温度对U165超高强度钻杆钢冲击韧性的影响

摘要：借助SEM、TEM及冲击试验机等设备，研究了U165超高强度钻杆钢在不同温度下的冲击韧性。试验结果表明：随着温度降低到某一临界值，裂纹扩展阻力急剧下降，且随温度降低而减小。同时在小裂纹扩展阻力下，裂纹扩展的位移比例也随温度降低而增加，从而使得U165钻杆钢的冲击韧性急剧减小，对应的冲击断口呈现为显著的脆性特征，主要由解理结构组成。利用Boltzmann函数对U165钻杆钢的冲击能值进行拟合分析，韧脆转变温度约为1.8℃，但在较低温度下，依旧呈现出较高的冲击能值，约为40J，表明该材料韧脆转变温度适中，更适合于普通地区服役，同时也可在高寒地区服役。随着温度的降低，U165钻杆钢纤维区和剪切唇区减少，放射区增加，导致脆性特征明显。

Effect of temperature on impact toughness of U165 ultra high strength drill steel

The impact toughness of U165 ultra-high strength drill pipe steel at different temperatures was studied by means of SEM, TEM and impact tester. The results show that as the temperature decreases to a certain critical point, the crack propagation resistance drops sharply, and decreases with temperature decreasing. And under the smaller crack propagation resistance, the proportion of crack propagation displacement also increases with the decreasing of temperature, which makes the impact toughness of U165 drill pipe steel decreases sharply. The corresponding impact fracture is characterized by a significant brittleness, which is mainly composed of cleavage structures. The impact energy value of U165 drill pipe steel is fitted by means of the Boltzmann function, the ductile-brittle transition temperature is 1.8℃, but at the lower temperature，the steel still exhibits high impact energy, and nearly up to 40 J, which indicates that the material possesses moderate ductile-brittle transition temperature, and is more suitable for service in ordinary areas, and can also service in cold districts. With the decreasing of temperature, the fiber zone and shear lip zone of U165 drill pipe steel decrease, the radiation zone increases, resulting in obvious brittleness characteristics.