The statistics and regression analysis on the effect of diameter of ESR ingot (Φ250 mm ~ Φ400 mm) and reduction ratio (11. 10 ~92.46) of high speed steel M2 (/% : 0.85 - 0.90C

5.8 - 6.2W

4. 6 - 5.0Mo

3.8- 4.4Cr

1.75 -1.95V) on non-uniformity of carbide in steel products (Φ26 mm - Φ120 mm) have been carried out

and a regression equation to predict the rating of non-uniformity of carbide in products is established. Results show that as reduction ratio is less than 20

with increasing reduction ratio the non-uniformity of carbide in steel decreases markedly

while as reduction ratio is more than 20

with increasing reduction ratio the non-uniformity of carbide in steel decreases lesser； with same reduction ratio the rating of carbide non-uniformity in smaller diameter steel forged and rolled products is smaller.