Thermographic and Microstructural Analysis of Martensitic Stainless Steel ASTM A743 CA6NM Arising out of Layered GMA Welding Process Using AWS 410 NiMo Welding Wire

2014 ◽  
Vol 936 ◽  
pp. 1303-1311
Author(s):  
Matheus Tabata Santos ◽  
Palloma Vieira Muterlle ◽  
Guilherme Caribé de Carvalho
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
High Resistance ◽  
Martensitic Stainless Steel ◽  
Fatigue Cracks ◽  
Microstructural Analysis ◽  
Base Material ◽  
Welding Process ◽  
Thick Sheet ◽  
Welding Wire

The martensitic stainless steel ASTM A743 CA6NM is typically used in the production of hydroelectric turbines due to its known high resistance to cavitation induced surface damages. Despite the fact the material presents a high resistance to cavitation, depending on the loading condition to which the turbine runner is subjected and on its geometry, fatigue cracks can develop, thus requiring repair by means of removing material around the crack, up to its complete elimination, and by depositing weld metal in the cavity followed by a grinding process, in order to recover the original runner geometry. Such a repair process is normally done on site, which means that it is not possible to carry out the post weld heat treatment necessary to bring the newly deposited weld metal and the base metal to the same microstructure encountered in the runner when it comes out of manufacture. In order to study the effect that a layered welding has on the base material and on the weld metal, this work aims at studying the microstructural changes that occur in the CA6NM stainless steel welded in multiple layers with a AWS 410 NiMo welding wire. In order to attain such an objective, several 410 NiMo weld beads were deposited in successive layers on the border of a 5mm thick sheet while the resulting temperature fields were monitored by a thermographic camera. After the welding process, the samples cut from the welded sheet were examined in the perpendicular direction of deposition and their resulting microstructures where analyzed and correlated with the temperature history recorded during the welding process. Hardness tests were also carried out.

scholarly journals Microstructural Analysis of Inconel 625 Nickel Alloy / UNS S31803 Duplex Stainless-Steel Dissimilar Weldments

2019 ◽  
Vol 44 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Tuba Karahan ◽  
Tolga Mert ◽  
Mustafa Tümer ◽  
Zaim Mithat Kerimak
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
Duplex Stainless Steel ◽  
Nickel Alloy ◽  
Nickel Content ◽  
Microstructural Analysis ◽  
Welding Process ◽  
Inconel 625 ◽  
Electron Microscopes ◽  
Dendritic Austenite

In this study, Inconel 625 nickel alloy and UNS 31803 duplex stainless steel (DSS) dissimilar pairs were welded with MIG welding process. Weld metal, obtained with ERNiCrMo-3 filler wire, was subjected to mechanical and microstructural investigations. Notch impact test and micro hardness measurements were realized on weld metal in order to evaluate31803 mechanical properties. Microstructural changes in fusion line of the base metals were examined using optical and electron microscopes. Phase precipitations rich of Ti and Mo elements were detected among dendritic austenite arms in the weld metal. It was observed that ERNiCrMo-3 filler metal had sufficient toughness because of high nickel content.

Influence of Weld Discontinuities on Strain Controlled Fatigue Behavior of 308 Stainless Steel Weld Metal

1994 ◽  
Vol 116 (2) ◽  
pp. 193-199 ◽  
Author(s):  
K. Bhanu Sankara Rao ◽  
M. Valsan ◽  
R. Sandhya ◽  
S. L. Mannan ◽  
P. Rodriguez
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Base Material ◽  
Welding Process ◽  
Single Strain ◽  
Damage And Fracture ◽  
Slag Inclusions ◽  
Type 304

