Comparison study on measurement of rail weld joint between inertial reference method and multi-point chord reference method

Purpose – Straightness measurement of rail weld joint is of essential importance to railway maintenance. Dueto the lack of efficient measurement equipment, there has been limited in-depth research on rail weld joint with a5-m wavelength range, leaving a significant knowledge gap in this field.Design/methodology/approach – In this study, the authors used the well-established inertial referencemethod (IR-method), and the state-of-the-art multi-point chord reference method (MCR-method). Two methodshave been applied in different types of rail straightness measurement trollies, respectively. These instrumentswere tested in a high-speed rail section within a certain region of China. The test results were ultimatelyvalidated through using traditional straightedge and feeler gauge methods as reference data to evaluate the railweld joint straightness within the 5-m wavelength range.Findings – The research reveals that IR-method and MCR-method produce reasonably similar measurementresults for wavelengths below 1 m. However, MCR-method outperforms IR-method in terms of accuracy forwavelengths exceeding 3 m. Furthermore, it was observed that IR-method, while operating at a slower speed,carries the risk of derailing and is incapable of detecting rail weld joints and low joints within the track.Originality/value – The research compare two methods’ measurement effects in a longer wavelength rangeand demonstrate the superiority of MCR-method.

An innovative joint interface design for reducing intermetallic compounds and improving joint strength of thick plate friction stir welded Al/Mg joints

Friction stir welding of dissimilar Al/Mg thick plates still faces severe challenges, such as poor formability, formation of thick intermetallic compounds, and low joint strength. In this work, two joint configurations, namely inclined butt(conventional butt) and serrated interlocking(innovative butt), are proposed for improving weld formation and joint quality. The results show that a continuous and straight intermetallic compound layer appears at the Mg side interface in conventional butt joint, and the maximum average thickness reaches about 60.1 μm.Additionally, the Mg side interface also partially melts, forming a eutectic structure composed of Mg solid solution and Al_(12)Mg_(17) phase.For the innovative butt joint, the Mg side interface presents the curved interlocking feature, and intermetallic compounds can be reduced to less than 10 μm. The joint strength of innovative butt joint is more than three times that of conventional butt joint. This is due to the interlocking effect and thin intermetallic compounds in the innovative joint.

Comprehensive study of microstructure and mechanical properties of friction stir welded 5182-O/HC260YD+Z lap joint

The welding of aluminum(Al)and steel has attracted more and more interest due to the weight reduction trend in vehicle and aerospace manufacturing industries.5182-O/HC260YD+Z lap joint was produced by friction stir welding(FSW),and the microstructure and mechanical property of the joint were systemically characterized.The microstructure in horizontal direction of the Al and steel near interface was similar to their corresponding conventional friction stir welded joint.The joint was divided into stir zone of Al(ST-Al),stir zone of interface(ST-I),thermal-mechanically affected zone of steel(TMAZ-Fe)and base material of steel(BM-Fe)according to their distinct microstructure vertically.Three kinds of intermetallic compounds(IMCs)of FeAl_(3),FeAl and Fe_(3)Al were formed at the interface.The horizontal micro hardness distribution exhibited a hat shape and“M”shape in Al and steel,respectively.The hardest region of the joint was located at the ST-I,with a hardness of 175 HV−210 HV.The joint was fractured along the hook structure,with an average shear strength of 73.9 MPa.Fractural morphology of Al and steel indicted a cleavage fracture mode.

Weld Joint Efficiency of the Kazakhstani Constructional Steel

In the Republic of Kazakhstan, the regulatory framework in construction based on Eurocodes has been in force since 2015. However, Kazakhstani produced steel has not been studied for compliance with the requirements of Eurocode 1993. This has resulted in limited use of Kazakhstani structural steel in construction. The feasibility of using structural steel in welded joints has been experimentally investigated. To verify the application of such joints in construction, including earthquake engineering, experimental studies of welded joints made of structural steel produced by Arcelor-Mittal in Temirtau have been carried out. In total, 7 types of structural steel of various thicknesses were selected. Five specimens have been used in each series of tests. The Brinell hardness values of the weld joint, yield strength of steel and tensile strength, relative rupture strain were determined. It was found that for all types of structural steel, the quality of weld joints complied with the requirements of Eurocode 1993—a sample rupture appeared along the plates (main body of the metal), not along the weld joints. It has been established that structural steel produced in the Republic of Kazakhstan fully complies with the requirements of Eurocode 1993. The studies on the dependence of Brinell hardness values of weld joint steel on the yield strength, tensile strength and relative rupture strain have been carried out. The correlation dependences between the values of yield strength of steel and tensile strength, relative rupture strain and BH Brinell hardness were studied. The results of work will allow for significantly increasing the use of Kazakhstani structural steel in seismic and conventional areas of the Republic of Kazakhstan.

