液化天然气罐用9%Ni钢板坯连铸工艺优化

分析了9%Ni钢(/%:≤0.10C、≤0.35Si、0.30～0.80Mn、≤0.005S、≤0.008P、8.5～10.0Ni、≤0.10Mo、≤0.10Al)200～220 mm板坯连铸试生产中出现的结晶器液面结壳、铸坯表面网裂纹产生原因,对连铸工艺进行优化。结果表明,液相线温度偏差是导致9%Ni钢液面结壳的主要原因,基于差示扫描量热法(DSC)的实测数据建立了新的液相线温度计算公式,得出试验的9%Ni钢的液相线温度,在钢水过热度为10～30℃时能较好地满足板坯的连铸要求。通过控制[N]≤25×10^-6,[Al]≤0.03%,二冷比水量由0.6L/kg降至0.4L/kg,使9%Ni钢连铸顺行,铸坯内部和表面质量良好。

Optimization of Slab Concasting Process of 9 % Ni Steel for Liquefied Natural Gas Tank

The formation causes of occurred shell at meniscus in mold and network crack of slab surface in pilot con- casting production of 200 - 220 mm slab of 9% Ni steel (/% : ≤0. 10C, ≤0. 35Si, 0. 30 〜0. 80Mn, ≤0. 005S, ≤0. 008P, 8. 5 ~ 10. ONi,≤0. 1OMo, ≤0. 10A1) are analyzed, and the optimization on concasting process has been carried out. Results show that the calculated deviation of liquidus temperature of 9% Ni steel is the main cause led to the shell occurred at meniscus and based on experimental data by differential scanning calorimetry (DSC), a new liquidus temperature calculation formula is established to get the liquidus temperature of tested 9% Ni steel, and as the overheat extent of liquid is 10 ~30 ℃, it is available to meet the requirement of slab concasting. With controlling [N] ≤25 x 10^-6, [ Al] ≤0. 03% and decreasing secondary cooling water rate from 0. 6 L/kg to 0. 4 L/kg the concasting of 9% Ni steel is going on smoothly, the inner and surface quality of slab is nice.