scholarly journals Low Temperature Deformation Induced Microstructure Refinement and Consequent Ultrahigh Toughness of a 20Mn2SiCrNi Bainitic Steel

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 19 ◽  
Author(s):  
Yu Tian ◽  
Zhunli Tan ◽  
Ji Li ◽  
Bo Gao ◽  
Min Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
High Strength Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Temperature Deformation ◽  
Air Cooling ◽  
Degree Of Deformation ◽  
Lower Temperature ◽  
The Impact

In this paper, we have studied the influence of deformation on the microstructure and mechanical properties of 20Mn2SiCrNi bainitic high strength steel processed through a hot rolling route. Simulation of different temperatures and degrees of deformation was carried out via Gleeble-1500. The study suggested that grain size is refined when the deformation is carried out at lower temperature (> Ac3). When the degree of deformation was increased from 20% to 60%, grain size and microstructure were both refined and the size of retained austenite was reduced. The tensile strength increased from 1345 MPa to 1432 MPa. The impact toughness increased from 115 J/cm2 to 210 J/cm2 at room temperature, from 63 J/cm2 to 142 J/cm2 at −40 °C. Furthermore, it was observed that the microstructure after air cooling was composed of granular bainite (GB), lath bainite (LB) and martensite/austenite (MA) island for different deformation conditions. The study reveals that the impact toughness of 20Mn2SiCrNi bainitic high strength steel can be increased by increasing the degree of deformation.

scholarly journals Impact Toughness of Gas Metal Arc Welded HY-80 Steel Plate at Sub-zero Temperatures

2019 ◽  
Vol 269 ◽  
pp. 06003
Author(s):  
Herry Oktadinata ◽  
Winarto Winarto
Keyword(s):  
Impact Toughness ◽  
Weld Joint ◽  
Heat Affected Zone ◽  
High Strength Steel ◽  
Steel Plate ◽  
Gas Metal Arc Welding ◽  
High Strength ◽  
Coarse Grain ◽  
Fracture Appearance ◽  
The Impact

Various welding methods are widely applied in large fabrication of high strength steel. However, commonly the problem occurs where a coarse grain is formed near fusion zone causing reduce the impact toughness due to the weld joint become brittle. Ductility and toughness in a coarse grain heat affected zone (CGHAZ) is low due to the formation of coarsening grain size. The objective of this research is to investigate the microstructure evolution, impact toughness and fracture appearance at sub-zero temperatures of the high strength steel arc welded. The steel that used in this experiment is a HY-80 steel welded by gas metal arc welding (GMAW) with a mixture of argon and carbon dioxide (90%Ar and 10%CO2) and ER100S solid wire. Microstructure observation and Charpy V-notch (CVN) tests were performed on the weld joint which consist of base metal (BM), heat affected zone (HAZ), and weld metal (WM). The CVN tests on the HY-80 steel plate at various temperatures (20, -20, -60 and -80 °C) show impact toughness decrease when the test temperature decrease. The CVN tests on the HY-80 weld joint at a temperature of 80 °C show the lowest impact toughness was measured at WM (61 J) and followed fusion line-FL (101 J) with brittle fracture appearance.

scholarly journals Study on Improvement of Welding Technology and Toughening Mechanism of Zr on Weld Metal of Q960 Steel

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 892
Author(s):  
Xingyu Ai ◽  
Zhengjun Liu ◽  
Dan Wu
Keyword(s):  
Impact Toughness ◽  
Weld Metal ◽  
High Strength Steel ◽  
Removal Rate ◽  
Welding Process ◽  
High Strength ◽  
Pressure Vessels ◽  
Slag Removal ◽  
The Impact ◽  
Strength And Toughness

Q960 high-strength steel is widely used in pressure vessels, bridges, offshore platforms and other important steel structural components because of its high strength and good plastic toughness, but alloy elements added to this kind of steel have strong hardenability, especially after welding, so the strength and toughness cannot meet the requirements, which limits its application in a wider range. In this paper, from the point of view of the metallurgical treatment of the weld, the goal is to improve the strength and toughness of the Q960 high strength steel weld metal In order to analyze the influence of Zr on the welding process of Q960 steel and the strengthening and toughening effect of weld metal, this paper takes Fe-Mn-Mo-Cr-Ni as the main alloy system, BaF2-CaF2-Al-Mg as the basic slag system, and adopts the method of melting consumable electrode self-shielded for welding, and analyzes the welding process, microstructure, tensile property and impact toughness of the welded joint. The experimental results show that when the weld metal contains 0.0061% Zr, the minimum spatter rate is only 7%, the maximum slag removal rate is 95%, the maximum hardness is 357HV, the maximum elongation is 34%, and the impact toughness is the highest. At this time, the acicular ferrite content in the weld microstructure is the highest, and there is a certain amount of equiaxed fine-grained ferrite, and the content of proeutectoid ferrite is the least, which effectively improves the strength and toughness of the weld metal.

