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.

Estimation of local properties in welded joints using samples with simulated microstructure

2016 ◽  
Vol 7 (6) ◽  
pp. 739-747
Author(s):  
Pawel Kucharczyk ◽  
Sebastian Münstermann
Keyword(s):  
Heat Treatment ◽  
Chemical Composition ◽  
Welded Joints ◽  
Fatigue Behavior ◽  
Base Material ◽  
Welding Process ◽  
Tensile Tests ◽  
Homogeneous Microstructure ◽  
Content Type ◽  
Local Properties

Purpose The purpose of this paper is to determine local properties in a coarse grain zone of 10 mm thick butt welded joints made of structural S355 and high strength S960 steels. Metallographic analyses showed that the width of the investigated zone for both S355 and S960 weldments was too small for direct sampling. Therefore, samples with reproduced microstructure were manufactured by heat treatment taking into account chemical composition and cooling conditions of weldments. Design/methodology/approach The basis for the heat treatment was the time-temperature-transition (TTT) curve, whose shape is defined by welding and cooling parameters. In this study the TTT curve was determined experimentally during welding as well as numerically simulated using SYSWELD program. The work pieces were heat-treated according to the TTT curves using thermomechanical treatment simulator and evaluated in terms of microstructure and micro hardness distribution. Finally, the secondary specimens were manufactured and investigated in monotonic tensile tests. Findings The presented approach allows for the determination of the local properties of welded joints. In this study mechanical properties (stress-strain curves) of heat affected zone (HAZ) were successfully estimated using samples with reproduced microstructure. Furthermore, it was found out that the chemical composition in the HAZ was not influenced by the welding process. Thus, the HAZ microstructure can be successfully reproduced using base material. Additionally, the paper contains recommendations for simulation of the local microstructure and suggestions for the evaluation of the obtained results. Originality/value The advantage of the proposed approach is the enlargement of the material volume with homogeneous microstructure so that different local properties like toughness, fatigue behavior, crack propagation or crashworthiness can be analyzed, what is technically infeasible for the weldments with small HAZ.

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.

scholarly journals A Combination of Keyhole GTAW with a Trapezoidal Interlayer: A New Insight into Armour Steel Welding

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3571 ◽  
Author(s):  
Zhenyu Fei ◽  
Zengxi Pan ◽  
Dominic Cuiuri ◽  
Huijun Li ◽  
Azdiar A. Gazder
Keyword(s):  
Chemical Composition ◽  
Weld Metal ◽  
Base Metal ◽  
Welding Process ◽  
Charpy Impact ◽  
Filler Materials ◽  
Temperature Phase ◽  
Ballistic Performance ◽  
Two Phase ◽  
Armour Steel

The ballistic performance of armour steel welds using austenitic filler materials is poor on account of the disparity in the mechanical properties of the weld and base metals. Consequently, a novel Keyhole Gas Tungsten Arc Welding process with a trapezoidal AISI309 austenitic stainless steel interlayer was developed to tailor chemical composition and microstructure by controlling the solidification sequence. Results show that the dilution rate in the weld metal region can reach up to 43.5% by placing a specially designed interlayer in between the base metal, providing a major scope for microstructure modification. Detailed weld analysis was undertaken by X-ray diffraction, optical and secondary and transmission electron microscopy, energy dispersive spectroscopy and electron back-scattering diffraction. The results from Vickers hardness indents and Charpy impact toughness testing at −40 °C show that the properties of the weld metal region are comparable to that of the base metal. This is ascribed to the weld metal comprising a two phase microstructure of martensite and retained austenite, which contribute to improvements in strength and toughness, respectively. Furthermore, the tailored chemical composition, microstructure and low temperature phase transformation in the weld metal may reduce the tendency toward both solidification cracking and hydrogen assisted cold cracking.

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].

