Causes and Improvement of Point Defects in 15-5PH Stainless Steel Producted by EAF+VAR
The new process of EAF→VOD→LF+VD→ pouring 6 t electrode rod → vacuum consumable remelting(VAR)with lower smelting cost was adopted to produce 15-5PH stainless steel instead of the traditional VIM+VAR process,the causes of point defects were analyzed by scanning electron microscopy and ASPEX detection methods.The results show that calcium aluminate and aluminum spinite exist in the self-consuming electrode,the instability of vacuum consumable remelting process will draw the ingot crown and non-metallic float into the melting pool and remain in the consumable in-got,resulting in point defects after forging.Through process optimization and improvement,the VOD reduction slag is ad-justed from 9 kg/t aluminum to 8 kg/t ferrosilicon and 5 kg/t aluminum,the composition of refining slag is adjusted from(mass fraction)CaO 50%-55%,SiO2 10%-15%,Al2O3 20%-25%to CaO 45%-50%,SiO2 5%-10%,Al2O3 33%-38%,vacuum consumable remelting speed is increased from 4.2 kg/min to 6 kg/min,and the melting drop time is increased from 0.23 s to 0.27 s,the cleanliness of consumable electrode has been greatly improved,the melting speed has been con-trolled steadily,the non-metal floating matter on the liquid surface of the molten pool has been removed,low and high mag-nification inspection of the finished material have met the standard requirements,and the inspection pass rate has been in-creased to more than 98%.
15-5PH Stainless SteelPoint DefectsRefining Slag SystemVARDroplet Time
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