Quality Of Butt Joints Research Articles

Effect of welding speed on butt joint quality of laser powder bed fusion AlSi10Mg parts welded using Nd:YAG laser

Abstract The invention of additive manufacturing technology, such as laser powder bed fusion, was initiated by the aerospace industries’ growing need for lightweight alloy components with intricate geometries. However, widespread adoption of lightweight alloy components is limited by size restrictions. Currently, only relatively small and simple-shaped objects can be efficiently produced using lightweight alloys. Thus, this research aims to investigate the effect of welding speed on butt joint quality of laser powder bed fusioned AlSi10Mg parts welded using an Nd:YAG laser. Laser beam welding is a method for welding small parts manufactured by laser powder bed fusion together to build large-scale and complex-shaped objects. Using a 2 kW continuous wave solid-state Nd:YAG laser with three different weld scan speeds (150, 175, and 200 mm min−1), autogenous, single-pass, square butt joints were created from 3 mm thick plates. Crystal orientation mapping and fractography results showed that the laser beam welding scan speed significantly impacts plastic deformation and fracture behavior. A significant amount of grain refinement and an Si-particle morphology change was realized in the weld zone’s microstructure, attributed to the increase in weld scanning speed. The transverse tensile test demonstrates that increasing the weld scan speed from 150 to 200 mm min−1 leads to significant growth in the efficiency of the weld joint, from 70 % to 77 %, arising from grain refinement (13–8 µm). However, a significant decrease in ductility is observed with increasing scan speed. In addition, it was determined that pores have substantial effect on tensile strength and ductility.

MICROSTRUCTURE AND PROPERTIES OF LASER-WELDED BUTT JOINTS OF X2CRTINB18 STEEL

The process of autogenous laser welding of stainless steel X2CrTiNb18 was investigated. The Yb:YAG disk laser was used in the study for welding of 1.5mm thick butt joins. The influence of basic laser welding parameters on the joint quality, fusion zone geometry, microhardness distribution across the butt joint, structure and microstructure of fusion zone (FZ) and heat affected zone (HAZ) was studied and determined. The quality level of the test joints was determined according to the PN-EN ISO 13919-1 standard. The chemical composition of the base metal was determined by spark emission spectroscopy. Results of the study have shown that laser welding parameters have a significant influence on the quality of butt joints. However, it is possible to produce joints that meet the high requirements and criteria of quality. The width of HAZ of the butt joints welded in the investigated range of parameters was narrow and did not exceed 0.2 mm. It was found that the most common imperfections of the analysed joints are concavity of the weld face and insufficient penetration. The HAZ region of joints is characterized by mainly ferritic microstructure with complex carbides precipitates. In turn, the fusion zone is dominated by a ferritic microstructure but also precipitates were observed, which were identified as fine dispersion carbides. Hardness of the base metal is round 160÷170HV0.3. A tendency to increase in hardness in the HAZ and FZ was observed. The maximum hardness measured in HAZ was approx. 220HV0.3, while in the FZ 190HV0.3.

Improving the Quality of Laser-Welded Butt Joints of Metal–Polymer Sandwich Composites

Sandwich panels are promising composite materials, although the possibilities for their thermal joining are limited due to the degradation of the polymer core at elevated temperatures. The purpose of this study is to improve the quality of the butt joints in metal–polymer sandwich composites performed by laser welding. A pulsed Nd:YAG Rofin StarWeld Performance laser was used to perform the two-sided welding of the metal–polymer three-layer composite material. On each of the two sides of the material, a welded joint was made with partial penetration of the covering steel sheets, which was considered a prerequisite for preventing the degradation of the core polymer layer. The energy density of the laser irradiation was redistributed by increasing the diameter of the laser spot. The structure of the welded joints was examined using a polarized optical microscope and a scanning electron microscope. It was determined that the laser treatment resulted in a partial penetration weld on each of the two covering metal sheets of the material, reaching a depth of more than 50% of the sheet’s thickness without damaging the polymer. The welding area consisted of two zones, one being the weld metal and the other the heat-affected zone. As a result of relatively rapid heating and cooling cycles, fine-dispersed structures were formed in the heat-affected and remelted zones. The performed tensile tests showed that the strength of the welded area was about 80% of that of the base material.

Effect of Magnetic Field Induce Arc in Autogenous TIG Welding of 304 Stainless Steel Butt Joint

This paper reports the use of External Magnetic Field-Tungsten Inert Gas (EMF-TIG) method in butt joint applications to determine the effect of welding arc compression on the quality of butt joint of SS 304 thin plate was reported. The welding process was performed without using filler or autogenous welds. The external magnetic field was generated by placing a magnetic solenoid around the TIG welding torch. The results of this study showed that EMF-TIG welding can produce a more uniform bead width along the weld line compare with conventional TIG. Moreover, the D/W ratio obtained under external magnetic field was higher than without magnetic. However, the tensile strength of butt joint decreased with EMF-TIG because there is constriction in arc welding which produces shrinkage weld pool volume. In addition, high welding speeds result in a decrease in the tensile strength of both conventional TIG and EMF-TIG welds.

