Effect of Nitrogen Content and Cooling Rate on Transformation Characteristics and Mechanical Properties for 600 MPa High Strength Rebar

2016 ◽  
Vol 35 (9) ◽  
pp. 905-912 ◽  
Author(s):  
Jing Zhang ◽  
Fu-ming Wang ◽  
Chang-rong Li ◽  
Zhan-bing Yang
Keyword(s):  
Nitrogen Content ◽  
Cooling Rate ◽  
Volume Fraction ◽  
High Strength ◽  
Tensile Tests ◽  
Comparative Investigation ◽  
Bainite Transformation ◽  
Performance Requirement ◽  
Nitrogen Contents ◽  
Strength And Ductility

AbstractTo obtain appropriate chemical composition and thermo-mechanical schedules for processing the V-N microalloyed 600 MPa grade high strength rebar, the microstructure analysis during dynamic continuous cooling and tensile tests of three experimental steels with different nitrogen contents were conducted. The results show that increasing nitrogen content promotes ferrite transformation and broadens the bainite transformation interval, when the nitrogen content is in the range of 0.019–0.034 mass%. Meanwhile, the martensite start temperatures decrease and the minimal cooling rate to form martensite increases. To achieve a good combination of strength and ductility, the cooling rates should be controlled in the range of 0.5–3°C/s, leading to the microstructure of ferrite, pearlite and less than 10% bainite (volume fraction). Furthermore, all the experimental steels satisfy the performance requirement of 600 MPa grade rebar and the rebar with nitrogen content of 0.034 mass% shows the highest strength through systematically comparative investigation.

Effects of Heat Treatment on Microstructure of High-Strength Manganese-Silicon Steels

2017 ◽  
Vol 270 ◽  
pp. 239-245
Author(s):  
Dagmar Bublíková ◽  
Štěpán Jeníček ◽  
Kateřina Opatová ◽  
Bohuslav Mašek
Keyword(s):  
Heat Treatment ◽  
Cooling Rate ◽  
Microstructure Evolution ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Quenching And Partitioning ◽  
Alloying Additions ◽  
New Procedures ◽  
Strength And Ductility

Today’s advanced steels are required to possess high strength and ductility. This can be accomplished by producing appropriate microstructures with a certain volume fraction of retained austenite. The resulting microstructure depends on material’s heat treatment and alloying. High ultimate strengths and sufficient elongation levels can be obtained by various methods, including quenching and partitioning (Q&P process). The present paper introduces new procedures aimed at simplifying this process with the use of material-technological modelling. Three experimental steels have been made and cast for this investigation, whose main alloying additions were manganese, silicon, chromium, molybdenum and nickel. The purpose of manganese addition was to depress the Ms and Mf temperatures. The Q&P process was carried out in a thermomechanical simulator for better and easier control. The heat treatment parameters were varied between the sequences and their effect on microstructure evolution was evaluated. They included the cooling rate, partitioning temperature and time at partitioning temperature. Microstructures including martensite with strength levels of more than 2000 MPa and elongation of 10–15 % were obtained.

Effect of nitrogen on transformation behavior and intragranular ferrite formation in a V–Ti microalloyed steel for forging

2018 ◽  
Vol 115 (3) ◽  
pp. 311 ◽  
Author(s):  
Ningbo Zhou ◽  
Fan Zhao ◽  
Yiqun Liu ◽  
Bo Jiang ◽  
Chaolei Zhang ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Volume Fraction ◽  
Microalloyed Steel ◽  
High Strength ◽  
Transformation Behavior ◽  
Ferrite Formation ◽  
High Toughness ◽  
Intragranular Ferrite ◽  
Production Experiment ◽  
Cct Diagrams

