The Effect of Weld Metal Manganese Content on the Microstructure, Mechanical Properties and Hot Crack Susceptibility of Helically Welded Linepipes

2008 ◽  
Author(s):  
Navid Pourkia ◽  
Pirooz Marashi ◽  
Rouzbeh Leylabi ◽  
Seyed Alireza Tabatabaei ◽  
Hadi Torshizi
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Weld Metal ◽  
Acicular Ferrite ◽  
Microalloyed Steels ◽  
Second Phase ◽  
Optimum Level ◽  
Hot Crack ◽  
Mn Content ◽  
Crack Susceptibility

The effect of manganese addition on decreasing hot crack susceptibility of submerged arc welding in microalloyed steels is well understood, but its increment should not cause unsuitable changes in metallurgical and mechanical properties of weld metal. Therefore, since weld metal Mn content in SAW process is mainly controlled by welding wire composition, the aim of this investigation is to study the effect of wire Mn content on the microstructure, mechanical properties and hot crack susceptibility of helical linepipes weld metal. In this regard, three different wires with 0.88, 1.05 and 1.54 wt% of Mn content were selected and welding was performed in both experimental and production process condition of X70 helical linepipes. As a result, 1.26, 1.44 and 1.67 wt% of Mn in weld metal was obtained respectively. Metallographical examinations using optical and scanning electron microscopy showed that, increasing the amount of Mn in weld metal, decrease the grain size of all phases (acicular ferrite, primary ferrite and ferrite with aligned second phase). Moreover, in the expense of increasing acicular ferrite, the volume fraction of primary ferrite (mostly grain boundary ferrite) and ferrite with aligned second phase decreased. Also, the results of mechanical properties indicated that the higher the amount of Mn, the higher the strength and hardness of weld metal, but in the case of impact toughness and tensile elongation, an optimum level was observed and lower toughness in the highest Mn content weld metal is attributed to the increasing hardenability and thus formation of martensite/retained austenite islands and grain boundary carbides in coincident sites of acicular ferrite grains. Moreover, analyzes in more than 1000m helical linepipes weld metal length showed that increasing weld metal Mn content up to 1.4wt%, reduced the possibility of hot crack formation from total percentage of 0.005 to around 0.001.

Effect of Post Weld Heat Treatment on Fusion and Heat Affected Zone Microstructure and Mechanical Properties of Inconel X-750 Welds

2011 ◽  
Vol 214 ◽  
pp. 108-112 ◽  
Author(s):  
Prachya Peasura ◽  
Bovornchok Poopat
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Aging Temperature ◽  
Post Weld Heat Treatment ◽  
High Aging Temperature ◽  
Zone Microstructure

The Inconel X-750 indicates good hot corrosion resistance, high stability and strength at high temperatures and for this reason the alloy is used in manufacturing of gas turbine hot components. The objective of this research was study the effect of post weld heat treatment (PWHT) on fusion zone and heat affected zone microstructure and mechanical properties of Inconel X-750 weld. After welding, samples were solutionized at 1500 0C. Various aging temperature and times were studied. The results show that aging temperature and time during PWHT can greatly affect microstructure and hardness in fusion zone and heat affected zone. As high aging temperature was used, the grain size also increased and M23C6 at the grain boundary decreased. This can result in decreased of hardness. Moreover excessive aging temperature can result in increasing MC carbide intensity in parent phase (austenite). It can also be observed that M23C6 at the grain boundary decreased due to high aging temperature. This resulted in decreasing of hardness of weld metal and heat affected zone. Experimental results showed that the aging temperature 705 0C aging time of 24 hours provided smaller grain size, suitable size and intensity of MC carbide resulting in higher hardness both in weld metal and HAZ.

Mechanical Properties and Fracture Analysis of Mn-Rich Ni-Mn-Ga Polycrystalline Alloys

2006 ◽  
Vol 324-325 ◽  
pp. 691-694 ◽  
Author(s):  
Feng Chen ◽  
Wei Cai ◽  
Lian Cheng Zhao ◽  
Yu Feng Zheng
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Intergranular Crack ◽  
Fracture Analysis ◽  
Compression Tests ◽  
Polycrystalline Alloys ◽  
Micro Cracks ◽  
Mn Content ◽  
Rupture Strain ◽  
Scanning Electron

In present paper, the mechanical properties and fracturegraphs of Mn-rich polycrystalline alloys are investigated by compression tests and scanning electron microscope (SEM) observations. It is shown that the fracture strength and the rupture strain decrease with the increase of Mn content. It is suggested that the substitution of Mn for Ga reduces the ductility of Ni-Mn-Ga alloys. SEM observations of fracture surface show us typical intergranular crack. There are many little holes and micro-cracks on the grain boundary, which weakens the bond strength of grain boundary causing the intercrystalline cracking.

