Study on the Microstructure and Mechanical Properties of a High Strength Crack-Free Steel

2012 ◽  
Vol 706-709 ◽  
pp. 2265-2270
Author(s):  
Chun Lin Qiu ◽  
Liang Yun Lan ◽  
De Wen Zhao ◽  
Xiu Hua Gao ◽  
Jing Lin Wen
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Accelerated Cooling ◽  
Strengthening Effect ◽  
Microstructural Characteristics ◽  
Tempering Temperature ◽  
Electron Backscattering Diffraction ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Ebsd Technique

Thermo-mechanical process followed by accelerated cooling and high temperature tempering was applied to investigate the microstructure evolution and mechanical properties of a high strength crack-free steel. Optical microscopy, transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) technique were employed to analyze the complex microstructural characteristics of the steel. The results indicated that the precipitation strengthening effect played an important role in optimizing the tempered strength. According to EBSD results, the average grain size of as-rolled specimens was about 3.2 μm, and it increased slightly with the tempering temperature. Therefore, the grain refinement wasthe major reason for the good mechanical properties of the crack-free steel.

Effect of Processing Route on Mechanical Behavior of C-Mn Multiphase High Strength Cold Rolled Steel

2007 ◽  
Vol 539-543 ◽  
pp. 4375-4380
Author(s):  
Dagoberto Brandão Santos ◽  
Élida G. Neves ◽  
Elena V. Pereloma
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Quantitative Relationship ◽  
High Strength ◽  
Microstructural Characterization ◽  
Processing Route ◽  
Accelerated Cooling ◽  
Microstructural Parameters ◽  
Transmission Electron

The multiphase steels have complex microstructures containing polygonal ferrite, martensite, bainite, carbide and a small amount of retained austenite. This microstructure provides these steels with a high mechanical strength and good ductility. Different thermal cycles were simulated in the laboratory in order to create the microstructures with improved mechanical properties. The samples were heated to various annealing temperatures (740, 760 or 780°C), held for 300 s, and then quickly cooled to 600 or 500°C, where they were soaked for another 300 s and then submitted to the accelerated cooling process, with the rates in the range of 12-30°C/s. The microstructure was examined at the end of each processing route. The mechanical behavior evaluation was made by microhardness testing. The microstructural characterization involved optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The use of multiple regression analysis allowed the establishment of quantitative relationship between the microstructural parameters, cooling rates and mechanical properties of the steel.

Microstructure and Mechanical Properties of the UFG Magnesium Alloy Mg-1%Ca

2021 ◽  
Vol 1016 ◽  
pp. 768-773
Author(s):  
Olga Kulyasova ◽  
Rinat K. Islamgaliev ◽  
Hsin Chih Lin ◽  
Hakan Yilmazer
Keyword(s):  
Mechanical Properties ◽  
High Pressure Torsion ◽  
High Strength ◽  
Tensile Tests ◽  
Good Combination ◽  
Small Samples ◽  
Uniform Structure ◽  
Transmission Electron ◽  
Average Grain Size ◽  
High Microhardness

The influence of grain refinement by high pressure torsion (HPT) on microstructure of the Mg-1%Ca alloy was investigated by scanning and transmission electron microscopy. To The microhardness measurements and tensile tests of small samples were used to determine the mechanical properties of UFG samples. It was found that a uniform structure with an average grain size of 210 nm processed by HPT lead to high microhardness equal to 100 HV. Investigations of thermal stability demonstrated that additional heat treatment of the UFG samples at 250 oC provides good combination of high strength of 245 MPa and ductility of 4%.

The Formation of Acicular Ferrite and Mechanical Properties Behaviors in a Low Welding Crack Susceptibility Steel

2010 ◽  
Vol 163-167 ◽  
pp. 337-341 ◽  
Author(s):  
Liang Yun Lan ◽  
Chun Lin Qiu ◽  
De Wen Zhao
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Accelerated Cooling ◽  
Transmission Electron ◽  
Crystallographic Characteristics ◽  
Backscatter Diffraction ◽  
Crack Susceptibility

The nucleation and crystallographic characteristics of acicular ferrite in the as-rolled and tempered steel were investigated by using an optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD). The results showed that acicular ferrite forms at nucleation sites such as dislocations within austenite grains under the heavy reduction in the austensite non-recrystallization region and accelerated cooling conditions, and the inclusions such as Al2O3•MnS may have promotion effect for the formation of acicular ferrite. Acicular ferrite has high misorientation angle boundaries and a number of sub-boundaries or high density of dislocations inside, which contributes to an excellent combination of high strength and toughness. And the morphology of acicular ferrite does not show obvious change in tempering microstructure due to high temperature thermal stability, which plays an important part in keeping good mechanical properties for tempered specimens.