The transformation behavior and intragranular ferrite formation in V–Ti microalloyed steel with a nitrogen content of 0.005 wt.% and 0.015 wt.% are studied by the DIL 805A dilatometer. The results show that increasing the nitrogen content has no significant effect on AC1, AC3and MStemperature. However, the continuous cooling transformation (CCT) diagrams are shifted to left side. The minimum cooling rates of bainitc and martensitic transformation are increased from 3 °C/s to 5 °C/s and from 5 °C/s to 10 °C/s, respectively. (Ti, V)(C, N) particles on MnS is the nuclei of intragranular ferrite, and (1 0 0)(Ti, V)(C, N)and (1̅ 0 1̅α) are just misoriented by 6.7°. With the increase of nitrogen content, the number of intragranular ferrite is increased from 73 to 170 per · mm2. The volume fraction of intragranular ferrite is increased from 0.23%∼0.79% to 0.79%∼4.6% at cooling rate of 1 °C/s∼0.1 °C/s. According to the industrial production experiment, the toughness of forging crankshaft is improved by increasing the nitrogen content. It is benefit for achieving fair matching of high strength and high toughness of crankshaft.

scholarly journals Development of Precipitation Hardening Parameters for High Strength Alloy AA 7068

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 918
Author(s):  
Julia Osten ◽  
Benjamin Milkereit ◽  
Michael Reich ◽  
Bin Yang ◽  
Armin Springer ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Cooling Rate ◽  
Maximum Yield ◽  
High Strength ◽  
Tensile Tests ◽  
Age Hardening ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Critical Cooling Rate ◽  
Kinetics Of

The mechanical properties after age hardening heat treatment and the kinetics of related phase transformations of high strength AlZnMgCu alloy AA 7068 were investigated. The experimental work includes differential scanning calorimetry (DSC), differential fast scanning calorimetry (DFSC), sophisticated differential dilatometry (DIL), scanning electron microscopy (SEM), as well as hardness and tensile tests. For the kinetic analysis of quench induced precipitation by dilatometry new metrological methods and evaluation procedures were established. Using DSC, dissolution behaviour during heating to solution annealing temperature was investigated. These experiments allowed for identification of the appropriate temperature and duration for the solution heat treatment. Continuous cooling experiments in DSC, DFSC, and DIL determined the kinetics of quench induced precipitation. DSC and DIL revealed several overlapping precipitation reactions. The critical cooling rate for a complete supersaturation of the solid solution has been identified to be 600 to 800 K/s. At slightly subcritical cooling rates quench induced precipitation results in a direct hardening effect resulting in a technological critical cooling rate of about 100 K/s, i.e., the hardness after ageing reaches a saturation level for cooling rates faster than 100 K/s. Maximum yield strength of above 600 MPa and tensile strength of up to 650 MPa were attained.

Fibers of Bamboo and Hem Palm Tree

2001 ◽  
Vol 702 ◽  
Author(s):  
Shigeyasu Amada
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
Volume Fraction ◽  
Young's Modulus ◽  
Simple Procedure ◽  
High Strength ◽  
Tensile Tests ◽  
Palm Tree ◽  
Bamboo Fibers ◽  
The One

ABSTRACTBamboo is a typical composite material which is axially reinforced by very strong fibers. So that, the fibers play an important role for the bamboo structure. The elastic properties of the bamboo culm have been measured only by tensile test so far, which needs a large specimen. Recently ultra-sonic technique, which has a simple procedure and uses a small specimen, has been applied to woods as well as metals. This report reviews about the elastic properties of bamboo and Hemp palm fibers. The Young's modulus and Poisson's ratio of the bamboo fibers are measured by ultra-sonic method with a transmitting wave. On the other hand, the strength of the bamboo and Hemp palm fibers are measured by the tensile tests. Using the volume fraction of fibers in the specimen and mixture principle, the Young's modulus and strength of the fibers and parenchyma were obtained. The fiber has a high strength up to 1GPa and an strong anisotropic property because its axial Young's modulus has 7 times higher than the one in the transverse direction.

