高温劣化方式对特种设备用Q345B钢宏观力学性能的影响

Influence of high⁃temperature deterioration method on the macroscopic mechanical properties of Q345B steel for special equipment

为了探究高温劣化后特种设备用钢的服役性能变化规律,本文以特种设备用Q345B钢为研究对象,采用高温空冷和水冷两种劣化方式,基于微观组织与断口观测结果和拉伸性能测试结果,研究了两种高温劣化方式对其抗拉性能和失效模式的影响规律。实验结果表明:当劣化温度低于700℃时,高温劣化方式对材料的抗拉性能影响较小,而当劣化温度超过700℃时,劣化处理对材料抗拉性能的影响增强,且空冷劣化的影响更为显著;与母材强度相比,劣化温度为1000℃时,空冷劣化和水冷劣化下材料抗拉强度的变化幅值分别为-18.71%和+100.96%,屈服强度则分别为-36.57%和+101.60%;劣化温度超过800℃后,空冷劣化下断口韧窝数量增加,韧性特征显著,而水冷劣化下断口则较为平整,呈现出典型的脆性特征。基于本文实验结果,提出了高温空冷和水冷劣化作用下材料的强度变化因子,建立了强度变化因子与劣化温度关系模型,并利用该模型对不同温度条件下材料的强度变化进行了预测,预测结果与实验值的偏差在5%以内。

To analyze the changes in service performance of special equipment steel after high-temperature deterioration,this study focuses on Q345B steel for special equipment.Two different methods of hightemperature deterioration,high-temperature air cooling and water cooling,are employed.Based on the microscopic structure and fracture observation results,as,well as tensile performance testing,the study examines the influence of these two high-temperature degradation methods on the tensile properties and failure modes of the steel.The experimental results show that when the deterioration temperature is below 700 C,high-temperature deterioration method has a minimal impact on the tensile properties of the material.However,when the deterioration temperature exceeds 700℃,the influence of high-temperature deterioration on the tensile properties of the material is more significant with air-cooling degradation showing a more pronounced effect.Compared with the strength of the base material,the variation amplitudes of tensile strength is-18.71%for air-cooling deterioration and+100.96%for water-cooling deterioration when the deterioration temperature reaches 1000℃,respectively.The yield strength changes by,-36.57%and+101.60%,respectively.When the degradation temperature exceeds 800℃,the number of fracture dimples increases under air cooling degradation and the toughness of the steel is remarkable.However,the fracture surface is relatively flat under water cooling deterioration and a typical britle characteristic is found in the steel.Based on the test results,the strength variation factors of the material are proposed under different conditions,of high temperature deterioration.,Moreover,a corresponding empirical prediction model is established between the factor of strength variation and the degradation temperature,using which the strength variation of the investigated material was predicted under different temperature conditions,and the deviation between the predicted results and experimental values was within 5%.