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Description
The Soft Quenching process applied to the Danieli Spooler incorporates a patented controlled cooling technology specifically developed to enhance the production of compact rebar coils.
In conventional spooler-based quenching systems, cooling is performed in a single high intensity stage immediately after the finishing rolling pass. This approach suppresses diffusive austenite transformation, producing a surface martensitic layer that then undergoes air equalization before coil formation. The resulting microstructure, martensitic-bainitic at the surface and ferritic–pearlitic at the core, meets the required strength standards but introduces heterogeneity and potential residual stresses within the coil.
Danieli’s Soft Quenching process overcomes these limitations through a multistage, modulated cooling strategy that completely suppresses martensite formation, a configuration also referred to as a martensitic-free process.
The process ensures an ultra-fine, fully uniform ferritic–pearlitic microstructure across the entire bar cross section, enhancing metallurgical homogeneity, mechanical consistency, dimensional stability, and product repeatability, while also reducing energy consumption and wear in downstream operations.
The real-time digital control, together with Danieli Automation’s big data and AI-driven systems, continuously regulates the cooling process, maintaining stable cooling rates tailored to product specifications and rolling conditions.
Industrial installations, including the most recent one in Germany at the ESF Elbe Stahlwerke Feralpi rolling mill, have demonstrated the capability to produce coils with markedly improved mechanical consistency across diameters ranging from 8 to 25 mm and coil weights of up to 8 tons.