15.17: Progress in the development of production of heavy plates. S355‐S460ML till 100 mm at NLMK DanSteel

Abstract

ABSTRACTAt the end of 2012 a new 4200 mm rolling mill was put into service in Frederiksvaerk at NLMK DanSteel. Since then the company has focused on production of heavy plates for construction, offshore, shipbuilding and boiler purposes, i.e. steel plates with higher mechanical properties. The company is constantly expanding its product program assortment with regards to sizes and grades. As an example of this, the company in 2015 expanded the range of thermomechanical rolled heavy plates, of structural steel of strength category S355ML, S420ML, S460ML up to 100 mm and received the achieved approval for CE‐marking of these grades.The article presents slab quality requirements, some features of production technology for specified quality and thickness categories as well as enhanced mechanical test results, including evaluation of the anisotropy of the hardness gradient and toughness downp to −80°C both in longitudinal and transverse directions, showing the actual level of low temperature impact toughness properties in ¼ and ½ of heavy plate thickness.Some additional investigations of weldability of low carbon heavy plates were done. The micro hardness of the basic sections in the weld joint of micro alloyed low‐carbon steel heavy plates is investigated. Two‐coordinate measurements of the micro hardness in the basic HAZ are described. The influence of post weld heat treatment on the micro hardness of opposite walls of the weld joint is determined.