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.

Metallurgical Design of High Strength/High Toughness Steels

2012 ◽  
Vol 706-709 ◽  
pp. 2084-2089
Author(s):  
Andrea di Schino ◽  
Mauro Guagnelli
Keyword(s):  
Impact Toughness ◽  
Yield Strength ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Steels ◽  
Main Concern ◽  
Microstructural Parameters ◽  
Fine Microstructure ◽  
The Impact ◽  
Strength And Toughness

The proper balance between yield strength, YS, and ductile to brittle transition temperature, DBTT, has been the main concern during development of high strength engineering steels and the effect of microstructure on impact toughness has attracted a great attention during the last decades. In this paper a review concerning the relationship between strength and toughness in steels will be presented and the effect of different microstructural parameters will be discussed, aiming toimprovesuch properties in designingnewhigh strength steels. Complex microstructures, obtained by quenching and tempering (Q&T) and thermo-mechanical (TM) processing are considered. The steels are low/medium carbon steels (C=0.04%-0.40%) with yield strength in the range YS=500-1000 MPa. Results show that the strength and the impact toughness behaviour are controlled by different microstructural parameters and not, as in the case of polygonal ferritic steels, by the same structural unit (the grain size) and that a “fine” microstructure is required in order to achieve high levels of both strength and toughness. The metallurgical design of high strength steels with toughness requirements is discussed using the same approach for both Q&T and TMCP processes.

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.

Mechanical Behaviour of Intercritically Reheated Coarse-Grained Heat Affected Zone in High Strength Line Pipe Steels

2018 ◽  
Author(s):  
Madhumanti Mandal ◽  
Warren J. Poole ◽  
Thomas Garcin ◽  
Matthias Militzer ◽  
Laurie Collins
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Welding Process ◽  
Charpy Impact ◽  
High Strength ◽  
Coarse Grained ◽  
Fracture Mechanisms ◽  
Line Pipe ◽  
Secondary Cracks ◽  
The Impact

Multipass welding of high strength steels used for fabrication and joining of transmission pipelines presents a number of metallurgical challenges. A key concern is both the strength and toughness of the heat affected zone (HAZ) adjacent to both seam and girth welds. In this work, a systematic study has been conducted on regions of the heat affected zone in the base metal where the first welding pass produces a thermal excursion which results in a coarse-grained heat affected zone (CGHAZ). The subsequent weld pass involves intercritical annealing of this region, i.e. a microstructure associated with intercritically reheated coarse grain heat affected zone (ICCGHAZ). The small ICCGHAZ region is often identified as being particularly susceptible to crack initiation. This work was undertaken to understand microstructure development in this zone and how the ICCGHAZ may affect the overall performance of the HAZ. Gleeble thermomechanical simulations have been conducted to produce bulk samples representative of different welding scenarios. Charpy impact tests and tensile tests have been performed over a range of temperatures. It was found that when a continuous necklace of martensite-austenite islands form on the prior austenite grain boundaries (i.e. for a M/A fraction of ≈10%), the Charpy impact toughness energy is dramatically decreased and the ductile brittle transition temperature is significantly raised. Detailed studies on the secondary cracks have been conducted to examine the fracture mechanisms in the different microstructures. The results show that the lower bainite microstructures obtained after the 1st thermal treatment, representative of CGHAZ have excellent impact properties. The impact toughness of the microstructures typical of ICCGHAZ is strongly dependent on the composition as well as morphology and spatial distribution of the resulting martensite-austenite (M/A) islands transformed from inter-critically formed austenite. This zone can play a significant role in fracture initiation and thus needs to be considered in alloy and welding process designs.

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.

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
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