50mm厚高强度低合金钢Q550D的成分优化

 为了解决50mm厚高强度低合金钢Q550D的低温冲击值不稳定的问题，对其合金成分进行了调整试验研究，结果表明，新成分50mm厚Q550D成品钢板强度稳定，伸长率较好，1/4厚度处的-20℃低温纵向冲击值都稳定在239~324J之间，试验批次一次性性能合格率达到100%，成品组织得到了明显改善，吨钢成本也有很大的降低，说明高强度低合金钢中的析出强化元素和固溶强化元素应视钢水冶炼情况及轧制工艺进行适当添加。同时对本钢种低温冲击不稳定争论较大的淬透性问题进行了端淬试验研究，结果表明，原成分钢的淬透性比新成分钢的淬透性要好，说明原成分钢板低温冲击值不稳定并不是钢的淬透性不好，而是成分设计不合理。

Composition Optimization of 50 mm-Thickness High Strength Low Alloy Steel Q550D

In order to solve the problem of poor stability of low temperature impact toughness in 50 mm thickness high strength low alloy steel Q550D, the industrial tests were carried out to adjust the alloy compositions. The results show that the strength of steel plates is stable and the elongation is good, the longitudinal impact values at -20℃ are stabilized between 239-324J in quarter thickness and in particular, the first qualification rate of impact toughness of the steels with new compositions can reach 100%, and the microstructure of finished product is improved obviously, and also the cost of unit steel drops much. The industrial tests also show that the elements of precipitation strengthening and solution strengthening in high strength low alloy steel should be added properly according to the smelting condition of molten steel and rolling technology. At the same time, the larger debate on the influence of hardenability on lower temperature impact instability of this steel has been clarified by means of jominy tests, and the tests show that the hardenability of original compositions is superior to that new compositions, that is to say, the poor stability of low temperature impact values of steel plates with original compositions is not due to its poor hardenability, but to its unreasonable compositional desigin is.