Electron-Beam Welding Joint Strength of Dissimilar Materials

This paper provides an in-depth discussion of the joint strength of electron beam welding of dissimilar materials.The effect of welding parameters and material properties on the joint strength was analyzed,and an argument for the optimal parameter combination is presented.Electron-beam welding technology offers several advantages,including high energy density and the ability to create fine weld seams.However,it also presents certain challenges,such as the complexity of welding parameters and the potential generation of brittle phases.The analysis conducted in this paper holds significant importance in enhancing the quality and efficiency of dissimilar material welding processes.

Effect of Ni content on the weldability of middle-chromium hyperpure ferritic stainless steels 00Cr21Ti

Excellent weldability substantially contributes to the intrinsic quality of steels,while appropriate chemical composition plays a primary role in the essential weldability of steels.The poor weldability of ferritic stainless steels could be improved through modification with minor alloy elements while minimally increasing the cost.Therefore,studying the effect of minor alloy elements on the weldability of steels is of considerable importance.In this study,several steels of middle-chromium hyperpure ferritic stainless 00Cr21Ti with different Ni content(0.3%,0.5%,0.8%,and 1.0%)were developed,and their weldabilities of butt joint samples welded using the metal inert gas welding process,including the influence of welded joints on the microstructure,tensile performance,corrosion resistance,and fatigue property,were investigated.Results show that the steels with w(Ni)≥0.8%exhibit excellent mechanical properties compared with those with low-Ni content steels,further,their impact toughness at normal atmospheric temperature meets the industrial application standard and the fatigue property is similar to that of 304 austenitic stainless steel.Moreover,results show that the corrosion resistance of all the samples is almost at the same level.The results acquired in this study are supposed to be useful for the optimization of the chemical composition of stainless steels aiming to improve weldability.

Effect of intermetallic compounds on the fracture behavior of dissimilar friction stir welding joints of Mg and Al alloys

Joining Mg to Al is challenging because of the deterioration of mechanical properties caused by the formation of intermetallic compounds(IMCs) at the Mg/Al interface. This study aims to improve the mechanical properties of welded samples by preventing the fracture location at the Mg/Al interface. Friction stir welding was performed to join Mg to Al at different rotational and travel speeds. The microstructure of the welded samples showed the IMCs layers containing Al12Mg17(γ) and Al3Mg2(β) at the welding zone with a thickness(< 3.5 μm). Mechanical properties were mainly affected by the thickness of the IMCs, which was governed by welding parameters. The highest tensile strength was obtained at 600 r/min and 40 mm/min with a welding efficiency of 80%. The specimens could fracture along the boundary at the thermo-mechanically affected zone in the Mg side of the welded joint.

Electrochemical impedance spectroscopy study on the corrosion of the weld zone of 3Cr steel welded joints in CO_2 environments

The welded joints of 3Cr pipeline steel were fabricated with commercial welding wire using the gas tungsten arc welding （GTAW） technique. Potentiodynamic polarization curves, linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EIS）, scan- ning electron microscopy （SEM）, and energy-dispersive spectrometry （EDS） were used to investigate the corrosion resistance and the growth of a corrosion film on the weld zone （WZ）. The changes in electrochemical characteristics of the film were obtained through fitting of the EIS data. The results showed that the average corrosion rate of the WZ in CO2 environments first increased, then fluctuated, and finally de- creased gradually. The formation of the film on the WZ was divided into three stages： dynamic adsorption, incomplete-coverage layer forma- tion, and integral layer formation.

The microscopic mechanical performance for nonuniform welded joint of nickel-based alloy with nanoindentation

To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected zone,partially melted zone,weld metal near the fusion boundary and weld metal center.The results showed that the strengthening effect of weld metal was more obvious than that of heat affected zone for nickel based welded joint and especially in coarse grained heat affected zone,the hardening resulted from overheating was not apparent.Nickel based weld metal with high content of alloying elements which were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification contributed to the characteristics that differ from conventional low alloy steel welded joint.

Improving the fatigue property of welded joints for AZ31 magnesium alloy by ultrasonic peening treatment

The fatigue property of AZ31 magnesium alloy and its TIG welded joints were investigated. The ultrasonic peening treatment （UPT） was used to improve the fatigue property of the TIG welded joints, which was treated at the weld toe by the UPT process. The test results show that the fatigue strength of the base metal of AZ31 magnesium alloys is 57.8 MPa, and those of the fillet joint and the transverse cross joint are respectively 20. 0 MPa and 17.2 MPa at 2 × 10^6 cycles. The fatigue strengths of two kinds of welded joints treated by the UPT are respectively 30. 3 MPa and 24. 7 MPa, which have been improved by 51.5% and 43.6%, respectively. The fatigue life of the fillet joint specimens is prolonged by about 2. 74 times and the fatigue life of the transverse cross joint specimens is prolonged by about 1.05 times when the stress range is at 40. 0 MPa.

