Influence of Manufacturing Processes and Microstructures on the Performance and Manufacturability of Advanced High Strength Steels

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
K. S. Choi ◽  
W. N. Liu ◽  
X. Sun ◽  
M. A. Khaleel ◽  
J. R. Fekete
Keyword(s):  
Material Properties ◽  
Thermomechanical Processing ◽  
High Strength Steels ◽  
High Strength ◽  
Processing Parameters ◽  
Martensite Phase ◽  
Basic Material ◽  
Manufacturing Processes ◽  
Localized Deformation ◽  
Advanced High Strength Steels

Advanced high strength steels (AHSS) are performance-based steel grades and their global material properties can be achieved with various steel chemistries and manufacturing processes, leading to various microstructures. In this paper, we investigate the influence of the manufacturing process and the resulting microstructure difference on the overall mechanical properties, as well as the local formability behaviors of AHSS. For this purpose, we first examined the basic material properties and the transformation kinetics of three different commercial transformation induced plasticity (TRIP) 800 steels under different testing temperatures. The experimental results show that the mechanical and microstructural properties of the TRIP 800 steels significantly depend on the thermomechanical processing parameters employed in making these steels. Next, we examined the local formability of two commercial dual phase (DP) 980 steels which exhibit noticeably different formability during the stamping process. Microstructure-based finite element analyses are carried out to simulate the localized deformation process with the two DP 980 microstructures, and the results suggest that the possible reason for the difference in formability lies in the morphology of the hard martensite phase in the DP microstructure. The results of this study suggest that a set of updated material acceptance and screening criteria is needed to better quantify and ensure the manufacturability of AHSS.

Quenching and Partitioning of Ni-Added High Strength Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4476-4481 ◽  
Author(s):  
F.C. Rizzo ◽  
A.R. Martins ◽  
John G. Speer ◽  
David K. Matlock ◽  
A. Clarke ◽  
...  
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
Processing Parameters ◽  
Carbide Formation ◽  
X Ray Diffraction ◽  
Quenching And Partitioning ◽  
Steel Microstructure ◽  
Advanced High Strength Steels ◽  
Treatment Procedures

High strength steels containing significant fractions of retained austenite have been developed in recent years, and are the subject of growing commercial interest when associated with the TRIP phenomenon during deformation. A new process concept “quenching and partitioning” (Q&P) has been proposed by CSM/USA, and the results show the potential to create a new kind of steel microstructure with controlled amounts of retained austenite, enriched by carbon partitioning. Four steels containing C, Si, Mn, Ni, Cr and Mo, were designed with variation in the Ni and C content, aiming to decrease Bs temperature and to suppress carbide formation during the partitioning treatment. Several heat-treatment procedures were performed in specimens previously machined for tensile testing, while x-ray diffraction was used to determine the fraction of retained austenite. The tensile test results showed that except for the high C high Ni alloy, most of the processing conditions resulted in strengths superior to those of advanced high strength steels (AHSS), although it is importantly recognized that higher alloy additions were used in this study, in comparison with conventional AHSS grades.. A variety of strength and ductility combinations were observed, confirming the potential of the Q&P process and illustrating the strong influence of the final microstructure on the mechanical properties. Experimental results for samples partitioned at 400 °C indicate that higher ultimate tensile strength is associated with higher fraction of retained austenite for multiple heat treatments of each alloy investigated. The amount of retained austenite obtained was generally lower than that predicted by the model. Further studies are in progress to understand the influence of alloying and processing parameters (time/temperature) on the partitioning of carbon and precipitation of transition carbides.

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 Effect of Quenching and Partitioning Heat Treatment on the Fatigue Behavior of 42SiCr Steel

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1699
Author(s):  
Marco Thomä ◽  
Guntram Wagner
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Heat Treatment ◽  
Material Properties ◽  
Retained Austenite ◽  
Fatigue Behavior ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
Scanning Electron

