Failure Analysis of Basic Oxygen Furnace Lance Head Assembly

In a steel plant, basic oxygen furnace (BOF) is a method to convert liquid hot metal and steel scrap into steel via the oxidizing action of oxygen blowing into the melt. This study investigates a failure of the BOF lance head assembly in an integrated steel plant, where a small oxygen leak ignited near the flange, leading to significant damage to the oxygen pipe elbow. The research conducted a rigorous failure analysis to identify the likely causes, focusing on the high-velocity oxygen injection process into molten, carbon-saturated hot metal that can generate flames, metal spitting, and high temperatures. It was found that the presence of a minute puncture in the oxygen pipeline could ignite the leaking oxygen under favorable thermodynamic conditions, suggesting potential sources of failure including material degradation, weld joints, or poor workmanship. The high-temperature conditions encountered during operation have the potential to alter the microstructure of the elbow's low-carbon-grade stainless steel parent material (SS310S), weakening it over time. The findings underscore the critical importance of monitoring and maintaining the integrity of BOF systems to prevent similar failures.