低屈强比超高强EH690钢板的研发

采用常规化学成分、轧制和调质热处理工艺生产的超高强EH690钢板屈强比在0.96以上,为了实现钢板较低的屈强比,一般采用低碳、高合金的化学成分设计,然后再进行两次淬火(常温淬火Q+两相区淬火Q＇)+回火的工艺,生产工艺复杂,生产成本较高。为此,采用低合金化学成分设计,合理的控轧控冷工艺及亚温淬火+回火的热处理工艺,研究了不同亚温淬火温度、回火温度对EH690钢板力学性能和显微组织的影响。结果表明:所设计化学成分的EH690钢板经过815 ℃的亚温淬火+480 ℃回火热处理后,钢板具有合适比例的软相铁素体和硬相马氏体双相组织,这种组织在保证钢板具有较好力学性能的同时屈强比也降低到0.90左右。采用该工艺,简化了生产工艺流程,降低了生产成本,实现了低屈强比超高强EH690钢板的工业化大规模生产。

Development of ultra-high strength EH690 plate with low yield ratio

The yield ratio of EH690 plate is higher than 0.96, which is produced by conventional chemical composition, rolling, quenching and tempering heat treatment process. In order to realize the low yield ratio, the chemical composition design of low carbon and high alloy is generally adopted, and then twice quenching (room temperature quenching Q+subcritical quenching Q′) +tempering process is used. The production process is complex and the production cost is high. Therefore, the effects of different temperatures of subcritical quenching and tempering temperatures on the mechanical properties and microstructure of EH690 plate were studied by using low alloy chemical composition design, reasonable controlled rolling and cooling process. The results show that the designed chemical composition EH690 plate has an appropriate proportion of soft phase ferrite and hard phase martensite dual-phase structure after subcritical quenching at 815 ℃ and tempering at 480 ℃. This structure not only ensures that the plate has good mechanical properties, but also reduces the yield ratio to about 0.90, Therefore, the production process was simpified and the production cost was reduced, the industrialization and large-scale production of EH690 plate with low yield strength ratio and ultra-high strength has been realized.