scholarly journals Influence of the Quenching and Partitioning Process on the Transformation Kinetics and Hardness in a Lean Medium Manganese TRIP Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 353 ◽  
Author(s):  
Simone Kaar ◽  
Reinhold Schneider ◽  
Daniel Krizan ◽  
Coline Béal ◽  
Christof Sommitsch
Keyword(s):  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Quenching Temperature ◽  
Quenching And Partitioning ◽  
Novel Approach ◽  
Medium Mn Steel ◽  
C Partitioning ◽  
Mn Steel ◽  
Isothermal Bainitic Transformation

The quenching and partitioning (Q&P) process of lean medium Mn steels is a novel approach for producing ultra-high strength and good formable steels. First, the steel is fully austenitized, followed by quenching to a specific quenching temperature (TQ) in order to adjust an appropriate amount of initial martensite (α’initial). Subsequently, the steel is reheated to a partitioning temperature (TP) in order to ensure C-partitioning from α’initial to remaining austenite (γremain) and thus retained austenite (RA) stabilization. After isothermal holding, the steel is quenched to room temperature (RT), in order to achieve a martensitic-austenitic microstructure, where the meta-stable RA undergoes the strain-induced martensitic transformation by the so-called transformation induced plasticity (TRIP) effect. This paper systematically investigates the influence of the Q&P process on the isothermal bainitic transformation (IBT) kinetics in a 0.2C-4.5Mn-1.3Al lean medium Mn steel by means of dilatometry. Therefore, the Q&P annealing approach was precisely compared to the TRIP-aided bainitic ferrite (TBF) process, where the samples were directly quenched to the temperature of the IBT after full austenitization. The results indicated an accelerated IBT for the Q&P samples, caused by the formation of α’initial during quenching below the martensite start (MS) temperature. Furthermore, a significant influence of the annealing parameters, such as TQ and TP, was observed with regard to the transformation behavior. For further characterization, light optical microscopy (LOM) and scanning electron microscopy (SEM) were applied, showing a microstructure consisting of a martensitic-bainitic matrix with finely distributed RA islands. Saturation magnetization method (SMM) was used to determine the amount of RA, which was primarily depending on TQ. Furthermore, the hardness according to Vickers revealed a remarkable impact of the annealing parameters, such as TQ and TP, on the predicted mechanical properties.

scholarly journals Effect of Quenching and Partitioning Temperatures in the Q-P Process on the Properties of AHSS with Various Amounts of Manganese and Silicon

2012 ◽  
Vol 706-709 ◽  
pp. 2734-2739 ◽  
Author(s):  
Hana Jirková ◽  
Ludmila Kučerová ◽  
Bohuslav Mašek
Keyword(s):  
Tensile Strength ◽  
Retained Austenite ◽  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Program ◽  
Quenching Temperature ◽  
Quenching And Partitioning ◽  
Advanced High Strength Steels

The use of the combined influence of retained austenite and bainitic ferrite to improve strength and ductility has been known for many years from the treatment of multiphase steels. Recently, the very fine films of retained austenite along the martensitic laths have also become the centre of attention. This treatment is called the Q-P process (quenching and partitioning). In this experimental program the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % was examined. The alloying strategies have a different content of manganese and silicon, which leads to various martensite start and finish temperatures. The model treatment was carried out using a thermomechanical simulator. Tested regimes resulted in a tensile strength of over 2000MPa with a ductility of above 14 %. The increase of the partitioning temperature influenced the intensity of martensite tempering and caused the decrease of tensile strength by 400MPa down to 1600MPa and at the same time more than 10 % growth of ductility occurred, increasing it to more than 20%.

Effect of quenching temperature on stretch flangeability of a medium Mn steel processed by quenching and partitioning

2018 ◽  
Vol 729 ◽  
pp. 276-284 ◽  
Author(s):  
Ji Hoon Kim ◽  
Eun Jung Seo ◽  
Min-Hyeok Kwon ◽  
Singon Kang ◽  
Bruno C. De Cooman
Keyword(s):  
Quenching Temperature ◽  
Quenching And Partitioning ◽  
Medium Mn Steel ◽  
Mn Steel

Investigation on Microstructure and Martensitic Transformation Mechanism for the Warm-Stamped Third-Generation Automotive Medium-Mn Steel

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Xiaodong Li ◽  
Ying Chang ◽  
Cunyu Wang ◽  
Shuo Han ◽  
Daxin Ren ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Strain Rate ◽  
Compressive Load ◽  
High Strength ◽  
Third Generation ◽  
Transformation Mechanism ◽  
Loading Method ◽  
Strain And Strain Rate ◽  
Medium Mn Steel ◽  
Mn Steel

With the development of the automotive industry, the application of the high-strength steel (HSS) becomes an effective way to improve the lightweight and safety. In this paper, the third-generation automotive medium-Mn steel (TAMM steel) is studied. The warm-stamped TAMM steel holds the complete and fine-grained martensitic microstructure without decarbonization layer, which contributes to high and well-balanced mechanical properties. Furthermore, the martensitic transformation mechanism of the TAMM steel is investigated by the dilatation tests. The results indicate that the effects of the loading method on the Ms temperature under different loads are different. The Ms temperature is hardly influenced under the tensile loads and low compressive load. However, it is slightly decreased under the high compressive load. Moreover, the effects of the strain and strain rate on the Ms temperature are insignificant and can be neglected. As a result, this research proves that the martensitic transformation of the TAMM steel is rarely influenced by the process parameters, such as stamping temperature, loading method, load, strain, and strain rate. The actual stamping process can be designed and controlled accurately referring to the continuous cooling transformation (CCT) curves to realize the required properties and improve the formability of the automotive part.