Recent Development in High Strength Linepipe for Sour Environment

2003 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Toyohisa Shinmiya ◽  
Shigeru Endo ◽  
Tsunemi Wada ◽  
Joe Kondo
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Controlled Rolling ◽  
Accelerated Cooling ◽  
Optimum Conditions ◽  
Microstructural Characteristics ◽  
Design Concepts ◽  
Bainitic Microstructure ◽  
Linepipe Steels ◽  
Sour Gas

This paper firstly summarizes the design concepts for controlling crack resistant property and mechanical properties of high strength linepipe steels for sour gas service. Optimum conditions of controlled rolling and accelerated cooling that balances crack resistant property and toughness were investigated. It was demonstrated that higher cooling rate in accelerated cooling process brings tremendous advantages for balancing toughness and strength by fine bainitic microstructure even for heavy wall thick pipes. Production results of high strength sour resistant linepipes were introduced. In order to increase strength grade of sour linepipes, further investigation was made using the steels with different microstructures. It was found that precipitation hardened ferrite-bainite steels have extremely high resistance against HIC even for Grade X80. Mechanical properties and microstructural characteristics of this newly developed steel were introduced in this paper.

Physical Simulation of Weldability of Weldox 1300 Steel

2013 ◽  
Vol 762 ◽  
pp. 551-555 ◽  
Author(s):  
Marek Stanislaw Węglowski ◽  
Marian Zeman ◽  
Miroslaw Lomozik
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Physical Simulation ◽  
High Strength ◽  
Parent Material ◽  
Cooling Time ◽  
Electron Microscopies ◽  
Transmission Electron ◽  
Transformation Diagrams ◽  
The Impact

In the present study, the investigation of weldability of new ultra-high strength - Weldox 1300 steel has been presented. The thermal simulated samples were used to investigate the effect of welding cooling time t8/5 on the microstructure and mechanical properties of the heat affected zone (HAZ). In the frame of these investigation the microstructure was studied by the light (LM) and transmission electron microscopies (TEM). It has been shown that the microstructure of the Weldox 1300 steel is composed of tempered martensite, and inside the laths the minor precipitations mainly V(CN) and molybdenum carbide Mo2C were observed. Mechanical properties of parent material were analysed by the tensile, impact and hardness tests. In details the influence of cooling time in the range of 2,5 - 300 s. on hardness, impact toughness and microstructure of simulated HAZ was studied by using welding thermal simulation test. The results show that the impact toughness and hardness decrease with the increase of t8/5 under the condition of a single thermal cycle in simulated HAZ. The continuous cooling transformation diagrams (CCT-W for welding conditions) of Weldox 1300 steel for welding purposes was also elaborated. The steel Weldox 1300 for cooling time in the range of 2,5 - 4 s showed martensite microstructure, for time from 4 s to 60 s mixture of martensite and bainite, and for longer cooling time mixture of ferrite, bainite and martensite. The results indicated that the weldability of Weldox 1300 steel is limited and to avoid the cold cracking the preheating procedure or medium net linear heat input should be used.

Microstructure and Mechanical Properties of High Strength Alloyed Steel for Aerospace Application

2018 ◽  
Vol 284 ◽  
pp. 351-356 ◽  
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
High Strength ◽  
Single Stage ◽  
The Novel ◽  
Tempering Temperature ◽  
Quenching And Partitioning ◽  
Aerospace Application ◽  
Cooling Conditions ◽  
Quenching And Tempering

The high strength aerospace steel alloyed with Cr, Mn, Si, Ni, W and Mo was studied. The austenite transformations under continuous cooling conditions were investigated using the dilatometer analysis at the cooling rates 0.1...30 °C/s. The mechanical properties of the studied steel were determined after the conventional quenching and tempering heat treatment. The dependences of the mechanical properties on the tempering temperature were obtained. The novel quenching and partitioning heat treatment was applied to the steel under consideration. The microstructure and the mechanical properties were studied after three different modes of the quenching and partitioning (QP) treatment: single-stage QP, two-stage QP and single-stage QP with subsequent tempering (QPT).