Experimental and Numerical Investigation on Laser Welding of 2205 Duplex Stainless Steel

Laser Welding is extensively used in many applications including aerospace, automotive, ship building, electronics, home appliance etc., due to its advantage of very low heat input to the weld, resulting in minimum distortion and the ability to weld heat sensitive materials. In this paper, an experimental investigation on laser welding of 2205 Duplex stainless steel has been carried out using a pulsed Nd: YAG laser source. The objective of the present research is to study the effects of welding speed and other parameters such as laser power and pulse width kept as constant on the quality of the butt weld. The quality of butt joints along with base material have been characterized in terms of microstructure and tensile properties. The effect of the welding speed on laser melt pool geometry i.e. penetration depth and bead width is simulated by anisotropic enhanced thermal conductivity approach and those are compared with experimental results. The study reveals that the weld strength increases with scanning speed up to a certain level, and thereafter it starts to reduce. It is also observed that the depth of penetration and bead width decreases with the increase in scanning speed. Moreover, all welded samples contains ferrite content is relatively higher and subsequently, austenite content is lower due to higher cooling rate. The Vickers micro hardness tests across the base material and butt joint samples have been carried out. The results show that the microhardness continuously decreasing from the fusion zone to the base material due to changes in metallurgical phase constituents due to higher cooling rate.

Investigations on the microstructure, mechanical properties and corrosion resistance of SUS 304 austenitic stainless steel welded joints by pulsed current gas tungsten arc welding

In the present research work, the joining of 3 mm thick sheets of SUS 304 stainless steel (SS) was addressed by pulsed current gas tungsten arc (PCGTA) welding techniques with ER308L filler wire, which came to a connection between the microstructure of the welds and the resultant mechanical and corrosion behavior. The main focus of the study involved the investigation on the effect of filler wire on welding quality of butt joints obtained. Trial experiments were carried out to find whether or not the proper filler wire was added could exert a great influence on the depth of penetration. The studies turned out that a full and sound penetration could be achieved with filler. Microstructure observations divulged the formation of different zones across the weldments, austenite/δ-ferrite at the weld zones (WZ), austenitic coarsening and growth at the heat affected zones (HAZ). Mechanical testing showed that better tensile properties and microhardness accrued in the filler weldments (FW) due to the presence of δ-ferrite and secondary phases which need further investigation, whose average tensile strength and maximum microhardness were 569 MPa and 392 HV respectively. For no filler weldments (NFW), its mechanical performances were distinctly inferior to FW. According to the electrochemical test results, base metal (BM) displayed the best corrosion resistance because it was far from such sources of pitting corrosion. Based on both passivation potential and breakdown potential, the ranking for corrosion resistance was: BM > FW > NFW. Practice proved that the results of the current study would also help in obtaining high-quality butt joints of SUS 304 SS sheets based on traditional PCGTA welding with ER308L filler wire.

Microstructure and Residual Stresses in a Friction Stir Welded Butt Joint of as-cast ZK60 Alloy Containing Rare Earths

The effect of a travel speed of 200 mm/min as well as a tool rotational speed of 1200 rpm on butt joint quality of friction stir welding (FSW) ZK60 magnesium casting alloy containing 1.5 wt.% rare earths (ZK60-1.5RE) was investigated to determine microstructure and residual stresses. FSW results in the generation of heterogeneous metallurgical structures consisting of the base material (BM), stirred zone (SZ) and thermo-mechanical affected zone (TMAZ). The stirring action also produced a non-uniform distribution and segregation of intermetalics. The transversal distribution of the longitudinal welding stresses exhibits a M-like shape with mostly tensile stresses under the shoulder region and only one compressive stress peak in the advancing side of the SZ and TMAZ. It could be demonstrated that FSW of ZK60-1.5RE alloy was successful in the welding conditions applied during the present work.

Калибровка валков догибки при производстве прямошовных труб вальцевой формовки

The quality of butt joints during the installation of main gas pipelines and indicators of their operational reliability depend to a large extent on the degree of deviation of the cross section of the pipe from the circle, especially in their end parts. Modern regulations of the quality of tubular products for the transportation of hydrocarbons, especially for underwater pipeline crossings, impose severe restrictions on the deflection of profile cross section from the circle. Tolerances in some cases do not exceed 3...5 mm, which corresponds to 0.45...0.8 % of the pipe diameter. In practice, the production of longitudinally welded pipes in the RBE-LSAW line using hem rolls by the HAEUSLER company can not consistently provide the quality of the hem geometry zones. The technique of calibrating hem rolls for the marginal portion of the blank for large diameter pipes which provides monotone transition of the hem zone to the main perimeter molded earlier on the roller sheet bending machine without local deviations from the circular geometry.

