On the Q&P Potential of a Commercial Spring Steel

Over the last years heat treatment concept of “quenching and partitioning” (Q&P) has reached popularity for its ability to precisely adjust material properties to desired values. Mostly, Q&P process are applied on tailor-made materials with high purities or prototype alloys. The research in hand presents the whole routine of how to investigate the potential of a commercial 0.54C-1.45Si-0.71Mn spring steel in terms of Q&P heat treatment from lab scale in dilatometer measurements to widely used inductive heat treatment on larger scale. In order to obtain the small process window for this material we were focusing on the interplay of the formed microstructure and the resulting mechanical properties in hardness measurements, compression tests as well as tensile tests. After full austenitizing, three different Q&P processing routes were applied. Microstructural analyses by optical microscopy, Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD) exhibit a condition with 6.4 % and 15 % volume fraction of fine distributed retained austenite. Interestingly, the 15 % of retained austenite developed during the partitioning heat treatment. Contradictory to our expectations, tensile and compression testing were showing that the 6.4 % condition achieved improved mechanical properties compared to the 15 % retained austenite condition. The remarkable conclusion is that not only volume fraction and fine distribution of retained austenite determines the potential of improving mechanical properties by Q&P in commercial alloys: also the process step when the retained austenite is developing as well as occurring parallel formation of carbides may strongly influence this potential.

Download Full-text

Quasi-Situ Characterization of Retained Austenite Orientation in Quenching and Partitioning Steel via Uniaxial Tensile Tests

Materials ◽

10.3390/ma13204609 ◽

2020 ◽

Vol 13 (20) ◽

pp. 4609

Author(s):

Pengfei Gao ◽

Jie Liu ◽

Weijian Chen ◽

Feng Li ◽

Jingyu Pang ◽

...

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Mechanical Stability ◽

Volume Fraction ◽

Electron Backscatter Diffraction ◽

Early Stage ◽

Tensile Tests ◽

Uniaxial Tensile ◽

Quenching And Partitioning ◽

Austenite Grains

As a representative of the third generation of advanced high strength steel, the quenching and partitioning steel has excellent potential in automobile manufacturing. The characterization and analysis of the mechanical properties and microstructure of the quenching and partitioning steel during deformation is an effective way to explore the microstructure evolution and transformation-induced plasticity effects of complex phase steels. The relationship between the microstructure morphology and mechanical properties of a 1180 MPa-grade quenching and partitioning steel was investigated through interrupted uniaxial tensile tests plus quasi-situ electron backscatter diffraction measurements. A mixture of ferrite, martensite, and retained austenite was observed in the microstructure. It was found that the volume fraction of global retained austenite decreased linearly with the increase of displacement (0 mm–1.05 mm). The evolution of the retained austenite with typical crystal direction ranges with deformation was characterized. Results show that the orientation (111) and (311) account for the highest proportion of retained austenite grains in the undeformed sample and the mechanical stability of the (311) retained austenite grains is the best. Moreover, the retained austenite grains rotated significantly in the early stage of the specimen deformation process (around yielding), and the work hardening of the specimen was weak at this stage, simultaneously.

Download Full-text

Effect of Si Content on Microstructure and Properties of 60Si2CrVA Spring Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.968.63 ◽

2014 ◽

Vol 968 ◽

pp. 63-66 ◽

Cited By ~ 1

Author(s):

Fei Zhao ◽

Zhan Ling Zhang ◽

Jun Shuai Li ◽

Cui Ye ◽

Ni Li

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Volume Fraction ◽

Testing Machine ◽

Spring Steel ◽

Impact Testing ◽

X Ray ◽

Comprehensive Properties ◽

Spring Steels ◽

Si Content

The microstructure and mechanical properties of the four spring steels with different Si content treated by Q-I-Q-T process were studied by metallographic microscope, MTS, impact testing machine and X-ray stress analyzer. The results show that the tensile strength and yield strength is first increased and then decreased with the increase of Si content, the volume fraction of retained austenite and elongation are fist decreased and then increased when the Si content is less than 2.1%, and the microstructure become finer and homogeneous. When Si content reaches 2.1%, the comprehensive properties of 60Si2CrVA spring steel is the best.

