Li Qi, Liu Weijie
School of Material Science and Engineering, Northeastern University, Shenyang 110819, China.
Materials (Basel). 2019 Jul 17;12(14):2290. doi: 10.3390/ma12142290.
Effect of boron on the hot ductility and room-temperature tensile properties of Ti-Nb-microalloyed steels containing 0.071 wt.% carbon was studied. The thermal stress and thermal strain of continuous casting billets during cooling were simulated via hot tensile tests at the deformation rate of (6 mm/11,000)/s, and the hot ductility of different microalloyed steels was evaluated according to the area reduction of hot tensile specimens. It was found that boron addition was beneficial to improve the hot ductility of continuous casting billets during straightening, and the reduction of area exceeded 60%. The addition of boron, as well as the removal of molybdenum and vanadium, can effectively lower the austenite-to-ferrite transformation temperature and restrain the formation of intergranular ferrite, so as to avoid the brittle zone. Moreover, the room-temperature tensile properties of the steels were explored at different cooling rates after the rolling process. The results showed that as the cooling rate increased from 0.0094 to 0.13 °C/s, the amount of carbonitride precipitate gradually decreased, such as titanium carbide, leading to the relatively low tensile strength. On the other hand, the addition of boron, as well as the removal of Mo and V, promoted the formation of bainite and acicular ferrite, playing an important role in structure strengthening, and compensated for the decrease of tensile strength caused by the low precipitation strengthening.
研究了硼对含0.071 wt.%碳的Ti-Nb微合金钢热塑性和室温拉伸性能的影响。通过在(6 mm/11,000)/s的变形速率下进行热拉伸试验，模拟了连铸坯冷却过程中的热应力和热应变，并根据热拉伸试样的断面收缩率评估了不同微合金钢的热塑性。结果发现，添加硼有利于提高连铸坯矫直过程中的热塑性，断面收缩率超过60%。硼的添加以及钼和钒的去除，可有效降低奥氏体向铁素体的转变温度，抑制晶界铁素体的形成，从而避免脆性区。此外，还研究了轧制后不同冷却速率下钢的室温拉伸性能。结果表明，随着冷却速率从0.0094℃/s增加到0.13℃/s，碳氮化物析出物（如碳化钛）的数量逐渐减少，导致抗拉强度相对较低。另一方面，硼的添加以及钼和钒的去除促进了贝氏体和针状铁素体的形成，在组织强化中发挥了重要作用，并补偿了因析出强化不足导致的抗拉强度下降。
