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An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics
Engineering ( IF 10.1 ) Pub Date : 2020-06-01 , DOI: 10.1016/j.eng.2019.12.004
Andrew Smith , Mohammad Asadikiya , Mei Yang , Jiuhua Chen , Yu Zhong

Abstract This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone (HAZ) of welded Grade 91 (Gr.91) steel parts. Type IV cracking has been observed in the HAZ, and it is widely accepted that the stabilities of the secondary phases in Gr.91 steel are critical to the creep resistance, which is related to the crack failure of this steel. In this work, the stabilities of the secondary phases, including those of the M23C6, MX, and Z phases, were simulated by computational thermodynamics. Equilibrium cooling and Scheil simulations were carried out in order to understand the phase stability in welded Gr.91 steel. The effect of four critical temperatures—that is, Ac1 (the threshold temperature at which austenite begins to form), Ac3 (the threshold temperature at which ferrite is fully transformed into austenite), and the M23C6 and Z phase threshold temperatures—on the thickness of the HAZ and phase stability in the HAZ is discussed. Overall, the simulations presented in this paper explain the mechanisms that can affect the creep resistance of Gr.91 steel, and can offer a possible solution to the problem of how to increase creep resistance at elevated temperatures by optimizing the steel composition, welding, and heat treatment process parameters. The simulation results from this work provide guidance for future alloy development to improve creep resistance in order to prevent type IV cracking.

中文翻译:

通过计算热力学研究 91 钢的抗蠕变性

摘要 本研究旨在了解各种临界温度与焊接 91 级 (Gr.91) 钢零件热影响区 (HAZ) 内第二相稳定性之间的关系。在 HAZ 中观察到 IV 型开裂,人们普遍认为 Gr.91 钢中第二相的稳定性对抗蠕变性至关重要,这与该钢的裂纹失效有关。在这项工作中,通过计算热力学模拟了第二相的稳定性,包括 M23C6、MX 和 Z 相的稳定性。为了了解焊接的 Gr.91 钢的相稳定性,进行了平衡冷却和 Scheil 模拟。四个临界温度的影响——即 Ac1(奥氏体开始形成的阈值温度),Ac3(铁素体完全转变为奥氏体的阈值温度)以及 M23C6 和 Z 相阈值温度——对 HAZ 的厚度和 HAZ 中的相稳定性进行了讨论。总的来说,本文中的模拟解释了可能影响 Gr.91 钢抗蠕变性的机制,并且可以为如何通过优化钢成分、焊接和提高高温下的抗蠕变性提供可能的解决方案。热处理工艺参数。这项工作的模拟结果为未来的合金开发提供了指导,以提高抗蠕变性,以防止 IV 型开裂。讨论了 M23C6 和 Z 相阈值温度——关于 HAZ 的厚度和 HAZ 中的相稳定性。总的来说,本文中的模拟解释了可能影响 Gr.91 钢抗蠕变性的机制,并且可以为如何通过优化钢成分、焊接和提高高温下的抗蠕变性提供可能的解决方案。热处理工艺参数。这项工作的模拟结果为未来的合金开发提供了指导,以提高抗蠕变性,以防止 IV 型开裂。讨论了 M23C6 和 Z 相阈值温度 - 对 HAZ 的厚度和 HAZ 中的相稳定性进行了讨论。总的来说,本文中的模拟解释了可能影响 Gr.91 钢抗蠕变性的机制,并且可以为如何通过优化钢成分、焊接和提高高温下的抗蠕变性提供可能的解决方案。热处理工艺参数。这项工作的模拟结果为未来的合金开发提供了指导,以提高抗蠕变性,以防止 IV 型开裂。并且可以为如何通过优化钢成分、焊接和热处理工艺参数来提高高温下的抗蠕变性问题提供可能的解决方案。这项工作的模拟结果为未来的合金开发提供了指导,以提高抗蠕变性以防止 IV 型开裂。并且可以为如何通过优化钢成分、焊接和热处理工艺参数来提高高温下的抗蠕变性问题提供可能的解决方案。这项工作的模拟结果为未来的合金开发提供了指导,以提高抗蠕变性,以防止 IV 型开裂。
更新日期:2020-06-01
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