Comparison of the Hardness-Toughness Relationship of Medium-Mn Steels after Q&T and Q&P Treatments*

2021 ◽  
Vol 76 (6) ◽  
pp. 445-457
Author(s):  
R. Schneider ◽  
S. Kaar ◽  
S. Schneider ◽  
D. Krizan ◽  
C. Sommitsch
Keyword(s):  
Tensile Testing ◽  
Retained Austenite ◽  
Room Temperature ◽  
Carbon Diffusion ◽  
Temperature Quenching ◽  
Optimum Parameters ◽  
The Stability ◽  
Relationship Of ◽  
Quenching And Tempering ◽  
Strength And Ductility

Abstract In contrast to quenching and tempering (Q&T), with quenching to room temperature, quenching and partitioning (Q&P) usually applies quenching to a temperature between Ms and room temperature. To stabilize a sufficient amount of retained austenite (RA), carbon diffusion from martensite into austenite and a prevention of cementite formation takes place during the successive partitioning step. Larger amount of RA, and its transformation into martensite during plastic deformation, provides Q&P treated steels with an enhanced combination of strength and ductility. In this investigation, the effect of different Q&T and Q&P treatments on the hardness-toughness relationship was determined. These results are compared with the RA contents and mechanical properties provided by tensile testing. The obtained results clearly demonstrate that the optimum parameters for strength and ductility do not match with the best combinations of hardness and toughness. Furthermore, the stability of the RA plays an important role in the understanding of toughness properties of the investigated Q&P steels.

scholarly journals EFFECTS OF Q&P PROCESS PARAMETERS ON PROPERTIES OF 42SiCr STEEL

2018 ◽  
Vol 24 (2) ◽  
pp. 126
Author(s):  
Kateřina Rubešová ◽  
Ivan Vorel ◽  
Hana Jirková ◽  
Štěpán Jeníček
Keyword(s):  
Heat Treatment ◽  
Ultimate Strength ◽  
Retained Austenite ◽  
High Strength ◽  
Carbon Diffusion ◽  
Salt Bath ◽  
Treatment Techniques ◽  
Microstructure Effects ◽  
The Impact ◽  
Quenching And Tempering

<p class="AMSmaintext"><span lang="EN-GB">The requirement for high strength and good ductility poses problems in today’s advanced steels. This problem can be tackled by appropriate heat treatment which produces suitable microstructures. By this means, ultimate strengths of about 2000 MPa and elongations of more than 10% can be obtained. One of such advanced heat treatment techniques is the Q&amp;P (Quenching and Partitioning) process. It produces a mixture of martensite and retained austenite, where the latter is an important agent in raising the ductility of steel. </span></p><p class="AMSmaintext"><span lang="EN-GB">In this experiment, a low-alloy steel with 0.41% carbon and manganese, silicon and chromium was used. An air furnace and a salt bath were employed for heat treatment and quenching, respectively. In order to obtain the best ultimate strength and elongation levels, partitioning temperatures of 250°C and 300°C were applied. Partitioning involves carbon diffusion from super-saturated martensite into retained austenite, and tempering of hardening microstructure. Effects of the quenching temperatures of 200°C and 150°C were studied as well. To map the impact of the Q&amp;P process on mechanical properties, an additional schedule with conventional quenching and tempering was carried out. Upon optimization of the parameters, the process produced martensite with a small amount of bainite and retained austenite. The ultimate strength was between 1930 and 2080 MPa and the elongation levels were from 9 to 16%.</span></p><p class="AMSmaintext"><span lang="EN-GB"> </span></p>

