Quantification of Qualitative Defects for Automobile Customers

Abstract

Increasing productivity by minimizing the defects is of utmost importance to any steel industry. Cold Rolling Mill plays a very important role due to its very complex processes and the products end use. Deliverance of high quality product to the customer, relentlessly understanding their requirement and regular feedback became the basis for working on this project. During the process where a coil from Hot Strip Mill (HSM) goes into the Pickling Line to Cold Rolling Mill to Batch Annealing to Final Packaging and Dispatch amidst various other processes, it acquires various defects that need to be catered before delivery to the customer. Some defects can be minimized through improvement in maintenance and some are inherent (where CRM is a customer). The aim of the project is form a quantitative comparative study with the help of profilometer analysis of Raw CRCA, Phospotised CRCA, and Painted CRCA of stainless steel samples. On the basis of comparison, one will be able to conclude upto what severity a particular defect will be passed. Among the various defects analyzed by profilometer, the Lamination & Gouge Mark are the most severed defects. The difference in total roughness obtained between defected and non-defected area after 1st layer of painting was the order of 5 – 40 µm for Lamination & 8 – 10 µm for Gouge mark. This shows that these defects are highly prone to customer complaints and often goes for rejection. The difference upto 1 µm are passed without much scrutiny. Anything beyond 1 µm difference calls for action by both manufacturer & customer.