Effects of Different Microalloying and Controlled Cooling Technology on Microstructure and Properties of 500MPa High-Strength Rebars

2014 ◽  
Vol 633-634 ◽  
pp. 168-175
Author(s):  
Wei Chen ◽  
Jian Chun Cao ◽  
Zhe Shi ◽  
Yin Hui Yang ◽  
Yu Zhao
Keyword(s):  
Testing Machine ◽  
High Strength ◽  
Good Effect ◽  
Tensile Fracture ◽  
Controlled Cooling ◽  
Tensile Testing Machine ◽  
Impact Machine ◽  
Obvious Effect ◽  
Tensile Fracture Surface ◽  
Cooling Technology

The mechanical properties and microstructures of three different VN, Nb, V-Nb microalloyed rebars were investigated by using tensile testing machine, impact machine, metallographic microscopy, scaning electron microcopy, transmission electron microscopy and X-ray diffraction apparatus. The results showed that the microstructure of V-Nb microalloyed specimen is consisted of ferrite, pearlite and a small amount of fine bainite (6.7wt%), and obvious effect of grain refinement was obtained with more than 10 size grade of ferrite grain, showing optimal comprehensive properties. SEM micrograph of tensile fracture surface for V-Nb microalloyed 500MPa high-strength rebar is dimple and ductile, ductile-brittle transformation temperature is lower than-30°C, which has good plasticity-toughness and impact toughness at low temperature. The results of precipitates have shown that a large number of small and dispersive V(CN) and Nb (CN) precipitates with size of 5~30nm are formed, good effect of precipitation strengthening was achieved in 500MPa high-strength rebars produced by different microalloying and controlled cooling technology.

Material Behaviour Modelling for Finite Element Vehicle Crash Simulation

2009 ◽  
Vol 410-411 ◽  
pp. 521-532
Author(s):  
Khawar Rabbani ◽  
Mike Daniels ◽  
Neil Walker ◽  
Bez Shirvani
Keyword(s):  
Finite Element ◽  
Mild Steel ◽  
Constitutive Equations ◽  
High Strength Steel ◽  
Piecewise Linear ◽  
Testing Machine ◽  
High Strength ◽  
Tensile Testing Machine ◽  
Material Models ◽  
Safety Research

Vehicle safety has increasingly become an economical factor for vehicle manufacturers and this has become most apparent in car safety [1-4]. Manufacturers are now spending considerable resources on safety research. Government requirements on safety have compelled manufacturers to carry out considerable number of crash tests to validate the safety of their cars [6-7]. The data from these tests is important in the development of simulation models employing finite element (FE) software. Many companies predict crashworthiness using commercially available software such as PAMCARSH and LS-DYNA. These simulations are based on mathematical constitutive equations and hence any simulation created is only as representative as the constitutive equations used. This project has studied the reliability of the material models used by LS-DYNA. Material models selected for analysis are used extensively by impact simulations software and were namely: Power Law Plasticity and Cowper/Symonds. Piecewise Linear Plasticity was also selected because it is based on a true stress/strain and is expected that the simulation would be representative. The models were developed using Belytschko-Lin-Tsay shell elements and were compared with experimental tests employing uni-axial tension strips carried out on three materials – aluminium, high strength steel and mild steel. The tests were carried out using a DARTEC tensile testing machine (up to strain rate of 2.0s-1) at UCE in Birmingham. Testing for the higher strain rates (aluminium up to 269.1s-1, mild steel up to 460s-1, and high strength steel up to 456.9s-1), were carried out at The Royal Military College, Shrivenham using a ROSAND tester.

Drop-Load Testing of Pipe-Grade Polyethylenes

2017 ◽  
Vol 44 (12) ◽  
pp. 33-38
Author(s):  
M.S. Ivanov ◽  
V.N. Kuleznev
Keyword(s):  
Tensile Testing ◽  
Testing Machine ◽  
Load Testing ◽  
Tensile Testing Machine ◽  
Impact Machine ◽  
Relative Strain ◽  
Load Impact

The nature of strain of pipe-grade polyethylenes in drop-load impact machine tests in comparison with elongation on a tensile testing machine is analysed. A procedure for the drop-load testing of dumb-bell testpieces is described, the relative strain and the stress acting on the specimen are calculated, and the nature of failure of the materials is analysed.