Download Full-text

Assessment of Retained Austenite in Fine Grained Inductive Heat Treated Spring Steel

Materials ◽

10.3390/ma12244063 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4063 ◽

Cited By ~ 2

Author(s):

Anna Olina ◽

Miroslav Píška ◽

Martin Petrenec ◽

Charles Hervoches ◽

Přemysl Beran ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Cross Section ◽

Retained Austenite ◽

Quantitative Assessment ◽

Spring Steel ◽

Rapid Phase ◽

Fine Grained ◽

The Core ◽

Heat Treated

Advanced thermomechanical hot rolling is becoming a widely used technology for the production of fine-grained spring steel. Different rapid phase transformations during the inductive heat treatment of such steel causes the inhomogeneous mixture of martensitic, bainitic, and austenitic phases that affects the service properties of the steel. An important task is to assess the amount of retained austenite and its distribution over the cross-section of the inductive quenched and tempered wire in order to evaluate the mechanical properties of the material. Three different analytical methods were used for the comparative quantitative assessment of the amount of retained austenite in both the core and rim areas of the sample cross-section: neutron diffraction—for the bulk of the material, Mössbauer spectroscopy—for measurement in a surface layer, and the metallographic investigations carried by the EBSD. The methods confirmed the excessive amount of retained austenite in the core area that could negatively affect the plasticity of the material.

Download Full-text

Microstructural Features of Strain-Induced Martensitic Transformation in Medium-Mn Steels with Metastable Retained Austenite/ Cechy Mikrostrukturalne Indukowanej Odkształceniem Przemiany Martenzytycznej W Stalach Sredniomanganowych Z Metastabilnym Austenitem Szczątkowym

Archives of Metallurgy and Materials ◽

10.2478/amm-2014-0283 ◽

2014 ◽

Vol 59 (4) ◽

pp. 1673-1678 ◽

Cited By ~ 2

Author(s):

A. Grajcar ◽

A. Kilarski ◽

K. Radwanski ◽

R. Swadzba

Keyword(s):

Electron Microscopy ◽

Retained Austenite ◽

Volume Fraction ◽

Electron Backscatter Diffraction ◽

Bainitic Ferrite ◽

Tensile Tests ◽

Bainitic Steels ◽

Transmission Electron ◽

Strain Induced Martensite ◽

Backscatter Diffraction

Abstract The work addresses relationships between the microstructure evolution and mechanical properties of two thermomechanically processed bainitic steels containing 3 and 5% Mn. The steels contain blocky-type and interlath metastable retained austenite embeded between laths of bainitic ferrite. To monitor the transformation behaviour of retained austenite into strain-induced martensite tensile tests were interrupted at 5%, 10%, and rupture strain. The identification of retained austenite and strain-induced martensite was carried out using light microscopy (LM), scanning electron microscopy (SEM) equipped with EBSD (Electron Backscatter Diffraction) and transmission electron microscopy (TEM). The amount of retained austenite was determined by XRD. It was found that the increase of Mn addition from 3 to 5% detrimentally decreases a volume fraction of retained austenite, its carbon content, and ductility.

Download Full-text

The Effect of Heat Treatment on Microstructure and Mechanical Properties of Cast Bainitic Steel Used for Frogs in Railway Crossovers

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0317 ◽

2017 ◽

Vol 62 (4) ◽

pp. 2147-2151 ◽

Cited By ~ 1

Author(s):

