Influence of Welding Speed on Microstructure and Oxidation Behaviour of Laser Welded Austenitic Stainless Steels (original) (raw)
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Acta Materialia Transylvanica, 2020
The purpose of our study was to investigate the properties of welded joints formed by 1.5 mm thick plates with a diode laser beam equipment. The technological parameters influence the shape of the weld metal. In the heat affected zone no grain coarsening appeared. Increasing the welding speed, in case of similar laser power, the ferrite content of weld metal decreases. The hardness’ of the streams are higher than that of base metal, but the highest values were measured in heat affected zones.
Oxidation Behaviour of Laser Welding of TP347HFG and VM12-SHC Stainless Steels
2015
The oxidation behaviour of laser welded of TP347HFG and VM12-SHC stainless steels in air atmosphere were investigated. The temperature was changed from 25 to 1400 0 C. The stainless steels butt were welded. Materials were examined by the thermogravimetric method. The surface and microstructure of the sample were observed in an optical microscope (OM) and a scanning electron microscope (SEM). The X-ray fluorescence spectrometer (XRF) was used to observation change in chemical composition along the cross-section of specimen. The results showed the substantial intermixing of both substrates within the fusion zone. The thermogravimetric data indicate that the investigated materials undergo chemical corrosion. The thermodynamic parameters formation oxides on substrates were calculated and discussed. The CO2 laser welding technique was suggested as a good method for joining dissimilar steels.
Gazi University Journal of …, 2012
In this study, microstructural characteristic of dissimilar welded components (AISI 430 ferritic-AISI 304 austenitic stainless steels) by CO 2 laser beam welding (LBW) was investigated. Laser beam welding experiments were carried out under argon and helium atmospheres at 2000 and 2500 W heat inputs and 100-200-300 cm/min. welding speeds. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy, SEM, EDS and XRD analysis. The tensile strengths of the welded joints were measured. The result of this study indicated that; the width of welding zone and HAZ became much thinner depending on the increased welding speed, on the other hand, this width become wider depending on the increased heat input. Tensile strength values also confirmed this result. The best properties were observed at the specimens welded under helium atmosphere, at 2500 W heat input and at 100 cm/min welding speed.
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Small differences in the contents of surface active elements can change flow direction and thus heat transfer, even for different batches of a given alloy. This study aims to determine the effects of sulfur on weld bead morphology in the laser process. The paper presents the results related to the weld bead shape of two thin AISI 304 industrial stainless steel casts. One cast contains 80 ppm (0.008%) of sulfur, considered as a high sulfur content, and the other one contains 30 ppm (0.003%) sulfur, which can be considered low sulfur. The welds were executed using a CO2 laser. The effects of laser power (3.75, 3.67, 6 kW), welding speed (1.25, 2.40, 2.45, 3.6 m/min), focus point position (2, 7, 12 mm), and shield gas (Helium, mixed 40% helium + 60% argon and mixed 70% helium + 30% argon) with a flow rate of 10 L/min on the depth of the weld (D) and the aspect ratio (R = D/W) were investigated using RSM (response surface methodology). The experimental results show that the transfer of ...
Pitting and galvanic corrosion behavior of laser-welded stainless steels
Autogenous welded specimens of austenitic (S30400 and S31603), duplex (S31803) and super duplex (S32760) stainless steels were fabricated by laser penetration welding (LPW) with a CW Nd:YAG laser in an argon atmosphere. The microstructure and the phases present in the resolidified zone of the laser-welded specimens were analyzed by optical microscopy and X-ray diffractometry, respectively. The pitting and galvanic corrosion behavior of the stainless steels in the laser-welded and unwelded conditions in 3.5% NaCl solution at 23 • C was studied by means of electrochemical measurements. X-ray diffraction analysis showed that the phases present in the weld metal depended on the composition of the base metal. While the laser weld for S31603 retained the original austenitic structure, the laser weld of S30400 contained austenite as the major phase and ␦-ferrite as the minor phase. On the other hand, a slight change of ␦-ferrite to austenite ratio was found in both the laser welds of S31803 and S32760, with austenite present at the ␦-ferrite grain boundaries. The welds exhibited passivity but their pitting corrosion resistance was in general deteriorated as evidenced by a lower pitting potential and a higher corrosion current density compared with those of the unwelded specimens. The decrease in pitting corrosion resistance of the welds was attributed to microsegregation in the weld zone of S31603, and to the presence of ␦-ferrite in S30400. For the duplex grades S31803 and S32760, the disturbance of the ferrite/austenite phase balance in the weld zone could be the cause of the decrease in corrosion resistance. The initial free corrosion potentials of the unwelded specimens were considerably higher than those of the corresponding laser welds, indicating that the welds were more active and were expected to act as anodes in the weldment. The ranking of galvanic current densities (I G ) of the couples formed between the laser-welds (LW) and the as-received (AR) specimens with area ratio 1:1, in ascending order, is: AR S31603/LW S31603 < AR S31803/LW S31803 < AR S32760/LW S32760 < AR S30400/LW S30400. The recorded I G in all couples was low (in the range of nA/cm 2 ). welding (LPW) can produce low-distortion and precise weldments with minimal heat-affected zones . In LPW of stainless steels, phase transformation