S31803 Duplex Stainless Steel Research Articles

Effects of post weld heat treatment on friction welded duplex stainless steel joints

In the present work, the effects of post weld heat treatment (PWHT) on friction welded UNS S31803 duplex stainless steel samples at three different temperatures namely 1080°C, 1150°C and 1200°C followed by water quenching were studied. Microstructural evaluations such as volume fraction of austenite/ferrite, grain size measurements, SEM-EDS, TEM and microhardness aspects were carried out. The volume fraction of ferrite to austenite ratio was balanced at 1080°C. Ni element is more effective in controlling the dual phase balance. Finer grains were obtained at 1080°C due to recrystallization effect. Microhardness was affected by reduction of ferrite percentage. Dual phase presence and absence of precipitates were conformed through XRD and TEM which follow Kurdjumov–Sachs relationship. Under the following: heating pressure: 40 heating time: 4 upsetting pressure: 80 upsetting time: 2 (Experiment no. 5) on PWHT at 1080°C, the balance of dual phase ratio, finer grains and increased microhardness were obtained.

Dubleks Paslanmaz Çeliklerde Sigma Fazının Korozyon Dayanımına Etkileri

800x600 Normal 0 21 false false false TR X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Normal Tablo"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman",serif;} Duplex stainless steels consistsof approximately half austenitic and half δ-ferritic phases and are preferred due to applications demanding both satisfactory corrosion and strength properties versus solely ferritic and austenitic grades. In this work; deleterious sigma phase that may form in microstructures of S32205 (2205) duplex stainless steel plates was intended to be quantified after various thermal conditions such as heat treatments, welding and service life and also the effects of sigma phase on microstructural and corrosion properties were investigated. Sigma phase was formed in two distinct raw material by applying heat treatments, and microstructural and corrosion states were analyzed. For this purpose; 800°C was adjusted as heat treatment temperature and two seperate specimens were heated through 5,5 and 16 hours of duration time in consequenceof the most rapidly formation rate of sigma phase at this temperature.

S32205 Dubleks Paslanmaz Çeliğin TIG Kaynağında Soğuma Hızının Mikroyapısal Özelliklere Etkileri

800x600 Normal 0 21 false false false TR X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Normal Tablo"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman",serif;} Welding of duplex stainless steels gains interest, significantly due to their increasing application fields. The problems come into question about the weldments of these steels improper distribution of important phases like delta-ferrite, austenite and other intermetallics. In order to maintain sufficient corrosion and mechanical properties in welding, the optimum delta-ferrite phase ratios must be kept within approximately %35-65 by volume. In this study; thicknesses of 3mm S32205 (2205) duplex stainless steel plates were TIG welded by pure argon shielding gas. The effects of various welding cooling circumstances on microstructural developments were examined.

Evaluation of Microstructural Effects on the Degree of Sensitization (DOS) of a UNS S31803 Duplex Stainless Steel Aged at 475°C

In this study, microstructural and electrochemical behavior of a UNS S31803 duplex stainless steel aged at 475°C were investigated. Hardness values increased with aging at 475°C and evidence of alpha prime (α′) phase formation was confirmed by transmission electron microscopy analysis. Double loop electrochemical potentiokinetic reactivation measurements in a 2 M H2SO4 + 0.5 M NaCl + 0.01 M KSCN solution showed an increase in the degree of sensitization values, mainly for the sample aged for 360 h at 475°C. Moreover, the results suggest that α′ phase formation occurred via spinodal decomposition mechanism.

Corrosion behavior of UNS S31803 steel with changes in the volume fraction of ferrite and the presence of chromium nitride

The goal of this study was to examine the changes caused in stress corrosion cracking and the critical pitting temperature behavior of a UNS S31803 duplex stainless steel due to variations in the ferrite fraction and the presence of chromium nitride in their microstructure. The steel plates were cold rolled and annealed at 1060°C. Microstructural variations in the plates were produced by thermal annealing treatments at 1200°C and 1300°C. Steel annealed at 1060°C showed greater resistance to stress corrosion cracking than steel annealed at 1300°C. Steel annealed at 1300°C had the lowest critical pitting temperature.