Temperature Development during Step-Wise Tensile Tests on a TRIP Steel

2010 ◽  
Vol 638-642 ◽  
pp. 3579-3584
Author(s):  
Lie Zhao ◽  
Corinna Thomser ◽  
Kirsten Schneider ◽  
Wolfgang Bleck ◽  
Jilt Sietsma
Keyword(s):  
Trip Steel ◽  
Retained Austenite ◽  
Room Temperature ◽  
Longitudinal Direction ◽  
Tensile Tests ◽  
Transformation Induced Plasticity ◽  
Trip Steels ◽  
Loading Process ◽  
Temperature Development ◽  
The Stability

Temperature development during plastic deformation affects the stability of retained austenite and thus the mechanical properties in transformation-induced plasticity (TRIP) steels. In this work, we used a thermo-camera to monitor the temperature development during a step-wise tensile test of an Al-containing multiphase TRIP steel. The tensile tests were performed by loading the specimen at six straining rates ranging from 5 to 30 s-1 to a stress of 700 MPa and then holding for 15 min, followed by further loading at 50 s-1 until fracture. It is found that temperature increases about 13 – 18 °C during the first loading process and drops back to room temperature with a time-constant of around 2 min. The increment of temperature increases with increasing straining rate. The temperature increases around 30 °C during the second loading process. The distribution of temperature over the specimen surface is found to be rather homogeneous along the longitudinal direction in most cases, except for the ending points of two loading processes. The measurement of temperature development is found to be consistent with previous numerical simulation on the temperature development under constant stress in TRIP steels.

Effect of Partitioning Temperature on Work Hardening Behavior of Q&P Steels

2011 ◽  
Vol 299-300 ◽  
pp. 403-407 ◽  
Author(s):  
Shuai Zhu ◽  
Yong Lin Kang ◽  
Kang Kang Ren ◽  
Sheng Ci Li
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
Uniform Elongation ◽  
True Strain ◽  
N Value ◽  
The Stability ◽  
Relationship Of ◽  
The Relationship ◽  
Step Quenching ◽  
Quenching And Partitioning Process

Study on the instantaneous n-value of 0.3C-1.5Mn-1.5Si steel subjected to 1-step quenching and partitioning process (Q&P) is presented. The result indicated that the curves of instantaneous n-value vs. true strain could be divided into three stages. First, the instantaneous n-value shows a rapid decrease, then a comparative stable stage was observed due to the TRIP phenomenon of retained austenite, at last the instantaneous n-value decreases sharply to zero when necking appearance. The relationship of instantaneous n-value and partitioning temperature (PT) was analyzed; n-value decreased along with the rise of PT due to a higher carbon concentration and lower volume fraction of retained austenite was obtained at higher PT which could influence the uniform elongation and the stability of retained austenite.

Ferrite-Martensite Dual-Phase Steel Produced by a Modified Quenching and Partitioning Process

2018 ◽  
Vol 941 ◽  
pp. 251-256
Author(s):  
Hong Shuang Di ◽  
Yong Gang Deng ◽  
Jian Ping Li
Keyword(s):  
Retained Austenite ◽  
Dual Phase Steel ◽  
Uniform Elongation ◽  
Continuous Annealing ◽  
Dual Phase ◽  
Quenching And Partitioning ◽  
The Stability ◽  
Mn Steel ◽  
Quenching And Tempering ◽  
Quenching And Partitioning Process

One industrially C-Mn steel was studied in the present work. The Mn pre-partitioning process during continuous annealing was used. The results showed that the stability of retained austenite is increased because of the Mn pre-partitioning. The amount of retained austenite was about 5%, when increase the partition time to 100s. With the increase of the partition time, the amount of retained austenite increases, the tensile strength decreases, the yield strength and elongation both increase. Compared with quenching and tempering (Q&T) process, the tested steel after pre-partitioning quenching and partitioning (PQ&P) process has higher uniform elongation and the product of strength and elongation (UTS×TEL).

scholarly journals Effect of Pre-Quenching Process on Microstructure and Mechanical Properties in a Nb-Microalloyed Low Carbon Q-P Steel

