The Effect of Si on the Toughness of High Strength Mn-Si-Cr Series Bainitic Steels

2005 ◽  
Vol 475-479 ◽  
pp. 213-216 ◽  
Author(s):  
Zhun Li Tan ◽  
Bing Zhe Bai ◽  
Hong Sheng Fang ◽  
Fu Bao Yang
Keyword(s):  
Silicon Content ◽  
Retained Austenite ◽  
High Strength ◽  
Onset Temperature ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
Minimum Value ◽  
Bainitic Steels ◽  
The Stability ◽  
The Relationship

The relationship between the toughness and silicon content of high strength Mn-Si-Cr series bainitic steels has been investigated. The results show that with increasing in silicon content, the onset temperature of the steel’s tempered martensite embrittlement (TME) rises; moreover, the minimum value of tested toughness decreases and the tempering temperature corresponding to the minimum value of toughness increases. This phenomenon results from the effect of silicon on the stability of filmy carbon-enriched retained austenite in carbide-free bainite/martensite (CFB/M) microstructure.

scholarly journals Substructure Development and Damage Initiation in a Carbide-Free Bainitic Steel upon Tensile Test

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1261
Author(s):  
Mari Carmen Taboada ◽  
Amaia Iza-Mendia ◽  
Isabel Gutiérrez ◽  
Denis Jorge-Badiola
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Formation Mechanisms ◽  
Tempered Martensite ◽  
Damage Initiation ◽  
Advanced High Strength Steels ◽  
Significant Strength ◽  
The Stability

Carbide-free bainitic (CFB) steels belong to the family of advanced high strength steels (AHSS) that are struggling to become part of the third-generation steels to be marketed for the automotive industry. The combined effects of the bainitic matrix and the retained austenite confers a significant strength with a remarkable ductility to these steels. However, CFB steels usually show much more complex microstructures that also contain MA (Martensite–Austenite) phase and auto-tempered martensite (ATM). These phases may compromise the ductility of CFB steels. The present work analyzes the substructure evolution during tensile tests in the necking zone, and deepens into the void and crack formation mechanisms and their relationship with the local microstructure. The combination of FEG-SEM imaging, EBSD, and X-ray diffraction has been necessary to characterize the substructure development and damage initiation. The bainite matrix has shown great ductility through the generation of high angle grain boundaries and/or large orientation gradients around voids, which are usually found close to the bainite and MA/auto-tempered martensite interfaces or fragmenting the MA phase. Special attention has been paid to the stability of the retained austenite (RA) during the test, which may eventually be transformed into martensite (Transformation Induced Plasticity, or TRIP effect).

Influence of the Processing Variables on the Microstructure Evolution of a Bainitic Carbide-Free Steel

2016 ◽  
Vol 879 ◽  
pp. 867-872 ◽  
Author(s):  
M.C. Taboada ◽  
I. Gutiérrez ◽  
D. Jorge-Badiola ◽  
S.M.C. van Bohemen ◽  
F. Hisker ◽  
...  
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
High Volume ◽  
X Ray Diffraction ◽  
Tempered Martensite ◽  
Trip Steels ◽  
Volume Fractions ◽  
Advanced High Strength Steels ◽  
Processing Variables

New trends focused on achieving higher performance steels has led to a so-called 3rd Generation Advanced High Strength Steels (AHSS), in which the typical polygonal ferrite found in TRIP steels as a matrix phase is replaced by harder phases as Carbide-Free Bainite (CFB) and/or (tempered) martensite. Besides, large volume fractions of retained austenite (R.A.) with adequate stability are aimed for to improve the formability of the steels. Si containing steels are regarded as the most suitable to retard cementite formation and consequently reach high volume fractions of RA. In this work, CFB annealing schedules were applied to dilatometer samples of Fe-0.22C-2.0Mn-1.3Si. The overaging temperature TB was varied between 390 oC and 480 oC, and other processing variables investigated were the austenitizing temperature Taus, and the overaging holding time tB. The annealed samples analyzed with LOM, FEG-SEM, EBSD and X-ray diffraction techniques show that markedly different complex microstructures made up of bainite, ferrite, MA phase and retained austenite (R.A) are accomplished depending on the specific thermal cycle. These results are described in detail and discussed in relation to the dilatometry measurements.

scholarly journals The Mechanism of High-Strength Quenching-Partitioning-Tempering Martensitic Steel at Elevated Temperatures