EFFECT OF MEAN STRESS ON FATIGUE PERFORMANCE OF WELDED JOINTS TREATED BY UPT

The fatigue contrast tests of unload longitudinal direction comer joints asoriginal welded and treated by ultrasonic peening of Q235B in various stress ratio are directed. Theimprovements of fatigue performance of unload longitudinal direction corner joints resulted byultrasonic peening are studied. The effect pattern of stress ratio on fatigue performance of weldedjoints that are treated by ultrasonic peening is studied. As tests results indicate that: ① In thecondition of stress ratio .R=-l, the fatigue strength 'of specimen treated by ultrasonic peening isincreased by 165 percent of that of the original welded specimen. And the fatigue life of specimentreated by ultrasonic peening is as much as 75 approx 210 times of that of the latter. When R=0.1,the fatigue strength is increased by 87 percent and the fatigue life is extended by 21 approx 29times. When R=-0.5, the fatigue strength is increased by 123 percent and the fatigue life isextended by 42 approx 59 times. When R=0.45, the fatigue strength is increased by 51 percent and thefatigue life is extended by 3 approx 14 times. ② If the welded joints are treated by ultrasonicpeening, the fatigue strength is no longer independent on the applied mean stress. The more thestress ratio R, the less the fatigue stress range which can be sustained by the joints is. ③Whether the high value residual stress is in the joints or not, the dead load portion of the appliedload must be considered in the design of the joints which should be treated by ultrasonic peening.

Microstructures of 2219 twin wire welded joints

With thick plates of 2219 high-strength alloy, the microstructures of welded joints with twin wire MIG welding were analyzed. Experimental results show that no hot crack was found in the weld due to discontinuous distribution of cocrystallization with low melting temperature, but porosity is serious in the first weld seam that is mainly composed of equiaxial grains with uneven sizes. As the poor position of the whole welded joint, fusion zone has big and coarse grains, uneven microstructures ; In quenching zone, there exist a lot of soaked microstructures that cocrystallizntion with low melting temperature solute into matrix, thus strengthening the metal in this zone; In excessive aging zone, much more phases that distribute evenly will be separated from the matrix; Ontside this zone, properties and microstructures of the metal are basically similar to matrix due to the relatively low temperature or unaffected heat in the zone during welding.

Effects of laser heat treatment on the fracture morphologies of X80 pipeline steel welded joints by stress corrosion

The surfaces of X80 pipeline steel welded joints were processed with a CO2 laser, and the effects of laser heat treatment （LHT） on H2S stress corrosion in the National Association of Corrosion Engineers （NACE） solution were analyzed by a slow strain rate test. The fracture morphologies and chemical components of corrosive products before and after LHT were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively, and the mechanism of LHT on stress corrosion cracking was discussed. Results showed that the fracture for welded joints was brittle in its original state, while it was transformed to a ductile fracture after LHT. The tendencies of hydrogen-induced corrosion were reduced, and the stress corrosion sensitivity index decreased from 35.2% to 25.3%, indicating that the stress corrosion resistance of X80 pipeline steel welded joints has been improved by LHT.

An investigation on the performance of stress corrosion cracking in aluminum-copper alloy welded joint

With the resistance to stress corrosion of the base metal as a reference, the contrast result of stress corrosion cracking （ SCC） susceptibility of aluminum-copper alloy 2219 and 2014 welded joints under different welding processes （ VP-TIG welding, HF-TIG hybrid welding, laser-TIG hybrid welding and laser HF-TIG hybrid welding） is obtained via the slow strain rate testing （ SSRT） , scanning electron microscope （ SEM） and microstructure observation auxiliary technologies. Test results show that the joints of aluminum alloy 2219, welded by hybrid welding processes, have superior resistance to stress corrosion compared to those welded by the VP-TIG welding process in varying degrees, especially, the joint welded by the laser HF-TIG hybrid welding process, where the resistance to stress corrosion is almost the same as that of the base material. However, the HF or laser hybrid welding effect is not significant under the same welding conditions for welded joints of aluminum alloy 2014.