2015 ◽  
Vol 816 ◽  
pp. 729-735 ◽  
Author(s):  
Jun Zhang ◽  
Hua Ding ◽  
Jing Wei Zhao
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Room Temperature ◽  
Volume Fraction ◽  
Total Elongation ◽  
Trip Effect ◽  
Low Carbon ◽  
Quenching And Partitioning ◽  
The Stability ◽  
Critical Annealing

A refined microstructure consisting of martensite and retained austenite at room temperature has been produced in a Nb-microalloyed low carbon Si-Mn steel by a novel heat-treatment, pre-quenching prior to quenching and partitioning processes (Q&Q-P). The results showed that compared with the conventional quenching and partitioning steel the mechanical properties of steel obtained by the novel treatment have been significantly improved, with a good combination of ultimate tensile strength (1000MPa) and total elongation (above 30%). Meanwhile, the volume fraction of retained austenite has been increased. It was found that the improvement of mechanical properties was mainly attributed to the enhanced TRIP effect due to the relatively high fraction of metastable retained austenite at room temperature. The increased stability of austenite results from the C and Mn partitioning during inter-critical annealing, which increased the chemical stability of austenite. The formation of refined austenite at inter-critical annealing also had a positive effect on the stability of the austenite. As a consequence, the volume fraction of retained austenite at room temperature was significantly increased. Compared with the Q-P steel, the Q&Q-P steel exhibited higher work hardening exponents during the stage of TRIP effect and had the higher ductility.

Effect of Thermomechanical Processing on the Microstructure and Retained Austenite Stability during In Situ Tensile Testing Using Synchrotron X-Ray Diffraction of NbMoAl TRIP Steel

2011 ◽  
Vol 172-174 ◽  
pp. 741-746 ◽  
Author(s):  
Elena V. Pereloma ◽  
Lai Chang Zhang ◽  
Klaus Dieter Liss ◽  
Ulf Garbe ◽  
Jonathan Almer ◽  
...  
Keyword(s):  
Tensile Testing ◽  
Retained Austenite ◽  
Thermomechanical Processing ◽  
Critical Role ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Stability

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.

Relationships between the Microstructure, Hardness and Fracture Toughness of Differently Sub-Zero Treated Tool Steel

2019 ◽  
Vol 395 ◽  
pp. 95-112 ◽  
Author(s):  
Peter Jurči ◽  
Ivo Dlouhý ◽  
Jakub Horník ◽  
Petra Priknerová ◽  
Zdeněk Mrštný
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Population Density ◽  
Tool Steel ◽  
Retained Austenite ◽  
Room Temperature ◽  
Secondary Hardening ◽  
Temperature Quenching ◽  
Treated Steel ◽  
Different Temperatures

A PM made Cr-V ledeburitic tool steel Vanadis 6 has been subjected to conventional austenitizing and quenching, which was followed by sub-zero treatment at different temperatures, and by tempering treatments. The microstructure, hardness and fracture toughness of sub-zero treated steel have been investigated with reference to the same material after conventional room temperature quenching. The main findings are that sub-zero treatments reduce the retained austenite amount, enhance the population density of small carbides, refine the martensite and change the precipitation of carbides during tempering. These alterations are reflected in elevated hardness after low-temperature tempering but slightly lowered hardness after tempering within the normal secondary hardening temperature range, except the specimens treated at-140 °C where the hardness improvement was maintained. The fracture toughness is rather negatively influence by the sub-zero treatments, except the treatment at-140 °C where no impact or rather improvement has been recorded; thus, the treatment at a temperature of-140 °C seems to be a promising way how to improve the hardness and the fracture toughness pf the Vanadis 6 steel simultaneously.

