Physical Simulation for Evaluating Heat-Affected Zone Toughness of High and Ultra-High Strength Steels

2013 ◽  
Vol 762 ◽  
pp. 711-716 ◽  
Author(s):  
Risto O. Laitinen ◽  
David A. Porter ◽  
L. Pentti Karjalainen ◽  
Pasi Leiviskä ◽  
Jukka Kömi
Keyword(s):  
Heat Affected Zone ◽  
Heat Input ◽  
Physical Simulation ◽  
Energy Requirement ◽  
High Strength Steels ◽  
High Strength ◽  
Coarse Grained ◽  
Test Results ◽  
Ultra High Strength Steels ◽  
The Impact

Physical simulation of the most critical sub-zones of the heat-affected zone is a useful tool for the evaluation of the toughness of welded joints in high-strength and ultra-high-strength steels. In two high-strength offshore steels with the yield strength of 500 MPa, the coarse grained, intercritical and intercritically reheated coarse grained zones were simulated using the cooling times from 800 to 500 °C (t8/5) 5 s and 30 s. Impact and CTOD tests as well as microstructural investigations were carried out in order to evaluate the weldability of the steels without the need for expensive welding tests. The test results showed that the intercritically reheated coarse grained zone with the longer cooling time t8/5=30 s was the most critical sub-zone in the HAZ due to the M-A constituents and coarse ferritic-bainitic microstructure. In 6 mm thick ultra-high-strength steel Optim 960 QC, the coarse grained and intercritically reheated coarse grained zones were simulated using the cooling times t8/5 of 5, 10, 15 and 20s and the intercritical zone using the cooling times t8/5 of 5 and 10 s in order to select the suitable heat input for welding. The impact test results from the simulated zones fulfilled the impact energy requirement of 14 J (5x10 mm specimen) at -40 °C for the cooling times, t8/5, from 5 to 15 s, which correspond to the heat input range 0.4-0.7 kJ/mm (for a 6 mm thickness).

Effect of Welding Processes with High Heat Input on the Microstructure and Toughness of Coarse-Grained Heat-Affected Zone of a High-Strength High-Toughness Steel

2018 ◽  
Vol 937 ◽  
pp. 61-67
Author(s):  
Yu Jie Li ◽  
Jin Wei Lei ◽  
Xuan Wei Lei ◽  
Oleksandr Hress ◽  
Kai Ming Wu
Keyword(s):  
Low Temperature ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
High Strength ◽  
High Heat ◽  
Coarse Grained ◽  
Low Temperature Impact Toughness ◽  
The Impact ◽  
Welding Processes

Utilizing submerged arc welding under heat input 50 kJ/cm on 60 mm thick marine engineering structure plate F550, the effect of preheating and post welding heat treatment on the microstructure and impact toughness of coarse-grained heat-affected zone (CGHAZ) has been investigated. The original microstructure of the steel plate is tempered martensite. The yield and tensile strength is 610 and 660 MPa, respectively. The impact absorbed energy at low temperature (-60 °C) at transverse direction reaches about 230~270 J. Welding results show that the preheating at 100 °C did not have obvious influence on the microstructure and toughness; whereas the tempering at 600 °C for 2.5 h after welding could significantly reduce the amount of M-A components in the coarse-grained heat-affected zone and thus improved the low temperature impact toughness.

scholarly journals USE OF MULTI-PHASE TRIP STEEL FOR PRESS-HARDENING TECHNOLOGY

2019 ◽  
Vol 25 (2) ◽  
pp. 101 ◽  
Author(s):  
Hana Jirková ◽  
Kateřina Opatová ◽  
Štěpán Jeníček ◽  
Jiří Vrtáček ◽  
Ludmila Kučerová ◽  
...  
Keyword(s):  
Trip Steel ◽  
Physical Simulation ◽  
Isothermal Holding ◽  
High Strength Steels ◽  
High Strength ◽  
Press Hardening ◽  
Passenger Safety ◽  
Ultra High Strength Steels ◽  
New Treatments ◽  
Multi Phase

<p class="AMSmaintext">Development of high strength or even ultra-high strength steels is mainly driven by the automotive industry which strives to reduce the weight of individual parts, fuel consumption, and CO<sub>2</sub> emissions. Another important factor is to improve passenger safety. In order to achieve the required mechanical properties, it is necessary to use suitable heat treatment in addition to an appropriate alloying strategy. The main problem of these types of treatments is the isothermal holding step. For TRIP steels, the holding temperature lies in the field of bainitic transformation. These isothermal holds are economically demanding to perform in industrial conditions. Therefore new treatments without isothermal holds, which are possible to integrate directly into the production process, are searched. One way to produce high-strength sheet is the press-hardening technology. Physical simulation based on data from a real-world press-hardening process was tested on CMnSi TRIP steel. Mixed martensitic-bainitic structures with ferrite and retained austenite (RA) were obtained, having tensile strengths in excess of 1000 MPa.</p>

