The production flow sheet for 4mm sheet of steel 14MnVTiRE [/%: 0. 10 ~ 0. 15C

0. 30 ~ 0. 60Si

1. 20 〜1. 60Mn

0. 03 ~0. 09V

0. 07 -0. 16Ti

0. 10 -0. 15RE (adding amount)] is 180 t top and bottom combined blowing converter-180 mm x 1 260 mm casting slab-continuous rolling-coiling process. During casting the φ2. 5 mm RE wire is feeding in mold. The effect of 950℃ normalizing and 950℃ T normalizing + 690℃ 1 ~ 5 h tempering on structure and mechanical properties of sheet is tested and studied. Results show that structure of normalized steel is ferrite + fine pearlite

in normalized + 690 ℃ 1 ~ 3 h tempered steel the spheroidizing of lamella carbide in pearlite occurs and the spheroidized carbide is distributed at grain boundary and inner of grain

with further increasing tempering time the carbide presents particle and triangle shape and all carbide is distributed at grain boundary led to large decrease of material strength. The optimum heat treatment process for steel 14MnVTiRE sheet is 950 °C normalizing + 690 Y 1 ~2 h tempering

its yield strength is 510 〜610 MPa

tensile strength 630 〜680 MPa and elongation 22% ~ 25%.