Effect of Quenching and Partitioning Processing on Microstructure and Mechanical Properties of a Low Alloyed Steel

2018 ◽  
Vol 941 ◽  
pp. 52-57
Author(s):  
Bernd Pfleger ◽  
Marina Gruber ◽  
Gerald Ressel ◽  
Peter Gruber ◽  
Matthew Galler ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Phase Evolution ◽  
Tensile Tests ◽  
Austenite Phase ◽  
Phase Fraction ◽  
Quenching Temperature ◽  
Quenching And Partitioning ◽  
Low Alloyed Steel ◽  
A Minor

The concept of quenching and partitioning (Q&P) is a tool to generate steels with high strength and high ductility resulting from a relatively high amount of martensite and austenite. As the parameters of the Q&P treatment influence the strength and ductility properties, the goal of this work was to analyze the effects of varying quenching and partitioning temperatures on the phase evolution, on the retained austenite phase fraction and on the mechanical properties. The phase evolution during heat treatment was analyzed by dilatometer and the microstructure after processing was characterized by light microscopy in combination with color etching according to Klemm. The austenite phase fraction and its carbon content were determined by X-Ray diffraction and the mechanical properties were evaluated by tensile tests. It is shown that the quenching temperature has a minor impact on the phase fraction of austenite as well as its stabilization by carbon and thus, also the mechanical properties. Furthermore, austenite transformation during the partitioning treatment is illustrated.

Quenching and partitioning (Q&P) processed medium Mn steel starting from heterogeneous microstructure

Materialia ◽  
2020 ◽  
Vol 12 ◽  
pp. 100757
Author(s):  
Ji Hoon Kim ◽  
Min-Hyeok Kwon ◽  
Guiyoung Gu ◽  
Jae Sang Lee ◽  
Dong-Woo Suh
Keyword(s):  
Heterogeneous Microstructure ◽  
Quenching And Partitioning ◽  
Medium Mn Steel ◽  
Mn Steel

Influence of Multi-Step Austempering Temperature on Tensile Performance of Unalloyed Ductile Iron

2019 ◽  
Vol 803 ◽  
pp. 3-7
Author(s):  
Wei Ci Zhuang ◽  
Ying Ming Jiang ◽  
Wen Tao Zhou ◽  
Zhong Yang Liang ◽  
Derek O. Northwood ◽  
...  
Keyword(s):  
Ductile Iron ◽  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Rapid Quenching ◽  
Air Cooling ◽  
Strengthening Effect ◽  
Multiphase Structure ◽  
Tensile Performance ◽  
Austempering Temperature

Austempered ductile iron (ADI) has been widely used in various industries due to its excellent combination of high strength, ductility and good wear resistance. The tensile behavior of an unalloyed commercial ADI with a multiphase structure designed by a novel multi-step austempering treatment is investigated. The developed austempering process consists of austenitizing at 890°C for 20min, then initial rapid quenching to 180°C, and isothermal holding at 190, 220, 250°Cfor 120min, and finally air cooling to room temperature. The optimum mechanical properties with an ultimate tensile strength of 1350MPa, a yield strength of 1090MPa, as well as an elongation of 3.5% is achieved at 220°C. This is attributed to a synergistic strengthening effect of multiphase structure including a prior martensite with fine needle bainitic ferrite and film retained austenite.

scholarly journals Physical simulation and dilatometric study of double-step heat treatment of medium-Mn steel

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
A. Skowronek ◽  
M. Morawiec ◽  
V. Ruiz-Jimenez ◽  
C. Garcia-Mateo ◽  
A. Grajcar
Keyword(s):  
Heat Treatment ◽  
Retained Austenite ◽  
Physical Simulation ◽  
Isothermal Holding ◽  
Heat Treatments ◽  
Double Step ◽  
Dilatometric Study ◽  
Medium Mn Steel ◽  
One Step ◽  
Mn Steel

Abstract The work addresses physical simulation and dilatometric study of one-step and double-step heat treatments of medium-Mn steel designed for automotive sheets. The conventional one-step isothermal bainitic transformation was applied as the reference heat treatment. The newly implemented heat treatment consisted of isothermal holding in a bainitic region followed by additional holding of the material at reduced temperature also in the bainitic range. This step was added to refine the microstructure, which led to the stabilization of the retained austenite. Calculations of equilibrium state and non-equilibrium cooling and simulations of the developed thermal cycles were performed using the thermodynamic JMatPro software. The physical simulations of the heat treatment were performed in the dilatometer. The obtained samples were subjected to microscopic observations using light and SEM microscopy. One- and two-step heat treatments allowed to obtain bainitic structures with high contents of retained austenite. Lowering the temperature of one-step isothermal holding resulted in the bainite refinement and adjacent retained austenite. The increased Mn content in steel increased its susceptibility to form coalesced bainite resulting in the partial formation of thicker plates despite a decrease in a process temperature.

scholarly journals Application of Quenching and Partitioning Processing to Medium Mn Steel

2014 ◽  
Vol 46 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Eun Jung Seo ◽  
Lawrence Cho ◽  
Bruno C. De Cooman
Keyword(s):  
Quenching And Partitioning ◽  
Medium Mn Steel ◽  
Mn Steel
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