Appearance of 120 ton-class 9CrMoCoB steel of ESR ingot

Appearance of 120 ton-class 9CrMoCoB steel of ESR ingot - ESR ingot defects

Figure 1: Appearance of 120 ton-class 9CrMoCoB steel of ESR ingot.

Defect name: No data
Record No.: 2942
Type of defect (Internal/Surface): Surface
Defect classification: ESR ingot defects
Steel name: 9CrMoCoB steel
Steel composition in weight %: No data.
Note: In case of 9CrMoCoB (COST FB2) steel, equilibrium relation between [B]/[Si] ratio and (B2O3)/(SiO2) ratio is very important to control [Si] and [B] in optimum range. Therefore, in this work, to investigate the thermodynamic equilibrium relation between [B]/[Si] ratio and (B2O3)/(SiO2) ratio, pilot ESR experiments of 9CrMoCoB steel were carried out using the CaF2-CaO-Al2O3-SiO2-B2O3 slag system according to change of Si content in electrode and B2O3 content in the slag. Furthermore, through the test melting of the 20ton-class ESR ingot, the merits and demerits of soft arcing were investigated. From these results, it is concluded that oxygen content in the ESR ingot decrease with decreasing SiO2 content in the slag, relation function between [B]/[Si] ratio and (B2O3)/(SiO2) ratio derived by Pilot ESR test shows a good agreement as compared to the calculated line with a same slope and soft arcing makes interior and surface quality of ingot worse. With the optimized ESR conditions obtained from the present study, a 1000mm diameter (20 tons) and 2200mm diameter (120ton) 9CrMoCoB steel of the ESR ingot were successfully manufactured with good homogeneity by the ESR process.
Reference: Not shown in this demonstration version.