Charpy Impact Properties of Grain Boundary Allotriomorphic Ferrite and Granular Bainite Duplex Microstructure

2014 ◽  
Vol 1004-1005 ◽  
pp. 1236-1244 ◽  
Author(s):  
Ping Luo ◽  
Gu Hui Gao ◽  
Xiao Lu Gui ◽  
Bai Feng An ◽  
Zhun Li Tan ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Grain Boundary ◽  
Crack Path ◽  
High Strength ◽  
Propagation Path ◽  
Granular Bainite ◽  
Air Cooling ◽  
Low Carbon ◽  
Allotriomorphic Ferrite ◽  
The Impact

A new type of high strength and low cost bainitic steel with ultra-low carbon content and high Si content has been developed on the basis of Mn-series air-cooling bainitic steels. The tensile properties of YS>690MPa and the impact toughness of AKV>60J at-40°C were obtained by controlling the processing parameters. This was attributed to the formation of the grain boundary allotriomorphic ferrite (FGBA) and the granular bainite (GB) with different shape of M/A islands. The high strength due to the inter-lath lamellar M/A islands or retained austenite companying with high dislocated bainitic ferrite laths of average 300nm width. The effect of microstructure on the impact crack initiation and propagation was studied. The results showed that crack initiation occurred in two different types of sites: at interphase boundaries of bainite ferrite (BF) and M/A islands, at grain boundaries. The FGBA and bainite ferrite (BF) both had blunting effect on microcrack tip to reduce the crack propagation path. Because of the presence of FGBA, the unit crack path was short, at less than 5μm. The blunting effect of BF could be enhanced by the M/A islands, which force the cracks change the propagation path and reduce the unit crack path to less than the size of bainite packets. The mechanism of low temperature microcrack origin of the ultra-low carbon bainitic (ULCB) steel with the microstructure of the FGBA and GB was also discussed.

Weldability of Ti-Microalloyed Advanced High Strength Steel CP 800

2013 ◽  
Vol 634-638 ◽  
pp. 2899-2903 ◽  
Author(s):  
Mei Zhang ◽  
Qing Shan Li ◽  
Chao Bin Huang ◽  
Ru Yi Wu ◽  
Ren Yu Fu ◽  
...  
Keyword(s):  
Impact Toughness ◽  
High Strength Steel ◽  
High Strength ◽  
Butt Joint ◽  
Carbon Equivalent ◽  
Joint Control ◽  
Gas Shielded Arc Welding ◽  
Advanced High Strength Steel ◽  
The Impact ◽  
Crack Susceptibility

Complex phase steel CP 800, a kind of advanced high strength steel (AHSS), exhibited quite high carbon equivalent (CE) which was a detrimental factor for weldability of steels. Thus the weldability of CP 800 steels containing (in wt%) 0.06C-0.45Si-1.71Mn-0.11Ti was extensively studied. Mechanical properties and impact toughness of butt joint, the welding crack susceptibility of weld and heat-affected-zone (HAZ) for tee joint, Control Thermal Severity (CTS) welded joint, and 60°Y-groove butt joint were inspected after gas shielded arc welding tests. The impact toughness was larger than 27J either at room temperature (RT) or at -20°C, indicating good impact toughness of the weld of the steel. In addition, welding crack susceptibility tests revealed that the weldments were free of surface crack and other imperfection, showed fairly good weldability. In application, the longitudinal control arm of automobile made of this steel exhibited excellent fatigue and durability performance.

scholarly journals Effect of Welding Thermal Cycles on Microstructure and Mechanical Properties of Simulated Heat Affected Zone for a Weldox 1300 Ultra-High Strength Alloy Steel

2016 ◽  
Vol 61 (1) ◽  
pp. 127-132 ◽  
Author(s):  
M. St. Węglowski ◽  
M. Zeman ◽  
A. Grocholewski
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
High Strength Steel ◽  
High Strength ◽  
Parent Material ◽  
Cooling Time ◽  
Microstructure And Mechanical Properties ◽  
Ultra High Strength Steel ◽  
The Impact

In the present study, the investigation of weldability of ultra-high strength steel has been presented. The thermal simulated samples were used to investigate the effect of welding cooling time t8/5 on microstructure and mechanical properties of heat affected zone (HAZ) for a Weldox 1300 ultra-high strength steel. In the frame of these investigation the microstructure was studied by light and transmission electron microscopies. Mechanical properties of parent material were analysed by tensile, impact and hardness tests. In details the influence of cooling time in the range of 2,5 ÷ 300 sec. on hardness, impact toughness and microstructure of simulated HAZ was studied by using welding thermal simulation test. The microstructure of ultra-high strength steel is mainly composed of tempered martensite. The results show that the impact toughness and hardness decrease with increase of t8/5 under condition of a single thermal cycle in simulated HAZ. The increase of cooling time to 300 s causes that the microstructure consists of ferrite and bainite mixture. Lower hardness, for t8/5 ≥ 60 s indicated that low risk of cold cracking in HAZ for longer cooling time, exists.