Detailed investigations have been performed for assessing the importance of weld discontinuities in strain controlled low cycle fatigue (LCF) behavior of 308 stainless steel (SS) welds. The LCF behavior of 308 SS welds containing defects was compared with that of type 304 SS base material and 308 SS sound weld metal. Weld pads were prepared by shielded metal arc welding process. Porosity and slag inclusions were introduced deliberately into the weld metal by grossly exaggerating the conditions normally causing such defects. Total axial strain controlled LCF tests have been conducted in air at 823 K on type 304 SS base and 308 SS sound weld metal employing strain amplitudes in the range from ±0.25 to ±0.8 percent. A single strain amplitude of ±0.25 percent was used for all the tests conducted on weld samples containing defects. The results indicated that the base material undergoes cyclic hardening whereas sound and defective welds experience cyclic softening. Base metal showed higher fatigue life than sound weld metal at all strain amplitudes. The presence of porosity and slag inclusions in the weld metal led to significant reduction in life. Porosity on the specimen surface has been found to be particularly harmful and caused a reduction in life by a factor of seven relative to sound weld metal. Defect combination of porosity and slag inclusions was found to be more deleterious than the case when either the slag inclusions or porosity was present alone. Discontinuties acted as crack initiation sites and also enhanced crack propagation. The LCF properties of weld samples containing discontinuities have been correlated with the damage and fracture behavior.

Experimental Investigations on Aluminium Ultrasonic Welding Parameters

2014 ◽  
Vol 657 ◽  
pp. 306-310
Author(s):  
Lăcrămioara Apetrei ◽  
Vasile Rață ◽  
Ruxandra Rață ◽  
Elena Raluca Bulai
Keyword(s):  
Microstructural Analysis ◽  
Base Material ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Experimental Investigations ◽  
Welding Parameters ◽  
Material Structure ◽  
Welding Temperature ◽  
Wide Range ◽  
Made In

Research evolution timely tendencies, in the nonconventional technologies field, are: manufacture conditions optimization and complex equipments design. The increasing of ultrasonic machining use, in various technologies is due to the expanding need of a wide range materials and high quality manufacture standards in many activity fields. This paper present a experimental study made in order to analyze the welded zone material structure and welding quality. The effects of aluminium ultrasonic welding parameters such as relative energy, machining time, amplitude and working force were compared through traction tests values and microstructural analysis. Microhardness tests were, also, made in five different points, two in the base material and three in the welded zone, on each welded aluminium sample. The aluminum welding experiments were made at the National Research and Development Institute for Welding and Material Testing (ISIM) Timişoara. The ultrasonic welding temperature is lower than the aluminium melting temperature, that's so our experiments reveal that the aluminium ultrasonic welding process doesn't determine the appearance of moulding structure. In the joint we have only crystalline grains deformation, phase transformation and aluminium diffusion.

Effect of Ar-N2 Mixed Gas on Morphology and Microstructure of Type 316L Stainless Steel TIG Weld Metal

2011 ◽  
Vol 295-297 ◽  
pp. 1919-1924 ◽  
Author(s):  
Kuang Hung Tseng ◽  
Kai Chieh Hsien
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
316L Stainless Steel ◽  
Welding Process ◽  
Ferrite Content ◽  
Shielding Gas ◽  
Mixed Gas ◽  
Nitrogen Gas ◽  
Type 316L ◽  
Type 316L Stainless Steel

The aim of the present work was to investigate the effects of specific nitrogen gas additions to argon shielding gas on morphology and microstructure of austenitic stainless steel TIG welds. An autogenous TIG welding process was applied on type 316L stainless steel to produce a bead-on-plate weld. The ferrite content of weld metal was measured using a Feritscope. The results indicated that the arc voltage increase as the amount of nitrogen gas added to the argon atmosphere increases. The retained ferrite content of type 316L stainless steel TIG weld metal decreased rapidly as nitrogen gas addition to the argon shielding gas was increased.

Computer Prediction of Phase Fraction in Multipass Weld of Duplex Stainless Steel - Proposal of Microstructural Improvement Welding Process -

2021 ◽  
Vol 1016 ◽  
pp. 206-212
Author(s):  
Kazuyoshi Saida ◽  
Tomo Ogura ◽  
Shotaro Yamashita ◽  
Yusuke Oikawa
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Microstructural Analysis ◽  
Kinetic Equations ◽  
Welding Process ◽  
Phase Fraction ◽  
Isothermal Heat Treatment ◽  
Computer Prediction ◽  
Incremental Method ◽  
Multipass Weld