Influence of Grain Size on Mechanical Properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP Steel

2011 ◽  
Vol 197-198 ◽  
pp. 655-661
Author(s):  
Ze Bin Yang ◽  
Ding Yi Zhu ◽  
Wei Fa Yi ◽  
Shu Mei Lin ◽  
Cheng Mei Du
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Strain Hardening ◽  
Twip Steel ◽  
Optical Microscope ◽  
Coarse Grained ◽  
Microstructure Observation ◽  
Transmission Electron ◽  
Average Grain Size

We investigate the influence of grain size on mechanical properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP steel by unidirectional tensile. Meanwhile the microstructures of the TWIP steel were observed and analyzed by optical microscope (OM) and transmission electron microscope (TEM). The experimental results show that the TWIP steel’s yield strength and tensile strength decrease with the increasing of grain size, whereas the plasticity increases with it. When the average grain size reaches to 27μm, the tensile strength is 1080MPa, the elongation percentage is 77%, and the strength-plasticity product achieves the 83160MPa•%. Steel’s strain hardening rate can be changed from three-stage to four-stage with the increasing of grain sizes, the areas of strain hardening by twin deformation mechanism are expanded. Through the microstructure observation we found that, coarse-grained TWIP steel conducts to twinning formation, the high density twins can increase the alloy’s ductility by splitting the grain.

Microstructure and Mechanical Properties in QT-Treated 9Ni Steel

2012 ◽  
Vol 562-564 ◽  
pp. 39-42
Author(s):  
Hang Su ◽  
Xi Qing Zhao ◽  
Tao Pan ◽  
Xiao Rong Lei ◽  
Qing Feng Wang
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Optical Microscope ◽  
Reversed Austenite ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
Scavenging Effect ◽  
Microstructure And Mechanical Properties ◽  
Transmission Electron ◽  
9Ni Steel

Microstructure and mechanical properties in QT-Treated 9Ni steel were investigated. The detail microstructures were observed by optical microscope (OM) and transmission electron microscope (TEM). The volume fraction of austenite was estimated by XRD. Tensile test at room temperature and Charpy-V-Notch (CVN) impact test at -196°C were carried out. The results showed that the microstructure of QT-treated 9%Ni steel was composed of tempered martensite and reversed austenite. The brittle cementite was absorbed gradually by the increasing reversed austenite as the tempering temperature increased. The optimum tempering temperature range was 560°C~580°C. The reversed austenite could improve the cryogenic toughness of 9Ni steel through the combination of the scavenging effect and the TRIP effect.

Microstructure and Mechanical Properties of Twinning M/A Islands in a X100 High Strength Pipeline Steel

2017 ◽  
Vol 896 ◽  
pp. 182-189 ◽  
Author(s):  
Ji Ming Zhang ◽  
Qiang Chi ◽  
Ling Kang Ji ◽  
Hui Feng ◽  
Yan Hua Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
High Strength ◽  
Pipeline Steels ◽  
Transmission Electron ◽  
Fine Microstructure ◽  
X100 Pipeline Steel ◽  
Deformation Hardening

Fine microstructure of twinning Martensite/austenite (M/A) islands in a X100 high strength pipeline steel were analyzed by the scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM), and a uniaxial compressive experiment of micro-pillar for a twinning M/A island was conducted in present paper. The experimental results showed that M/A islands in X100 pipeline steels were consisted of retained austenite and nanoscale twins with sizes of less than ten nanometers. There were a few small blocks of nanoscale twins in an M/A island. Volume fraction of twinning M/A islands had an important effect on mechanical properties of X100 pipeline steels, with the increase of twinning M/A islands fraction, yield strength of X100 pipeline steel increased, and impact toughness of X100 pipeline steel decreased. The micro-pillar compression showed that the nanoscale twinning M/A island exhibited the higher deformation hardening during the compressive test, and its uniaxial compressive strength could up to 1.35GPa ultrahigh stress level.

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