S. Parzych

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Retained Austenite ◽

Volume Fraction ◽

Cast Steel ◽

Pearlitic Steel ◽

Strength Properties ◽

Tensile Yield Strength ◽

Bainitic Steel ◽

Microstructure And Mechanical Properties

Abstract This work deals with the effect of heat treatment on a microstructure and mechanical properties of a selected cast steel assigned as a material used for frogs in railway crossovers. Materials used nowadays in the railway industry for frogs e.g. Hadfield cast steel (GX120Mn13) or wrougth pearlitic steel (eg. R260) do not fulfil all exploitation requirements indicated in the UIC (International Union of Railways) Decision No. 1692/96 in terms of train speed that should be reached on railways. One of the possible solution is using a cast steel with bainitic or bainitic-martensitic microstructure that allows to gain high strength properties the ultimate tensile strength (UTS) of 1400 MPa, the tensile yield strength (TYS) of 900 MPa and the hardness of up to 400 BHN. The tested material is considered as an alternative to Hadfield cast steel that is currently used for railway frogs. Results of an experimental analysis of the effect of conducted heat treatment on a microstructure, the volume fraction of retained austenite and mechanical properties of bainitic steel, are shown in this paper. It was found that, the heat treatment leads to a stabilization of retained austenite in grain boundaries area of the primary austenite. Additionally, the heat treatment according to the variant #3 results with an almost 3-times higher impact toughness to that exhibited by material subjected to the other treatments.

Download Full-text

The Impact of Retained Austenite on the Mechanical Properties of Bainitic and Dual Phase Steels

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-06547-w ◽

2022 ◽

Author(s):

Bogusława Adamczyk-Cieślak ◽

Milena Koralnik ◽

Roman Kuziak ◽

Kamil Majchrowicz ◽

Tomasz Zygmunt ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Transformation Temperature ◽

Retained Austenite ◽

Tensile Tests ◽

Total Elongation ◽

Isothermal Transformation ◽

Bainitic Transformation ◽

Bainitic Steel ◽

Continuous Cooling

AbstractThis paper presents the microstructural changes and mechanical properties of carbide-free bainitic steel subjected to various heat treatment processes and compares these results with similarly treated ferritic–pearlitic steel. A key feature of the investigated steel, which is common among others described in the literature, is that the Si content in the developed steel was >1 wt.% to avoid carbide precipitation in the retained austenite during the bainitic transformation. The phase identification before and after various heat treatment conditions was carried out based on microstructural observations and x-ray diffraction. Hardness measurements and tensile tests were conducted to determine the mechanical properties of the investigated materials. In addition, following the tensile tests, the fracture surfaces of both types of steels were analyzed. Changing the bainitic transformation temperature generated distinct volume fractions of retained austenite and different values of mechanical strength properties. The mechanical properties of the examined steels were strongly influenced by the volume fractions and morphological features of the microstructural constituents. It is worth noting that the bainitic steel was characterized by a high ultimate tensile strength (1250 MPa) combined with a total elongation of 18% after austenitizing and continuous cooling. The chemical composition of the bainitic steel was designed to obtain the optimal microstructure and mechanical properties after hot deformation followed by natural cooling in still air. Extensive tests using isothermal transformation to bainite were conducted to understand the relationships between transformation temperature and the resulting microstructures, mechanical properties, and fracture characteristics. The isothermal transformation tests indicated that the optimal relationship between the sample strength and total elongation was obtained after bainitic treatment at 400 °C. However, it should be noted that the mechanical properties and total elongation of the bainitic steel after continuous cooling differed little from the condition after isothermal transformation at 400 °C.

Download Full-text

Study on the Mechanical Stability of Retained Austenite in Cold-Rolled Medium-Mn Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.936.1283 ◽

2014 ◽

Vol 936 ◽

pp. 1283-1289

Author(s):

Jun Hu ◽

Wen Quan Cao ◽

Jie Shi ◽

Han Dong

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Mechanical Stability ◽

Volume Fraction ◽

Residual Austenite ◽

Tensile Tests ◽

Medium Mn Steel ◽

Cold Rolled ◽

Mn Steel ◽

High Mechanical Stability

The mechanical stability of the retained austenite in the cold-rolled medium-Mn steel was studied. Tensile tests were carried out to measure the mechanical properties of the annealed steel. Scanning electron microscopy was applied to characterize the microstructure evolution during the tensile process; X-ray diffraction analysis was used to determine the residual austenite content in the deformed steel. It was found that the volume fraction of retained austenite gradually decreases with strain .The value of the stability coefficient of retained austenite k was small in the test steel, which indicated high mechanical stability of retained austenite. Due to TRIP effect, the high mechanical stability of the retained austenite strongly delays the onset of necking, which resulted in good comprehensive mechanical properties with ultrahigh strength and plasticity.