is common. The mechanical properties and corrosion resistance of laser-welded stainless steels may be deteriorated due to microsegregation, unfavorable phase content, presence of porosities, solidification cracking, micro-fissures and loss of materials by vaporization. Galvanic cell may also be set up between different parts of the weldment. Galvanic corrosion in weldments should not be overlooked because it can lead to accelerated deterioration of the anodic region especially in hostile environments. Pitting corrosion and galvanic corrosion have been investigated in the couples between dissimilar alloys such as 316L, Ti, Nb and [3], CoCr and REX 734 [4], annealed and cold-worked 316L [5], and GTAW welded and unwelded N08031 [6]. The pitting corrosion resistance of several austenitic stainless steels welded by a CO 2 laser has been investigated by Vilpas [7]. However, reports on the galvanic 0924-0136/$ -see front matter
2021
Today is the world of stiff and cut-throat competitiveness among the manufacturing industries. The objective of every industry is to produce better quality products at minimum cost and increase productivity. Welding is a process where the coalescence of two metals is achieved by the application of heat and/or pressure with or without filler metal. This is the only technique for developing the monolithic structure. Welding defects can cause practical problems if not solved. The TIG welding is also called Gas Tungsten Arc Welding (GTAW), which uses a nonconsumable tungsten electrode to produce the weld. TIG welding is used to produce high-quality welds and is popular among welding processes. Its productivity depends upon many factors like arc voltage, shielding gas, weld speed, and heat generated during the welding process. This paper is an attempt to present a review about the welding of ferritic stainless steel between AISI 410S and AISI 430 by the TIG welding process.
Development of Weld Metal Microstructures in Pulsed Laser Welding of Duplex Stainless Steel
Journal of Materials Engineering and Performance, 2012
The microstructure of the weld metal of a duplex stainless steel made with Nd:YAG pulsed laser is investigated at different travel speeds and pulse frequencies. In terms of the solidification pattern, the weld microstructure is shown to be composed of two distinct zones. The presence of two competing heat transfer channels to the relatively cooler base metal and the relatively hotter previous weld spot is proposed to develop two zones. At high overlapping factors, an array of continuous axial grains at the weld centerline is formed. At low overlapping factors, in the zone of higher cooling rate, a higher percentage of ferrite is transformed to austenite. This is shown to be because with extreme cooling rates involved in pulsed laser welding with low overlapping, the ferrite-to-austenite transformation can be limited only to the grain boundaries.
Laser Dissimilar Welding of AISI 430F and AISI 304 Stainless Steels
Materials, 2020
A dissimilar autogenous laser welded joint of AISI 430F (X12CrMoS17) martensitic stainless steel and AISI 304 (X5CrNi18-10) austenitic stainless steel was manufactured. The welded joint was examined by non-destructive visual testing and destructive testing by macro- and microscopic examination and hardness measurements. With reference to the ISO 13919-1 standard the welded joint was characterized by C level, due to the gas pores detected. Microscopic observations of AISI 430F steel revealed a mixture of ferrite and carbides with many type II sulfide inclusions. Detailed analysis showed that they were Cr-rich manganese sulfides. AISI 304 steel was characterized by the expected austenitic microstructure with banded δ-ferrite. Martensitic microstructure with fine, globular sulfide inclusions was observed in the weld metal. The hardness in the heat-affected zone was increased in the martensitic steel in relation to the base metal and decreased in the austenitic steel. The hardness range in the weld metal, caused by chemical inhomogeneity, was 184–416 HV0.3.
Studies in Engineering and Technology, 2014
Laser-welded joints of stainless steel AISI304 are investigated experimentally to determine the transfor- mation of austenite to martensite during the welding process. This transformation, which occurs in the welded region due to heating and residual stresses, can influence the fatigue and fracture properties of the affected material. Therefore, the scope of the present study is to determine the quantity of introduced martensite in the welded region and hereby clarify the influence of laser welding on the fatigue and fracture properties of welded AISI304 joints. The quantification of martensite concentration is carried out by use of four different methods, namely Lichtenegger and Bloech (LB1) etching, Ferritescope, X-ray diffraction (XRD), and Vickers hardness. It is found that a concentration of 1-1.6 % martensite is introduced in the laser-welded area; a quantity that has insignificant influence on the fatigue properties of the joints.
Materials, 2021
In this study, ultra-high-strength steels, namely, cold-hardened austenitic stainless steel AISI 301 and martensitic abrasion-resistant steel AR600, as base metals (BMs) were butt-welded using a disk laser to evaluate the microstructure, mechanical properties, and effect of post-weld heat treatment (PWHT) at 250 °C of the dissimilar joints. The welding processes were conducted at different energy inputs (EIs; 50–320 J/mm). The microstructural evolution of the fusion zones (FZ) in the welded joints was examined using electron backscattering diffraction (EBSD) and laser scanning confocal microscopy. The hardness profiles across the weldments and tensile properties of the as-welded joints and the corresponding PWHT joints were measured using a microhardness tester and universal material testing equipment. The EBSD results showed that the microstructures of the welded joints were relatively similar since the microstructure of the FZ was composed of a lath martensite matrix with a small ...