Mechanical Properties Of Weld Metal Research Articles

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

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.

Influence of the chemical composition of weld electrode on the mechanical properties of submerged arc welded pipe

Submerged arc welding (SAW) is extensively used in pipe production. Because of the need for high toughness in a pipeline, it is necessary to develop wires and fluxes for high-efficiency SAW to produce weld metal (WM). Investigations are carried out in real spiral pipe production factory by the multi-wire double seam SAW process using constant welding parameters and the same flux. Two different chemical compositions of API-X65 steel and four different chemical compositions of weld electrodes have been used in this investigation to evaluate the effect of WM chemical composition on the mechanical behaviour of welded X65 steels. Vickers hardness, Charpy V-notch (CVN) impact toughness and tensile strength tests have been conducted. The toughness of the WM is lower than BM and HAZ. The WM toughness improvement depends on the weld electrode that is used and increases with increasing Mn content of the weld electrode used. The weld electrode contains B and Ti micro-alloy elements that can produce high toughness WM. The mechanical properties of WM are changed by using different weld electrodes. This work shows the importance of the selection of weld electrode composition in order to improve the mechanical properties of steel welds.

Effect of cooling rate on microstructure, inclusions and mechanical properties of weld metal in simulated local dry underwater welding

Quenched and tempered E550 steel was joined using flux-cored arc welding. The effect of cooling rate on microstructure, inclusions and mechanical properties of the weld metal was investigated by optical microscope, scanning electron microscope, transmission electron microscope and mechanical testing. Results show that weld metal microstructures consist of proeutectoid ferrite, ferrite side plate and acicular ferrite. As the cooling rate increased, the volume fraction of proeutectoid ferrite and ferrite side plate decreased, acicular ferrite increased accompanied with refined grain. Furthermore, inclusions of Ti, Mn oxide with diameter below 2.0μm were found in the weld metal and rapid cooling rate causes distinct Mn-depleted zone between inclusions and matrix. Excellent balance of high strength and toughness is obtained as more acicular ferrite in weld metal with rapid cooling rate. This can attribute to the increased of acicular ferrite with its refined grain and high density dislocation. These findings suggest that the rapid cooling rate can improve the impact toughness and tensile strength of weld metal in local dry underwater welding.

Prediction of Microstructure and Mechanical Properties of Weld Metal in Hybrid Laser-Arc Welding

Calculation technique in order to reconstruct the 3D temperature field and predict the microstructure and mechanical properties of the weld metal in hybrid laser-arc welding is developed. The technique is based on the solution of the direct 3D temperature problem by a function-analytical method, the numerical solution of the inverse problem for the unknown parameters of a volume heat source, the employment of the known models for prediction of the microstructure and mechanical properties. The proposed calculation technique makes it possible to reduce considerably the total time for data input and solution. It is demonstrated with an example of butt hybrid laser-arc welding.

Phase Transformation and Its Effect on Mechanical Properties of C300 Weld Metal after Aging Treatment at Different Temperatures

The influence of aging temperature on phase transformation and mechanical properties of weld metal of maraging steel (grade C300) was studied. Microstructure was analyzed by means of optical microscopy, transmission electron microscopy, scanning electron microscopy and energy dispersive spectrum analysis. Gibbs free energy of Ni3Ti and Fe2Mo at different temperature was calculated by Thermal-calc software. The microstructure of weld metal in as-welded state is martensite. The yield strength of weld metal after 430 °C aging process may increase to 1561 MPa from 890 MPa in as-welded state, which is ascribed to the formation of spinodal constitute and GP zones. After 480 °C aging process, there are great deal of Ni3Ti precipitates in the martensite matrix and 10% reverted austenite phase in the cellular grain boundary, and the yield strength increases to 1801 MPa. After aging process at 580 °C, there are many Fe2Mo precipitates in the martensite matrix and 30% reverted austenite phase in the cellular grain boundary, and the yield strength is 1329 MPa, which is the lowest among the three cases. The phase transformation may also influence the toughness. It is found that precipitates make the toughness decrease and reverted austenite increases it. The mechanism of phase transformation on strength and toughness is discussed.

Inclusions, microstructure and properties of flux copper backing submerged arc weld metal

This paper investigates the effect of Ce on inclusions, microstructure and mechanical properties of the weld metal in flux copper backing submerged arc welding. The results show, with the addition of Ce in weld metal, the inclusions are mainly composed of Al2O3, MnO, SiO2, TiO, Ce2S3, CeS and Ce2O2S compound, and the proportion of the inclusions of < 1.0 μm in size increased. In competitive nucleation, acicular ferrite nucleates on the oxysulphides of Ce and inhibits the formation of proentectoid ferrite and ferrite side plate. This led to a high proportion of acicular ferrite, good mechanical properties of weld metal. A small lattice disregistry between CeS, Ce3S4, Ce2O2S and acicular ferrite contributed to low energy for nucleation of acicular ferrite.

