DEVELOPMENT OF A METHOD FOR IDENTIFYING THE CAUSES OF DEFECTS IN GALVANIZED SHEET METAL PRODUCED ON CONTINUOUS

In recent years, the range of products manufactured on continuous hot-dip galvanizing units has expanded significantly, including the development of several dozen new automotive steels. At the same time, the technology for the production of galvanized sheet metal for various purposes is insufficiently developed. Varying the line speed and strip heat treatment modes can lead to product defects. Quality can be affected by process control features at different stages. However, there are currently no highly effective tools for analyzing retrospective data to identify the impact of control features on product quality. The work is devoted to the development of a method for identifying concomitant circumstances of product defects caused by features of the process signals dynamics over time. The method proposed in this paper is based on the use of a set of templates and events to classify the signal dynamics over time, allowing one to assess the impact of control on the occurrence of product defects without significant computational costs. We developed method for assessing the influence of control quality on the occurrence of product defects, based on identifying the most problematic events from the standpoint of control quality for each roll, as well as using templates and events that have an analog classifier to assess the degree of influence of an event on the quality of control and the occurrence of defects. This made it possible to apply a standard approach to eliminating interfering factors based on the stratification of retrospective data, and to apply the previously proposed methods of sequential data stratification to determine the accompanying circumstances of the occurrence of product defects, taking into account the process signals dynamics over time. The proposed method allows us not only to identify the accompanying circumstances of product defects, but also to offer recommendations for improving management to prevent them. Using the example of applying the method to a number of unacceptable coating defects at the MMK Metallurgy plant in Turkey, a number of management problems were identified and restrictions were proposed, the consideration of which should reduce the share of defective products.