为了开发低成本Q690D高强钢，在C-Mn-Nb-V成分基础上，设计含Mo及不含Mo的2种成分试验钢，并对比研究不同成分不同工艺条件下钢板力学性能及微观组织的变化。试验结果显示，在轧制工艺相同条件下，随终冷温度降低，含Mo钢强度上升，断后伸长率基本不变，当终冷温度在350~400℃时，-20℃冲击功可达到200 J以上。在轧制工艺及终冷温度相同条件下，冷却速度对不含Mo钢强度影响不大，断后延伸率及冲击功变化规律同含Mo钢；降低钢板始冷温度，强度有一定程度降低，冲击韧性及断后伸长率变化不明显。回火前后，含Mo的1#钢，终冷温度在450℃以上（工艺1）时的力学性能，与不含Mo的2#钢终冷温度在350~400℃（工艺5及工艺6）时的力学性能结果相近。研究表明，在不添加合金Mo的前提下，适当降低终冷温度及淬火+回火工艺，钢板性能完全可以满足Q690D要求。%In order to develop low cost Q690D steel, based on the C-Mn-Nb-V chemical composition, two kinds of trial steel containing Mo or not were designed. The changes about mechanical properties and microstructures of the trial steel were comparatively studied under different chemical compositions and rolling processes. Test results indicated that, under the same rolling process, with final cooling temperature decrease, the strength of the Mo steel was increased, and the elongation basically remain unchanged. When the final cooling temperatures was in 350~400℃,-20℃impact energy could reach more than 200 J. Under same rolling process and final cooling temperature, cooling rate had little effect on strength of steel without Mo, and the variation of the elongation and impact energy was the same with the steel containing Mo. By reducing start cooling temperature, the strength was lowered at some extent, impact toughness and elongation did not change significantly. Before and after tempering, the mechanical properties of 1# steel containing Mo, final cooling temperature above 450 ℃(process 1) are close to the mechanical properties of 2# steel final cooling temperature at 350~400 ℃(process 5 and process 6). The results showed that under the premise of without adding alloy Mo, properly decreasing the final cooling temperature and quenching+tempering process, the steel plate performance can completely satisfy the requirements of Q690D.
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