多層かど継手部の溶接割れに関する研究

A new multiple-electrode submerged arc welding technique has been developed that imparts improved fracture toughness properties in the heat affected zone, produces a narrower weld bead geometry, and can also be employed with lower heat inputs than conventional SAW. This study examines how the difference in the weld fusion zone profile affects residual stresses for weldments of API X70 steel made using the same consumable, heat input and restraint, varying only the shape of the weld fusion zone. The contour method and neutron diffraction have been employed to map and compare longitudinal and transverse residual stresses. Results show peak longitudinal stresses in the weld are within 50 MPa for both, and this is believed to be because they have the same heat input and hence similar heat affected zone size. By contrast, the peak stress in the transverse direction is 120 MPa lower for the new SAW technique. The reduction in transverse stress is attributed to a narrower fusion zone profile. The new SAW technique opens up the possibility of producing high quality narrower welds with lower heat input which could lead to significant reductions in residual stress.

In research organizations and industries, most widely used welding methods are shield metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW) and submerged arc welding (SAW).The SAW process is often preferred because it offers high production rate, high melting efficiency, ease of automation and low operator skill requirement.This study expose the different works have been done in the past for improving different properties of welded material.This study also exhibits the effect of different welding process parameters that affect the weld chemistry.Depending upon the requirement the details of past work will we easily obtained for future work with the help of this study.

This article presents a cost-effective and reliable method for welding 30 mm thick sheets of shipbuilding steel EH36. The method proposes to perform butt welding in a two-run technique using hybrid laser arc welding (HLAW) and submerged arc welding (SAW). The HLAW is performed as a partial penetration weld with a penetration depth of approximately 25 mm. The SAW is carried out as a second run on the opposite side. With a SAW penetration depth of 8 mm, the weld cross-section is closed with the reliable intersection of both passes. The advantages of the proposed welding method are: no need for forming of the HLAW root; the SAW pass can effectively eliminate pores in the HLAW root; the high stability of the welding process regarding the preparation quality of the weld edges. Plasma cut edges can be welded without lack of fusion defects. The weld quality achieved is confirmed by destructive tests.

Experimental investigations and statistical modelling of dilution rate and area of penetration in submerged arc welding of SS316-L

In this study, Submerged Arc Welding (SAW) and Gas Metal Arc Welding (GMAW) processes were used in multi-pass welding of 33 mm thickness super duplex stainless steel plates. Recommended and higher than recommended arc energy and interpass temperatures were used. Both GMAW and SAW processes were able to produce large thickness weldments meeting the microstructural, mechanical, and corrosion resistance requirements, and also when using higher than recommended arc energy and interpass temperature. It was possible to reduce the number of welding passes by half when using higher than recommended arc energy and interpass temperature. The SAW process needed only half of the welding time required for the GMAW process to produce a weldment with nearly the same number of weld passes, when using recommended arc energy and interpass temperature. Based on the results of this investigation, the practical recommendations for welding large thicknesses should be revised and updated.

In the fabrication of steel bridge, submerged arc welding (SAW) is widely utilized. In order to increase the efficiency for the production of welds, the increase in electrode such as SAW with multiple wire electrodes is effective. However, heat input also increases with increasing the number of electrode. The new welding method based on SAW method with one electrode, F-SAW, was developed in the present investigation. An electrically heated filler wire, hereafter referred to as hot wire, was inserted into the rear part of weld pool made with leading SAW electrode. By using the hot wire without arc, increase in heat input could be suppressed but the amount of weld deposit could be greatly increased. Welding speed of F-SAW for deck plate 16-mm thick became two times compared with that with ordinary SAW. In the present study, mechanical properties of the weld metal formed with F-SAW were clarified. Mechanical properties of the weld metal formed with F-SAW could be improved, compared with those with SAW. Moreover, those with F-SAW was greatly improved by selecting the hot wire and cut wire. The microstructure formed with F-SAW was so fine. The refined microstructure in F-SAW might improve the mechanical properties of the weld metal.

