低成本薄规格L485M管线钢的研制开发

Research and development of low-cost light gauge L485M pipeline steel

研究了不同加热温度、轧制工艺和冷却速率在内的低成本L485M管线钢组织及性能变化。结果表明:随着加热温度升高,奥氏体晶粒尺寸逐渐长大,当加热温度≤1 200℃时,奥氏体平均晶粒尺寸可控制在50μm以内;通过增加中间坯厚度,使其精轧阶段累计压下量增加,可显著细化钢板心部组织,同时增加析出相密度;通过提高轧后钢板的冷却速率,既抑制了先共析铁素体的转变,也促进了针状铁素体和粒状贝氏体形成。当冷却速率为25℃/s时,可得到有利于试验钢性能的由针状铁素体和粒状贝氏体为主的复相组织,钢板的强韧性得到显著改善;生产的L485M级管线钢满足技术条件要求,可实现L485M级别管线钢降低成本生产。目前,鞍钢已可以实现无Mo低成本薄规格L485M管线钢稳定化批量生产。

Effects of heating temperature, rolling process, and cooling rates on microstructure variation and mechanical properties for low-cost L485M were studied. The results show that the austenite grains grow continuously with increasing temperatures. The average austenite grains can be controlled within50 μm by maintaining the heating temperature below 1200 ℃. The grains can be refined by increasing the thickness of the intermediate slab to enhance the cumulative reduction rates and increase the number density of precipitates. Eventually, the cooling rate is improved, which inhibits pro-eutectoid ferrite transformation and promotes the formation of ultrafine granular bainite and acicular ferrite. In addition,the microstructure of investigated steel consists of acicular ferrite and granular bainite at the cooling rate of 25 ℃/s, which was beneficial to improving the strength and toughness of steel. The L485M grade pipeline steel satisfies the requirements of the technical agreements, which can provide a route to produce the low-cost L485M plates. A batch of L485M plates without Mo addition was steadily produced in Ansteel Company.