Mechanical properties and microstructural evaluation of the heat-affected zone in ultra-high strength steels

2020 ◽  
Vol 157 ◽  
pp. 107072
Author(s):  
Mohsen Amraei ◽  
Shahriar Afkhami ◽  
Vahid Javaheri ◽  
Jari Larkiola ◽  
Tuomas Skriko ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Affected Zone ◽  
High Strength Steels ◽  
High Strength ◽  
Microstructural Evaluation ◽  
Ultra High Strength Steels

scholarly journals Pulse spray gas metal arc welding of advanced high strength S650MC automotive steel

10.30544/682 ◽  
2021 ◽  
Vol 27 (4) ◽  
pp. 505-517
Author(s):  
Ashok Kumar Srivastava ◽  
Pradip K Patra
Keyword(s):  
Weld Joint ◽  
Heat Input ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Filler Wire ◽  
Advanced High Strength Steels ◽  
Metal Arc Welding ◽  
The Impact

With an increasing demand for safer and greener vehicles, mild steel and high strength steel are being replaced by much stronger advanced high strength steels of thinner gauges. However, the welding process of advanced high strength steels is not developed at the same pace. The performance of these welded automotive structural components depends largely on the external and internal quality of weldment. Gas metal arc welding (GMAW) is one of the most common methods used in the automotive industry to join car body parts of dissimilar high strength steels. It is also recognized for its versatility and speed. In this work, after a review of GMAW process and issues in welding of advanced high strength steels, a welding experiment is carried out with varying heat input by using spray and pulse-spray transfer GMAW method with filler wires of three different strength levels. The experiment results, including macro-microstructure, mechanical properties, and microhardness of weld samples, are investigated in detail. Very good weldability of S650MC is demonstrated through the weld joint efficiency > 90%; no crack in bending of weld joints, or fracture of tensile test sample within weld joint or heat affected zone (HAZ), or softening of the HAZ. Pulse spray is superior because of thinner HAZ width and finer microstructure on account of lower heat input. The impact of filler wire strength on weldability is insignificant. However, high strength filler wire (ER100SG) may be chosen as per standard welding practice of matching strength.

scholarly journals Effect of tempering on the impact-abrasive and abrasive wear resistance of ultra-high strength steels

Wear ◽  
2019 ◽  
Vol 440-441 ◽  
pp. 203098 ◽  
Author(s):  
Oskari Haiko ◽  
Kati Valtonen ◽  
Antti Kaijalainen ◽  
Sampo Uusikallio ◽  
Jaakko Hannula ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Abrasive Wear ◽  
High Strength Steels ◽  
High Strength ◽  
Abrasive Wear Resistance ◽  
Ultra High Strength Steels ◽  
The Impact

Effect of Nb Content on the Impact Toughness of Coarse-Grained Heat-Affected Zone of Pipeline Steels under Large Heat Input

2014 ◽  
Vol 1078 ◽  
pp. 3-7
Author(s):  
Feng Zhou ◽  
Zhou Gao ◽  
Kai Ming Wu
Keyword(s):  
Heat Affected Zone ◽  
Heat Input ◽  
Optical Microscope ◽  
Coarse Grained ◽  
Electron Backscattered Diffraction ◽  
Pipeline Steels ◽  
Nb Content ◽  
Large Heat ◽  
Austenite Grains ◽  
The Impact

The effect of large heat inputs (200 kJ/cm) on the microstructures and toughness of heat-affected zone of Nb microalloyed X70 pipeline steels were simulated utilizing Gleeble-3800. The microstructures were observed by optical microscope, scanning electron microscope and electron backscattered diffraction technique. Results showed that when the large heat input welding was applied, big austenite grains and coarse microstructures were formed in the coarse-grained heat-affected zone, and thus the toughness of the coarse-grained heat-affected zone was seriously reduced. With the increase of Nb content, the toughness of the CGHAZ did not change remarkably under the large heat input welding.