Changing Rule of Carbon-Enriched Zone and Diffusion Behavior of Carbon in Aging 0Cr6Mn13Ni10MoTi/1Cr5Mo Dissimilar Welded Joints

The microstructures, the changing rule of carbon-enriched zone, the diffusion behaviors of elements C and Cr, and thecarbide type of 0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints after aging at 500℃ for various times and afterlong-term service in technical practice were investigated by using the optical microscopy electron probe microanalysis,scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that in aging0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints, the main carbides are M_3C and a few carbides are M_7C_3 andM_(23)C_6. The M_3C carbide decomposition and dissolution with increasing aging time or aging temperature and theanti-diffusion of C and Cr cause the decrease and disappearance of the carbon-enriched zone. The results are differentfrom those of the A302/1Cr5Mo dissimilar welded joints in previous studies.

EFFECT OF CARBON MIGRATION ON CREEP PROPERTIES OF Cr5Mo DISSIMILAR WELDED JOINTS WITH Ni-BASED AND AUSTENITIC WELD METAL

In this paper, the effect of carbon migration on creep properties of Cr5Mo dissimilar welded joints with Ni-based (Inconel 182) and Cr23Nil3 (A302) austenitic weld metal was investigated. Carbon migration near the weld metal/ferritic steel interface of Cr5Mo dissimilar welded joints was analyzed by aging method. Local creep deformations of the dissimilar welded joints were measured by a long-term local creep deformation measuring technique. The creep rupture testing was performed for Cr5Mo dissimilar welded joints with Inconel 182 and A302 weld metal. The research results show that the maximum creep strain rate occurs in the decarburized zone located on heat affect zone (HAZ) of Cr5Mo ferritic steel. The creep rupture life of Cr5Mo dissimilar welded joints with A 302 weld metal decreases due to carbon migration and is about 50% of that welded with Inconel 182 weld metal.

Investigation on LCF Behavior of Welded Joint at Di erent Temperatures for Bainite Steel

The current research of low cycle fatigue(LCF) is mainly focused on the components with uniform microstructure.Compared with these typical components, LCF behavior of welded components are more complex due to their great gradient microstructure, especially for di erent temperature. In this paper, LCF properties were conducted on the welded joint at di erent temperatures for bainite steel, and the failure mechanism was systematically discussed.Fatigue parameters derived from fitting curves indicated that welded joint had worse plastic deformation resistance and experienced more significantly strain hardening e ect at 300 °C. The joint failed in the weld metal at room temperature, which attributed to the softening in weld metal combined with cyclic strain hardening e ect in heata ected zone, which meant the joint was more sensitive with the hardness at this condition. When it came to 300 °C,more cracks appeared near to HAZ and the heterogeneous distributed surface inclusion was responsible for the fracture transition to HAZ adjacent to bainite steel rather than the softest zone in HAZ, reflecting the joint was more sensitive with the surface inclusion at 300 °C. This research could support the design on loading of welded component at di erent temperature, and further ensure the safe operation.

Residual stress relaxation in typical weld joints and its effect on fatigue and crack growth

Many factors influence the fatigue and crack growth behavior of welded joints. Some structures often undergo fairly large static loading before they enter service or variable amplitude cyclic loading when they are in service. The combined effect of both applied stress and high initial residual stress is expected to cause the residual stresses relaxation. Only a few papers seem to deal with appropriate procedures for fatigue analysis and crack growth by considering the combined effect of variable amplitude cyclic loading with residual stresses relaxation. In this article, some typical welded connections in ship-shaped structures are investigated with 3-D elastic-plastic finite element analysis. The effect of residual stress relaxation, initial residual stress, and the applied load after variable amplitude cyclic loading is revealed, and a formula for predicting the residual stress at hot spot quantitatively is proposed. Based on the formula, an improved fatigue procedure is introduced. Moreover, crack growth of typical weld joints considering residual stresses relaxation is studied.

New Developed Welding Electrode for Improving the Fatigue Strength of Welded Joints

A new welding electrode, low transformation temperature electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods. It was proved that the best transformation starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue strength of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve the fatigue performance of welded joints.

Research on the creep damage and interfacial failure of dissimilar metal welded joint between 10Cr9Mo1VNbN and 12Cr1MoV steel

The mechanical properties, creep damage, creep rupture strength and features of interfacial failures of welded joints between martensite (SA213T91) and pearlite steel (12Cr1MoV) have been investigated by means of argon tungsten pulsed arc welding, high temperature accelerated simulation, creep rupture, mechanical property tests and scanning electronic microscope (SEM). The research results indicate that the mechanical properties of overmatched and medium matched joint deteriorate obviously, and they are susceptible to creep damage and failure after accelerated simulation operation 500 h, in the condition of preheat 250℃, and post welding heat treatment 750℃×1 h. However, the mechanical properties of undermatched joint are the best, the interfacial failure tendency of undermatched welded joint is less than those of medium and overmatched welded joint. Therefore, it is reasonable that low alloy material TR31 is used as the filler metal of weld between SA213T91and 12Cr1MoV steel.