The mechanical properties of Φ13 mm bar forged from 70 mm casting thin slab of high grade non-oriented silicon steel (/%: 0. 002 7C

3. 06Si

0. 32Mn

0. 013P

0. 004S

0. 50Al

0.002 7Ti

0.004 2N) at elevated temperature 600 ~ 1 250℃ are measured by Gleeble-1500 stress-strain thermal simulation machine. Results show that with strain rate 1 x 10

-3

s

-1

only I brittle zone (1 250 ℃ to melting point) exists in the high grade non-oriented silicon steel

and the II brittle zone and Ⅲ brittle zone are all of no-occurrence. The main cause is that the extra-low carbon content ( ≤50 X 10

-6

) and high silicon content (3%Si) in steel lead to no-course of α-γ-α phase transformation during silicon steel solidifying and

cooling process to avoid the sulfur

oxygen etc elements in solid solution status in forms of ( Fe

Mn) 0

(Fe

Mn)S and AI

2

O

3

precipitated and grown at austenite grain boundary resulting in the strength of grain boundary decreasing and the cracks occurring.