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 94 ◽  
Author(s):  
Ke Zhang ◽  
Maoyuan Zhu ◽  
Bitong Lan ◽  
Ping Liu ◽  
Wei Li ◽  
...  
Keyword(s):  
Retained Austenite ◽  
Elevated Temperatures ◽  
Martensitic Steel ◽  
Lath Martensite ◽  
Temperature Stability ◽  
High Strength ◽  
High Temperature Stability ◽  
High Deformation ◽  
Heat Treated ◽  
The Relationship

High-strength medium-carbon martensitic steel was heat treated through a quenching-partitioning-tempering (Q-P-T) treatment. Both the mechanism for improved ductility and the high temperature stability of austenite were investigated. The Q-P-T martensitic steel showed good products of strength and elongation (PSE) at various deformation temperatures ranging within 25–350 °C. The optimum PSE value (>57,738 MPa%) was achieved at 200 °C. The microstructure of the Q-P-T steel is constituted of laths martensite with dislocations, retained austenite located within lath martensite and small niobium carbides (NbC), and/or transitional ε-carbides that precipitated in the lath martensite. The good ductility can be mainly attributed to the laminar-like austenite that remained within the lath-martensite. The austenite can effectively enhance ductility through the effect of dislocation absorption by the retained austenite and through transformation-induced plasticity. The relationship between the microstructures and mechanical properties was investigated at high deformation temperatures.

Hydrogen Assisted Tempered Martensite Embrittlement of Ultra High Strength Martensitic Steel

2016 ◽  
Vol 880 ◽  
pp. 29-32
Author(s):  
T.C. Chen ◽  
Wen Hao Chien ◽  
Yuan Tsung Wang ◽  
Ching Yuan Huang ◽  
Hung Wei Yen ◽  
...  
Keyword(s):  
Hydrogen Charge ◽  
High Strength Steels ◽  
High Strength ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
High Strength Level ◽  
Tempering Treatment ◽  
Ultra High Strength Steels ◽  
Mechanical Strengths ◽  
Tempering Process

The demand for new materials that provide excellent structural performance while reducing weight and being cost-effectively manufactured is increasing. For applications with high strength requirements, ultra-high strength steels (UHSS) have been widely used. However, with such a high strength level, UHSS are very sensitive to the hydrogen that could be ease by the tempering process. In this research, the correlation of hydrogen and tempering process on commercial UHSS 15B30 has been studied. Results show that the tensile strength (TS) of as-quenched 15B30 is about 1900MPa. After tempering treatment of the quenched 15B30, the TS decreases from 1600MPa to 1200MPa with tempering temperature increased from 200°C to 400°C. The 15B30 specimens, being subjected to hydrogen charge, exhibit the dramatic reduction of mechanical strengths.

Investigation of Microstructure and Mechanical Properties of Ultra High Strength Bainitic Steel

2013 ◽  
Vol 313-314 ◽  
pp. 77-81
Author(s):  
M.H. Sheikh Ansari ◽  
M. Aghaie-Khafri
Keyword(s):  
Mechanical Properties ◽  
Alloy Steel ◽  
High Strength ◽  
Lower Bainite ◽  
Good Combination ◽  
Bainitic Steel ◽  
Low Alloy Steel ◽  
Tempered Martensite ◽  
Medium Carbon ◽  
Bainitic Steels

In this study, medium carbon low alloy steel was used to obtain bainitic structures. The lower bainite and tempered martensite-lower bainite structures were achieved by isothermal austempering and up quenching treatment, respectively. Based on the results obtained these structures showed a very good combination of strength and toughness. Furthermore, it has been shown that austenitization time and temperature, as well as austempering time and temperature play a major role in achieving ultra-high strength bainitic steels.

Microstructural Observations of the Direct Quenched Offshore Steel

2017 ◽  
Vol 732 ◽  
pp. 55-58
Author(s):  
Chieh Yu ◽  
Ta Chien Cheng ◽  
Ren Kae Shiue ◽  
Tze Ching Yang ◽  
Ching Yuan Huang
Keyword(s):  
Retained Austenite ◽  
Vickers Microhardness ◽  
Iron Carbide ◽  
High Strength ◽  
Heat Treating ◽  
Carbide Formation ◽  
Tempered Martensite ◽  
Depth Profiles ◽  
Quenched Steel ◽  
Direct Quench

The purpose of this investigation is focused on the direct quench and temper mechanisms of the high strength offshore steel. Microstructural analyses of martensite and retained austenite in the direct quenched steel, simulations of martensitic transformation temperatures, Ms/Mf, and morphologies of bainite and ferrite have been evaluated in the experiment. Additionally, carbide formation after temped at various temperatures and microhardness depth profiles after heat treating are also included in the study. The direct quenched steel is primarily comprised of martensite, bainite and a few retained austenite with Vickers microhardness above 300. Tempered martensite, iron carbide and bainite are widely observed from all tempered specimens.