Influence of Welding Process on the Microstructure of Carbon Steel and Stainless Steel Heterogeneous Welded Joints

2016 ◽  
Vol 1138 ◽  
pp. 31-36
Author(s):  
Maria Cristina Dijmarescu ◽  
Dumitru Titi Cicic ◽  
Corneliu Rontescu ◽  
Gheorhe Solomon
Keyword(s):  
Chemical Composition ◽  
Carbon Steel ◽  
Structural Characterization ◽  
Base Material ◽  
Welding Process ◽  
Cored Wire ◽  
Base Materials ◽  
Flux Cored Arc Welding ◽  
Welded Seam

The reactions of the base material, during the welding process, consist in chemical composition, volume, structure and granulation changes. There are multiple problems which can occur by welding two steels with totally different chemical composition, i.e. carbon steel S235JR + AR and austenitic stainless X2CrNiMo17-12-2. The process used for making the heterogeneous joint was flux cored arc welding (FCAW), numerically coded 136. The paper presents the effects of welding through heat input, on the structural characterization of welded seam and heat affected zone. It also focuses on the structural characterization of the welded joint obtained using the flux cored wire T 23 12 L P C/M 1, and determining how the base materials participate at the formation of the welding joint.

scholarly journals Evaluation of Crack Occurrence Probability of T-Shape Welded Structures

2011 ◽  
Vol 27 (2) ◽  
pp. 279-286
Author(s):  
Y. Hsu ◽  
W.-F. Wu ◽  
H.-T. Kuo
Keyword(s):  
Residual Stress ◽  
Chemical Composition ◽  
Hydrogen Content ◽  
Welded Joints ◽  
Occurrence Probability ◽  
Diffusible Hydrogen ◽  
Element Analysis ◽  
Welded Structures ◽  
Welded Structure ◽  
Major Factors

ABSTRACTWelded structures are vulnerable to fracture due to cracks, especially at the welds. To investigate the safety of T-Shape welded structures used in some construction sites, a method is proposed in this paper to evaluate the crack occurrence probabilities of the structures. Three major factors that affect the crack occurrence are taken into consideration. They are residual stress, diffusible hydrogen content and chemical composition of the weld metal. In the analysis, finite element analysis is performed to find the residual stress distribution of the structures. The uncertainties of diffusible hydrogen content and chemical composition are treated as random variables. The critical cooling time is found and utilized for evaluating the crack occurrence probability of the welded structure. Numerical results indicate that T-shape welded joints lead to higher residual stresses and higher crack occurrence probabilities in comparison with the traditional butt joints. Therefore, more attention should be paid to this kind of welded joints when they are used.

Weld Hardness Study of P91 Welded Pipes with Post Weld Heat Treatment for Elevated Temperature Application in Power Plants

2015 ◽  
Vol 1115 ◽  
pp. 503-508 ◽  
Author(s):  
Muhammad Sarwar ◽  
Mohd Amin bin Abd Majid
Keyword(s):  
Heat Treatment ◽  
Power Plant ◽  
Weld Metal ◽  
Creep Strength ◽  
Power Plants ◽  
Thermal Power ◽  
Base Material ◽  
Welding Process ◽  
Post Weld Heat Treatment ◽  
Weld Heat

The creep strength-enhanced ferritic (CSEF) steels are undergoing an encouraged use around the world especially in power plant construction. On construction sites, it has always been the target to have no problems in welded joints but premature failures are being encountered. The primary reason of these premature failures is found to be the improper heat treatment that is mandatorily carried out to achieve the required weld hardness. Weld hardness has close relationship with creep strength and ductility of the welded structures. Hence it is important for any weld to achieve certain level of weld hardness. This study aims at ascertaining the importance of Post Welding Heat Treatment (PWHT) in achieving the required hardness in creep-strength enhanced ferritic (CSEF) materials.The study was carried out on the welding of alloy steel ASTM A335 Gr. P-91 with the same base material (ASTM A335 Gr. P-91) by Gas Tungsten Arc Welding (GTAW) process using ER90S-B9 filler wire with pre-heat of 200oC (min) and inter-pass temperature of 300oC (max). After welding, the joints were tested for soundness with Radiography testing. Induction heating was used for heat treatment of P91 pipes during welding and post weld heat treatment. The effect of Post Weld Heat Treatment (PWHT) was investigated on the Weld metal and the Heat Affected Zones (HAZ) by hardness testing. It is perceived that the scattered and higher hardness values, more than 250HB in 2” P91 pipes in the weld metal and in the heat affected zones, can be brought into the lower required level, less than 250HB, with an effective post weld heat treatment at 760°C for 2hrs.It is concluded that PWHT is the most effective way of relieving the welding stresses that are produced due to high heat input in the welding process and to achieve the required level of hardness in the weld as well as in the heat affected zones (HAZ) in thermal power plant main steam piping.