Effect of Root Flaw on Tensile Behavior of Friction Stir Welded A6061-T6 Aluminum Alloy

2012 ◽  
Vol 482-484 ◽  
pp. 1343-1349
Author(s):  
Ben Yuan Lin ◽  
Ju Jen Liu ◽  
Lee Der Lu ◽  
Hsien Lung J Tsai
Keyword(s):  
Early Stage ◽  
Testing Machine ◽  
Ccd Camera ◽  
Local Strain ◽  
Tensile Tests ◽  
Tensile Behavior ◽  
Tensile Fracture ◽  
Tensile Fracture Surface ◽  
Friction Stir ◽  
Tensile Experiment

The tensile behavior of friction stir joints containing root flaw in A6061-T6 aluminum alloys was investigated. First, plates of this material were butt-jointed by friction stir welding, and the metallographic observation and micro-hardness analysis were made on the cross-section of the weld. Then, tensile tests were performed in MTS 810 testing machine, and a digital CCD camera was used to monitor the process during testing.. Finally, the tensile fracture surface analysis was examined by scanning electron microscopy (SEM). The results show that the root flaw has no apparent effect on the tensile properties. However, it was observed that a crack about 0.3 mm in length occurred in the root part of the weld center in the early stage of tensile test, and the crack did not further propagate during the sequent tensile experiment. The tensile specimens were all fractured in the heat-affected zone (HAZ) of the retreating side, which is the area coincident with the region of maximum local strain and lowest hardness.

The Basic Research and Application on Hot Forming of High Strength Steel

2013 ◽  
Vol 800 ◽  
pp. 280-283
Author(s):  
Fu Li Lu ◽  
Ji Shun Song ◽  
Jian Zhang ◽  
Xiu Ping Yan
Keyword(s):  
Process Parameters ◽  
High Strength Steel ◽  
Lath Martensite ◽  
Testing Machine ◽  
Basic Research ◽  
High Strength ◽  
Hot Forming ◽  
Tensile Testing Machine ◽  
Hardness Tester ◽  
The Impact

Taking the high-strength steel 22MnB5 as the research object, starting from the phase transformation and the performance of the sheet at high temperature, the impact of various process parameters on the part was studied, pressing the stringers with hot forming technology simultaneously. Using metallurgical microscope, hardness tester and universal tensile testing machine, the microstructure and mechanical properties of the parts were analysed. The result show that, under the selected process parameters, the microstructure of the workpiece is desired lath martensite, the hardness is above 450HV, the tensile strength is above 1450MPa, which meet the production requirements.

500MPa Seismic Rebars Developed by Nitrogen-Rich and Vanadium-Microalloyed, Controlled Cooling Technology

2011 ◽  
Vol 189-193 ◽  
pp. 752-761 ◽  
Author(s):  
Wei Chen ◽  
Zhe Shi ◽  
Yu Zhao ◽  
Jian Chun Cao ◽  
Yu Mei Yu
Keyword(s):  
Mechanical Properties ◽  
Dislocation Line ◽  
High Strength ◽  
Ferrite Matrix ◽  
Rolling Process ◽  
Controlled Cooling ◽  
Butt Welding ◽  
Fine Grain ◽  
Transmission Electron ◽  
Cooling Technology

500MPa high-strength seismic rebars was developed by nitrogen-rich & vanadium -microalloyed, controlled cooling technology in domestic steel plant of china, microalloy precipitates, microstructure, mechanical properties, welding performance and aging properties of rebars were researched by using metallographic microscopy, scaning electron microcopy, transmission electron microscopy, x-ray diffraction apparatus, flash-butt welding and mechanical properties testing. The results show that a large number of the dispersed V (C, N) precipitates are precipitated in the grain boundary, dislocation line and the ferrite matrix, precipitation size in the ferrite matrix is 10~ 20nm, V(C,N) precipitates amount accounts for 67.54% of the total amount of vanadium in steel, effect of precipitation strengthening is remarkable; when termination temperature after controlled cooling for rebars is controlled at 710°C ～750°C , the core microstructure is polygonal ferrite and pearlite, ferrite grain grade is 11.0, outer layer microstructure is acicular ferrite, pearlite and a small amount of bainite, good effects on fine-grain strengthening and seismic performance are obtained; rebars have low strain aging and good welding performance; production cost is reduced by RMB 100 Yuan per ton steel compared with VN micro-alloyed and hot-rolling process, benefit is obvious.

Evaluation of the Failure Elongation of Steel Sheets for an Auto-Body at the Intermediate Strain Rate

2008 ◽  
Vol 385-387 ◽  
pp. 749-752 ◽  
Author(s):  
Seok Bong Kim ◽  
Hoon Huh
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Tensile Elongation ◽  
Testing Machine ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Result ◽  
Tensile Testing Machine ◽  
Static State ◽  
Steel Sheets

This paper deals with the dynamic failure elongation of mild steel, SGACD and advanced high strength steel sheets such as TRIP600, DP600 and TWIP steels. The failure elongation has been obtained from the high speed tensile testing machine with various strain rates ranged from 0.003/s to 200/s. The experimental result demonstrates that the tensile elongation does not simply decrease as the strain rate increases, but it decreases from the quasi-static state to the strain rate of 0.1 or 1/s and increases again up to the strain rate of 100/s. Furthermore, some high strength steels have the tendency that the tensile elongation increases as the strain rate increases. Moreover, the localized strain rate hardening in the necking region induces the increase of elongation.