Computer simulation of the α/γ phase transformation in multipass weld of duplex stainless steel was made for predicting the distribution of the γ phase fraction in the weld metal (WM) and HAZ. The kinetic equations including rate constants of the dissolution behaviour as well as precipitation behaviour of γ phase were determined by isothermal heat treatment test. Based on the kinetic equations determined, the distribution of the γ phase fraction in multipass weld of duplex stainless steel was calculated applying the incremental method combined with the heat conduction analysis in welding process. The γ phase fraction was reduced in the higher temperature HAZ and WM, however, that in the reheated HAZ and WM was increased and recovered to the base metal level. Microstructural analysis revealed that the calculated results of the γ phase fraction in multipass weld were consistent with experimental ones. Based on the computer prediction, the microstructural improvement welding (“reheat bead welding”) process, with analogous concept to the temper bead welding technique, was newly proposed for recovering the γ phase fraction in weld even in the as-welded situation.

Characterization of Local Deformation in Welded Joints Using a Combined Experimental and Numerical Approach

2014 ◽  
Vol 627 ◽  
pp. 241-244 ◽  
Author(s):  
Pawel Kucharczyk ◽  
Sebastian Münstermann
Keyword(s):  
Chemical Composition ◽  
Weld Metal ◽  
Welded Joints ◽  
Base Material ◽  
Welding Process ◽  
Numerical Approach ◽  
Geometrical Model ◽  
Local Deformation ◽  
Heat Treated ◽  
Welded Structure

The microstructure of welded joints differs significantly from that of the base material, what changes their mechanical properties and influences fatigue life. The aim of this work was the investigation of the local deformation field within a butt joint made of 10 mm thick structural steel S355. However, a direct sampling even of the weld metal was impossible due to small dimensions of butt joints. Therefore, the following procedure was utilized in order to manufacture big samples of the microstructure identical to that of the local weldment areas.A geometrical model of the welded structure describing the relevant areas e.g. weld metal, heat-affected zone was established. It was based on the results of the metallographic investigations, hardness mapping and electron-probe-micro-analysis of the local chemical composition. The welding process was numerically simulated using SYSWELD program to estimate the time-temperature-transition (TTT) curves for each identified area. The parameters of the heat input source were calibrated. Afterwards, the material of the defined chemical composition was heat-treated according to the TTT curves. For the validation purpose the heat-treated work pieces were evaluated in terms of microstructure and hardness distribution. Finally, the up-scaled samples of the respective bulk microstructure were manufactured and investigated in monotonic tests.

Recommendations for Submerged Arc Spiral Welding With Optimized CTOD Properties

2018 ◽  
Author(s):  
Martin Liebeherr ◽  
Özlem E. Güngör ◽  
Nuria Sanchez ◽  
Hervé Luccioni ◽  
Nenad Ilic
Keyword(s):  
Weld Metal ◽  
Base Material ◽  
Welding Process ◽  
Experimental Program ◽  
Welding Parameters ◽  
Pipe Production ◽  
Filler Wire ◽  
Crack Tip Opening Displacement ◽  
Wide Range ◽  
Submerged Arc

Many pipe mills may not be familiar with a Crack Tip Opening Displacement (CTOD) requirement on the pipe seam weld, nor will they find easily relevant information in open literature. Influencing — and certainly not independent — factors are: welding parameters, base material and consumable selection. Out of these, the welding parameters such as heat input and cooling rate cannot be varied over a wide range during the pipe production, which means that the leverage is rather limited at the given welding process. The properties of the heat affected zone will be mainly affected by the base material, while the properties of the weld metal will be affected by both, base material and filler wire selection. In particular with respect to the weld metal properties it will be difficult to obtain general quantitative information. For example, a welding consumable supplier will readily provide the properties of the filler wires but would be unable to predict the changes caused by the dilution from any base material in the weld pool and specific welding procedures that may have been used. To support the pipe mills in the selection of the consumables for submerged arc welding, an experimental program was launched with the aim to provide recommendations on how to optimize CTOD toughness of the spiral weld seam. For this, a large number of welds were produced on 20 mm thick X70 coil samples, with eight different filler wire combinations, using a 2-wire (tandem) set-up for both the inside and outside weld. Welding parameters were kept constant. The welding program was applied to two different X70 steels to determine a potential influence of the micro-alloying elements, particularly Nb. The results show clearly that a careful consumable selection is required for obtaining acceptable CTOD toughness in the weld metal. Ni-Mo and Ti-B additions to the weld metal are found to be beneficial with both steel concepts. Mo addition alone both to the ID and OD welds was clearly not a suitable selection.

