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针对API X80管线钢在生产实际中遇到的落锤性能较低的问题进行了分析。结果表明,该管线钢在落锤撕裂试样断口处存在大量的异常球形析出物,这些析出物为Mo、Ti、Ni等合金元素的碳化物,尺寸约为几个微米,不但削弱了这些合金元素在钢中的弥散强化作用,而且降低了管线钢的落锤撕裂性能。结合热处理实验,探讨了这些异常长大碳化物的生成机理,即钢板的冷却速度影响碳的扩散,并最终对碳化物的形成产生决定性的作用。减少析出物较好的办法是终轧后空冷至碳化物形成温区的上限附近,然后再强制水冷,保证钢板快速通过碳化物形成区间,从而抑制碳化物的异常长大行为。
The problem of low drop weight performance encountered in the production of API X80 pipeline steel was analyzed. The results show that there are a lot of abnormal spherical precipitates at the fracture surface of the drop-weight tear specimen. These precipitates are carbides of alloying elements such as Mo, Ti, Ni and the like, and the sizes are about several micrometers, which not only weaken these Alloying elements in the steel dispersion strengthening effect, but also reduces the drop-line steel pipe tear performance. Combined with the heat treatment experiments, the formation mechanism of these abnormally grown carbides was discussed, that is, the cooling rate of the steel sheet affected the diffusion of carbon and finally played a decisive role in the formation of carbides. To reduce the precipitation is better after the finish rolling air cooling to the upper limit of the temperature of the formation of carbide near the upper limit, and then forced water cooling, to ensure that the rapid formation of steel plate by the formation of intervals, thereby inhibiting the abnormal carbide growth behavior.