Moravec Jaromír, Bukovská Šárka, Švec Martin, Sobotka Jiří
Department of Engineering Technology, Faculty of Mechanical Engineering, Technical University of Liberec, 46117 Liberec, Czech Republic.
Materials (Basel). 2021 Nov 10;14(22):6791. doi: 10.3390/ma14226791.
Dual phase steels combine very good corrosion resistance with relatively high values of mechanical properties. In addition, they can maintain good plastic properties and toughness at both room temperature and lower temperatures as well. Despite all the advantages mentioned above, their utility properties can be reduced by technological processing, especially by the application of the temperature cycles. As a result, in the material remain residual stresses with local stress peaks, which are quite problematic especially during cyclic loading. Moreover, determining the level and especially the distribution of such residual stresses is very difficult for duplex steels both due to the structure duality and in light of the very small width of the heat-affected zone (HAZ). This is why the paper presents the possibilities of using physical simulations to study the effect of temperature cycles in residual stresses' magnitude and distribution, where it is possible to study the HAZ in more detail as well as on a much larger sample width due to the utilization of special samples. In the thermal-mechanical simulator Gleeble 3500, temperature-stress cycles were applied to testing samples, generating stress fields with local peaks in the testing samples. In addition, the supplied steel X2CrMnNiN21-5-1 had different phase rations in the individual directions. Therefore, as the residual stresses were measured in several directions and at the same time, it was possible to safely confirm the suitability of the used measurement method. Moreover, the effect of the stress and strain on the change of partial phases' ratios was observed. It has been experimentally confirmed that annealing temperatures of at least 700 °C are required to eliminate local stress peaks after welding. However, an annealing temperature of 550 °C seems to be optimal to maintain sufficient mechanical properties.
双相钢兼具非常良好的耐腐蚀性和相对较高的力学性能值。此外，它们在室温及更低温度下也能保持良好的塑性和韧性。尽管有上述所有优点，但它们的使用性能可能会因工艺加工而降低，尤其是温度循环的应用。结果，材料中会残留带有局部应力峰值的残余应力，这在循环加载过程中尤其成问题。此外，由于双相钢的结构双重性以及热影响区（HAZ）非常窄，确定此类残余应力的水平，尤其是分布非常困难。这就是为什么本文介绍了使用物理模拟来研究温度循环对残余应力大小和分布影响的可能性，通过使用特殊样品，可以更详细地研究热影响区以及更大的样品宽度。在热机械模拟器Gleeble 3500中，对测试样品施加温度 - 应力循环，在测试样品中产生带有局部峰值的应力场。此外，所供应的X2CrMnNiN21 - 5 - 1钢在各个方向上具有不同的相比例。因此，由于在几个方向上同时测量残余应力，能够可靠地确认所使用测量方法的适用性。此外，还观察到应力和应变对部分相比例变化的影响。实验证实，焊接后消除局部应力峰值至少需要700°C的退火温度。然而，550°C的退火温度似乎是保持足够力学性能的最佳温度。
