scholarly journals High Versatility of Niobium Alloyed AHSS

2017 ◽  
Vol 62 (3) ◽  
pp. 1485-1491 ◽  
Author(s):  
L. Kučerová ◽  
K. Opatová ◽  
J. Káňa ◽  
H. Jirková
Keyword(s):  
Heat Treatment ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Processing Parameters ◽  
High Ductility ◽  
Processing Strategies ◽  
Cooling Schedules ◽  
Final Microstructure ◽  
Steel Processing

AbstractThe effect of processing parameters on the final microstructure and properties of advanced high strength CMnSiNb steel was investigated. Several processing strategies with various numbers of deformation steps and various cooling schedules were carried out, namely heat treatment without deformation, conventional quenching and TRIP steel processing with bainitic hold or continuous cooling. Obtained multiphase microstructures consisted of the mixture of ferrite, bainite, retained austenite and M-A constituent. They possessed ultimate tensile strength in the range of 780-970 MPa with high ductility A5mmabove 30%. Volume fraction of retained austenite was for all the samples around 13%. The only exception was reference quenched sample with the highest strength 1186 MPa, lowest ductility A5mm= 20% and only 4% of retained austenite.

Microstructure and Tensile Properties of TRIP-Aided Steel Sheet Subjected to Hot-Rolling and Austempering

2021 ◽  
Vol 1016 ◽  
pp. 732-737
Author(s):  
Junya Kobayashi ◽  
Hiroto Sawayama ◽  
Naoya Kakefuda ◽  
Goroh Itoh ◽  
Shigeru Kuraoto ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Hot Rolling ◽  
Manufacturing Process ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Isothermal Holding ◽  
High Strength ◽  
Isothermal Transformation ◽  
Transformation Process ◽  
Steel Sheets

Various high strength steel sheets for weight reduction and safety improvement of vehicles have been developed. TRIP-aided steel with transformation induced plasticity of the retained austenite has high strength and ductility. Conventional TRIP-aided steels are subjected to austempering process after austenitizing. Generally, elongation and formability of TRIP-aided steel are improved by finely dispersed retained austenite in BCC phase matrix. The finely dispersed retained austenite and grain refinement of TRIP-aided steel can be achieved by hot rolling with heat treatment. Therefore, the improvement of mechanical properties of TRIP-aided steel is expected from the manufacturing process with hot rolling and then isothermal transformation process. In this study, thermomechanical heat treatment is performed by combining hot rolling and isothermal holding as the manufacturing process of TRIP-aided steel sheets. The complex phase matrix is obtained by hot rolling and then isothermal holding. Although the hardness of the hot rolled and isothermal held TRIP-aided steel is decreased, the volume fraction of retained austenite is increased.

Effects of Heat Treatment on Microstructure of High-Strength Manganese-Silicon Steels

2017 ◽  
Vol 270 ◽  
pp. 239-245
Author(s):  
Dagmar Bublíková ◽  
Štěpán Jeníček ◽  
Kateřina Opatová ◽  
Bohuslav Mašek
Keyword(s):  
Heat Treatment ◽  
Cooling Rate ◽  
Microstructure Evolution ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Quenching And Partitioning ◽  
Alloying Additions ◽  
New Procedures ◽  
Strength And Ductility

Today’s advanced steels are required to possess high strength and ductility. This can be accomplished by producing appropriate microstructures with a certain volume fraction of retained austenite. The resulting microstructure depends on material’s heat treatment and alloying. High ultimate strengths and sufficient elongation levels can be obtained by various methods, including quenching and partitioning (Q&P process). The present paper introduces new procedures aimed at simplifying this process with the use of material-technological modelling. Three experimental steels have been made and cast for this investigation, whose main alloying additions were manganese, silicon, chromium, molybdenum and nickel. The purpose of manganese addition was to depress the Ms and Mf temperatures. The Q&P process was carried out in a thermomechanical simulator for better and easier control. The heat treatment parameters were varied between the sequences and their effect on microstructure evolution was evaluated. They included the cooling rate, partitioning temperature and time at partitioning temperature. Microstructures including martensite with strength levels of more than 2000 MPa and elongation of 10–15 % were obtained.