Impact of Reversed Austenite on the Impact Toughness of the High-Strength Steel of Low Carbon Medium Manganese

JOM ◽  
2018 ◽  
Vol 70 (5) ◽  
pp. 672-679 ◽  
Author(s):  
Guanqiao Su ◽  
Xiuhua Gao ◽  
Dazheng Zhang ◽  
Linxiu Du ◽  
Jun Hu ◽  
...  
Keyword(s):  
Impact Toughness ◽  
High Strength Steel ◽  
High Strength ◽  
Low Carbon ◽  
Reversed Austenite ◽  
The Impact

scholarly journals Effect of Welding Peak Temperature on Microstructure and Impact Toughness of Heat-Affected Zone of Q690 High Strength Bridge Steel

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2981
Author(s):  
Yue Zhang ◽  
Jun Xiao ◽  
Wei Liu ◽  
Aimin Zhao
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Lath Martensite ◽  
Testing Machine ◽  
High Strength ◽  
Peak Temperature ◽  
Granular Bainite ◽  
Fine Grain ◽  
Bridge Steel ◽  
The Impact

The effect of peak temperature (TP) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble-3500 thermal simulation testing machine. The results show that the microstructure of the inter critical heat-affected zone (ICHAZ) was ferrite and bainite. The microstructure of fine grain heat-affected zone (FGHAZ) and coarse grain heat-affected zone (CGHAZ) was lath bainite (LB) LB, lath martensite (LM), and granular bainite (GB), but the microstructure of FGHAZ was finer. With the increase in peak temperature, the content of LB and GB decreased, the content of LM increased, and the lath bundles of LM and LB gradually became coarser. With the increase in peak temperature, the grain size of the original austenite increased significantly, and the impact toughness decreased significantly. When the peak temperature was 800 °C, the toughness was the best. For CGHAZ, the peak temperature should be less than 1200 °C to avoid excessive growth of grain and reduction of mechanical property.

scholarly journals Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1988
Author(s):  
Tibor Kvackaj ◽  
Jana Bidulská ◽  
Róbert Bidulský
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
High Strength Steel ◽  
Single Phase ◽  
Hsla Steel ◽  
High Strength ◽  
Strength Properties ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Steel Grades

This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) depending on differences in their final microstructural components, chemical composition, alloying elements and strengthening contributions to determine strength and mechanical properties. HSS is characterized by a final single-phase structure with reduced perlite content, while AHSS has a final structure of two-phase to multiphase. UHSS is characterized by a single-phase or multiphase structure. The yield strength of the steels have the following value intervals: HSS, 180–550 MPa; AHSS, 260–900 MPa; UHSS, 600–960 MPa. In addition to strength properties, the ductility of these steel grades is also an important parameter. AHSS steel has the best ductility, followed by HSS and UHSS. Within the HSS steel group, high-strength low-alloy (HSLA) steel represents a special subgroup characterized by the use of microalloying elements for special strength and plastic properties. An important parameter determining the strength properties of these steels is the grain-size diameter of the final structure, which depends on the processing conditions of the previous austenitic structure. The influence of reheating temperatures (TReh) and the holding time at the reheating temperature (tReh) of C–Mn–Nb–V HSLA steel was investigated in detail. Mathematical equations describing changes in the diameter of austenite grain size (dγ), depending on reheating temperature and holding time, were derived by the authors. The coordinates of the point where normal grain growth turned abnormal was determined. These coordinates for testing steel are the reheating conditions TReh = 1060 °C, tReh = 1800 s at the diameter of austenite grain size dγ = 100 μm.

scholarly journals Tempforming as an Advanced Processing Method for Carbon Steels

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1566
Author(s):  
Anastasiya Dolzhenko ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov
Keyword(s):  
Impact Toughness ◽  
Crack Propagation ◽  
Large Strain ◽  
High Strength ◽  
Close Relation ◽  
Carbon Steels ◽  
Processing Method ◽  
Propagation Mode ◽  
Displacement Curve ◽  
The Impact

The microstructural mechanisms providing delamination toughness in high-strength low-alloyed steels are briefly reviewed. Thermo-mechanical processing methods improving both the strength and impact toughness are described, with a close relation to the microstructures and textures developed. The effect of processing conditions on the microstructure evolution in steels with different carbon content is discussed. Particular attention is paid to tempforming treatment, which has been recently introduced as a promising processing method for high-strength low-alloyed steel semi-products with beneficial combination of strength and impact toughness. Tempforming consists of large strain warm rolling following tempering. In contrast to ausforming, the steels subjected to tempforming may exhibit an unusual increase in the impact toughness with a decrease in test temperature below room temperature. This phenomenon is attributed to the notch blunting owing to easy splitting (delamination) crosswise to the principle crack propagation. The relationships between the crack propagation mode, the delamination fracture, and the load-displacement curve are presented and discussed. Further perspectives of tempforming applications and promising research directions are outlined.

Sign in / Sign up

Export Citation Format

Share Document