THE CHANGE IN THE CHEMICAL COMPOSITION AND TOUGHNESS OF API 5L-X70 WELDS BY ADDITION OF TITANIUM

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1209-1216 ◽  
Author(s):  
BEHROOZ BEIDOKHTI ◽  
AMIR HOSEIN KOUKABI ◽  
ABOLGHASEM DOLATI ◽  
PENG HE
Keyword(s):  
Grain Boundary ◽  
Weld Metal ◽  
Acicular Ferrite ◽  
Titanium Content ◽  
Weld Deposit ◽  
Steel Weld Metal ◽  
Metal Properties ◽  
Api 5L X70 Steel ◽  
The Relationship ◽  
Grain Boundary Ferrite

The objective of this work was to study the influence of titanium variations on the API 5L-X70 steel weld metal properties. The relationship between microstructure and toughness of the weld deposit was studied by means of full metallographic, longitudinal tensile and Charpy- V notch tests on the specimens cut transversely to the weld beads. The best combination of microstructure and impact properties was obtained in the range of 0.02-0.05% titanium. By further increasing of titanium content, the microstructure was changed from a mixture of acicular ferrite, grain-boundary ferrite, Widmanstätten ferrite to a mixture of acicular ferrite, grain-boundary ferrite, bainite and ferrite with M/A microconstituent. Therefore, the mode of fracture also changed from dimpled ductile to quasi-cleavage. Titanium-base inclusions improve impact toughness by increasing the formation of acicular ferrite in the microstructure. The amount of manganese in inclusions was decreased with addition of titanium to the weld metal.

scholarly journals Cold Crack Susceptibility studies on High Strength Low Alloy Steel 950A using Tekken Test

2017 ◽  
Vol 13 ◽  
pp. 25-31
Author(s):  
Manivelmuralidaran Velumani ◽  
M. Sakthivel ◽  
M. Balaji
Keyword(s):  
Weld Metal ◽  
Alloy Steel ◽  
Acicular Ferrite ◽  
Test Procedure ◽  
High Strength ◽  
Cold Cracking ◽  
Low Alloy Steel ◽  
Cracking Resistance ◽  
Preheating Temperature ◽  
Crack Susceptibility

In This research article deals with the study of cold cracking susceptibility of High Strength Low Alloy Steel (HSLA) 950A using Gas Metal Arc Welding process (GMAW). The cold cracking is a general problem while welding HSLA steels. It thus becomes mandatory to have a novel method of welding to minimize the effects of cold cracking. The cold cracking tendency of the material is determined using the Y groove Tekken test and the test is carried out with DIN EN ISO 17642–2 standard. The welding of the base metal has been carried out using the low hydrogen electrode ER 70SD2. The test procedure is followed under self-restraint condition for determining cold cracking susceptibility of weld metal. Micro structural constituent of the weld metal plays an important role in determining the cold crack susceptibility of the weld metal. Hence an attempt has been made to impart the microstructure having high resistance to cold cracking.  It has been observed that Acicular ferrite microstructure in the weld metal increases the cold cracking resistance of the welded joint.  In the present study, the effect of preheating temperature on cold crack susceptibility analyzed by varying the preheating temperature 100ºC, 150ºC and acicular ferrite microstructure observed in the microstructure analysis of the welded specimen. The effect of microstructure on cold cracking has also been established. But due to very limited range of temperature, the effect of preheating temperature on cold crack susceptibility was inconclusive. But the formation of acicular ferrite microstructure will have greater influence on cold crack susceptibility. In future, effects of Nickel, Manganese and other alloying elements of the filler material in increasing cold cracking resistance can also be studied for far reaching prospects of the research.

