0. 153Ti-0. 038Nb and 0. 080Ti-0. 062Nb two kind of Ti-Nb microalloying low carbon steel (/% : 0. 061 ~ 0. 075C

0. 22Si

1.76 〜1.77Mn

0. 002 〜0. 003S

0. 006P

0.003Als

0.003 8 ~0. 004 2N

0.004 0 ~0. 004 50) are melted by a 50 kg vacuum induction furnace and rolled to 10 mm plate with finishing rolling at 880 ℃

water cooling to 630 ℃.Test results show that the precipitates in both Ti-Nb microalloying steels are ( Nb

Ti) ( C

N) compound precipitates； with increasing Ti content from 0. 080% to 0. 153% and decreasing Nb content from 0. 062% to 0. 038%

the yield and tensile strength of steel respectively increase from 558 MPa and 653 MPa to 633 MPa and 756 MPa

besides

the variations in ratio between yield and tensile strength

elongation and reduction of area of steels are minor. It indicates the strength of steel products could be increased by adding Ti to replace part of Nb to carry out compound microalloying and the production cost is decreased.