Structure and Property Formation for Pipe Coiled Rolled Product During Manufacture Under Casting And Rolling Complex Conditions

The article considers results of the study of microstructure parameters effect on the impact strength in temperature range from 0 to –80 °C in 20 °C increments of Charpy samples with a sharp stress concentrator and Mesnager test pieces with a circular stress concentrator from rolled coils of low-carbon microalloyed steel with various thicknesses. The used roll products were produced in conditions of JSC “Vyksa Metallurgical Plant”. The tests were performed using optical and scanning electron microscopy. It is shown that with the same chemical composition and thermomechanical treatment modes, the metal of smaller thickness (6, 8 mm) is characterized by higher strength properties (on average, by 10 MPa for temporary resistance, by 30 MPa for yield strength) and a margin for viscous properties at negative temperatures at close values of grain score and average grain size corresponding to 10 – 11 numbers according to the State standard GOST 5639. The metal with a thickness of 12 mm has the lowest level of cold resistance, and the temperature of brittle transition is minus 50 °C. Structure of rolled products of various thicknesses has a variation in grain size. Rolled metal of smaller thicknesses have a smaller grains corresponding to number 14, rolled metal of larger thicknesses has a larger grains corresponding to number 8. By conducting electron microscopic studies using the backscattered electron method, it was found that a greater number of large-angle boundaries, which are barriers for brittle cracks propagation, are observed in the 6, 8 mm thick rolled products. The constructed orientation maps of the microstructure showed the presence of pronounced deformation texture corresponding to the orientations <110>||RD (rolling direction) and (<113>...<112>)||RD for rolled products with a thickness of 6 mm.

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Metallographic study on the structural features of thin slab and rolled products made from it

Vorozheva¹,

Сметанин²,

Kislitsa³

et al. 2023

Izv. vysš. učebn. zaved., Čern. metall.

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The authors determined the level of zonal and dendritic segregation in slabs poured by thin-slab technology. The calculated variation coefficients of the content of basic and impurity chemical elements over the slab cross-section do not exceed 10 %, zonal segregation is low. The manganese content measured with the area occupied by the dendritic axes and the interstitial spaces showed the level of dendritic segregation. The manganese concentration varies from 0.6 to 1.1 %, respectively. It was established that the use of dynamic soft compression during solidification makes it possible to grind the primary dendritic structure to form additional centers during the phase transformation of δ-ferrite into austenite. Dimensions of the initial austenitic grains formed taking into account the primary dendritic structure are 3 times smaller in a thin slab than in a slab with a thickness of more than 200 mm. Transformations of the dendritic structure during compression show high workability necessary for the formation of uniform austenitic grains in the fullering before finishing rolling. The study has not confirmed the hypothesis that bainite of coarse morphology in the microstructure of hot-rolled products is formed in segregation areas. The hereditary influence of the primary dendritic structure on the structure formation during rolling was revealed. The manganese concentration varies between the bainite and the “neighboring” structure from 0.68 to 1.01 %, similar to the level of the initial dendritic segregation. Difference in the content of chemical elements affects the processes of recrystallization of austenitic grains during high-temperature rough rolling. Bainite was formed within the framework of chemically “depleted” large austenitic grains that are stable during phase transformation.

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Structure and Property Formation for Pipe Coiled Rolled Product During Manufacture Under Casting And Rolling Complex Conditions

Cited by 4 publications

References 1 publication

Austenitic Structure Evolution During Pipe Steel Coiled Rolled Product Manufacture in Casting and Rolling Complexes of Different Configurations

Austenitic Structure Evolution During Pipe Steel Coiled Rolled Product Manufacture in Casting and Rolling Complexes of Different Configurations

Features of the formation of structure and mechanical properties in rolled products of various thicknesses from low-carbon microalloyed steel produced by casting and rolling complex

Metallographic study on the structural features of thin slab and rolled products made from it

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