加热炉炉况对700 MPa级高强钢性能的影响

Effect of Operating Condition in Heating Furnace on Properties of 700 MPa Grade High Strength Steel

采用直读光谱仪、金相显微镜及透射电子显微镜对700 MPa级高强钢卷性能波动现象进行了研究。结果表明:炉膛中堆积的氧化铁皮降低了加热炉的加热效果,导致钢坯在加热过程中受热不均。钢坯中部温度偏低,固溶的微合金元素量减少,使得冷却过程中第二相析出量减少,析出强化效果减弱,造成整卷性能波动达130 MPa。通过定期清理加热炉,对检修中后期的加热炉适当提高加热温度和保温时间,可提高钢卷性能的均匀性,使整卷性能波动不大于40 MPa。

Fluctuation in mechanical properties of 700 MPa grade high strength steel coil was studied by using direct-reading spectrometer, metallurgical microscope and transmission electron microscope. The results showed that the iron oxide scale accumulating in the furnace hearth reduced the heating effect of the heating furnace, resulting in the uneven heating of the billet during the heating. The lower temperature in the middle of the billet decreased the content of microalloying elements in solution, which reduced the amount of second phases precipitated during the cooling and weakened the precipitation strengthening effect, resulting the fluctuation of up to 130 MPa in mechanical properties of the whole coil. By periodic cleaning the heating furnace and appropriately increasing the heating temperature and holding time for the heating furnace in the middle and later stage of maintenance, the performance uniformity of the coil was likely to be improved, and the fluctuation in mechanical properties of the whole coil was not greater than 40 MPa.