An EERZ (effective equilibrium reaction zone) model was applied to the modified SAW (submerged arc welding) process to simulate the SAW process metallurgy in the gas-slag-metal reaction system. The SAW process was modified by adding Al as a de-oxidizer with alloying metal powders of Cr, Cu, and Ti. The static gas-slag-metal equilibrium model can accurately calculate the weld metal oxygen content (ppm O) for conventional SAW but not for the modified SAW process. The static equilibrium model overpredicts the reaction of Al. EERZ model runs were made for 2000–2500°C because this is the reported temperature range in the SAW arc cavity. The weld metal composition was adequately calculated, especially the weld metal ppm O, at the following effective equilibrium temperatures: 2400°C for Al-Cr additions, 2200°C for Al-Cr-Cu additions, and 2000°C for Al-Cr-Cu-Ti additions. Model results show that Ti metal powder can serve a de-oxidizer role in the presence of Al, resulting in Ti loss to the slag. Ti is also lost to the gas phase as TiF3(g) and TiF2(g) compared to little loss of Cr to the gas phase as Cr(g) and CrO to the slag phase.

Deep-sea resource exploration vessels operating in extreme marine environments require exceptional structural strength and welding quality. This study focuses on mature high-efficiency welding techniques for deep-sea vessels, summarizing the characteristics of four commonly used methods: Gas Tungsten Arc Welding (GTAW), Gas Metal Arc Welding (GMAW), Submerged Arc Welding (SAW), and high-energy density welding. Experimental comparisons between FluxCored Arc Welding (FCAW) and SAW revealed that when the carbon equivalent (Ceq) of CCSB, CCSD, and CCSEH36 steel materials is 0.37%, preheating before welding or post-weld heat treatment is necessary to ensure welding quality. The YCJ501-1 flux-cored wire showed higher yield strength, tensile strength, and impact energy compared to H10Mn2 submerged arc welding wire, though their elongation values were similar. Based on the structural characteristics of deepsea resource exploration vessels, the study identified suitable welding processes, planned efficient welding implementation areas, and established corresponding welding procedures. This approach reduces welding difficulty, enhances overall efficiency and quality, and minimizes deformation.

Ramor 500 steel plates are used as a ballistic material due to their greater hardness and strength properties. This steel can be produced with a 2-30 mm thickness sheet which may attain 505-590 HV hardness. In the present work, Ramor 500 steel pairs are joined using a submerged arc welding (SAW) process and taking various parameters into consideration. An austenitic additional wire is used for the welding process which contains Cr, Ni, and Mn. The source model prototype was developed using ANSYS software and considering a time-dependent three dimensional thermal model with source cooling. The highest tensile stress voltage value was determined in the sample applying a constant current of 250 A, 25 V and 30 cm × min-1welding speed. It was observed that the welding seam width increases as welding tension grows and that welding height and depth increase and decrease more or less in tandem. A ANSYS thermal cooling analysis revealed that welding tension grows with heat transfer which increases 15 mm from the main center of the welding area.

The effect of process variables such as current, voltage, electrode extension, electrode diameter, etc., on the electrode melting and plate melting efficiencies of submerged arc welding (SAW) and gas metal arc welding (GMAW) has been studied. It has been shown that there is an increase in the electrode extension or a decrease in the voltage and electrode diameter. For the same welding parameters, the electrode melting efficiency is higher when the electrode is negative. A similar relationship was observed for GMAW. The results also indicated that the shielding gas in GMAW also had an effect on the electrode melting efficiency. The plate melting efficiency of GMAW increases with an increase in the welding current, voltage, and electrode diameter, and decreases with an increase in the electrode extension. For the same welding parameters, the plate melting efficiency is lower when the electrode is negative. For SAW there is an increase in the plate melting efficiency with an increase in the welding current and voltage. It was also observed that the plate melting efficiency was lower for the negative electrode. Although there was an indication of a decrease in the plate melting compared with similar effects in GMAHI: this decrease in plate melting efficiency did not seem significant. An attempt attempt has also been made to develop numerical models to predict the electrode and plate melting efficiencies from the process variables.MST/1096

Abstract. In the arc welding processes, the parts to be connected are subjected to thermal cycles that can generate distortions. Furthermore, owing to clamping constraints, residual stresses can arise affecting the mechanical properties of the welding bead. In the work proposed, multi-pass submerged arc welding (SAW) process was investigated by a numerical analysis, properly set by experimental evidence. Indeed, the welding bead of a reference sample, was section and etched before performing micrograph inspections to achieve the contours of both welded material and affected zone for each welding pass. Arc current, voltage and welding speed were the investigated process parameters. Their values were changed proportionally to maintain constant the generated specific heat of the process. Furthermore, the effect of different clamping set up was considered. As a result of the analysis, process configurations, according to the employed process parameters, able to reduce distortions and to minimize residual stress, were identified.