A REVIEW OF EFFECT OF WELDING AND POST WELD HEAT TREATMENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF GRADE 91 STEEL

Today getting high thermal efficiency in thermal and nuclear power plant is a big challenge. Many new material are developed. SA 335 grade 91 steel is modified high chrome-moly martenstitic steel. This material is having excellent toughness and high temperature creep strength. During welding, this material is having tremendous change in its microstructure and hence mechanical property. Many research works were done in this area. This paper discusses weld ability of P91 material. Effect of different welding process, type of filler wire, its chemical composition and type of flux is discussed in this paper. PWHT is necessary after welding of P91 steel. PWHT temperature and its duration affects phase transformation and mechanical properties of weld metal, HAZ and parent metal. Major focus is given on hardness, creep resistance and notch toughness.

Microstructure, Texture, and Mechanical Property Analysis of Gas Metal Arc Welded AISI 304 Austenitic Stainless Steel

The present study elaborately explains the effect of welding parameters on the microstructure, texture, and mechanical properties of gas metal arc welded AISI 304 austenitic stainless steel sheet (as received) of 4 mm thickness. The welded joints were prepared by varying welding speed (WS) and current simultaneously at a fixed heat input level using a 1.2-mm-diameter austenitic filler metal (AISI 316L). The overall purpose of this study is to investigate the effect of the variation of welding conditions on: (i) Microstructural constituents using optical microscope and transmission electron microscope; (ii) Micro-texture evolution, misorientation distributions, and grain boundaries at welded regions by measuring the orientation data from electron back scattered diffraction; and (iii) Mechanical properties such as hardness and tensile strength, and their correlation with the microstructure and texture. It has been observed that the higher WS along with the higher welding current (weld metal W1) can enhance weld metal mechanical properties through alternation in microstructure and texture of the weld metal. Higher δ-ferrite formation and high-angle boundaries along with the 〈101〉 + 〈001〉 grain growth direction of the weld metal W1 were responsible for dislocation pile-ups, SFs, deformation twinning, and the induced martensite with consequent strain hardening during tensile deformation. Also, fusion boundary being the weakest link in the welded structure, failure took place mainly at this region.

Effects of Hot Bending Parameters on Microstructure and Mechanical Properties of Weld Metal for X80 Hot Bends

Mechanical properties of weld metal are the key factors affecting the quality of heavy-wall X80 hot induction bends. The effects of bending parameters on the mechanical properties of weld metal for hot bends were investigated by simulation conducted on a Gleeble-3500 thermal simulator. Continuous cooling transformation (CCT) diagrams of the weld metal were also constructed. The influences of hot bending parameters (such as reheating temperature, cooling rate, and tempering temperature) on the microstructure and mechanical properties of weld metal were also analyzed. Results show that the strength of all weld metal specimens is higher than the value indicated in the technical specification and increases with the increase of reheating temperature, cooling rate, and tempering temperature. The impact toughness is apparently related to the variation of reheating temperature, cooling rate, and tempering temperature.

Effect of chemical composition on microstructure and mechanical properties of laser weld metal of high-tensile-strength steel

Laser beam welding (LBW) and laser-arc hybrid welding are expected to be applied to welding of high-strength steel plates over 780 MPa, because they have advantages such as low distortion and a narrow heat-affected zone. This research examined the relationship between the chemical composition of high-strength steel plates and the microstructure and mechanical properties of the weld metal with the aim of improving the toughness of welded joints of high-strength steels by the LBW process. The results revealed that weld metal toughness is strongly dependent on the carbon (C) content of the steel plates, and excellent toughness can be obtained in weld metals with low C contents having an almost fully lower bainite structure without formation of slender martensite austenite constituent (MA). Based on these results, a guideline for appropriate alloying element design for high-strength steels for LBW was proposed, targeting mechanical properties of tensile strength ≥980 MPa and toughness vE−40 °C ≥ 47 J.

Properties of a creep resistant 9Cr-1.5Mo-1Co cast steel joint welded with a matching flux-cored wire

For years, it has been the aim to improve the efficiency of thermal power plants by increasing the steam temperature. Therefore, appropriate steels and welding consumables are needed. Latest developments in cast materials have shown that the boron-alloyed 9Cr-1.5Mo-1Co steel called CB2 enables steam temperatures up to 620 °C. As flux-cored wires for gas metal arc welding offer several technical and economic advantages, they are getting more and more popular. Therefore, a matching flux-cored wire for production welding of cast components has been developed. To obtain the required mechanical properties in weld metal and heat-affected zone, an appropriate welding technology has been established. This paper deals with the influence of welding parameters on the mechanical properties at ambient temperature. Best results could be obtained with higher heat input and lower cooling rate. Additionally, first results of creep tests are presented and show that weld metal and cross-weld samples are within the scatter band of the base material. MatCalc calculations describe the microstructural evolution in the heat-affected zone (HAZ) during welding, post weld heat treatment (PWHT) and service.