Exploring Possibilities of Implementation of Special Rutile Electrodes for Welding Microalloyed Steels

2016 ◽  
Vol 1138 ◽  
pp. 19-24
Author(s):  
Mihailo Mrdak ◽  
Nikola Bajić ◽  
Marko Rakin ◽  
Darko Veljić ◽  
Zoran Karastojković ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Microalloyed Steel ◽  
Raw Materials ◽  
Microalloyed Steels ◽  
Test Results ◽  
Medium Thickness ◽  
Cored Wire ◽  
Ni Content

The paper presents test results of a new quality of a special rutile electrode, with a core of flux-cored wire made from local raw materials, based on analyzing mechanical properties and microstructure of the weld metal in MMA welding. The base metal for experimental welding was microalloyed steel marked J55 (thickness 7.0 mm) according to API Spec 5L standards (EN 10113-3. and JUS C.B0 502) which was produced in Smederevo steelworks. For experimental welding a special electrode IHIS E 35 R-2 was used, with a medium thickness rutile coating, a core of flux-cored wire and Ni content of 2.5%. The results of the analyzes indicate that the new quality special rutile electrode with the flux-cored wire core provides good structural and mechanical properties of weld metal in microalloyed steel welded joints.

scholarly journals Influence of Long-Period-Stacking Ordered Structure on the Damping Capacities and Mechanical Properties of Mg-Zn-Y-Mn As-Cast Alloys

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4654
Author(s):  
Ruopeng Lu ◽  
Kai Jiao ◽  
Yuhong Zhao ◽  
Kun Li ◽  
Keyu Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Second Phase ◽  
Ordered Structure ◽  
Long Period ◽  
Circular Structure ◽  
Strong Orientation ◽  
Cast Alloys ◽  
Mn Content ◽  
Better Than

Magnesium alloys are concerned for its mechanical properties and high damping performance. The influence of Mn toward the internal organization morphology of long-period stacking ordered (LPSO) second phase and the consistent damping performance in Mg-4.9Zn-8.9Y-xMn have been studies in this work. It has shown that the addition of Mn tends to diffuse to the LPSO interface and causes the LPSO phase to expand in the arc direction. The circular structure of LPSO can optimize the damping property of the alloy better than the structure with strong orientation, especially at the strain of 10−3 and 250 °C. With more additions of Mn, damping would have a reduction due to the dispersed fine LPSO phases and α-Mn particles. When the Mn content is higher than 1.02%, the grain is refined, and mechanical properties have been significantly improved. Mg-4.9%Zn-8.9%Y-1.33%Mn shows the best mechanical property.

scholarly journals Effect of the Zn/Mg Ratio on Microstructures, Mechanical Properties and Corrosion Performances of Al-Zn-Mg Alloys

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3299
Author(s):  
Keda Jiang ◽  
Yanquan Lan ◽  
Qinglin Pan ◽  
Yunlai Deng
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Grain Boundary ◽  
Stress Corrosion ◽  
Intergranular Corrosion ◽  
Optical Microscope ◽  
Mg Alloys ◽  
Sensitivity Index ◽  
Second Phase ◽  
Mechanical Properties And Corrosion

The effect of the Zn/Mg ratio on microstructures, mechanical properties and corrosion performances of Al-Zn-Mg alloys was studied. Microstructures were characterized using the optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). Tensile tests, intergranular corrosion (IGC) and stress corrosion cracking (SCC) tests were conducted to study the properties. Microstructures results indicated that with the decrease of the Zn/Mg ratio, the recrystallization proportion and the fraction of second phase decreased, while the size of η’ (MgZn2) phases in grain interior also significantly decreased. The number density of η’ phases in grain interior increased and grain boundary precipitates developed discontinuous distribution with the decrease of the Zn/Mg ratio. These microstructures contributed to the significant improvement of the strength and corrosion resistance. The tensile strength and yield strength increased by 34.1% and 47.4%, respectively, with the Zn/Mg ratio decreased from 11.4 to 6.1. Calculating results indicated that the enhancement of strength mainly contributed from the solid-solution strengthening, grain-boundary strengthening and precipitation strengthening. The intergranular corrosion degree was greatly relieved and the stress corrosion sensitivity index decreased from 0.031 to 0.007 with the Zn/Mg ratio decreased from 11.4 to 6.1.

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