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.

Transformation Induced Plasticity (TRIP) Effect Used in Forming of Carbon CMnSi Steel

2005 ◽  
Vol 500-501 ◽  
pp. 461-470 ◽  
Author(s):  
Jiří Kliber ◽  
Bohuslav Mašek ◽  
Ondrej Zacek ◽  
H. Staňková
Keyword(s):  
Continuous Casting ◽  
Hot Rolling ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Thermomechanical Processing ◽  
High Strength ◽  
Ferrite Matrix ◽  
Transformation Induced Plasticity ◽  
Trip Steels ◽  
Forming Temperature

Transformation induced plasticity (TRIP) steel combines high strength and high ductility that makes it particularly suitable for forming. Martensite within a ferrite matrix is usually obtained either by continuous casting of slabs followed by hot rolling (which is the fastest method, hence the most economical one, producing, however, relatively thick products) or by the continuous casting of slabs followed by hot rolling, cold rolling and annealing (the method used for thin products). High cooling rates, low coiling temperatures and low reduction during hot deformation were generally found to suppress the formation of polygonal ferrite and promote the presence of retained austenite. This paper focuses on development and modifications of two CMnSi-based TRIP steels with 0,23 % C;1,4 % Mn; 1,9 % Si; ( 0,08 % Nb) by means of laboratory thermomechanical processing. Description of experimental devices for the analysis of transformation plasticity under tensioncompression loading is given. Experiments were carried out on the simulator for thermaldeformation cycles SMITWELD and TANDEM was used for thermomechanical processing on the laboratory rolling mill. The maximum volume fraction of retained austenite and the resulting optimum combination of tensile strength and ductility were achieved in testing heats. Special attention was paid to volume fraction changes of single phases and to changes in morphology of phases. The results suggest that rather short isothermal bainite transformation times are sufficient to obtain TRIP microstructure. The influence of parameters of thermomechanical processing such as the amount of strain, forming temperature and austenitization time and temperature on microstructures of TRIP steels were evaluated.

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.

scholarly journals STUDY ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF 42CrMo4/NANOS-BA® HIGH-STRENGTH CLAD PLATES AFTER THE PROCESS OF HOT ROLLING AND TWO-STAGE HEAT TREATMENT WITH ISOTHERMAL TRANSFORMATION

2021 ◽  
Vol 73 (1) ◽  
pp. 22-31
Author(s):  
Bartłomiej WALNIK ◽  
Dariusz Woźniak ◽  
Aleksandra NIESZPOREK ◽  
Mariusz ADAMCZYK
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Hot Rolling ◽  
High Strength ◽  
Isothermal Transformation ◽  
Two Stage ◽  
Physical Experiments ◽  
Microstructure Examination ◽  
Steel Grades ◽  
Stage Heat Treatment

The aim of the study was to develop a technology for welding non-weldable 42CrMo4 and NANOS-BA® steel grades in the process of hot rolling and two-stage heat treatment. As a result of physical experiments carried out in a line for semi-industrial simulation of the production of metals and their alloys (LPS) and additional heat treatment, a durable combination of 42CrMo4 and NANOS-BA® steels with high mechanical properties was obtained, including: Rp0.2 = 1036 MPa, Rm = 1504 MPa and A = 10.9%, without microscopically visible cracks and other discontinuities in the joined surface. The quality of the 42CrMo4/NANOS-BA® clad plates produced in this way was assessed on the basis of microstructure examination as well as bending, shear and tensile strength tests.

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 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.

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%.

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