With the increasing use of thermomechanically processed steels for pipelines, the alloy content of each steel grade decreases from year to year. Using welding processes which result in high dilution of the weld metal by parent material, such as conventional submerged arc welding, it becomes increasingly difficult to achieve the very high weld metal yield strength demanded when welding X80 and X100 steels, especially when strain-based design is used. For X80 steels, submerged arc welding with tubular wires and with twin arcs can allow high productivity to be maintained while limiting the heat input and dilution, and satisfactory results produced by this route are presented. Special boron-containing wires can also be used where high dilution cannot be avoided. For X100 steels, the use of gas metal arc welding with a fixed welding head and a rotating pipe, combined with a narrow bevel preparation, allows excellent mechanical properties to be achieved without excessively high alloy contents in the welding wire. Because of the small joint volume, productivity need not be unduly lower than that of submerged arc welding. Substitution of metal-cored tubular wire for solid wire can give a further increase in productivity.

Among the several arc welding methods, the submerged arc welding is the preferred method for welding thick sections in the industry because of its several advantages which include high production rates, good weld quality, ease of automation and minimum operator skill requirement. This paper represents a study on the effect of B2O3 additions in fluxes on the microstructure and mechanical properties of the weld metal formed during Submerged Arc Welding of Mild Steel plates. Five fluxes with about 2.5, 5, 7.5, 10 and 12.5% B2O3 were used with a low carbon electrode. Welding process parameters were kept constant for all the conditions. The microstructure of weld metal for each flux consisted mainly of acicular ferrite, polygonal ferrite, grain boundary ferrites and equiaxed pearlite. It was noted that Vicker’s hardness value was a function of boron content and showed a mixed trend. Impact Energy and Tensile Strength were increased with the increase in boron content in welds this can be attributed to relation with the higher acicular ferrite percentage. However, an optimum level of toughness and tensile strength was available with 7.5% and 5% of B2O3 respectively. A qualitative comparison has also been made with fresh flux through full metallography and mechanically.

Demand for double jointing technology is increasing to improve pipeline construction productivity. Submerged arc welding (SAW) utilized for double jointing is likely to cause a much wider heat affected zone (HAZ) than those of typical field welding by gas metal arc welding (GMAW), and it should be taken into account for strain-based design of high strength line-pipes. However, guidelines for SAW welds properties to ensure strain capacity of high strength line-pipes such as X80 have not been established yet. In this study, a submerged arc weld joint was produced using tensile strength (TS) over-matching welding consumable. API standard type transverse weld tension test was conducted to measure local elongation at weld metal, HAZ, and base material. Elongation at weld metal increases prior to base material, but soon after that elongation at the HAZ softening region and base material adjacent to the HAZ catch up with the elongation in the weld metal, and finally, deformation concentrates at the HAZ softening region before final fracture. Deformation behavior of the joint was analyzed to verify applicability to double jointing girth welds for strain-based design. From finite element (FE) analysis of notched wide plate test which characterizes tensile strain capacity of a pipeline, it is suggested that ductile crack would not initiate before base material start necking in this particular TS over-matching weld joint in which the defect size is 1mm of notch depth and 25mm of notch length. Thus, the weld joint would be applicable for double jointing girth welds based on strain-based design.

Slag generated during conventional submerged arc welding (SAW) has been recycled by mixing varying percentages of crushed slag with fresh flux to use in subsequent runs. The influence of using flux-slag mixture on various aspects of SAW weld parameters of bead geometry have been investigated in a quantitative basis. Slag has been reprocessed and reused in submerged arc welding to produce bead-on-plate weld on mild steel plates. Apart from conventional process parameters: voltage (OCV), wire feed rate, nozzle to plate distance (stick-out) and traverse speed, welding has been carried out using various percentages of flux-slag mixture; the % of fused flux in the mixture has been treated as a process parameter. Various bead geometry parameters viz. bead width; reinforcement, depth of penetration and depth of HAZ have been measured for each of weld prepared in the study. Using experimental data, a grey-based Taguchi approach has been applied for parametric optimization of this non-conventional SAW process. The aim was to reveal the optimal amount of slag-mix%, which could be applied in SAW process without imposing any adverse effect on features of bead geometry and HAZ. Optimal result has been checked through confirmatory test.