Effects of TIG Pulse Current and Nitrogen Content in Argon Shielding Gas on Microstructure and Mechanical Properties of 15Cr-4Ni-8Mn-1.3Cu Stainless Steel Weld Metal

The TIG pulse welding of 15Cr-4Ni-8Mn-1.3Cu austenitic stainless steel at pulse currents of 130 and 160 A with Argon shielding gases containing 0%, 5% and 10% (v/v) Nitrogen was investigated. The effects of pulse current and Nitrogen content in Argon shielding gas on the microstructure and mechanical properties of weld metal were studied. Based on the results found in this study, the nitrogen content in weld metal was found to increase with increasing nitrogen content in argon shielding gas and pulse current. With the addition of nitrogen in Argon shielding gas, the morphology of delta-ferrites was changed from the conventional TIG pulse welding using pure Argon shielding gas where both lathy and vermicular types were found. However, with the Nitrogen + Argon shielding gas, only vermicular type was observed. Moreover, the arm spacing of delta-ferrite can be enlarged by increasing the pulse current. Those results are the reason for the observed decrease in tensile strength and percent elongation with increasing nitrogen content in argon shielding gas and the pulse current.

Microstructural evolution and mechanical properties of high strength 3–9% Ni-steel alloys weld metals produced by electron beam welding

The microstructures and mechanical properties of weld metals of high strength steels having 3–9% Ni content have been investigated with getting a better insight into the role of retained austenite. The weld metals were produced autogenously by electron beam welding (EBW) process. The results showed that once Ni content exceeded 4% prior austenitic grains of the weld metals were rapidly coarsened and solidified into a cellular dendritic structure. The content of retained austenite increased with Ni addition and was preferentially distributed along the lath boundary, edges of coalesced bainite, cellular dendritic boundaries and at prior austenite grain boundaries. Retained austenite morphology was also changed on increasing nickel content from a discontinuous film into a continuous one. The impact toughness for half-size specimens has shown a significant drop from 126J to 40J when Ni content increased from 3% to 5%, while further addition of Ni partially recovered the toughness. Thorough investigation of fracture surface of weld metals, after impact test, elucidated that retained austenite was beneficial and has an effective role in reducing the detrimental effect of coalesced bainite that formed in the microstructure.

Determination of the mechanical properties of weld metal on the basis of the hardness parameters in stress concentration zones detected by the method of magnetic memory of metal

This article describes the results of investigations of the strength properties of welded joints using a specimen-free method based on indentor tests of materials in stress concentration zones detected in advance by the method of magnetic memory of metal.

Properties of a creep resistant 9Cr-1.5Mo-1Co cast steel joint welded with a matching flux-cored wire

For years, it has been the aim to improve the efficiency of thermal power plants by increasing the steam temperature. Therefore, appropriate steels and welding consumables are needed. Latest developments in cast materials have shown that the boron-alloyed 9Cr-1.5Mo-1Co steel called CB2 enables steam temperatures up to 620°C. As fluxcored wires for gas metal arc welding offer several technical and economic advantages, they are getting more and more popular. Therefore, a matching flux-cored wire for production welding of cast components has been developed. To obtain the required mechanical properties in weld metal and heat-affected zone, an appropriate welding technology has been established. This paper deals with the influence of welding parameters on the mechanical properties at ambient temperature. Best results could be obtained with higher heat input and lower cooling rate. Additionally, first results of creep tests arepresented and show that weld metal and cross-weld samples are within the scatter band of the base material. MatCalc calculations describe the microstructural evolution in the heat-affected zone (HAZ) during welding, post weld heat treatment (PWHT) and service.

Engineering Critical Assessment of Clad Pipeline Installed by S-lay for the Operation Phase

Pipeline material with internal cladding or liner of corrosion resistant material has become more customary in the later years as a replacement for carbon steel with high corrosion allowance due to the high corrosivity of unprocessed hydrocarbons. Clad material however, offer new challenges in the fracture assessment methodology due to inhomogeneous material, where the backing steel usually is low alloy carbon steel of 415 or 450MPa yield stress and the clad layer basically has a significantly lower yield stress. In addition, the weld metal mechanical properties may only be partly overmatching compared to the base material. For operational conditions where the local material utilization exceeds the elastic limit, commonly used assessment methods based on analytical fracture models such as BS7910 might be inadequate for clad pipelines, and more detailed finite element modeling must be performed.This paper addresses the relevant load scenarios for a clad steel pipeline installed by S-lay. A dedicated finite element program, LINKpipe has been used for the analyses to verify the acceptance criteria for defects in the girth welds. Input data for the analyses are taken from the detailed pipeline design calculations and material testing of the actual welding procedures of girth welds.