Corrosion of an UNS S31803 distillation column for acetic acid recovery

Unusually extended corrosion phenomena were detected in a distillation column, made of UNS S31803 duplex stainless steel, of a plant for the production of cellulose acetate. The process fluid was an aqueous solution of 80% acetic acid to separate by simple rectification. Corrosion was in the form of uniform attack mainly on downcomers and plates corresponding to the feedstock line.The phenomenon was a consequence of incomplete neutralization of sulphuric acid in the process fluid, used as a catalyst for the hydrolysis of esters. Controlled addition of H2O2 was proposed to solve the problem.

Corrugated stainless steels embedded in mortar for 9 years: Corrosion results of non-carbonated, chloride-contaminated samples

Mortar samples reinforced with 5 different corrugated stainless steels were tested for 9years in 2 different conditions: partial immersion (PI) in 3.5% NaCl, and chloride addition to the mortar and exposure to high relative humidity (HRH). The monitoring during the exposures was carried out with corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS) measurements. A year before finishing (after 8years of exposure), the reinforced mortar samples were anodically polarised to obtain more information about the pitting resistance of the passive layers formed under the different conditions. The last year of exposure was established to study the progress or repassivation of the pits. The PI is the most aggressive testing condition and it causes low-intensity corrosion in S20430 austenitic stainless steel after 7years of exposure. The S32205 duplex stainless steel shows very good corrosion behaviour.

Finite element modelling and characterization of friction welding on UNS S31803 duplex stainless steel joints

Solid state joining techniques are increasingly employed in joining duplex stainless steel materials due to their high integrity. Continuous drive friction welding is a solid state welding technique which is used to join similar and dissimilar materials. This joining technique is characterized by short cycle time, low heat input and narrow heat affected zones. The simulation becomes an important tool in friction welding because of short welding cycle. In the present work, a three dimensional non-linear finite element model was developed. The thermal history and axial shortening profiles were predicted using ANSYS, a software tool. This numerical model was validated using experimental results. The results show that the frictional heating stage of the process has more influence on temperature and upsetting stage has more impact on axial shortening. The knowledge of these parameters would lead to optimization of input parameters and improvement of design and machine tools.

Multiobjective optimization of friction welding of UNS S32205 duplex stainless steel

Abstract The present study is to optimize the process parameters for friction welding of duplex stainless steel (DSS UNS S32205). Experiments were conducted according to central composite design. Process variables, as inputs of the neural network, included friction pressure, upsetting pressure, speed and burn-off length. Tensile strength and microhardness were selected as the outputs of the neural networks. The weld metals had higher hardness and tensile strength than the base material due to grain refinement which caused failures away from the joint interface during tensile testing. Due to shorter heating time, no secondary phase intermetallic precipitation was observed in the weld joint. A multi-layer perceptron neural network was established for modeling purpose. Five various training algorithms, belonging to three classes, namely gradient descent, genetic algorithm and Levenberg–Marquardt, were used to train artificial neural network. The optimization was carried out by using particle swarm optimization method. Confirmation test was carried out by setting the optimized parameters. In conformation test, maximum tensile strength and maximum hardness obtained are 822 MPa and 322 Hv, respectively. The metallurgical investigations revealed that base metal, partially deformed zone and weld zone maintain austenite/ferrite proportion of 50:50.

The impact of heat input on the strength, toughness, microhardness, microstructure and corrosion aspects of friction welded duplex stainless steel joints

The impact of heat input on mechanical aspects like joint strength, toughness, microhardness and metallurgical and corrosion characterization of UNS S31803 duplex stainless steel (DSS) in solid state continuous drive friction welding was studied. The experiments were carried out according to Design of Experiments (DOE) with L9 orthogonal array by varying the four different parameters namely friction pressure, friction time, upsetting pressure and upsetting time, keeping spindle speed as constant. Detailed analysis of fracture morphology, presence of elements and its distribution on joint zone were performed through scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS). No intermetallic phases were observed by X-ray diffraction (XRD) technique. Tensile strength results showed that higher the heat input the better was the preservation of joint strength. At room temperature, toughness decreased as heat input increased. At −100°C and −196°C, toughness of weld metal was comparatively higher than other fusion processes. Microhardness increased with an increase in heat input due to grain refinement. In addition, the corrosion behavior of the weld metal was also evaluated through potentio-dynamic polarization curve. Corrosion resistance of weld was better than that of base material and it is increased with an increase in the heat input.