The critical influence of La content on the microstructure-toughness relationship in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels

2021 ◽  
Vol 118 (2) ◽  
pp. 212
Author(s):  
Yuxin Cao ◽  
Xiangliang Wan ◽  
Feng Zhou ◽  
Hangyu Dong ◽  
Kaiming Wu ◽  
...  
Keyword(s):  
Heat Affected Zone ◽  
Acicular Ferrite ◽  
High Strength ◽  
Coarse Grained ◽  
Low Alloy Steels ◽  
Fine Grained ◽  
Welding Thermal Cycle ◽  
Alloy Steels ◽  
High Fraction ◽  
The Impact

The present study was envisaged to investigate the role of La content on the particle, microstructure and toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels. Three steels with La content of 0.016 wt.%, 0.046 wt.% and 0.093 wt.% were prepared and simulated in a 100 kJ/cm heat input welding thermal cycle. Subsequently, the particle and microstructure of selected specimens were characterized and the impact absorb energy was measured at −20 °C. The results indicated that the La2O2S inclusions in 0.016 wt.%-La steel were gradually modified to LaS-LaP in 0.046 wt.%-La steel and to LaP in 0.093 wt.%-La steel. A higher fraction of acicular ferrite was obtained in the simulated CGHAZ of 0.016 wt.%-La steel, since the inclusion of La2O2S was more powerful to induce the formation of acicular ferrite. Furthermore, the fraction of M-A constituents in the simulated CGHAZ increased with increasing La content. The impact toughness in the simulated CGHAZ of 0.016 wt.%-La steel was the highest, owing to the high fraction of the fine-grained acicular ferrite and low fraction of M-A constituent.

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.

Study in Simulated Heat-Affected Zone of Ship Steel

2011 ◽  
Vol 228-229 ◽  
pp. 1196-1200
Author(s):  
Wen Yan Liu ◽  
Ji Bin Liu ◽  
Cong Mao Zhu ◽  
Hui Wang
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Physical Simulation ◽  
Wide Range ◽  
Lath Bainite ◽  
Quench Hardening ◽  
Impact Energies ◽  
The Impact ◽  
Cct Diagrams

The experiments were carried out upon the determination of simulated heat-affected zone continuous cooling transformation (SH-CCT) diagrams, the characteristics of microstructure and Vickers hardness of SH-CCT specimens, and impact toughness in simulated coarse grain heat-affected zone (CGHAZ) of ship steels under different heat input based on physical simulation. The SH-CCT diagram reveals that bainite is always obtained in a wide range of cooling rates. When the maximum cooling rate reaches 100 °C/s (t8/5=3 seconds), the maximum fraction of martensite (8%) is obtained and the microstructures mainly consist of lath bainite and the hardness is only 255 HV. This demonstrates that the steel has a low quench-hardening tendency and excellent resistance to cold cracking. There are no obvious hardening and softening phenomena in simulated CGHAZ. Test results of impact toughness under different heat input in simulated CGHAZ show that the impact energies reach over 30 J at -40 °C when t8/5 is less than 20 s, meeting the stipulated requirements of ship steel (≥22 J at -40 °C) but no great allowance. Thus, to meet the requirement of properties during welding, it is proposed to choose t8/5 ranging from 5 to 20 s, correspondently the line energies ranging from 14 to 37 KJ/cm for 30 mm thick plate.

Effect of Nb on Microstructure Evolution of Coarse-Grained Heat-Affected Zone with Large Heat Input Welding

2011 ◽  
Vol 284-286 ◽  
pp. 1174-1179 ◽  
Author(s):  
Xue Li Tao ◽  
Kai Ming Wu ◽  
Xiang Liang Wan
Keyword(s):  
Grain Boundary ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Acicular Ferrite ◽  
High Strength ◽  
Coarse Grained ◽  
Granular Bainite ◽  
Low Alloy Steels ◽  
Alloy Steels ◽  
Grain Boundary Ferrite

The effect of Nb microalloying on microstructure transformation of coarse-grained heat-affected zone of high strength low alloy steels were investigated utilizing different heat input welding simulation. For the low-Nb steel, the microstructures of coarse-grained heat-affected zone mainly consisted of acicular ferrite, bainite and grain boundary ferrite for small heat input welding; the amount of acicular ferrite decreased whereas grain boundary ferrite, polygonal ferrite and pearlite increased with increasing heat input. In constrast, for the high-Nb steel, granular bainite was the dominant microstructure. The formation of granular bainitic microstructure was associated with the solid solution of Nb, which suppressed ferrite transformation and promoted the formation of granular bainite. The hardness of coarse-grained heat-affected zone increased with increasing Nb content, and decreased with decreasing heat input, which was attributed to the microstructural change.

Sign in / Sign up

Export Citation Format

Share Document