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Correct Liner Characteristics Based On Mill Type & Liner Location

Choosing liner material based on mill type and liner location improves quality and performance. Table 1 gives the most effective liner characteristics for each type of mill and location in the mill.

• Housing Liners - Close clearances between the mill housings and the backup roll chocks are maintained by housing liners, enabling the mill to roll strip to a precise shape and gauge. High wear resistance is important for housing liners, therefore, these liners are manufactured from steels capable of attaining very high hardness and toughness levels.
• Backup Roll Chock Liners - Backup roll outside chock liners protect the chock from wear and allow close clearances between the mill housings and the backup roll chocks. This helps to maintain roll alignment and gaps, which both contribute to the ability of the mill to roll strip to a precise shape and gauge. Wear resistance is important for both outside and inside backup roll chock liners.

The important material consideration for backup roll chock liners is the hardness of the parts they contact. A part with higher hardness will abrade one of lower hardness. Thus, outside backup roll chock liners should be lower in hardness than the housing liners they contact. In some mill designs, inside backup roll chock liners contact the work roll bearing box liners. Since backup rolls are replaced less frequently than work rolls, backup roll liners are not as accessible. Inside backup roll chock liners are designed to wear longer than work roll bearing box liners.

• Work Roll Bearing Box Liners - Work roll bearing box liners protect the work roll bearing box from wear and allow for close clearances between the work roll chock and either the backup roll chock or the Mae West block. These close clearances help to maintain roll alignment and the roll gaps and to contribute to precise strip shape and gauge. Work roll bearing box liners contact the inside leg liners of the backup roll chocks. In mills of a Mae West design, the work roll chocks contact the Mae West block.

Since work rolls are frequently changed, work roll liners are very accessible. Due to their size, they are inexpensive to replace. For these reasons, work roll liners are manufactured from steels with slightly lower hardnesses and wear properties than the liners they contact.

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