The manufacturing of advanced high-strength steels with enhanced ductility is a persistent aim of research. The ability of a material to absorb high loads while showing a high deformation behavior is a major task for many industrial fields like the mobility sector. Therefore, the material properties of advanced high-strength steels are one of the most important impact factors on the resulting cyclic fatigue behavior. To adjust advanced material properties, resulting in high tensile strengths as well as an enhanced ductility, the heat treatment process of quenching and partitioning (QP) was developed. The quenching takes place in a field between martensite start and martensite finish temperature and the subsequent partitioning is executed at slightly elevated temperatures. Regarding the sparsely investigated field of fatigue research on quenched and partitioned steels, the present work investigates the influence of a QP heat treatment on the resulting microstructure by light and scanning electron microscopy as well as on the mechanical properties such as tensile strength and resistance against fatigue regarding two different heat treatment conditions (QP1, QP2) in comparison to the cold-rolled base material of 42SiCr steel. Therefore, the microscopic analysis proved the presence of a characteristic quenched and partitioned microstructure consisting of a martensitic matrix and partial areas of retained austenite, whereas carbides were also present. Differences in the amount of retained austenite could be observed by using X-ray diffraction (XRD) for the different QP routes, which influence the mechanical properties resulting in higher tensile strength of about 2000 MPa for QP1 compared to about 1600 MPa for QP2. Furthermore, the transition for the fatigue limit was approximated by using stepwise load increase tests (LIT) and afterwards verified by constant amplitude tests (CAT) in accordance with the staircase method, whereas the QP 1 condition reached the highest fatigue strength of 900 MPa. Subsequent light and scanning electron microscopy of selected fractured surfaces and runouts showed a different behavior regarding the size of the fatigue fracture area and also differences in the microstructure of these runouts.

Thermomechanical Processing of Medium Manganese Steels

2016 ◽  
Vol 879 ◽  
pp. 90-94 ◽  
Author(s):  
Atsushi Ito ◽  
Akinobu Shibata ◽  
Nobuhiro Tsuji
Keyword(s):  
Dual Phase Steel ◽  
Thermomechanical Processing ◽  
High Strength Steels ◽  
High Strength ◽  
Heat Treatments ◽  
Dual Phase ◽  
Advanced High Strength Steels ◽  
Ferrite Transformation ◽  
Thermomechanical Processes ◽  
Manganese Steels

As third generation advanced high strength steels (AHSS) managing both high strength and good ductility/formability, medium manganese steels containing 3-7 wt% Mn have attracted attentions recently. However, the fundamental microstructure evolution during thermomechanical processing and heat treatments in medium-Mn steels is still unclear. In the present study, changes in microstructure and mechanical properties during various heat treatments and thermomechanical processes of 4Mn-0.1%C steel were studied. It was clarified from dilatometric measurements that ferrite transformation in the 4Mn-0.1C steel was quite slow, so that fully martensitic structures were obtained in many cases after cooling from austenite. On the other hand, hot-deformation of austenite greatly accelerated ferrite transformation, and dual phase microstrcutures composed of ferrite and martensite could be obtained. The dual phase steel showed good combinations of high strength and adequate tensile ductility.

Aspects of Thermomechanical Processing of 3rd Generation Advanced High Strength Steels

2014 ◽  
Vol 783-786 ◽  
pp. 3-8 ◽  
Author(s):  
Evgueni I. Poliak ◽  
Debanshu Bhattacharya
Keyword(s):  
Thermomechanical Processing ◽  
High Strength Steels ◽  
High Strength ◽  
Continuous Annealing ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Advanced High Strength Steels ◽  
Hot Strip ◽  
High Elongation

The production of advanced high strength steels (AHSS) has been rapidly expanding in recent years as these steels allow for considerable reduction in weight and enhancement of car safety due to the unique combination of high strength, toughness and formability. Driven by growing demand for sheet AHSS products from carmakers, steel producers are currently developing AHSS of the so called 3rdGeneration to further facilitate weight reduction of critical safety parts while ensuring crash worthiness and high absorbed energy. Such steels not only possess tensile strength above 1000 MPa but also are being designed for exceedingly high formability: high elongation, bendability, hole expansion and strain hardening. These enhanced properties are to be achieved in final operations of continuous annealing and/or galvanizing. However, due to complicated alloy designs of 3G AHSS the role of each manufacturing stage becomes progressively significant due to its impact on the final microstructure. Therefore, hot strip rolling gains increasing importance as one of the most critical stages responsible for producing the microstructure optimal for achieving the final properties of the sheet products without impairing downstream operations. In other words, hot rolling of AHSS has to be viewed as thermomechanical processing.