scholarly journals Addressing Retained Austenite Stability in Advanced High Strength Steels

2013 ◽  
Vol 738-739 ◽  
pp. 212-216 ◽  
Author(s):  
Elena V. Pereloma ◽  
Azdiar A. Gazder ◽  
Ilana B. Timokhina
Keyword(s):  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
High Strength Steels ◽  
High Strength ◽  
Processing Parameters ◽  
Advanced High Strength Steels ◽  
Austenite Stability ◽  
Retained Austenite Stability ◽  
Size And Morphology

Advances in the development of new high strength steels have resulted in microstructures containing significant volume fractions of retained austenite. The transformation of retained austenite to martensite upon straining contributes towards improving the ductility. However, in order to gain from the above beneficial effect, the volume fraction, size, morphology and distribution of the retained austenite need to be controlled. In this regard, it is well known that carbon concentration in the retained austenite is responsible for its chemical stability, whereas its size and morphology determines its mechanical stability. Thus, to achieve the required mechanical properties, control of the processing parameters affecting the microstructure development is essential.

scholarly journals NEW TREATMENT ROUTE FOR CLOSED-DIE FORGINGS OF STEELS WITH 2.5% MANGANESE

2018 ◽  
Vol 24 (2) ◽  
pp. 119
Author(s):  
Dagmar Bublíková ◽  
Štěpán Jeníček ◽  
Michal Peković ◽  
Hana Jirková
Keyword(s):  
Heat Treatment ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Quenching Temperature ◽  
Treatment Processes ◽  
Martensitic Microstructure ◽  
Heat Treated ◽  
Forged Parts ◽  
New Treatment

<p>The requirements placed on closed-die-forged parts of advanced steels have been increasing recently. Such forgings demand an innovative approach to both design and heat treatment. It is important to obtain high strength and sufficient ductility in closed-die forgings. High strength, mostly associated with martensitic microstructure, is often to the detriment of ductility. Ductility can be improved by incorporating a certain volume fraction of retained austenite in the resulting microstructure. Among heat treatment processes capable of producing martensite and retained austenite, there is the Q&amp;P process (Quenching and Partitioning). This process is characterized by rapid cooling from the soaking temperature to the quenching temperature, which is between Ms and Mf, and subsequent reheating and holding at the partitioning temperature. Thus, strength levels of more than 2000 MPa combined with more than 10% elongation can be obtained. This experimental programme involved steels with 2.5% manganese. Forgings of these steels were heat treated using an innovative process in order to obtain an ultimate strength of more than 2000 MPa combined with sufficient elongation. Thanks to a higher manganese level, the Mf was depressed as low as 78°C, and therefore quenching was carried out not only in air but also in boiling water. Holding at the partitioning temperature of 180°C, when carbon migrates from super-saturated martensite to retained austenite, took place in a furnace. The effects of heat treatment parameters on the resulting mechanical properties and microstructure evolution in various locations of the forging were studied.</p>

Two-Step Quenching & Partitioning of 42SiCrB Steel

2014 ◽  
Vol 783-786 ◽  
pp. 738-743 ◽  
Author(s):  
Niko Grosse-Heilmann ◽  
Isabella Maria Zylla ◽  
Ernst Kozeschnik ◽  
Andreas Peters
Keyword(s):  
Heat Treatment ◽  
Retained Austenite ◽  
Thermal Process ◽  
Treatment Process ◽  
Volume Fraction ◽  
High Strength ◽  
Carbon Diffusion ◽  
Process Route ◽  
Low Alloyed Steel ◽  
Step Quenching