Download Full-text

Effects of Heat Treatment on Morphology, Texture and Mechanical Properties of a MnSiAl Multiphase Steel with TRIP Behavior

10.20944/preprints201811.0104.v1 ◽

2018 ◽

Author(s):

Alvaro Salinas ◽

Alfredo Artigas ◽

Juan Pérez-Ipiña ◽

Felipe M. Castro-Cerda ◽

Nelson F. Garza-Montes-de-Oca ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Retained Austenite ◽

Room Temperature ◽

Single Phase ◽

Intercritical Annealing ◽

Tensile Tests ◽

Temperature Homogenization ◽

Cold Rolled ◽

Multiphase Steel

: The effect that the microstructure exerts on the TRIP phenomenon and on the mechanical properties in a multiphase steel was studied. Samples of an initially cold-rolled ferrite-pearlite steel underwent different intercritical annealing treatments at 750 °C until an equal fractions of austenite/ferrite was reached; the intercritical treatment was followed by isothermal bainitic treatments before cooling the samples to room temperature. Samples in the first treatment were heated  directly to the intercritical temperature, whereas other samples were heated to either 900 or 1100 °C to obtain a fully homogenized, single phase austenitic microstructure prior to the conducting the intercritical treatment. The high temperature homogenization of austenite resulted in the decrease in its stability, so a considerable austenite fraction transformed into martensite by cooling to room temperature after the bainitic heat treatment. Most of the retained austenite transformed during the tensile tests, and as a consequence, the previously homogenized steels showed the highest UTS. In turn, the steel with a ferritic-pearlitic initial microstructure, exhibited higher ductility than the other steels and texture components that favor forming processes.     

Download Full-text

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

Acta Metallurgica Slovaca ◽

10.12776/ams.v25i2.1266 ◽

2019 ◽

Vol 25 (2) ◽

pp. 93 ◽

Cited By ~ 1

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&P process. Q&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>

Download Full-text

Heat Treatment Evaluation for the Camshafts Production of ADI Low Alloyed with Vanadium

Metals ◽

10.3390/met11071036 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1036

Author(s):

Eduardo Colin García ◽

Alejandro Cruz Ramírez ◽

Guillermo Reyes Castellanos ◽

José Federico Chávez Alcalá ◽

Jaime Téllez Ramírez ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Tensile Strength ◽

Ductile Iron ◽

Volume Fraction ◽

Energy Impact ◽

Treatment Conditions ◽

Mold Casting ◽

Grade 3 ◽

Good Agreement

Ductile iron camshafts low alloyed with 0.2 and 0.3 wt % vanadium were produced by one of the largest manufacturers of the ductile iron camshafts in México “ARBOMEX S.A de C.V” by a phenolic urethane no-bake sand mold casting method. During functioning, camshafts are subject to bending and torsional stresses, and the lobe surfaces are highly loaded. Thus, high toughness and wear resistance are essential for this component. In this work, two austempering ductile iron heat treatments were evaluated to increase the mechanical properties of tensile strength, hardness, and toughness of the ductile iron camshaft low alloyed with vanadium. The austempering process was held at 265 and 305 °C and austempering times of 30, 60, 90, and 120 min. The volume fraction of high-carbon austenite was determined for the heat treatment conditions by XRD measurements. The ausferritic matrix was determined in 90 min for both austempering temperatures, having a good agreement with the microstructural and hardness evolution as the austempering time increased. The mechanical properties of tensile strength, hardness, and toughness were evaluated from samples obtained from the camshaft and the standard Keel block. The highest mechanical properties were obtained for the austempering heat treatment of 265 °C for 90 min for the ADI containing 0.3 wt % V. The tensile and yield strength were 1200 and 1051 MPa, respectively, while the hardness and the energy impact values were of 47 HRC and 26 J; these values are in the range expected for an ADI grade 3.

Download Full-text