Effects of tension levelling process parameters on cold rolled strip characteristics using a designed factorial analysis approach

Abstract

Tension levelling is a process used in the steel industry to remove any shape defects (i.e. out of flatness) present in coiled material. It is generally the final process before the cold rolled product is dispatched to the customer, and is therefore a process which plays an important role in delivering the desired material properties and the product standards required by the customer. In this paper a designed factorial analysis has been employed to study the effect of tension levelling process parameters on the shape characteristics of the levelled product. These characteristics include residual flatness (longitudinal curvature, referred to as longbow), centreline elongation and residual (or internal) stress imbalances; criteria that determine whether the customer accepts the material or not. It has been identified that in a basic five roll leveller the final (adjustable) roll wrap angle has the most significant influence on these characteristics in over 70% of cases. It has also been recognised that final flatness is dictated by many second order process interactions.

Keywords:

• COILED MATERIAL
• TENSION LEVELLING
• SHAPE DEFECTS
• PROCESS PARAMETERS
• MATERIAL PROPERTIES