【作者】 徐斌；

【导师】 颜银标；

【作者基本信息】 南京理工大学 ， 材料学， 2012， 硕士

【摘要】 Q690E及S355钢板在工程装备制造领域均是市场需求量很大的钢种,作为装备的关键零部件制造用钢,其断裂韧度性能及疲劳性能都非常重要。本文所研究内容可分为三个部分：首先,本文对Q690E控轧控冷态及其调质态宽厚钢板以及S355ML、S355NL宽厚钢板进行了CTOD韧度测定,并将断裂韧度CTOD性能进行了分析比较。第二,本文对从Q690E控轧控冷态及其调质态钢以及S355ML、S355NL钢进行了低周疲劳试验,并分别将Q690E控轧控冷态及其调质态钢以及S355ML与S355NL钢的低周疲劳性能进行对比分析。第三,将各材料的CTOD韧度性能与低周疲劳性能分别进行对比。试验表明：Q690E、S355接近理想弹塑性,适用于CTOD韧度技术评定,采用多试样法对Q690E、S355两种工艺钢板进行了CTOD阻力曲线测定,Q690E、S355宽厚钢板的阻力曲线均可用δ=α+β△aγ拟合。调质态Q690E钢板的CTOD韧度优于控轧控冷态Q690E钢板的CTOD韧度,且随着扩展量的增大,CTOD韧度值显示出越来越大的差异,经过调质后的钢板显示出更好地阻止裂纹扩展的能力。S355ML与S355NL宽厚板CTOD拟合曲线在裂纹扩展量较小时显示出较好的贴合性,但在裂纹扩展量增加后两组试样拟合曲线差距逐渐趋于变大。表明随裂纹的扩展,正火后的S355NL钢比S355ML钢有更强的抑制裂纹扩展能力。Q690E控轧控冷态及其调质态钢在较高应变幅下均表现出较明显的循环软化特性。热轧态S355ML显示出较好的疲劳循环稳定性,正火后钢S355NL在各应变幅下都显示出较明显的循环软化性能。表明不同工艺对材料的循环软硬化性能会产生影响。Q690E控轧控冷态及其调质态钢以及S355ML与355NL的塑性应变幅及弹性应变福与失效反向数在双对数坐标下呈线性关系。其疲劳寿命均可用曼森-柯芬公式表示。循环应变幅与循环应力幅之间在双对数坐标下呈线性关系。Q690E调质态钢板具有优于控轧控冷态Q690E钢板的低周疲劳性能,S355正火态钢板具有优于S355热轧态钢板的低周疲劳性能。Q690E钢及S355钢在疲劳加载时,裂纹均产生于光滑试样的表面；并且在扩展区以裂纹的合并、发散方式向前发展,可以观测到明显的二次裂纹及疲劳条纹；瞬断区存在有大量韧窝,表明两种钢材均有很好的韧性。对于上述钢种,当材料具有更好的CTOD韧度性能时,其低周疲劳性能也会有所提高。更多还原

【Abstract】 Q690E and S355 steel plate are in great demand of steel in engineering equipment manufacturing field, as the key components in the equipment, the fracture toughness properties and fatigue performance of them is very important,hi this paper the content can be divided into three parts:first of all, the fracture toughness CTOD performance of Q690E(TMCP) and Q690E (hardened and tempered) are analyzed and compared, as for S355ML and S355NL steel, too. Second, the low cycle fatigue properties of Q690E(TMCP) and Q690E (hardened and tempered) are analyzed and compared, and the same to S355ML and S355NL steel. Third, the low cycle fatigue performance and CTOD toughness properties are compared for the steel of the same ingredient.The experiment shows that:The CTOD toughness assessment technology apply to the steel of Q690E and S355, and then the curve of CTOD are tested and fitted, it shows that all the CTOD curves of the steels above can be fitted with the index equation:8=α+β△aγ. The F-V curves of three point bending test of Q690E shows different characteristics.The curve of Q690E(hardened and tempered) steel presents very smooth shape, it shows the excellent toughness of this kind of steel; And the curve of Q690E(TMCP) steel presents multiple pop-in points. Meanwhile, the CTOD toughness properties of Q690E(hardened and tempered) steel is better than the CTOD toughness of Q690E(TMCP), and with the increase of the quantity of crack propagation, CTOD toughness values shows bigger differences. This content shows that:after tempering, the Q690E steel plate shows better crack resistance ability.The F-V curves of three point bending test of S355ML and S355NL steel shows similar characteristics. Both of them present very smooth shape. In the loading process, there is nearly no significantly pop-in point. And the CTOD curves of S355ML and S355NL is very close during the small quantity of crack propagation, but with the increase of the quantity of crack propagation, the gap of the two fitted curve tends to get big gradually. This content shows that:after normalizing, the S355 steel plate shows better crack resistance ability.Both of the Q690E(TMCP) and the Q690E (hardened and tempered) steels exhibit the cyclic softening properties in the high strain amplitudes (more than 0.54%), and the cyclic softening feature ofQ690E(TMCP) is less obvious than the Q690E(hardened and tempered). The S355ML exhibits the cyclic softening properties in the all the strain amplitudes in the fatigue process. This test shows that different heat treatment process has very big effect on cycle performance.The relations between the plastic strain amplitude, elastic strain and reversals to failure ofQ690E steel and S355ML,355 NL steel can be described as a line relationship. The fatigue life can be described by Manson-Coffin formula. In addition, a linear relationship between cyclic stress amplitude and plastic strain amplitude is also noted in the low cycle fatigue test.It is noted that the low cycle fatigue properties of Q690E(hardened and tempered) steel is better than Q690E(TMCP), while leads to a reduction in fatigue lives at a lower strain amplitudes. It is also noted that the low cycle fatigue properties of S355NL steel is better than S355ML, while leads to a reduction in fatigue lives at a lower strain amplitudes.During the fatigue loading, the fatigue cracks initiate at the surface of fatigue specimens; And move forward in a mode of the merger and divergent of the crack, in this area obvious secondary cracks and fatigue stripe can be observed. Instant rupture zone exists lots of dimples, it shows that the toughness of this two kinds of steel are both very excellent.For the above kinds of steel, when the steel has better CTOD toughness properties, it also reflects the better low cycle fatigue properties.更多还原