Economical Nb, Ti and N composite reinforced 400MPa-grade steel bar and manufacturing method thereof

The invention discloses an economical Nb, Ti and N composite reinforced 400Mpa-grade steel bar and a manufacturing method thereof. The steel bar is prepared from the chemical components in percentageby mass: 0.20-0.25% of C, 1.20-1.50% of Mn, 0.008-0.02% of Nb, 0.01-0.03% of Ti, 0.006-0.012% of N, less than or equal to 0.45% of Si, less than or equal to 0.045% of P, less than or equal to 0.045% of S, and the balance of Fe and other unavoidable impurities. The economical Nb, Ti, and N composite reinforced 400MPa-grade steel bar and the manufacturing method thereof have the advantages that technical problems of an abnormal bainite structure in the Nb and Ti micro-alloyed steel bar and unobvious or no yield point in a tensile test are solved. 本申请公开了种经济型Nb、Ti、N复合强化400MPa级钢筋及制造方法，该钢筋化学成分按质量百分比包括：C：0.20～0.25％、Mn：1.20～1.50％、Nb：0.008～0.02％、Ti：0.01～0.03％、N：0.006～0.012％、Si≤0.45％、P≤0.045％、S≤0.045％，其余为Fe及不可避免杂质。本发明的优点在于解决了Nb、Ti微合金化钢筋的中异常贝氏体组织及拉伸试验屈服点不明显或无屈服点技术难题。