Derin Kriyojenik İşlemin Kalıntı Gerilme ve Kalıntı Östenit Üzerindeki Etkisinin Araştırılması

Abstract

Sıfırın altındaki sıcaklıklarda malzemelerin bekletilmesi olarak bilinen kriyojenik işlem, son yıllarda metal ve metal olmayan malzemelerin özelliklerini iyileştirmek için uygulanan bir yöntemdir. Bu yöntem daha çok kalıp yapımında kullanılan takım çelikleri için uygulanmaktadır. Ülkemizde, birçok özel sektör kuruluşu tarafından öncelikle kalıp malzemeleri olmak üzere birçok üründe kriyojenik işlem kullanımı yaygınlaşmaya devam etmektedir. Savunma sanayiinden otomotiv sanayiine kadar birçok sektörde bu işlemin faydaları kabul görmüştür. Bu çalışmada, geleneksel ısıl işlem uygulanmış (CHT) ve 24 saat derin kriyojenik işlem uygulanmış (DCT-24) Sleipner soğuk iş takım çeliğinin makro sertlik, mikro sertlik ve mikroyapı özellikleri incelenerek, malzemenin mekanik özellikleri ve mikroyapısındaki değişimler tespit edilmiştir. Bununla birlikte, X-Işını Kırınımı (XRD) Yöntemi ile malzemelerdeki kalıntı gerilme ve kalıntı östenit miktarları ölçülerek, numuneler arasındaki fark belirlenmiştir. CHT ve DCT-24 numunelerinin makro sertliği sırasıyla 60,96 HRC ve 61,46 HRC olarak ölçülmüştür. Mikro sertlik değerleri de sırasıyla 734,26 HV ve 761,83 HV olarak ölçülmüştür. Derin kriyojenik işlem makro ve mikro sertliği sırasıyla 0,5 HRC ve 27,57 HV arttırmıştır. Kalıntı östenit miktarı derin kriyojenik işlemden sonra % 36 oranında düşmüştür. Eksenel ve çevresel kalıntı gerilme değerleri de sırasıyla % 48,84 ve % 36,52 oranında düşmüştür. Sonuç olarak derin kriyojenik işlem Sleipner soğuk iş takım çeliğinin sertliği arttırmış, mikroyapıyı homojenleştirmiş, kalıntı östenit ve kalıntı gerilme değerlerini düşürerek olumlu iyileşmeler sağlamıştır.

Keywords

• Sleipner
• Kalıntı gerilme
• Kalıntı östenit
• Kriyojenik işlem

Investigation of the Effect of Deep Cryogenic Process on Residual Stress and Residual Austenite

Abstract

The cryogenic treatment, known as holding materials at sub-zero temperatures, is a method used to improve the properties of metal and non-metallic materials in recent years. This method is mainly applied to tool steels used in mold making. In our country, the use of cryogenic processes continues to be widespread by many private sector organizations, primarily in mold materials. The benefits of this process have been recognized in many sectors, from the defense industry to the automotive industry. Sleipner cold work tool steel is widely used in blanking and fine blanking, shearing, forming, coining, cold forging, cold extrusion, thread rolling, drawing and deep drawing, powder pressing molds where high wear resistance, high chipping resistance and high compressive strength are required. In this study, the macro hardness, micro hardness and microstructure properties of Sleipner cold work tool steel, which was applied traditional heat treatment and deep cryogenic process for 24 hours, were examined and the changes in the mechanical properties and microstructure of the material were determined. However, by measuring the residual stress and residual austenite amounts in the materials with the X-Ray Diffraction (XRD) Method, the difference between the samples was determined. Deep cryogenic treatment increased the macro and micro hardness by 0.5 HRc and 27.57 HV, respectively. The amount of residual austenite decreased by 36% after deep cryogenic processing. Axial and circumferential residual stress values also decreased by 48.84% and 36.52%, respectively. As a result, the deep cryogenic process provided positive improvements by increasing the hardness of Sleipner cold work tool steel, homogenizing the microstructure, reducing the residual austenite and residual stress values.

Keywords

• Sleipner
• Residual Stress
• Retained Austenite
• Cyrogenic Treatment

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