Effect of Cr and Thermomechanical Processing on the Microstructure and Mechanical Properties of Advanced High-Strength Steel

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Abdel-Wahab El-Morsy ◽  
Ahmed I. Z. Farahat
Keyword(s):  
Thermomechanical Processing ◽  
High Strength Steels ◽  
High Strength ◽  
Air Cooling ◽  
Third Generation ◽  
Advanced High Strength Steel ◽  
Thermomechanical Process ◽  
Advanced High Strength Steels ◽  
Treatment Processes ◽  
Cooling Air

In this work, two advanced high-strength steels (AHSS) have been developed by designing alloy systems with suitable alloying elements, Mn, Si, Al, and Cr, and postforming heat treatment processes. Thermomechanical process of ∼90% forging reductions has been applied on the designed alloys at a temperature of 1100 °C, followed by austenitizing above AC3. Four cooling rates, air-cooling, air-cooling with tempering, oil quenching with tempering, and water quenching with tempering, have been applied on the forged samples. The results revealed that the estimated tensile properties of the ferrite/bainite microstructures of alloy A, without Cr, is situated between the bands of the first and the current third generation AHSS, whereas the estimated properties corresponding to the ferrite/fine bainite with 8% retained austenite of alloy B, with Cr, is overlapped with the properties exhibited by the current third generation of AHSSs. The thermomechanical process conducted on the alloy containing Cr has developed steel with tensile strength up to 1790 MPa.

scholarly journals Development of Advanced High Strength Steels Using Hydrogen Quench Continuous Annealing Technology

2019 ◽  
Author(s):  
Francys Barrado ◽  
Tihe Zhou ◽  
Chad Cathcart ◽  
Peter Badgley ◽  
Sarah Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Strength Steels ◽  
High Strength ◽  
Product Yield ◽  
Processing Parameters ◽  
Continuous Annealing ◽  
Advanced High Strength Steels ◽  
Unique Customer ◽  
High Product Yield ◽  
Multi Phase

By using hydrogen quench continuous annealing technology, Stelco Inc. has developed a suite of Advanced High Strength Steel (AHSS) grades with tensile strength greater than 1000MPa to meet standard automotive specifications and for unique customer requirements. These grades were optimized by correlating chemical composition and processing parameters with microstructures and mechanical properties. Dual-Phase 980 (Stelco trademarked STELMAXTM 980DP), Multi-Phase 1180 (STELMAXTM 1180MP), Martensitic Steel 1300 (STELMAXTM 1300M) and 1500 (STELMAXTM 1500M) products met strength and formability requirements with excellent flatness and surface quality. Hydrogen quench continuous annealing technology not only ensures all developed AHSS grades have consistent mechanical properties across the entire strip length (from strip head to tail) and width (from edge to edge), but also produces high product yield compared with other continuous annealing processes.

scholarly journals Influence of thermomechanical processing parameters on critical temperatures to develop an Advanced High-Strength Steel microstructure

2021 ◽  
Vol 56 (33) ◽  
pp. 18710-18721
Author(s):  
L. F. Romano-Acosta ◽  
O. García-Rincon ◽  
J. P. Pedraza ◽  
E. J. Palmiere
Keyword(s):  
Mechanical Properties ◽  
Thermomechanical Processing ◽  
High Strength Steels ◽  
High Strength ◽  
Transformation Products ◽  
Processing Parameters ◽  
Deformation Bands ◽  
Critical Temperatures ◽  
Transformation Temperatures ◽  
Steel Microstructure

AbstractA good selection of the thermomechanical processing parameters will optimize the function of alloying elements to get the most of mechanical properties in Advanced High-Strength Steels for automotive components, where high resistance is required for passenger safety. As such, critical processing temperatures must be defined taking into account alloy composition, in order for effective thermomechanical processing schedules to be designed. These critical temperatures mainly include the recrystallization stop temperature (T5%) and the transformation temperatures (Ar1, Ar3, Bs, etc.). These critical processing temperatures were characterized using different thermomechanical conditions. T5% was determined through the softening evaluation on double hit tests and the observation of prior austenite grain boundaries on the microstructure. Phase transformation temperatures were measured by dilatometry experiments at different cooling rates. The results indicate that the strain per pass and the interpass time will influence the most on the determination of T5%. The range of temperatures between the recrystallized and non-recrystallized regions can be as narrow as 30 °C at a higher amount of strain. The proposed controlled thermomechanical processing schedule involves getting a severely deformed austenite with a high dislocation density and deformation bands to increase the nucleation sites to start the transformation products. This microstructure along with a proper cooling strategy will lead to an enhancement in the final mechanical properties of a particular steel composition.

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