Application of FIB/SEM/EBSD for Evaluation of Residual Strains and Their Relationship to Weld Metal Hydrogen Assisted Cold Cracking

2012 ◽  
Author(s):  
W. L. Costin ◽  
I. H. Brown ◽  
L. Green ◽  
R. Ghomashchi
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Ion Beam ◽  
Base Material ◽  
Welding Process ◽  
Cold Cracking ◽  
Predictive Methods ◽  
Residual Strains

Hydrogen assisted cold cracking (HACC) is a welding defect which may occur in the heat affected zone (HAZ) of the base metal or in the weld metal (WM). Initially the appearance of HACC was associated more closely with the HAZ of the base metal. However, recent developments in advanced steel processing have considerably improved the base material quality, thereby causing a shift of HACC to the WM itself. This represents a very serious problem for industry, because most of the predictive methods are intended for prevention of HACC in the HAZ of the base metal, not in the weld metal [1]. HACC in welded components is affected by three main interrelated factors, i.e. a microstructure, hydrogen concentration and stress level [2–4]. In general, residual stresses resulting from the welding process are unavoidable and their presence significantly influences the susceptibility of weld microstructures to cracking, particularly if hydrogen is introduced during welding [5]. Therefore various weldability tests have been developed over the years which are specifically designed to promote HACC by generating critical stress levels in the weld metal region due to special restraint conditions [4, 6–8]. These tests were used to develop predictive methods based on empirical criteria in order to estimate the cracking susceptibility of both the heat-affected zone and weld metal [4]. However, although the relationship between residual stress, hydrogen and HACC has received considerable attention, the interaction of residual stresses and microstructure in particular at microscopic scales is still not well understood [5, 9–21]. Therefore the current paper focuses on the development and assessment of techniques using Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction for the determination of local residual strains at (sub) micron scales in E8010 weld metal, used for the root pass of X70 pipeline girth welds, and their relationship to the WM microstructure. The measurement of these strains could be used to evaluate the pre-existing stress magnitudes at certain microstructural features [22].

SHIELDING GAS AND HEAT INPUT EFFECTS ON THE MECHANICAL AND METALLURGICAL CHARACTERIZATION OF GAS METAL ARC WELDING OF SUPER MARTENSITIC STAINLESS STEEL (12Cr5Ni2Mo) JOINTS

2016 ◽  
Vol 24 (05) ◽  
pp. 1750069
Author(s):  
T. PRABAKARAN ◽  
M. PRABHAKAR ◽  
P. SATHIYA
Keyword(s):  
Stainless Steel ◽  
Heat Input ◽  
Arc Welding ◽  
Martensitic Stainless Steel ◽  
Gas Metal Arc Welding ◽  
Microstructural Analysis ◽  
Tensile Tests ◽  
Shielding Gas ◽  
Metal Arc Welding ◽  
Super Martensitic Stainless Steel

This paper deals with the effects of shielding gas mixtures (100% CO2, 100% Ar and 80 % Ar [Formula: see text] 20% CO[Formula: see text] and heat input (3.00, 3.65 and 4.33[Formula: see text]kJ/mm) on the mechanical and metallurgical characteristics of AISI 410[Formula: see text]S (American Iron and Steel Institute) super martensitic stainless steel (SMSS) by gas metal arc welding (GMAW) process. AISI 410[Formula: see text]S SMSS with 1.2[Formula: see text]mm diameter of a 410 filler wire was used in this study. A detailed microstructural analysis of the weld region as well as the mechanical properties (impact, microhardness and tensile tests at room temperature and 800[Formula: see text]C) was carried out. The tensile and impact fracture surfaces were further analyzed through scanning electron microscope (SEM). 100% Ar shielded welds have a higher amount of [Formula: see text] ferrite content and due to this fact the tensile strength of the joints is superior to the other two shielded welds.

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