Título

DESENVOLVIMENTO DE ROLAMENTOS PARA LAMINAÇÃO DE PRODUTOS SIDERÚRGICOS - NSK ROLAMENTOS WATER TOUGH - WTF

DEVELOPMENT OF WATER-TOUGH (WTF®) BEARINGS FOR STELL MILLS LONGER LIFE IN HARSH ENVIRONMENTS

Autoria

Matsumoto, Yoichi

DOI

10.5151/2594-5297-0081

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Resumo

Este relatório apresenta o desenvolvimento NSK de rolamentos para cilindros de laminação, que possuem melhor performance quando submetidos a infiltração de água. Para entender o mecanismo de falha prematura induzida pela infiltração de umidade no interior do rolamento e permitir planos de controle, foram realizadas análises de experimentos do passados e análises de rolamentos que falharam em serviço. Foram desenvolvidos métodos de teste que reproduzem a falha prematura relacionada a contaminação do lubrificante do rolamento. Utilizando estes métodos foi possível observar precisamente o processo de fadiga prematura e estudar quais os parâmetros afetam os materiais que compõem os rolamentos. A propagação das microtrincas inicialmente eram intergranular e posteriormente passavam a ser transgranular, ocasionando eventualmente o lascamento de componentes e a falha prematura. O desenvolvimento e utilização de materias com teor de pureza mais elevado foram fundamentais para reforçar os contornos dos grãos e torná-los mais resistentes a contaminação por água.

 

NSK contributes to energy saving through bearing life extension. This report introduces that NSK has developed Water Tough Bearing (WTF® bearing), which has longer life than conventional bearings under water-infiltrated lubrication such as in steel mill. To understand the mechanism of water-induced flaking and thereby enable countermeasures to be devised, the analyses of past experiments, including bearings that actually failed in services were carried out. In addition, fatigue life test methods that reproduce short life under water-infiltrated lubrication were developed. Using these methods it was possible to observe the flaking process precisely and to study what material parameters affect the bearing life. It was found that failure water-infiltrated lubrication initiated from non-metallic inclusions on the rolling contact surface. The fatigue crack propagation was initially intergranular and then changed to transgranular, eventually resulting in flaking. Higher cleanliness, which means less failure initiation sites, and nickel, which strengthens the grain boundaries, were found to improve bearing life under water-infiltrated lubrication. Water Tough Bearing material has such the higher cleanliness and stronger grain boundaries.

Palavras-chave

NSK; Rolamento; Materiais; Performance.

Bearing; Steel mills.