NLMK DanSteel

Frederiksværk, Denmark

NLMK DanSteel

Frederiksværk, Denmark
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Goli-Oglu E.A.,NLMK DanSteel | Kichkina A.A.,Bardin Central Research Institute for The Iron And Steel Industry
Metallurgist | Year: 2017

Traditionally high strength (σy ≥ 400 N/mm2) rolled sheet thicker than 50–60 mm of low-carbon structural steel is produced by hot rolling technology followed by normalizing or hardening and tempering. Contemporary equipment makes it possible to produce rolled product 50–140 mm thick of low carbon steel by thermomechanical rolling and to obtain a required set of properties without expenditure on production operations connected with additional metal heating such as normalizing and tempering. Results are given in this article for studying one of the thick sheet property indices, i.e., structure nonuniformity through plate thickness. The microstructure is compared for rolled sheet 100 mm thick of low-carbon microalloyed steel structural steel produced in the 4200 NLMK Dansteel mill by thermomechanical rolling technology (TMT) with the microstructure obtained as a result of hot rolling followed by normalizing (HT). Grain sizes are determined at different points of rolled product layer thickness, and histograms are plotted for their distribution, making it possible to compare the degree of inhomogeneity for the microstructure with respect to grain size. The type, size, and density of carbonitride particles are determined at distances of 1/2 and 1/4 through the thickness of 100 mm plate after TMT and HT. © 2017 Springer Science+Business Media New York

Goli-Oglu E.A.,NLMK DanSteel
Steel in Translation | Year: 2016

The alloying of steel resistant to atmospheric corrosion is discussed. The differences and similarities of the Russian GOST, European EN, and United States ASTM standards regarding the chemical composition of such steel are analyzed. The prospects for the production of corrosion-resistant high-strength steel sheet exceeding the requirements in the EN 10025-5 standard are considered. In trials, the possibility of producing steel sheet with elevated low-temperature impact strength is demonstrated. Production technology for high-strength steel resistant to atmospheric corrosion is developed. © 2016, Allerton Press, Inc.

Rolled sheets with a thickness of 60 mm are studied after thermomechanical rolling and after an additional heat treatment. The conditions of the deformation and thermal deformation aging are shown to affect the impact toughness of the low-carbon microalloyed steel. The changes in the critical temperatures of the impact toughness due to increase in the degree of preliminary cold deformation and under additional heating of the steel to 250°C are determined. The parameter of the susceptibility of surface and central (over the thickness) layers of a thick sheet to mechanical aging is computed. © 2017 Springer Science+Business Media, LLC

Weld joints in fixed marine platforms must be highly reliable. Certain zones of the weld seam may be very hard and hence may act as stress concentrators. Therefore, in some cases, additional heat treatment is required after welding. The microhardness of the basic sections in the weld joint of microalloyed low-carbon streel sheet (thickness 60 mm) obtained by thermomechanical rolling is investigated. Two-coordinate measurements of the microhardness in the basic thermal-influence zones are described. The influence of postweld heat treatment on the microhardness of opposite walls of the weld joint is determined. © 2016, Allerton Press, Inc.

Goli-Oglu E.A.,NLMK DanSteel | Bokachev Y.A.,NLMK DanSteel
Metallurgist | Year: 2015

Lamellar tearing may develop in building metal structures using low-carbon steels in welded joints and assemblies. A reason for its occurrence is an inadequate level of ductility with respect to the degree of welded structure stress in the plate thickness direction. Using results of thick plate tests, we demonstrate the effect of harmful impurities and also of the strength level, structural inhomogeneity, and low-carbon steel slab thickness on the level of relative reduction of area in the thickness direction of plate produced in the NLMK DanSteel 4200 rolling mill. © 2015 Springer Science+Business Media New York.

Investigation of the microstructure and mechanical properties of heavy plates strength grade S355 in thickness range 5–150 mm from low carbon structural steels, microalloyed with vanadium and regulated nitrogen content was made. Main parameters of the microstructure and mechanical properties after hot rolling, normalizing and normalizing rolling were compared. The influence of temperature during heat treatment on the level of mechanical properties was determined in laboratory conditions. The contribution of hardening effect of second phase particles to the strength level of the studied steels was defined. © 2015, Allerton Press, Inc.

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