高耐候结构用Q355GNH钢的开发与性能研究

The Development and Properties study of High Weathering Structural Steels Q355GNH

通过对高耐候钢产品的性能要求分析,本试验钢在成分设计上以Cu、P为基,添加少量Cr、Ni,并制定相应的轧制及卷取工艺而成功开发了355强度级别的高耐候结构用钢。对该试验钢的各项性能进行检测,同时根据其成分设计进行了耐腐蚀性能预测,并利用实验室加速腐蚀试验方法对Q355GNH试验钢及Q345B对比钢的腐蚀速率以及其锈层构成进行了评估与观察。结果表明:试验钢的各力学性能指标及低温(-40℃)冲击韧性均远满足国标要求;经成分预测分析,试验钢的耐大气腐蚀性指数为7.13,远超标准要求;且在相同腐蚀条件下,Q355GNH试验钢平均相对腐蚀速率仅为对比Q345B钢的47.40%;与Q345B钢相比,Q355GNH试验钢在周浸腐蚀后表面生成一种呈絮状团簇、致密的锈层。经观察,该锈层中具有保护作用的稳定相α-FeOOH含量相对较高(α-FeOOH:18.2%、Fe_(3)O_(4):9.1%),使得该锈层结构对基体起到了保护作用。

Through the analysis of the performance requirements of high weathering steels,the composition design of test steel is based on Cu and P,with the addition of a small amount of Cr and Ni.Combined with the corresponding rolling and coiling process,and a 355 strength grade high weathering steels was successfully developed.The mechanical properties of test steels were tested,and the corrosion resistance was predicted according to its composition design.The corrosion rate and rust layer composition of Q355 GNH test steels and Q345B steels were evaluated and observed by the method of laboratory accelerated corrosion test.The results show that the various mechanical properties and low temperature(-40℃)impact toughness of test steels far meet the requirements of national standard;The atmospheric corrosion resistance index of test steels is 7.13,far exceeding the standard requirements.The average relative corrosion rate of Q355 GNH test steel is only 47.40% of the comparative Q345B steel under the same corrosion conditions.Compared with Q345B steel,a flocculent,dense rust layer is formed on the surface of Q355 GNH test steel after alternate immersion test,and it is observed that the content of stable phaseα-FeOOH with protective effect is relatively high in the rust layer(α-FeOOH:18.2%、Fe_(3)O_(4):9.1%),which makes the structure of the rust layer play a protective role on the matrix.