scholarly journals The Role of Retained Austenite in Tempered Martensite Embrittlement of 4340 and 300-M Steels Investigated through Rapid Tempering

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1349
Author(s):  
Virginia K. Euser ◽  
Don L. Williamson ◽  
Kip O. Findley ◽  
Amy J. Clarke ◽  
John G. Speer
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Austenite Decomposition ◽  
Tempered Martensite ◽  
Mechanical Transformation ◽  
Fresh Martensite ◽  
Rapid Tempering

Tempered martensite embrittlement (TME) is investigated in two medium carbon, high strength steels, 4340 (low silicon) and 300-M (high silicon), via rapid (1, 10, or 100 s) and conventional (3600 s) tempering. Rapid tempering of 4340 diminishes the depth of the TME toughness trough, where improvements in impact toughness correspond to the suppression of retained austenite decomposition. In 300-M, retained austenite decomposition is suppressed to an even greater extent by rapid tempering. While toughness improves overall after rapid tempering, TME severity remains consistent in 300-M across the tempering conditions examined. Through interrupted tensile tests, it was found that the 300-M conditions that exhibit TME are associated with mechanically unstable retained austenite. Unstable retained austenite is shown to mechanically transform early in the deformation process, presumably resulting in fresh martensite adjacent to interlath cementite that ultimately contributes to TME. The present results emphasize the role of both the thermal decomposition and mechanical transformation of retained austenite in the manifestation of TME.

The development of a588 modified laterite steel using thermomechanical and low-temperature tempering process for weather resistant steel

Teknik ◽  
2021 ◽  
Vol 42 (2) ◽  
pp. 149-159
Author(s):  
Miftakhur Rohmah ◽  
Dedi Irawan ◽  
Dedi P. Utama ◽  
Toni B. Romijarso
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Cooling Rate ◽  
Nickel Content ◽  
High Strength ◽  
Water Medium ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
Thermomechanical Process ◽  
Tempering Process

Laterite Steel A-588 has the potential to be a high strength low alloy for Corten steel application. Laterite steel A-588 is developed through a thermomechanical process followed by a tempering process to obtain high strength and corrosion resistance. This study aims to determine the correlation between the addition of nickel content, the variation of the cooling rate during heat treatment to the mechanical properties, and the corrosion resistance of A-588 laterite steel. The Cu, Cr, Ni, P, and Si elements significantly impact microstructure transformation. Laterite Steel A-588 with nickel and thermo-mechanical process variation has been focused on in this research. Laterite steel with 0,42%, 1%, 2%, and 3% nickel varied was homogenized, hot rolled, and heat treated with three cooling variations by water, oil, and air. They are processed with 150 C tempering. Low tempering temperature caused fine carbide precipitation and phase transition of martensite to bainite. This resulted in bainite as the final microstructure, lath tempered martensite, carbide, and ferrite. 3% Ni with a fast cooling rate increased the tempered martensite and bainite phase formation. It allowed the strength and hardness to increase relatively, followed by decreased elongation and corrosion resistance caused by the galvanic reaction. Most optimal of mechanical properties determined at a sample with 2% nickel in a water medium (strength 1203 MPa, elongation 10%, hardness 404 BHN, corrosion rate 1,306 mpy).

Observation of Retained Austenite Amount of Repeatedly Induction Heated SUJ2 Bearing Steels

2016 ◽  
Vol 867 ◽  
pp. 55-59
Author(s):  
Isamu Yoshida ◽  
Katsuya Yamamoto ◽  
Kenta Domura ◽  
Koshiro Mizobe ◽  
Katsuyuki Kida
Keyword(s):  
Fatigue Strength ◽  
Induction Heating ◽  
Retained Austenite ◽  
High Strength ◽  
Bearing Steel ◽  
Rolling Contact ◽  
High Carbon ◽  
Bearing Steels ◽  
High Fatigue ◽  
The Relationship

Martensitic high-carbon, high-strength bearing steel is used for rolling contact applications when high wear and fatigue resistance are required. Due to its high fatigue strength, SUJ2 is not used for only bearings but for shafts. The objective of this work is a clarification of the relationship between quenching times and retained austenite amount of SUJ2 steel. It was found that repeatedly induction heating increased the retained austenite amount, but did not change the Vickers hardness.

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