Modern Method for Investigating Normalised Condition
of Steel Wide Strips

Dr. Zsolt Csepeli, Gyula Kralik, Jozsef Lorinczi

DUNAFERR Research Institute, Dunaujváros, Hungary

The hot rolled structural steel sheets and strips are used in every steel construction. During this wide utilisation it is essentially important demand, that the properties of the sheet – first of all its strength and toughness – suit the requirements after processing as well. However the manufacturing processes has the risk to influence material properties. Essential change of properties can be expected mainly during hot forming and welding. The risk of these changes can be eliminated by normalised delivery condition of the sheet and strip. This state can be achieved by normalising rolling. With this method we get a condition similar to the metallurgical state after normalising heat treatment.

In our paper we present the research work to investigate the safety of the high-strength, unalloyed structural steel products made at DUNAFERR Co. meet the requirements of European standards and how the products can be regarded normalising rolled.

In the first part of the research work we examined the characteristics of the applied technology by mathematical, statistical evaluation of production data. The used modern analysing and evaluating method covered every important stage of production and material testing. The investigation of data for products with the same strength parameters was carried out in groups and subgroups based on the production technology. The analysis explores the relationship between production parameters and material properties.

In the second part of the research work we compared the mechanical properties and grain morphological parameters on hot rolled and normalised probes of normalising rolled steels.

Summary

The outlined research method can be successfully applied for investigating connection between parameters of similar vertical production technologies. From a database suitable for statistical evaluation we can deduce the relationships of the fundamental variety.

The applied image analysing method gives detailed, objective and reproducible results of the steel microstructure.

Both the mechanical properties and the result of the microstructure investigation proves that the normalising rolled products of the pilot production meet the requirements of the normalised delivery conditions.

The result of our knowledge based investigation founded on research and literature exploration is the revealing of important connections that must be regarded authoritative planning the technology. The products based on new technology conception meets the European standards. Adopting the technology and its experimental control are in progress according to a determined program. The results obtained so far demonstrate that the technological developments progress in a good direction.

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