The chemical composition, rolling and cooling process parameters for production of 100 mm heavy plates from low-carbon microalloyed structural steel grades S420M and S420ML were developed at the NLMK DanSteel Mill Quarto 4200 by using TMCP+ACC processing. The application of thermomechanical processing method combined with accelerated cooling ensured for steel heavy plates with CEQ 0.34% and Pcm 0.15% the required level of mechanical properties with the following average parameters: Rm : 503 MPa, ReH : 413 MPa, El : 27%, KVLav-20 : 322 Joules, KVLav-40: 235 Joules, KVLav-50 : 114 Joules.
The results of investigations and mechanical testing were used for extension of allowed production range heavy plate grades S420M and S420ML in thicknesses from the maximum 60 mm to the maximum 100 mm under EN 10025-4:2019, based on the TUV 0035-CPR-A199 certificate, in accordance with Regulation (EU) No. 305/2011: System 2+.
* +N stands for “hotrolling ofh eavy plates with subsequent furnace normalizing heat treatment”.
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