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Hot Ductility of High-Mn Steel with Niobium and Titanium

Opiela Marek, Fojt-Dymara Gabriela

Advances in Science and Technology. Research Journal

2024

Vol. 18, no 3

200--213

The work presents the results of research on the effect of deformation parameters on hot ductility of high-Mn austenitic steel with niobium and titanium. The investigations were carried out on steel with 0.05% C, 24% Mn, 3.5% Si, 1.5% Al, 0.030% Nb and 0.075% Ti. Hot static tensile test was performed using Gleeble 3800 thermomechanical simulator. Samples were deformed in a temperature range from 1050°C to 1200°C with a strain rate of 3·10-3 s-1. The reduction in area (RA), determined in the static tensile test, was the basis for determining the hot ductility of the examined steel. Reduction in area of examined steel decreases from 88% at the temperature of 1050°C to 59% at 1200°C. High hot ductility of the investigated steel is the result of the synergy of chemical composition optimization, properly conducted modification of non-metallic inclusions and formed fine-grained microstructure of dynamically recrystallized austenite. In addition to hot ductility, parameters characterizing susceptibility of studied steel to high temperature cracking were also defined, namely: ductility recovery temperature (DRT), nil ductility temperature (NDT) and nil strength temperature (NST) were determined. The values of these temperatures are 1240°C, 1250°C and 1270°C, respectively. This means that the temperature of the beginning of plastic deformation of ingots of this steel may be equal even slightly above 1200°C. In addition, the high-temperature brittleness range (HTBR) was determined, which is equal 30°C.

Effect of plastic deformation rate at room temperature on structure and mechanical properties of high-Mn austenitic Mn-Al-Si 25-3-3 type steel

Borek W., Lis M., Gołombek K., Sakiewicz P., Piotrowski K.

Archives of Materials Science and Engineering

2019

Vol. 96, nr 1

22--31

Purpose: The aim of the paper is to determine influence of plastic deformation rate at room temperature on structure and mechanical properties of high-Mn austenitic Mn-Al-Si 25-3-3 type steel tested at room temperature. Design/methodology/approach: Mechanical properties of tested steel was determined using Zwick Z100 static testing machine for testing with the deformation speed equal 0.008 s-1, and RSO rotary hammer for testing with deformation speeds of 250, 500 and 1000s-1. The microstructure evolution samples tested in static and dynamic conditions was determined in metallographic investigations using light microscopy as well as X-ray diffraction. Findings: Based on X-ray phase analysis results, together with observation using metallographic microscope, it was concluded, that the investigated high-Mn X13MnAlSiNbTi25-3-3 steel demonstrates austenitic structure with numerous mechanical twins, what agrees with TWIP effect. It was demonstrated, that raise of plastic deformation rate produces higher tensile strength UTS and higher conventional yield point YS0.2. The UTS strength values for deformation rate 250, 500 and 1000 s-1 grew by: 35, 24 and 31%, appropriately, whereas in case of YS0.2 these were: 7, 74 and 130%, accordingly, in respect to the results for the investigated steel deformed under static conditions, where UTS and YS0.2 values are 1050 MPa and 700 MPa. Opposite tendency was observed for experimentally measured uniform and total relative elongation. Homogeneous austenitic structure was confirmed by X-ray diffractometer tests. Research limitations/implications: To fully describe influence of strain rates on structure and mechanical properties, further investigations specially with using transmission electron microscope are required. Practical implications: Knowledge about obtained microstructures and mechanical properties results of tested X13MnAlSiNbTi25-3-3 steel under static and dynamic conditions can be useful for the appropriate use of this type of engineering material in machines and equipment susceptible to static or dynamic loads. Originality/value: The influence of plastic deformation at room temperature under static and dynamic conditions of new-developed high-manganese austenitic X13MnAlSiNbTi25-3-3 steels were investigated.