Effect of volume fraction of phases and precipitates on the mechanical behavior of UNS S31803 duplex stainless steel

Mechanical properties of a grade UNS S31803 duplex stainless steel were studied. Samples were annealed at three different temperatures, 1060°C, 1200°C, and 1300°C, to change the α/γ proportion, to precipitate undesirable phases (for example, α′, σ and chromium nitrides), and to study the effect of the microstructure on the mechanical behavior. Specimens with a thickness of 1.8mm were prepared according to ASTM standards and tested at room temperature. Tensile tests were conducted using displacement control at a rate of 5mm/min. Force-controlled constant amplitude axial fatigue tests were conducted at a frequency of 30Hz and an R stress ratio of 0.1. Microstructural analyses, performed by optical microscopy and scanning electron microscopy, showed the following modifications to the microstructure: changes in the phase volume fractions, the phase grain growths, and the morphology of the γ-phase and the precipitation of chromium nitrides in the α-phase. The mechanical properties of the steel were significantly changed due to the changed microstructure. The results demonstrate the sensitivity of the steel to the annealing temperature.

Investigations on the structure – Property relationships of electron beam welded Inconel 625 and UNS 32205

• Joining of dissimilar metals of Inconel 625 and UNS S32205 using electron beam welding. • Detailed structure – property relationship of dissimilar welds. • Improved metallurgical and tensile properties from the EB welding. The metallurgical and mechanical properties of electron beam welded Ni based superalloy Inconel 625 and UNS S32205 duplex stainless steel plates have been investigated in the present study. Interface microstructure studies divulged the absence of any grain coarsening effects or the formation of any secondary phases at the heat affected zone (HAZ) of the electron beam (EB) weldments. Tensile studies showed that the fracture occurred at the weld zone in all the trials and the average weld strength was reported to be 850 MPa. Segregation of Mo rich phases was witnessed at the inter-dendritic arms of the fusion zone. The study recommended the use of EB welding for joining these dissimilar metals by providing detailed structure – property relationships.

Surface Crack and Organization of Hot Rolled S31803 Duplex Stainless Steel Bars

In bar rolling of S31803 duplex stainless steel, the surface crack is easy to appear. Through the observation on the microstructure, ferrite and austenite morphology and phase ratio were analyzed. The surface cracks of S31803 duplex stainless steel bar is mainly because of the dual phase microstructure softening mechanism of different in thermal processing, and the double phase stainless steel heat plasticity decrease. When the ferrite and austenite proportion close, and the heating temperature is too high, to reduce the binding force between the grains of billet surface, easy to cause the crack surface of a bar.

Corrosion Properties and Impact Toughness of 2205 Duplex Stainless Steel after TIG Welding*

Abstract Application fields for duplex stainless steels are drastically increasing. Industries producing and operating petrochemical process equipment, pipelines, bridges, pressure vessels, heat exchangers, rotors, and sea-water systems have a high demand for these steels. In this study, UNS S32205 duplex stainless steel plates of 3 × 40 × 145 mm were TIG welded with welding wires of W22 9 3 NL (2209). The main aim was to investigate the effects of various amounts of magnetic δ-ferrite and other important phases or intermetallic compounds that are formed during and after welding. The phase quantities differing by the welding conditions and argon shielding gas mixtures containing 0, 1, 3, 6, and 9 vol.-% N2 are studied. The investigations included Charpy V-notch impact tests, weight loss corrosion tests, and microstructural analyses according to ASTM A 923 and magnetic δ-ferrite measurements according to EN ISO 17655, and EN ISO 8249 as well as image analyses according to ASTM E-562, ASTM E 1245 for a comparision of the effect of the amounts of all phases. The differences with respect to the welding parameters were also identified.

