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目的:奥氏体不锈钢(ASS)在深冷压力容器中应用广泛。ASS较高的应变硬化特性有助于其产生应变强化。在应变强化过程中,保载时间是影响材料最终变形量的关键参数。基于室温蠕变应变弛豫理论,本文旨在提出一种S30408深冷压力容器应变强化过程中的保载时间预测方法。创新点:1.根据室温蠕变应变弛豫理论,保载过程即为材料在室温蠕变中应变速率逐渐减缓、材料结构逐渐稳定的过程;本文据此获得了保载时间的计算模型。2.结合材料试验与容器试验,将计算模型中涉及的多个微观变量转换为唯一宏观变量——圆柱壳上的最大环向应力,可为常规工业生产提供定量的、具有实际可操作性的技术支持。方法:1.根据室温蠕变应变弛豫理论,建立蠕变本构关系,得出保载时间计算模型。2.通过材料试验,考虑实际生产中的特定条件,将保载时间计算模型的多个微观变量简化为唯一宏观变量。3.通过在多个工业规模的容器上进行实验,比较验证所提计算方法的可靠性。结论:1.室温蠕变应变弛豫理论可以用于描述应变强化保载过程中的材料变化。2.容器保载时长,即材料应变弛豫时长,与其所承受的最大应力有关。3.所提出的保载时间计算方法可以为容器保载时间提供可靠预测;其平均绝对误差为7.53%,且绝大部分情况下偏于保守。
Objective: Austenitic stainless steel (ASS) is widely used in cryogenic pressure vessels. The higher strain hardening properties of ASS contribute to its strain hardening. During strain hardening, hold time is the key parameter that affects the final amount of material deformation. Based on the creep strain relaxation theory at room temperature, this paper aims to propose a method for predicting the hold-time in the process of strain hardening of S30408 cryogenic pressure vessel. Innovative points: 1. According to creep strain relaxation theory at room temperature, the loading process is the process of material strain slowing down and the material structure is gradually stabilized during creep at room temperature. The calculation model of the loading time is obtained in this paper. 2. Combined with the material test and the container experiment, the micro-variables involved in the calculation model are converted into the only macroscopic variable-the maximum hoop stress on the cylindrical shell, which can provide quantitative and practical operability for the conventional industrial production Technical Support. According to creep strain relaxation theory at room temperature, the creep constitutive relation was established, and the model for calculating the loading time was obtained. 2. Through the material test, taking into account the specific conditions in the actual production, the multiple microscopic variables of the model of the hold time are reduced to the only macro variables. 3. By comparing experiments on a number of industrial-scale containers, the reliability of the proposed method is verified. Conclusions: 1. Room temperature creep strain relaxation theory can be used to describe the material changes during strain hardening. 2. Container holding time, that is, the material strain relaxation time, with its maximum stress-related. 3. The proposed method for calculating the hold time provides a reliable prediction of the hold time of the container; its average absolute error is 7.53% and is conservative in most cases.