Mechanism of the Flux Improving the Microstructure and Mechanical Properties of AZ91D Magnesium Alloy

2011 ◽  
Vol 194-196 ◽  
pp. 1309-1313
Author(s):  
Zhi Xiang Wang ◽  
Yang Liu ◽  
Ya Ting Le ◽  
Feng Liu
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Mechanical Performance ◽  
Energy Dispersive Spectrometer ◽  
Testing Machine ◽  
Performance Testing ◽  
Optical Microscope ◽  
Tensile Fracture ◽  
Tensile Fracture Surface ◽  
Az91d Magnesium Alloy

The microstructures and mechanical properties of AZ91D magnesium alloy produced by two kind of fluxes were analyzed by using mechanical performance testing machine, optical microscope, differential thermal analysis (DTA), X-ray diffraction(XRD), scanning electron microscope（SEM）and energy dispersive spectrometer(EDS) analysis, etc.. The results show that the comprehensive properties of AZ91D magnesium alloy produced by the new flux named NF were better than traditional flux named RJ-2. Phase Mg17Al12 was improved enormously. In addition, not only the nuclear particle A14C3 was formed, but also the grain of the alloy was refined remarkably，and the σb，σs and δ were increased eventually. The tensile fracture surface was made of deeper dimples with rolling patterns, which was relevant to the smaller microstructure.

The Experimental Study on Sensitivity of Hydrogen Embrittlement of 20Cr2Ni4A High-Strength Steel Cleaned by Ultrasonic and Deruster

2011 ◽  
Vol 291-294 ◽  
pp. 1136-1140
Author(s):  
Ling Dong Meng ◽  
Qing Zhang ◽  
Zhi Jie Liang
Keyword(s):  
Experimental Study ◽  
Hydrogen Embrittlement ◽  
High Strength ◽  
Sem Analysis ◽  
Tensile Fracture ◽  
Tensile Fracture Surface ◽  
Mechanics Performance ◽  
Long Time ◽  
Short Time ◽  
Rupture Mechanism

In order to test whether there is the change of mechanics performance cleaned by ultrasonic and deruster, the experiments on mechanics performance and sensitivity of hydrogen embrittlement have been conducted. During the experiments, 20Cr2Ni4A steel are selected as the materials, which endure the relatively great concussion load in the bad condition, and the gaps’ long-time permanence experiments and short-time tension and concussion experiments have been done. Through the compare of mechanics performances and the SEM analysis of tensile fracture surface of the samples, it can be proved that the mechanics performances and rupture mechanism are the same, no matter whether the materials are cleaned by ultrasonic and deruster or not. These indicate that it doesn’t bring the change of mechanics performances and hydrogen embrittlement to clean the materialss by ultrasonic and deruster.

scholarly journals Design and Optimization of Processing Conditions for a Recent Quenched and Partitioned Steel

2021 ◽  
Author(s):  
Eman Hassan El-Shenawy ◽  
Hoda Nasr El-Din Hedia ◽  
Mai Mohamed Kama-El-Din ◽  
Hoda Refaiy Badwy
Keyword(s):  
Heat Treatment ◽  
Tensile Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Testing Machine ◽  
High Strength ◽  
Processing Conditions ◽  
Critical Temperatures ◽  
Tensile Testing Machine ◽  
Heat Treated

Q&P steels as a "Third Generation" of (AHSS) exhibit excellent tensile properties, which enable producing lightweight sections for the automotive industry and at the same time keep safety requirements. This research aims to predict the proper processing conditions for developing ultra-high-strength Q&P steel with a novel chemical composition of 0.37 C-3.65 Mn- 0.65Si- 0.87 Al- 1.5 Ni- 0.05P, wt. %. To design and optimize proper heat treatment conditions, the phase diagram, CCT curve, and critical temperatures of these alloys were first implemented using THERMO-CALC and JMATE PRO software and Gleeble 3500 machine. The heat treatment process included full austenitization, then quenching at 120°C followed by partitioning at 450°C for different times. The tensile properties, microstructure, and retained austenite volume fraction of heat-treated steel was studied at room temperature by tensile testing machine, optical microscope, and XRD. The finding summarized that partitioning of this steel for 100 s during processing had developed Q&P steel with ultra-high-strength of 1104 MPa with maximum total elongation and strength elongation balance 8.1 % and 8932 MPa %, respectively. The optical micrograph showed that heat-treated specimens at different partitioning times have had a microstructure of tempered martensite, carbide free bainite, and retained austenite. Besides, the retained austenite volume fraction has decreased with increasing partitioning time, which may be due to carbide precipitation during partitioning.

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