In recent years, Quenching and Partitioning (Q&P) became an interesting thermal process route for semi-finished high strength low alloyed steel components. Recent publications demonstrate promising mechanical properties with considerable ductility enhancement. To assess the potential of the two-step Q&P heat treatment in seamless tube production, corresponding tests are carried out on 42SiCrB steel (0.42wt% C, 2.0wt% Si, 1.3wt.% Cr, 0.6wt.% Mn, 0.002wt.% B). Feasible Q&P heat treatment process parameters are identified using the Constrained-Carbon-Equilibrium (CCE) model, carbon diffusion calculations and isothermal TTT curves with previous quenching. Furthermore achieved volume fraction of retained austenite is analyzed by XRD experiments.

scholarly journals Design and Optimization of Processing Conditions for a Recent Quenched and Partitioned Steel

2021 ◽  
Author(s):  
Eman Hassan El-Shenawy ◽  
Hoda Nasr El-Din Hedia ◽  
Mai Mohamed Kama-El-Din ◽  
Hoda Refaiy Badwy
Keyword(s):  
Heat Treatment ◽  
Tensile Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Testing Machine ◽  
High Strength ◽  
Processing Conditions ◽  
Critical Temperatures ◽  
Tensile Testing Machine ◽  
Heat Treated

Q&P steels as a "Third Generation" of (AHSS) exhibit excellent tensile properties, which enable producing lightweight sections for the automotive industry and at the same time keep safety requirements. This research aims to predict the proper processing conditions for developing ultra-high-strength Q&P steel with a novel chemical composition of 0.37 C-3.65 Mn- 0.65Si- 0.87 Al- 1.5 Ni- 0.05P, wt. %. To design and optimize proper heat treatment conditions, the phase diagram, CCT curve, and critical temperatures of these alloys were first implemented using THERMO-CALC and JMATE PRO software and Gleeble 3500 machine. The heat treatment process included full austenitization, then quenching at 120°C followed by partitioning at 450°C for different times. The tensile properties, microstructure, and retained austenite volume fraction of heat-treated steel was studied at room temperature by tensile testing machine, optical microscope, and XRD. The finding summarized that partitioning of this steel for 100 s during processing had developed Q&P steel with ultra-high-strength of 1104 MPa with maximum total elongation and strength elongation balance 8.1 % and 8932 MPa %, respectively. The optical micrograph showed that heat-treated specimens at different partitioning times have had a microstructure of tempered martensite, carbide free bainite, and retained austenite. Besides, the retained austenite volume fraction has decreased with increasing partitioning time, which may be due to carbide precipitation during partitioning.

scholarly journals EFFECTS OF COOLING RATE ON THE VOLUME FRACTION OF RETAINED AUSTENITE IN FORGINGS FROM HIGH-STRENGTH Mn-Si STEELS

2019 ◽  
Vol 25 (2) ◽  
pp. 93 ◽  
Author(s):  
Dagmar Bublíková ◽  
Hana Jirková ◽  
Kateřina Rubešová ◽  
Michal Peković ◽  
Julie Volkmannová ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Retained Austenite ◽  
Physical Simulation ◽  
Volume Fraction ◽  
High Strength ◽  
Hot Water ◽  
Quenching Temperature ◽  
Soaking Temperature

<p class="AMSmaintext"><span lang="EN-GB">Various ways are sought today to increase mechanical properties of steels while maintaining their good strength and ductility. Besides effective alloying strategies, one method involves preserving a certain amount of retained austenite in a martensitic matrix. The steel which was chosen as an experimental material for this investigation contained 2.5% manganese, 2.09% silicon and 1.34% chromium, with additions of nickel and molybdenum. An actual closed-die forged part was made of this steel. This forged part was fitted with thermocouples attached to its surface and placed in its interior and then treated using the Q&amp;P process. Q&amp;P process is characterized by rapid cooling from a soaking temperature to a quenching temperature, which is between the Ms and the Mf, and subsequent reheating to and holding at a partitioning temperature where retained austenite becomes stable. The quenchant was hot water. Cooling took place in a furnace. Heat treatment profiles were constructed from the thermocouple data and the process was then replicated in a thermomechanical simulator. The specimens obtained in this manner were examined using metallographic techniques. The effects of cooling rate on mechanical properties and the amount of retained austenite were assessed. The resultant ultimate strength was around 2100 MPa. Elongation and the amount of retained austenite were 15% and 17%, respectively. Microstructures and mechanical properties of the specimens were then compared to the real-world forged part in order to establish whether physical simulation could be employed for laboratory-based optimization of heat treatment of forgings.</span></p>

scholarly journals Designing Q&P Process for Experimental Steel with 0.47 % Carbon Content