scholarly journals Hexagonal Closed-Packed Precipitation Enhancement in a NbTiHfZr Refractory High-Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 485 ◽  
Author(s):  
Yueli Ma ◽  
Shiwei Wu ◽  
Yuefei Jia ◽  
Pengfei Hu ◽  
Yeqiang Bu ◽  
...  
Keyword(s):  
Volume Fraction ◽  
High Strength ◽  
High Entropy Alloy ◽  
Body Centered Cubic ◽  
Ductility Property ◽  
High Entropy ◽  
New Strategy ◽  
Precipitation Enhancement ◽  
Strength And Ductility ◽  
Hexagonal Closed Packed

A NbTiHfZr high-entropy alloy (HEA) with a main phase of body-centered cubic structure is fabricated. Some hexagonal closed-packed (hcp) precipitates are observed in this alloy. A thermal-mechanical process, i.e., cold-rolling followed by annealing, can manipulate the volume fraction of the hcp nano-precipitates that can enhance strength and ductility. The enhancement is tailorable as a function of the volume fraction of the hcp nano-precipitate. The results indicate that the strength-ductility property can be manipulated via adjusting post-deformation heat-treatment methods, which provide a new strategy by utilizing metastability at high-temperature to design high strength refractory HEAs (RHEAs) without lost in ductility.

scholarly journals Effect of microstructure and cooling rate on the fatigue performance of TIMETAL® 575

2020 ◽  
Vol 321 ◽  
pp. 12019
Author(s):  
M. Bodie ◽  
M. Thomas ◽  
A. Ayub
Keyword(s):  
Titanium Alloys ◽  
Cooling Rate ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Electron Backscatter Diffraction ◽  
Material Selection ◽  
Weight Ratio ◽  
High Strength ◽  
Fatigue Performance ◽  
Aerospace Applications

A key design consideration for material selection in the aerospace industry is weight reduction; with excellent strength to weight ratio, high temperature resistance, and fatigue performance, titanium alloys are extensively used. New titanium alloys continue to enhance performance and broaden the range of applications. Titanium Metals Corporation (TIMET) recently developed TIMETAL® 575 (Ti575), a high strength titanium alloy with superior fatigue performance over Ti-6Al-4V, aimed at aerospace applications where these properties are imperative i.e. aerospace turbine discs and blades. [1] [2] This work intends to advance the understanding of the effect of thermal processing of Ti575, by investigating the effect of primary alpha (αp) volume fraction and cooling rate on tensile and fatigue performance in post forged heat-treated microstructures. Microstructural assessment and mechanical performance were completed and are discussed. Three cooling methods from three solution heat-treat temperatures were investigated in this work. The results from these experiments were compared using optical microscopy, electron backscatter diffraction (EBSD), room temperature tensile and high cycle fatigue (HCF) tests.

Effect of Cooling Rate below Ms Temperature on Hydrogen Embrittlement of TRIP-Aided Martensitic Steels

2021 ◽  
Vol 1016 ◽  
pp. 654-659
Author(s):  
Naoya Kakefuda ◽  
Shintaro Aizawa ◽  
Ryo Sakata ◽  
Junya Kobayashi ◽  
Goroh Itoh ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
Cooling Rate ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Martensitic Steels ◽  
The Matrix ◽  
Embrittlement Resistance ◽  
Hydrogen Embrittlement Resistance

Low alloy TRIP steel is expected to be applied to automobile bodies because of its high strength, high ductility, and excellent impact properties and press formability. It has been reported that the low alloy TRIP steel of hydrogen embrittlement resistance is improved by utilizing the hydrogen storage characteristics of highly stable retained austenite. Therefore, for the purpose of increasing the volume fraction of retained austenite, it was produced at various cooling rates below the martensite transformation start temperature. As a result, the volume fraction of retained austenite increased, and then the effect of hydrogen embrittlement decreased. The matrix phase and retained austenite is refined with decrees of the cooling rate. It is considered that the size and surface area of the retained austenite also affected the improvement of hydrogen embrittlement resistance.

