çeliği ise civata endüstrisinde sıklıkla kullanılan çelik kalitlerindendir. Bu çalışmada iki farklı ısıl işlemin, yumuşatma ve küreselleştirme tavlaması, çelik civatanın şekillendirebilirliği üzerine etkisi incelenmiştir. Tavlama işlemlerinin etkisi, 27MnB4 çelik civatanın soğuk dövülmesinin Thermo-Calc 2022a versiyonu ve sonlu elemanlar yazılımı olan Forge NxT 3.2 versiyonu kullanılarak ortaya konmuştur. Bu çalışma, 27MnB4 çeliğinin mikroyapısı ve şekillendirilebilirliği arasında bağlantı kurmaktadır. Sıcak haddelenmiş numunelerde tavlanmış numunelere göre mikroyapısal farklılıklar sebebiyle daha yüksek sıcaklıklar, von Mises gerilimleri ve gerinimler gözlenmiştir.

Keywords

• 27MnB4 Çeliği
• Soğuk Dövme
• Sonlu Elemanlar Metodu
• Forge NxT
• Thermo-Calc

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