Methods for determination of low-cycle properties from monotonic tensile tests of 1.2344 steel applied for hot forging dies

Abstract

Selected methods for determining fatigue life in the strain-life approach, described by the Manson-Coffin-Basquin (MCB) equation based on results of static tensile tests are presented in this paper. These methods served for determining low-cycle characteristics for 1.2344 steel applied for dies used in forging at high temperatures. The authors presented the results of tensile tests performed at room temperature and at elevated temperatures (300 °C, 500 °C, 600 °C, and 700 °C). Data obtained from these tests enabled to theoretically determine fatigue life characteristics according to the methods: universal slope, 4-point correlation, Mitchell’s, modified universal slope method, Bäumel’s and Seeger’s method, modified 4-point-correlation method, Roessle’s and Fatemi’s method, as well as median method. Curves obtained on this basis were then compared to charts obtained from periodic deformation tests. Results obtained in this manner were compared to actual wear of tools (made of 1.2344 steel) used in the hot forging process of a cover-type forging. Fatigue tests covered deformation of specimens with uniaxial, periodically variable load until their cracking, and were performed at temperatures 20 °C, 300 °C, and 600 °C and at four levels of total strain ε_ac: 0.5%, 0.8%, 1.0%, and 2.0%. Clear differences between the values of coefficients and exponents of the MCB equation were observed depending on the applied theoretical method and depending on test temperature. The research goal is description of different methods for determining fatigue life in strain-life approach based on results of static tensile tests and comparison them with the results from experiment. This will allow choosing the best method to predict the fatigue life of tools made of steel 1.2344 and usage of this method in the future, saving time, and costs related to the performance of experimental tests.