Powder Metallurgy of Nanostructured High Strength Materials

2007 ◽  
Vol 534-536 ◽  
pp. 1405-1408 ◽  
Author(s):  
Jürgen Eckert ◽  
S. Scudino ◽  
P. Yu ◽  
C. Duhamel
Keyword(s):  
Powder Metallurgy ◽  
Deformation Behavior ◽  
Volume Fraction ◽  
High Strength ◽  
Mechanical Deformation ◽  
Intrinsic Properties ◽  
Mechanical Attrition ◽  
Wide Range ◽  
Multi Phase ◽  
Strength And Ductility

Nanostructured or partially amorphous Al- and Zr-based alloys are attractive candidates for advanced high-strength lightweight materials. The strength of such materials is often 2 – 3 times higher than the strength of commercial crystalline alloys. Further property improvements are achievable by designing multi-phase composite materials with optimized length scale and intrinsic properties of the constituent phases. Such alloys can be prepared by quenching from the melt or by powder metallurgy using mechanical attrition techniques. This paper focuses on mechanically attrited powders containing amorphous or nano-(quasi)crystalline phases and on their consolidation into bulk specimens. Selected examples of mechanical deformation behavior are presented, revealing that the properties can be tuned within a wide range of strength and ductility as a function of size and volume fraction of the different phases.

scholarly journals Excellent mechanical properties of taenite in meteoric iron

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shohei Ueki ◽  
Yoji Mine ◽  
Kazuki Takashima
Keyword(s):  
Mechanical Properties ◽  
Nitrogen Solubility ◽  
High Strength ◽  
Tensile Tests ◽  
Metallographic Analysis ◽  
Advanced High Strength Steel ◽  
Analysis Techniques ◽  
Solid Solution Strengthening ◽  
Solution Strengthening ◽  
Strength And Ductility

AbstractMeteoric iron is the metal that humans first obtained and used in the earliest stage of metal culture. Advances in metallographic analysis techniques have revealed that meteoric iron largely comprises kamacite, taenite, and cohenite, which correspond to ferrite, austenite, and cementite in artificial steel, respectively. Although the mechanical properties of meteoric irons were measured previously to understand their origin and history, the genuine mechanical properties of meteoric iron remain unknown because of its complex microstructure and the pre-existing cracks in cohenite. Using micro-tensile tests to analyse the single-crystalline constituents of the Canyon Diablo meteorite, herein, we show that the taenite matrix exhibits excellent balance between yield strength and ductility superior to that of the kamacite matrix. We found that taenite is rich in nitrogen despite containing a large amount of nickel, which decreases the nitrogen solubility, suggesting that solid-solution strengthening via nitrogen is highly effective for the Fe–Ni system. Our findings not only provide insights for developing advanced high-strength steel but also help understand the mysterious relationship between nitrogen and nickel contents in steel. Like ancient peoples believed that meteoric iron was a gift from the heavens, the findings herein imply that this thought continues even now.

Deep Denitrogenization Technology of 23Co-Ni Steel in Vacuum Induction Melting Furnace

2014 ◽  
Vol 1004-1005 ◽  
pp. 227-230
Author(s):  
Rui Wang ◽  
Hui Shu Zhang ◽  
Lei Tang ◽  
Dong Ping Zhan ◽  
Zhou Hua Jiang ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Melting Furnace ◽  
High Strength ◽  
Electromagnetic Stirring ◽  
Vacuum Induction Melting ◽  
Melting Time ◽  
Induction Melting ◽  
Ultra High Strength Steel ◽  
Nitrogen Contents ◽  
Low Nitrogen

23Co-Ni is an ultra-high strength steel and it needs ultra low nitrogen content in the steel. The removal of nitrogen for 23Co-Ni steel in a 6t/12t Vacuum Induction Melting Furnace (VIM) with different melting processes was studied. The results show that, the longer of the melting time and the higher of the vacuum level, the lower of the final nitrogen contents is. The denitrogenization rate can reach 70% when the melting time is more than 8 hours. The electromagnetic stirring can increase the denitrogenization speed. When the VIM is vacuumed to 1-3 Pa, it can make the nitrogen content reaches 0.0005%-0.0008%.

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