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NISCO Plate/Coil Mill Level
2 Force Model Improvements
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2.6 Grade Families Design
Those grades with near parameters or properties are put into a grade family. Classification of the grade family may be based on physical, mechanical, thermal properties and mill operational parameters. About 100 data, which characterize a grade family, is put into a file called family file.
NISCO steel grades initially had 11 families, based on the purpose of steel application. Since steel grades for different applications may be overlapped in properties, operational parameters and chemical compositions, the old classification is not appropriate for the model design. In the new design, grade family has been designed following chemical composition, which roughly also indicates the basic strength. The old and new grade families are listed in the Table 3. Those steels, mostly HSLA, contain relative low carbon, so the "medium carbon" and "high carbon" in the table are only relative.
Table 3: Old and New Grade Families
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Family Name Old |
Family Name New |
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11
Families
Based on Application
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12
Families
Based on Composition
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2.7 Automatic Design of
Flow Stress Coefficients
Due to the highly diversified products and high requirements for controlled rolling, there were about 6500 model grades and accordingly about 20,000 sets of flow stress coefficients C1, C2, C3, and C4.
In this case, manual or half-manual design, as in the past
project, cannot meet the requirement. Automatic design, by
applying a long list of existing and newly created model data,
was performed.
In addition to great number of developments, there were numerous steps of data transformation. 28 tables in a database were employed for the data transformation, with each table containing dozens records to 20 thousands. The primary calculation for the flow stress coefficients were based on Metal Pass flow stress database. In the past 20 years, Metal Pass has intensively collected flow stress data and models from all sources in Germany, USA, Canada, Japan and China, etc., and closely studied advantages and disadvantages of flow stress models available. As demo, Metal Pass has posted a portion of its flow stress models, about 2000 in count, in its website www.meta 4-0.com. One more set of flow stress models, about 10,000 in count, is planned to be posted in this website for fee-based download [5].
Up to now, 19488 sets of flow stress coefficients (4 x 19488 values) have been completed, as indicated in the database.
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