Physical Modelling of Microstructure Development during Technological Processes with Intensive Incremental Deformation

Mašek, Bohuslav; Staňková, Hana; Malina, Jiří; Skálová, Ludmila; Meyer, Lothar

doi:10.4028/www.scientific.net/kem.345-346.943

Cited by 15 publications

(7 citation statements)

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“…Among them, the most important ones are the martensite-start Ms and martensite-finish Mf temperatures. In this steel, the Ms was calculated as 294°C and the Mf as 173°C [18][19][20]. The steel was supplied as rolled 10-mm plates with a pearlite-ferrite microstructure and a hardness of 290 HV10 (Fig.…”

Section: Experimental Materialsmentioning

confidence: 99%

EFFECTS OF Q&P PROCESS PARAMETERS ON PROPERTIES OF 42SiCr STEEL

Rubešová¹,

Vorel²,

Jirková³

et al. 2018

Acta Metall. Slovaca

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The requirement for high strength and good ductility poses problems in today’s advanced steels. This problem can be tackled by appropriate heat treatment which produces suitable microstructures. By this means, ultimate strengths of about 2000 MPa and elongations of more than 10% can be obtained. One of such advanced heat treatment techniques is the Q&P (Quenching and Partitioning) process. It produces a mixture of martensite and retained austenite, where the latter is an important agent in raising the ductility of steel. In this experiment, a low-alloy steel with 0.41% carbon and manganese, silicon and chromium was used. An air furnace and a salt bath were employed for heat treatment and quenching, respectively. In order to obtain the best ultimate strength and elongation levels, partitioning temperatures of 250°C and 300°C were applied. Partitioning involves carbon diffusion from super-saturated martensite into retained austenite, and tempering of hardening microstructure. Effects of the quenching temperatures of 200°C and 150°C were studied as well. To map the impact of the Q&P process on mechanical properties, an additional schedule with conventional quenching and tempering was carried out. Upon optimization of the parameters, the process produced martensite with a small amount of bainite and retained austenite. The ultimate strength was between 1930 and 2080 MPa and the elongation levels were from 9 to 16%.

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Section: Experimental Materialsmentioning

confidence: 99%

EFFECTS OF Q&P PROCESS PARAMETERS ON PROPERTIES OF 42SiCr STEEL

Rubešová¹,

Vorel²,

Jirková³

et al. 2018

Acta Metall. Slovaca

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“…The active part of the processed samples had 8 mm diameter and the length of 16 mm. Thermo-mechanical processing with bainitic hold and incremental deformation steps was designed ( Table 1) to simulate real processing of TRIP steels in rolling mills or by rotary spin extrusion and to enable higher total deformation to be applied to relatively small samples without the risk of cracking [17]. Various thermal parameters and numbers of deformation steps were applied to both steels, to evaluate their effect on the final microstructures and the mechanical properties.…”

Section: Thermo-mechanical Treatmentmentioning

confidence: 99%

Thermo-Mechanical Treatment of 42sicr and 42mnsi Steels

Kučerová

Jirková

Jandová

2017

Acta Metall Slovaca

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Two high strength low alloyed steels with 0.4%C, 0.6%Mn, 2%Si and either 1.3% of chromium or without chromium were used in this work to evaluate the effect of chromium on the final microstructure obtained by thermo-mechanical processing. Various heating temperatures, cooling rates and bainitic hold temperatures were tested. High strengths around 1700 MPa were achieved for the chromium alloyed steel, however total elongation reached only 9%. Chromiumfree steel turned out to be better suited for TRIP (transformation induced plasticity) processing. The relatively high strengths around 900 MPa were in this case accompanied by very high total elongations exceeding 30%. The final microstructure of chromium-free steel was also more typical for TRIP steel, as it consisted mainly of the mixture of bainite and polygonal ferrite.Keywords: TRIP steel, chromium, thermomechanical processing, scanning electron microscopy 1 Introduction TRIP (transformation induced plasticity) steels are advanced steel grades with high strength and enhanced total elongation and formability. Their good mechanical properties result from a complex microstructure containing ferritic matrix, carbide-free bainite and retained austenite [1,2]. Suitable microstructures with proper volume fractions, distributions and morphologies of individual phases and structural components are produced usually by thermo-mechanical treatment [1,3]. Ideal processing parameters vary according to the particular chemical composition of steel. The most conventional concept is based on C-Mn-Si alloying [1,[4][5]. Further TRIP steel variations were investigated in last decades, testing other alloying elements and their combinations. Silicon was fully or partially replaced by aluminium to improve galvanizing properties of thin sheets for automotive industry [6,7]. Micro alloying by Niobium was designed to refine the final microstructure and increase retained austenite content [8][9][10]. Chromium alloying of medium carbon TRIP steels has not been investigated very thoughtfully [11], probably due to its reputation of a carbide-forming element with a potential to increase the incubation time and decrease the transformation rate of isothermal bainite. The effect of chromium on higher hardenability is usually used in martensite-based steel, primarily to increase the strength [11][12][13]. However, chromium also retards pearlite growth rate and refines the microstructure by reducing the growth rate of prior austenite grain in steels [14][15] and improves corrosion resistance [16], which can be convenient for TRIP steels as well.

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“…It has made significant progress during the last five years, mainly thanks to the new possibilities opened up by sensor development and especially by new control procedures supported by innovative electronic elements and circuits [1,2]. The thermomechanical simulator is one such device.…”

Section: Introductionmentioning

confidence: 99%