Experimental Investigation on Friction Welding of UNS S32205 Duplex Stainless Steel

UNS S 32205 duplex stainless steel specimens were joined by continuous drive friction welding process. The experiments were conducted as per the Taguchi (L16 orthogonal array) method. The friction welding process parameters such as heating pressure, heating time, upsetting pressure, upsetting time, and speed of rotation were fixed with low, medium, and high levels of range based on the machine capacity, and the required knowledge was acquired from the preliminary experiments. The joint characterization studies included micro structural examination and evaluation of mechanical properties of the joints. Microhardness variation, impact toughness, and tensile strength of the joints were evaluated. Neither a crack nor an incomplete bonding zone was observed. The tensile strength of the joints was higher than the strength of the base material, and the friction and upsetting pressures were found to influence the joint strength. The tensile strength of all the welds was observed to be increasing with an increase in the rotational speed. The toughness of the friction welds was evaluated at room temperature and also at subzero (cryo) temperature conditions. The toughness for friction welds was found to be superior to the fusion welds of duplex stainless steel at room temperature and cryo conditions. Weldments exhibited better corrosion resistance than the parent material.

Optimization of process parameters of the activated tungsten inert gas welding for aspect ratio of UNS S32205 duplex stainless steel welds

The activated TIG (ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention. The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency. The major influencing ATIG welding parameters, such as electrode gap, travel speed, current and voltage, that aid in controlling the aspect ratio of DSS joints, must be optimized to obtain desirable aspect ratio for DSS joints. Hence in this study, the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array (OA) experimental design and other statistical tools such as Analysis of Variance (ANOVA) and Pooled ANOVA techniques. The optimum process parameters are found to be 1 mm electrode gap, 130 mm/min travel speed, 140 A current and 12 V voltage. The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.

Differential Evolution algorithm applied to FSW model calibration

Friction Stir Welding (FSW) is a solid state welding process that can be modelled using a Computational Fluid Dynamics (CFD) approach. These models use adjustable parameters to control the heat transfer and the heat input to the weld. These parameters are used to calibrate the model and they are generally determined using the conventional trial and error approach. Since this method is not very efficient, we used the Differential Evolution (DE) algorithm to successfully determine these parameters. In order to improve the success rate and to reduce the computational cost of the method, this work studied different characteristics of the DE algorithm, such as the evolution strategy, the objective function, the mutation scaling factor and the crossover rate. The DE algorithm was tested using a friction stir weld performed on a UNS S32205 Duplex Stainless Steel.

Characterization of microstructure, toughness, and chemical composition of friction-welded joints of UNS S32205 duplex stainless steel

Abstract Friction welding is a solid-state joining process which is applied extensively because of its advantages such as low heat input, efficient application, ease in manufacturing, and environmental friendliness. The present study investigates the mechanical and metallurgical properties of UNS S32205 duplex stainless steel friction-welded joints. The process parameters, namely friction pressure, upsetting pressure, and rotational speed are individually varied from low level to high level (within the range of the machine setup) and their effects on the joint properties are analyzed. The partial-deformation zone had higher hardness than the weld and base metal. The toughness of the joints was evaluated at room temperature and at subzero temperature conditions. The impact toughness of the friction-welded joints was found to be superior to fusion-joined duplex stainless steel in room and cryogenic conditions.

Thermal history in UNS S32205 duplex stainless steel friction stir welds

Consolidated UNS S32205 duplex stainless steel joints welds were performed using a friction stir welding (FSW) process. An experimental set-up was used to record the thermal history of duplex stainless steel FSW joint. For points at equal distance from the weld centreline, temperature measured near the beginning of the weld was lower than that measured in the middle of the welded joint. This was attributed to a non-stationary transfer condition. FSW thermal cycle showed shorter time spent at elevated temperature compared that presented by fusion welding, indicating less propensity to detrimental second phase precipitation. To support temperature measurements with thermocouples, a three-dimensional finite element thermal model of FSW was implemented, which provided a good agreement with experimental data.

In situ investigation of crevice corrosion on UNS S32101 duplex stainless steel in sodium chloride solution

Abstract The crevice corrosion of UNS S32101 in neutral 0.1 M NaCl solutions at room temperature was investigated directly by a facile method. Experimental results showed that both delayed and immediate crevice corrosion can be initiated. Morphology study indicated that the heaviest corrosion attack happened just below the passive/active boundary on the crevice wall. The relocation of the active dissolution regions during crevice corrosion was observed and explained by established theory. The mechanisms of the delayed and immediate types of crevice corrosion on UNS S32101 duplex stainless steel were discussed.