The Effect of Process Parameters on Pulsed Nd:YAG Laser Welding of Inconel 625

The bead on plate welding specimens with the 1mm thickness was fabricated by Nd:YAG pulsed laser SW-1 . The effects of laser process parameters on the weld dimensions, metallurgical and mechanical properties of weld metal were investigated. The results showed that both weld depth and weld width increase with voltage. Unlike base metal that has coaxial grain structure, weld metal is composed of a dendritic structure. Grain growth in the heat affected zone did not occur. However, ultrafine precipitations were deposited at the HAZ which their size was approximately between 500 nm to microns. All tensile specimens failed in the fusion zone.

Effects of hot wire on mechanical properties of weld metal using gas-shielded arc welding with CO2 gas

In the fabrication of steel structures, the method of gas-shielded arc welding is widely utilized with pure CO2 gas. However, the welding with pure CO2 gas is limited with respect to the heat input in order to maintain the fixed mechanical properties of weld metal. A new welding method for increasing weld deposit in every weld bead under keeping the fixed mechanical properties of the weld metal is proposed. An electrically heated filler wire, hereafter referred to as hot wire, was inserted to the weld pool neighboring the arc formed with a leading welding electrode. By using a hot wire without arc, the increase in heat input could be suppressed, but the amount of weld deposit could be greatly increased. In the present investigation, the effects of the welding conditions on both the microstructure and mechanical property of the weld metal are clarified and discussed from the view point of the improvement of welding conditions. Mechanical properties of the weld metal formed with F-metal active gas (MAG) could be greatly improved under high heat input. The microstructure formed with F-MAG is so fine because of the change in the chemical composition of the weld metal by the use of the hot wire. The refined microstructure in F-MAG might improve the mechanical properties of the weld metal.

Fracture assessment for electron beam welded damage tolerant Ti-6Al-4V alloy by the FITNET procedure

Fracture assessment of the cracked structures is essential to avoiding fracture failure. A number of fracture assessment procedures have been proposed for various steel structures. However, the studies about the application of available procedures for titanium alloy structures are scarcely reported. Fracture assessment for the electron beam(EB) welded thick-walled damage tolerant Ti-6Al-4V(TC4-DT) alloy is performed by the fitness-for-service(FFS) FITNET procedure. Uniaxial tensile tests and fracture assessment tests of the base metal and weld metal are carried out to obtain the input information of assessment. The standard options and advanced options of FITNET FFS procedure are used to the fracture assessment of the present material. Moreover, the predicted maximum loads of compact tensile specimen using FITNET FFS procedure are verified with the experimental data of fracture assessment tests. As a result, it is shown that the mechanical properties of weld metal are inhomogeneous along the weld depth. The mismatch ratio M is less than 10% at the weld top and middle, whereas more than 10% at the weld bottom. Failure assessment lines of standard options are close to that of advanced option, which means that the standard options are suitable for fracture assessment of the present welds. The accurate estimation of the maximum loads has been obtained by fracture assessment of standard options with error less than 6%. Furthermore, there are no potential advantages of applying higher options or mismatch options. Thus, the present welded joints can be treated as homogeneous material during the fracture assessment, and standard option 1 can be used to achieve accurate enough results. This research provides the engineering treatment methods for the fracture assessment of titanium alloy and its EB welds.

The Effect of Ultrasonic Vibration on Properties of Weld Metal

Weld metal mechanical properties and weldability of materials are closely related to the microstructure of the weld metal. A significant amount of research has been studied to improve microstructure of weldments such as weld pool stirring by using magnetic arc oscillation and arc pulsation. In this work, the effect of ultrasonic vibration was used to modify weld metal solidification to improve microstructure of the weld metal. Microstructure and mechanical properties of carbon steel weld metal (ER70S-G filler metal) were studied. Filler metal was melted by using Gas Tungsten Arc Welding (GTAW) in a water-cooled copper mold. Ultrasonic vibration with a frequency of 20 kHz was applied during solidification of the weld metal. Microstructure and mechanical properties of weld metal were compared with those of conventional weld metal (no ultrasonic vibration assistance). Scanning Electron Microscopy (SEM) was also used to determine microstructure and phases at high magnification. The results showed that ultrasonic vibration applied during solidification promoted grain refinement in the weld metal. Mechanical properties of weld metal were improved significantly, microstructure analysis correlated well with the mechanical test results.