摘要
目的:Q345R是中国应用最多、最广泛的压力容器钢板材料,其低温韧性在国际上被严重低估。本文旨在通过大量试验研究,探明Q345R在低温下的实际韧性表征,得到其特有的冲击试验豁免曲线,并确定其合适的使用温度范围。创新点:1.基于大量低温试验数据,并考虑应变率的影响,得到了Q345R特有的冲击试验豁免曲线;2.采用主曲线方法代替纯冲击试验方法评价Q345R低温韧性,得到了基于主曲线方法的Q345R豁免曲线;3.通过比较两类韧性评价方法所得的豁免曲线,最终确定合适的Q345R使用温度范围。方法:1.利用试验获得大量的冲击试验数据(图3),通过计算K1(min)–t关系(图5)和Kc–T关系(图9),并考虑应变率的影响(公式(18)),得到Q345R特有的冲击试验豁免曲线(图10);2.利用试验方法获得Q345R的主曲线(图4),并用其代替原来的Kc–T关系,得到基于主曲线方法的Q345R豁免曲线(图14);3.比较两类方法的K1d–T关系(图13)和豁免曲线(图14)。结论:1.Q345R的低温韧性在国际上被严重低估;2.得到了Q345R特有的冲击试验豁免曲线及其合适的使用温度范围;3.主曲线方法的引入能进一步拓展Q345R的使用温度范围。
As the material most widely used in manufacturing pressure vessels in China, Q345 R steel has been permitted in ASME Code Case 2642 to be used for fabricating pressure vessels since 2010. It is listed in the material group corresponding to the exemption curve A for Charpy V-notched（CVN） impact test requirements. However, recent studies indicate that the mechanical property of Q345 R has been underestimated and the curve A classification is over-conservative. In this paper, the K1 d–T relationship for two batches of Q345 R produced in 2009 and 2014 is empirically obtained by curve–fitting and regression analysis from a large amount of CVN data based on K1 c–CVN correlations and the temperature-shift method. Based on the theory of derivation for the ASME exemption curves, the specific exemption curves for the two batches are generated by combining the K1 d–T relationship and the K1（min）–t relationship developed from the failure assessment diagram（FAD）. Such exemption curve is not in parallel to the ASME curves, and lies over curve C and between curves B and D, but better reflects the actual toughness and expands the impact test exemption area, especially for small components with a thickness less than 20 mm. Furthermore, the method presented in this paper（the Materials Properties Council（MPC） method） is compared with the master curve（MC） method, concluding that the two methods are reliable for determining the exemption curve, and the MC method expands a further area for the impact test exemption and results in a lower minimum design metal temperature（MDMT） than the MPC method.
基金
Project supported by the National Key Research and Development Program of China(No.2016YFC0801905)
关键词
Q345R
低温韧性
冲击试验豁免曲线
使用温度
主曲线
Q345R steel
Exemption curve
Master curve （MC）
Charpy V-notched impact test
Fracture toughness