Effects of Tensile Testing Temperature on Mechanical Properties and Deformation Behavior in Medium Mn Steels

2021 ◽  
Vol 1016 ◽  
pp. 1823-1829
Author(s):  
Yoshiyasu Kawasaki ◽  
Yuki Toji ◽  
Yokota Takeshi ◽  
Yoshimasa Funakawa
Keyword(s):  
Mechanical Properties ◽  
Deformation Behavior ◽  
Deformation Temperature ◽  
Tensile Testing ◽  
Retained Austenite ◽  
Single Phase ◽  
Testing Temperature ◽  
Austenitic Steels ◽  
Transformation Rate ◽  
The Stability

In single-phase austenitic steels, the optimum deformation temperature in the tensile test to obtain high tensile strength-elongation balance (TS×El) and work hardening rate (dσ/dε) depends on control of the stability of austenite. In order to clarify the effects of the deformation temperature in complex phase steels containing austenite, in this study, the effects of the tensile testing temperature on mechanical properties and deformation behavior were investigated in detail using steel A and steel B with a chemical composition of 0.15C-0.5Si-5.0Mn (wt%). Steels A and B consisted of ferrite and retained austenite, but contained different volume fractions of retained austenite, namely, 29 % and 17 % as a result of annealing at 660 °C and 620 °C for 2 h, respectively. The stability of the retained austenite of steel B was higher than that of steel A. In steel A, TS×El and dσ/dε achieved their maximum values at 20 °C, decreased from 20 to 100 °C, and then remained almost unchanged at more than 150 °C. On the other hand, in steel B, TS×El and dσ/dε achieved their maximum values at -40 °C, decreased from -40 to 50 °C and remained almost unchanged at more than 100 °C. These results can be explained by the stability of retained austenite and the transformation rate from retained austenite to martensite. It should be noted that control of the stability of retained austenite and the transformation rate from retained austenite to martensite led to an adjustment of the optimum deformation temperature to achieve the high TS×El and dσ/dε in medium Mn steels, in the same manner as in single-phase austenitic steels.

scholarly journals Enhanced Strength and Ductility by Introducing Nanobainitic Ferrite in Bainitic Steel Used in Sports Equipment

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2007
Author(s):  
Han Meng ◽  
Zhenjun Hong ◽  
Yu Li ◽  
Xiaoshuai Jia ◽  
Zhihua Yin
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Total Elongation ◽  
Bainitic Steel ◽  
Bainitic Steels ◽  
Cottrell Atmosphere ◽  
The Stability ◽  
Strength And Ductility ◽  
Enhanced Stability

The mechanical properties of carbide-free bainitic steels used in sports equipment were investigated. The nanobainitic ferrite was introduced in bainitic steel to enhance the stability of blocky retained austenite (RA). The blocky RA formed in bainitic austempering process was coarse and led to poor mechanical properties. By introducing the nanobainitic ferrite into blocky RA, the yield strength was improved remarkably, which was increased from 706 to 1180 MPa. Furthermore, the total elongation was almost twice the value compared to the traditional bainitic treatment. The improved mechanical properties were attributed to the enhanced stability of blocky RA. Furthermore, the increased carbon content in RA derived from the carbon dissolved in bainitic ferrite and the carbon trapped in dislocation or Cottrell atmosphere.

Mechanical Stability and Deformation-Induced Transformation of Retained Austenite in TRIP Steels at Low Temperatures

2017 ◽  
Vol 741 ◽  
pp. 36-41 ◽  
Author(s):  
Takayuki Yamashita ◽  
Norimitsu Koga ◽  
Osamu Umezawa
Keyword(s):  
Low Temperature ◽  
Work Hardening ◽  
Low Temperatures ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
High Strain ◽  
Volume Fraction ◽  
Trip Steels ◽  
The Stability ◽  
Strength And Ductility

The tensile properties and the stability of retained austenite in TRIP steels with different volume fraction of retained austenite have been studied at low temperature. The steels showed a good valance of strength and ductility at 193 K. Their work-hardening rates were decreased linearly and kept a high value in the high strain regime at 193 K. The retained austenite was mostly transformed into martensite less than 10% strain at 193 K.

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