Friction stir welding of AZ-91 and AM-Lite magnesium alloys

The objective of this paper was to report the results of butt joint quality of friction stir welding (FSW) of samples of alloys of MgAlZn group. Welding has been carried out with the FSW tool of welding speed ranging from 140 to 355 mm/min. In the stir zone and the surrounding, neither porosity nor cracks have been obtained. Microhardness in the stir zone increased for all welds when compared to the base metals, as a consequence of the high grain refinement and increased precipitations at the grain boundaries. The decrease in plastic properties of metal in these regions is expected. The results show a strong relationship between properties of joints and welding parameters.

Discussion of Monitor and Control Strategies to Enhance Butt Joint Quality for Endless Bar Rolling System

Endless bar rolling technology with its intrinsic nature may be used to maximize the production efficiency and reduce production costs. While how to improve the butt joint quality of endless bar rolling system is of research worth with high application value. Hence, a novel control strategy based on the online feedback of process parameters is proposed to enhance the butt joint quality of endless bar rolling system. Firstly, with consideration of the features and state of the art for endless bar rolling system, influence factors over the butt joint quality of endless bar rolling system were analyzed. Secondly, to meet the requirements of high butt joint quality, the quality control strategy of flash butt welding was designed and online feedback from image measurement technology and eddy current array technology were introduced. Finally, the control strategy designed was verified by simulations. The results verify that the process parameters can be adjusted and optimized online via application of these nondestructive testing technologies for the welding quality, consequently, the numbers of shutdown the system is reduced and productivity is improved.

Tolerances of joint gaps in Nd:YAG laser welded Ti-6Al-4V alloy with the addition of filler wire

The effect of joint gap on the butt joint quality of Ti-6Al-4V alloy welded using a 4 kW Nd:yttrium aluminum garnet laser was evaluated in terms of the welding defects, microstructure, hardness, and tensile properties. The joint gap was proportionally filled using the filler wire with the compositions of the parent alloy. Fully penetrated welds without cracking were obtained up to a joint gap of 0.5 mm. The main defects observed in the welds were porosity and underfill. Specifically, the porosity area increased with increasing joint gap but remained less than 1% of the fusion zone area. Large underfill defects appeared in the weldments in the absence of a joint gap, but filler wire addition was observed to reduce this defect in the presence of a joint gap. The weld hardness decreased slightly with increasing joint gap, but the tensile properties were optimized at an intermediary gap size, probably due to the compromise between the low underfill (after the use of a filler wire) and a limited amount of porosity.

Effect of pre- and post-weld heat treatment on metallurgical and tensile properties of Inconel 718 alloy butt joints welded using 4 kW Nd:YAG laser

The effects of pre- and post-weld heat treatments on the butt joint quality of 3.18-mm thick Inconel 718 alloy were studied using a 4 kW continuous wave Nd:YAG laser system and 0.89-mm filler wire with the composition of the parent metal. Two pre-weld conditions, i.e., solution treated, or solution treated and aged, were investigated. The welds were then characterized in the as-welded condition and after two post-weld heat treatments: (i) aged, or (ii) solution treated and aged. The welding quality was evaluated in terms of joint geometries, defects, microstructure, hardness, and tensile properties. HAZ liquation cracking is frequently observed in the laser welded Inconel 718 alloy. Inconel 718 alloy can be welded in pre-weld solution treated, or solution treated and aged conditions using high power Nd:YAG laser. Post-weld aging treatment is enough to strengthen the welds and thus post-weld solution treatment is not necessary for strength recovery.

Effect of welding speed on butt joint quality of Ti–6Al–4V alloy welded using a high-power Nd:YAG laser

Annealed Ti–6Al–4V alloy sheets with 1 and 2 mm thickness are welded using a 4 kW Nd:YAG laser system. The effects of welding speed on surface morphology and shape, welding defects, microstructure, hardness and tensile properties are investigated. Weld joints without or with minor cracks, porosity and shape defects were obtained indicating that high-power Nd:YAG laser welding is a suitable method for Ti–6Al–4V alloy. The fusion zone consists mainly of acicular α′ martensite leading to an increase of approximately 20% in hardness compared with that in the base metal. The heat-affected zone consists of a mixture of α′ martensite and primary α phases. Significant gradients of microstructures and hardness are obtained over the narrow heat-affected zone. The laser welded joints have similar or slightly higher joint strength but there is a significant decrease in ductility. The loss of ductility is related to the presence of micropores and aluminum oxide inclusions.

Effect of welding speed on the quality of friction stir welded butt joints of a magnesium alloy

The effect of welding speed ranging from 5 to 30 mm/s on 2-mm butt joint quality of friction stir welded AZ31B-H24 magnesium alloy was investigated to determine defects, microstructures, hardness and tensile properties. High welding speed over a wide range can be used to weld this material at high tool revolution rates indicating the great potential of this technique for magnesium alloys. Equiaxed grains were observed in the stir and thermo-mechanically-affected zones. The grain size in the stir zone decreases with increasing welding speed due to lower heat input. Higher welding speeds produce slightly higher hardness in the stir zone. The yield strength increases with increasing welding speed. The tensile strength increases first with increasing welding speed but remains constant from 15 to 30 mm/s. A Hall–Petch linear relationship between yield strength and inverse square root of grain size in the stir zone illustrates the strong relationship between these parameters.