穿水冷却工艺对Q345E棒材冲击性能及组织的影响

针对低合金高强钢Q345E棒材低温冲击性能合格率低的问题，分析其原因主要是由于终轧温度较高，轧后棒材组织晶粒粗大造成的，生产中需采用正火处理来改善组织晶粒度，提高其低温冲击韧性，但同时也提高了生产成本。为此，对φ50、φ40、φ35 mm规格Q345E棒材进行了终轧3段穿水冷却试验，通过穿水冷却来降低终轧温度，以解决晶粒粗大的问题。结果表明，与轧后态、正火态棒材组织对比，经过3段穿水冷却后的棒材组织明显细化，铁素体晶粒度达到9.4级以上，低温冲击性能明显提高，φ35 mm规格低温冲击性能合格率达到90%以上。同时，采用穿水冷却工艺，可以省去正火处理工序，节省了生产成本。

Effect of through-water cooling process on impact property and microstructure of Q345E steel bar

In view of the problem of low qulified rate of low-temperature impact property of low-alloy high-strength steel Q345E bars,the causes were analyzed mainly due to the high finishing rolling temperature and coarse microstructure grains of the rolled bar.Normalizing treatment was used to improve the microstructure grain grade and increase its low temperature impact toughness,but the production costs was increased.To this end,φ50 、φ40、φ35 mm gauges Q345E bars were subjected to a three-stage through-water cooling test.By using through-water cooling,the low finishing temperature could be carried out,and the problem of coarse microstructure grain of bar could be avoided.The results show that compared with the rolled and normalized bars,the micrstructure of the bars by through-water cooling was significantly refined,the ferrite grain size is above 9.4 grade,and the low temperature impact property is significantly improved,the qualified rate of the low-temperature impact property of the φ35 mm gauge reaches more than 90%.Meanwhile，the normalizing process can be eliminated,and the production costs can be saved by using through-water cooling process.