Farklı ısıl işlemlerin takım çeliklerinin yorulma mukavemeti üzerine etkileri

Year 2022, , 888 - 895, 15.07.2022

Ruhi Yeşildal

https://doi.org/10.17714/gumusfenbil.1109552

Abstract

İstenilen kullanım amacına bağlı olarak çeliklerin mekanik özelliklerini iyileştirmek için çeşitli ısıl işlemler uygulanmaktadır. Bu çalışmada, bir GS 550 banyosunda H13 sıcak iş takım çeliğinin ısıl işlemle yorulma dayanımının değişimi araştırılmıştır. Birinci ön ısıtma, ikinci ön ısıtma, sertleştirme ve ikinci sertleştirme olmak üzere dört farklı ısıl işlem uygulanarak incelenmiştir. Her numune grubu, ısıl işlemden sonra oda sıcaklığında döner eğmeli yorulma testine tabi tutulmuştur. Isıl işlem görmemiş numunelerin yorulma dayanımı 470 MPa olarak belirlenmiştir. İkinci sertleştirme yapılmış temperlenmemiş numunelerin (1. Grup) yorulma mukavemeti 610 MPa'ya yükselmiştir. Sertleştirmeden sonra ikinci bir ısıl işlem olarak 550ºC'de iki saat tavlanan numunelerin (2. Grup) yorulma dayanımı 630 MPa olarak ölçülmüştür. 550ºC'de iki saat ve 610ºC'de iki saat tavlama olan üçüncü ısıl işlemin uygulanmasıyla numunelerin (3. Grup) yorulma dayanımı 720 MPa olarak bulunmuştur. Dördüncü ısıl işleme tabi tutulmuş ve sertleştirmeyi takiben 550ºC'de iki saat ve ardından 635ºC'de iki saat temperlenmiş numunelerin (4. Grup) yorulma mukavemeti 710 MPa olarak belirlenmiştir. Uygulanan tüm ısıl işlemlerin H13 sıcak iş takım çeliğinin yorulma mukavemetini olumlu etkilediği gözlemlenmiştir. Tüm ısıl işlemler artan yorulma mukavemeti ile sonuçlanırken, en yüksek yorulma mukavemeti, ilk ön ısıtma ve su verme işleminden sonra çift tavlama ısıl işlemi (550 °C ve 610 °C iki saat) ile elde edilmiştir.

Keywords

H13 sıcak iş takım çeliği, Isıl işlem, Yorulma

The effects of different heat treatments on the fatigue strength of tool steels

Abstract

Various heat treatments are applied to improve the mechanical properties of steels depending on the intended use. In this study, the variation of fatigue strength of H13 hot work tool steel with heat treatment in a GS 550 bath was investigated. It was investigated by applying four different heat treatments as first preheating, second preheating, hardening and second hardening. Each batch of samples was subjected to rotating bending fatigue test at room temperature after heat treatment. The fatigue strength of the untreated samples was determined as 470 MPa. The fatigue strength of the second hardened untempered samples (Group 1) increased to 610 MPa. The fatigue strength of the samples (Group 2), which were annealed for two hours at 550ºC as a second heat treatment after hardening, was measured as 630 MPa. The fatigue strength of the samples (Group 3) was found to be 720 MPa by applying the third heat treatment, which was annealing at 550ºC for two hours and at 610ºC for two hours. The fatigue strength of the samples (Group 4), which were subjected to the fourth heat treatment and tempered for two hours at 550ºC and then at 635ºC for two hours after hardening, was determined as 710 MPa. It has been observed that all applied heat treatments positively affect the fatigue strength of H13 hot work tool steel. While all heat treatments resulted in increased fatigue strength, the highest fatigue strength was obtained with double annealing heat treatment (550 °C and 610 °C two hours) after initial preheating and quenching.

Keywords

H13 hot-work tool steel, Heat treatment, Fatigue

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