According to metallurgical quality issue about low billet yield of hot working die steel H13 at steel works

the statistic analysis on relative quality to influence on billet yield has been carried out to get that the porosity defects caused by poor insulation of hot top make up 58%-76% of the total non-qualified ingot. With decreasing the volume density and heat conductivity of SiO

2

insulating board respectively from original 1.65 g/cm

3

and 0.317 W/(m • K) to 0.87 g/cm

3

and 0.21 W/( m • K)

and optimizing the ingredient of low carbon shield synthetic flux to decrease its melting point and viscosity respectively from original 1258 °C and 1.8 Pa • s to 1147 °C and 0.9 Pa • s

the average billet yield of ingot increases from original 75% to 80% .