Title

HIGH QUALITY PRODUCTION OF NIOBIUM MICROALLOYED STEELS

HIGH QUALITY PRODUCTION OF NIOBIUM MICROALLOYED STEELS

Authorship

Jansto, Steven George; Stalheim, Douglas Glenn

Jansto, Steven George

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Stalheim, Douglas Glenn

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DOI

10.5151/2594-5300-22861

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Abstract

Several key operational and metallurgical parameters must be properly balanced for the successful production of high quality niobium microalloyed steels. Over 200 million tonnes of niobium (Nb) microalloyed steels were produced last year globally across the automotive, pipeline and structural segments. The production of these defect free continuously cast microalloy Nb steel slabs, blooms and billets have increased in importance for both the producer and the end user. The minimization of surface and internal defects has a substantial impact on steel producing operating costs, internal and external cost of quality and delivery performance. There are universal fundamental operational and metallurgical principals when producing microalloyed steels regardless of the caster or mill configuration, equipment capabilities or layout. In addition, the proper slab selection, reheating parameters and practices, automatic or manual generated rolling schedules, carbon and alloy design, reduction schedules and overall proper process design affect the operational cost effectiveness. The interaction of these factors will govern the resultant hot roll surface quality and mechanical properties. This paper will present common as-cast and hot rolling defect characteristics, proper identification of such defects, cause and effect relationships, and corrective actions and will describe key casting, hot rolling operational/metallurgical parameters related to surface quality that need to be considered when producing all steels in addition to niobium microalloyed steels. It is extremely important that the proper identification of surface quality issues is determined so that the proper corrective actions can be employed. Steelmakers around the world who understand and implement this root-cause analysis and corrective action system increase their probability of successfully resolve their surface quality related issues.

Several key operational and metallurgical parameters must be properly balanced for the successful production of high quality niobium microalloyed steels. Over 200 million tonnes of niobium (Nb) microalloyed steels were produced last year globally across the automotive, pipeline and structural segments. The production of these defect free continuously cast microalloy Nb steel slabs, blooms and billets have increased in importance for both the producer and the end user. The minimization of surface and internal defects has a substantial impact on steel producing operating costs, internal and external cost of quality and delivery performance. There are universal fundamental operational and metallurgical principals when producing microalloyed steels regardless of the caster or mill configuration, equipment capabilities or layout. In addition, the proper slab selection, reheating parameters and practices, automatic or manual generated rolling schedules, carbon and alloy design, reduction schedules and overall proper process design affect the operational cost effectiveness. The interaction of these factors will govern the resultant hot roll surface quality and mechanical properties. This paper will present common as-cast and hot rolling defect characteristics, proper identification of such defects, cause and effect relationships, and corrective actions and will describe key casting, hot rolling operational/metallurgical parameters related to surface quality that need to be considered when producing all steels in addition to niobium microalloyed steels. It is extremely important that the proper identification of surface quality issues is determined so that the proper corrective actions can be employed. Steelmakers around the world who understand and implement this root-cause analysis and corrective action system increase their probability of successfully resolve their surface quality related issues.

Keywords

Casting; Defect identification; Hot rolling; Root-cause analysis.

Casting; Defect identification; Hot rolling; Root-cause analysis.