热加工对管线钢针状铁素体组织形成的影响

Influence of hot working on the formation of acicular ferrite in pipeline steel

以X70管线钢为实验材料,研究不同变形量和冷却速率对管线钢显微组织的影响。结果表明,在奥氏体未再结晶区进行适量的变形,从而形成位错、形变带和胞状组织等缺陷,可以增加铁素体在奥氏体晶内的形核位置和形核率,增大相变驱动力,有利于在随后的冷却过程中得到晶粒细小的针状铁素体组织;其中变形量2ε=0.4、冷却速率为30~60℃/s（油冷）下冷却的试样,能够得到最佳的针状铁素体组织,可以满足工程上要求组织中针状铁素体占80%以上的要求。

This paper,using X70 pipeline steel as the experimental material,studied the influence of different deformation degrees and cooling velocities on the microstructure of the steel.The result show that some deformation in uncrystallized area of austenite can produce dislocation,deformation band and cellular structure,which can increase the nucleation site and the nucleation rate of ferrite and enhance the driving force of phase transition,beneficial to the gain of acicular ferrite with fine grain in the later cooling process.When the deformation ε 2=0.40 and the oil cooling rate is 30~60 ℃/s,the best acicular ferrite structure can be obtained,which satisfies the demand of engineering projects on the acicular ferrite that must account for 80% of the structure.