scholarly journals Forming and Properties of Friction Stir Welding Process for Dissimilar Mg Alloy

2015 ◽  
Vol 9 (1) ◽  
pp. 859-864
Author(s):  
Tielong Li ◽  
Zhenshan Wang
Keyword(s):  
Magnesium Alloy ◽  
Process Parameters ◽  
Welded Joints ◽  
Defect Formation ◽  
Base Material ◽  
Welding Process ◽  
Fracture Initiation ◽  
Line Defect ◽  
Influence Of Process Parameters ◽  
Friction Stir

For hot extrusions of magnesium alloy sheets, Dissimilar AZ80 and AZ31 were used, in which AZ80 was placed on advancing side and AZ31 on retreating side, using friction stir butt welding with different process parameters. Some defect-free welded joints with good weld surfaces could be obtained with some suitable welding conditions. The maximum tensile strength of welded joint which is 225.5 MPa can reach 98% that of the AZ31 base material. Influence of process parameters on defects, weld shaping and mechanical property were discussed systematically. And the microstructure of different zones was compared. The fracture of the welded joints takes place at the junction of mechanical heat affected zone and nugget zone in AZ31 magnesium alloy set retreating side, since existing difference in metallographic structure of alloy diversely suffered by heat, pressure and depositing impurities. Fracture initiation site may be the P line defect which should be eliminated, and the P line defect formation was analyzed.

Chemical, Structural, Mechanical and Intergranular Corrosion Characterization of Welded Pipes Joints Made of TP 347 Steel

2013 ◽  
Vol 291-294 ◽  
pp. 2594-2604
Author(s):  
Doru Romulus Pascu ◽  
Roşu Radu Alexandru ◽  
Fulga Doru ◽  
Duma Iuliana
Keyword(s):  
Heat Treatment ◽  
Base Metal ◽  
Welded Joints ◽  
Intergranular Corrosion ◽  
Base Material ◽  
Chemical Compositions ◽  
Base Materials ◽  
Heat Treated ◽  
Complex Carbides ◽  
Precision Temperature

The paper presents the experimental results obtained on the pipes welded joints made of TP 347 steel in normal state, NT (welded) and heat-treated state, TT for post-welding stabilization. Heat treatment for stabilization was performed in an electric furnace which provided the process parameters (Theat = 900°C, Vheat = vcooling ≈ 300°C, etc.) and a precision temperature of ±10°C to 1000°C. Chemical compositions of TP 347 steel pipe and of the filler material (ER 347) have values falling within the manufacturing standards (Cr = 17 ... 19% and Ni = 9... 13%). In the specific areas of the welded joints were detected austenitic structures with heterophasic areas of ferrite and complex carbides areas, having the hardness between 162 and 225 HV10. No welding and heat treatment defects were detected, such as cracks and microcracks. The mechanical strength (Rp0,2 and Rm), determined on the base metal and on the welded joints presents high values. Thus, for the base metal were obtained values of Rp0,2 of minimum 212 N/mm2, respectively values of minimum 523 N/mm2 for Rm. For the welded joints, Rm has values between 522 N/mm2 and 527 N/mm2. All the values obtained are higher than those required by ASTM A370standard. The base materials in NT and TT state presents high values of impact energy KV at 20°C, between 72J and 78J, and for the welded joints, the values of KV are between 53J and 60J, with ductile breaking aspect of the specimens’surfaces. The surfaces of the tested specimens for resistance to intergranular corrosion according to ASTM A 262-2010, Method E, presented not specific defects, attesting a corresponding behavior of the intergranular corrosion of TP347 steel and of the welded joints made of the pipes having the dimensions of ø219 x 8.18 mm. The values of the chemical, structural, mechanical and intergranular corrosion characteristics determined on specific samples evidence a high quality of the base material and of the welded joints of TP 347steel pipe, conducted by qualified welding technology, commonly used in the manufacture of components from chemical and petrochemical industries.

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