2014 ◽  
Vol 887-888 ◽  
pp. 257-261 ◽  
Author(s):  
Vít Pileček ◽  
Hana Jirková ◽  
Bohuslav Mašek
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Heat Treating ◽  
Processing Parameters ◽  
Austenitizing Temperature ◽  
The Third ◽  
Martensitic Microstructure ◽  
The Impact ◽  
Correct Processing

The Q&P process (Quenching and Partitioning) is a heat treating method for high-strength low-alloyed steels. It delivers the desired combinations of high strength and adequate ductility. These properties are achieved thanks to the unique martensitic microstructure with a certain volume fraction of stable retained austenite. Retained austenite imparts plasticity to the otherwise brittle martensitic structure. Optimum mechanical properties are achieved by using correct processing parameters and chemistry of the material. The experimental material was a steel with 0.47 % carbon alloyed with silicon, manganese and chromium. The purpose of the effort was to optimise the heat treating parameters in order to obtain a strength level above 2000 MPa and an elongation of no less than 10%. In the first step, the appropriate austenitizing temperature was identified. In the second, effects of various quenching temperatures and cooling rates on the microstructure evolution were explored. In the third, the impact of raising the partitioning temperature on stabilization of retained austenite was examined. Adjustment of the parameters led to a strength of more than 2300 MPa and an elongation of 8 %.

Heat Treatment of the New High-Strength High-Ductility Al-Mg-Si-Mn Alloys with Sc, Zr and Cr Additions

2020 ◽  
Author(s):  
O. Trudonoshyn ◽  
O. Prach ◽  
P. Randelzhofer ◽  
K. Durst ◽  
С. Körner
Keyword(s):  
Heat Treatment ◽  
High Strength ◽  
High Ductility

scholarly journals Carbon Redistribution and Microstructural Evolution Study during Two-Stage Quenching and Partitioning Process of High-Strength Steels by Modeling

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2302 ◽  
Author(s):  
Yilin Wang ◽  
Huicheng Geng ◽  
Bin Zhu ◽  
Zijian Wang ◽  
Yisheng Zhang
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength Steels ◽  
High Strength ◽  
Simulation Method ◽  
Low Carbon ◽  
Two Stage ◽  
Quenching And Partitioning ◽  
Carbon Redistribution ◽  
Carbon Martensite

The application of the quenching and partitioning (Q-P) process on advanced high-strength steels improves part ductility significantly with little decrease in strength. Moreover, the mechanical properties of high-strength steels can be further enhanced by the stepping-quenching-partitioning (S-Q-P) process. In this study, a two-stage quenching and partitioning (two-stage Q-P) process originating from the S-Q-P process of an advanced high-strength steel 30CrMnSi2Nb was analyzed by the simulation method, which consisted of two quenching processes and two partitioning processes. The carbon redistribution, interface migration, and phase transition during the two-stage Q-P process were investigated with different temperatures and partitioning times. The final microstructure of the material formed after the two-stage Q-P process was studied, as well as the volume fraction of the retained austenite. The simulation results indicate that a special microstructure can be obtained by appropriate parameters of the two-stage Q-P process. A mixed microstructure, characterized by alternating distribution of low carbon martensite laths, small-sized low-carbon martensite plates, retained austenite and high-carbon martensite plates, can be obtained. In addition, a peak value of the volume fraction of the stable retained austenite after the final quenching is obtained with proper partitioning time.

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