Duplex Stainless Steel Material Research Articles

Analysis and Optimization of Super Duplex Stainless Steel Deposition in Wire Arc Additive Manufacturing Using Machine Learning Techniques

<div>This article presents experimental investigations and machine learning-based analysis on depositions of super duplex stainless steel (SDSS ER2594) material in wire arc additive manufacturing (WAAM) considering the process parameters namely voltage, wire feed rate, torch travel speed, and gas flow rate. Deposition efficiency and surface height values of the accumulated material were measured to build machine learning models using artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). The developed ANN model could predict the deposition efficiency and surface height with mean absolute deviations (MADs) of 8.9% and 16.1%, respectively. The MAD for prediction of the two responses for ANFIS model was found to be 6.1% and 14.9% as compared to the experimental data. Multi-objective optimization was also performed to obtain optimal solutions to achieve desired deposition results. Mechanical properties and microstructures of the deposited materials with optimal processing parameters were found comparable to that of the base materials.</div>

Effect of Powder Reuse on Powder Characteristics and Properties of DED Laser Beam Metal Additive Manufacturing Process with Stellite® 21 and UNS S32750

In this work, the influence of powder reuse up to three times on directed energy deposition (DED) with laser processing has been studied. The work was carried out on two different gas atomized powders: a cobalt-based alloy type Stellite® 21, and a super duplex stainless steel type UNS S32750. One of the main findings is the influence of oxygen content of the reused powder particles on the final quality and densification of the deposited material and the powder catch efficiency of the laser deposition process. There is a direct relationship between a higher surface oxidation of the particles and the presence of oxygen content in the particles and in the as-built materials, as well as oxides, balance of phases (in the case of the super duplex alloy), pores and defects at the micro level in the laser-deposited material, as well as a decrease in the amount of material that actually melts, reducing powder catch efficiency (more than 12% in the worst case scenario) and the initial bead geometry (height and width) that was obtained for the same process parameters when the virgin powder was used (without oxidation and with original morphology of the powder particles). This causes some melting faults, oxides and formation of undesired oxide compounds in the microstructure, and un-balance of phases particularly in the super duplex stainless steel material, reducing the amount of ferrite from 50.1% to 37.4%, affecting in turn material soundness and its mechanical properties, particularly the hardness. However, the Stellite® 21 alloy type can be reused up to three times, while the super duplex can be reused only once without any major influence of the particles’ surface oxidation on the deposited material quality and hardness.

Micromachined structures decoupling Joule heating and electron wind force

Microstructural changes in conductive materials induced by electric current treatments, such as electromigration and electroplasticity, are critical in semiconductor and metal processing. However, owing to the inevitable thermal effect (Joule heating), the athermal effect on microstructural modifications remains obscure. This paper presents an approach of utilizing pre-micromachined structures, which obstruct current flow but maintain a thermal history similar to that of the matrix, effectively disentangling the thermal and athermal effects. A duplex stainless-steel material is selected to validate the feasibility of this method. Microstructural characterizations show that the athermal effect, especially the electron wind force (EWF), primarily governs the element diffusion and phase transformation in this study. Moreover, many σ phases (Cr-enriched) are precipitated in the micromachined structures, whereas no precipitation occurred in the matrix, suggesting that the directional EWF disrupts the Cr aggregation caused by Joule heating. Furthermore, we present a critical formula for determining the dimensions of micromachined structures of commonly used metallic materials. The proposed method may serve as an effective and powerful tool for unveiling the athermal effect on microstructural alterations.

Establishing the hot working window for the forging of S32906 super duplex stainless steel through considering deformation parameter sensitivities

The evaluation of the hot workability of the super duplex stainless steel (SDSS) material still lacks scientific and theoretical basis, leading to the frequent occurrence of unacceptable defects in its forgings. In this study, a novel method for estimating the hot workability of S32906 SDSS was proposed and verified through forging. Firstly, the flow behavior and microstructural characteristics were demonstrated by conducting isothermal compression tests at the deformation temperature from 1000 °C to 1250 °C and the strain rate from 0.01 s−1 to 10 s−1. The influence of microstructure on flow and work hardening behaviors was correlated and displayed. Then, based on the deformation characteristics presented through the variations of strain rate sensitivity (SRS) and deformation temperature sensitivity (DTS) coefficients, the SRS and DTS maps were constructed and overlaid for obtaining the hot working window. Ultimately, a large plate type forging of S32906 SDSS applied in engineering was used to verify the applicability of the obtained window. The new method can provide an in-depth understanding of hot workability and enable control of the forming and microstructural properties for this unique material.

Study of fatigue fracture characteristics for duplex stainless steel STHE welded joint specimen

A shell and tube heat exchanger (STHE) welded joint is considered for fatigue fracture mechanism. The joint is made up of a protruding tube fabricated to a tubesheet by means of welding. A super duplex stainless steel (DSS) material is used for the tube and tubesheet. Fatigue test was newly conducted using the single tube test specimen. The initial cracking plane was moved from the minimum sectional-area plane that was perpendicular to the loading direction, and the crack growth was almost planar. Stress analysis is carried out using finite element method (FEM) and the stress distributions are carefully studied by comparing the simple perforated plate. In addition, three-dimensional crack propagation (CP) simulation is performed employing extended finite element method (X-FEM). Fracture phenomenon is verified using the experimental and numerical crack front geometries. The fracture mechanics parameter is evaluated and verified with empirical formulae. CP behaviors are carefully discussed based on the fracture mechanics parameter. The CP life is presented for three loading amplitudes. The FAT class of the STHE welded joint is studied based on the available design standards such as BS, IIW and JSSC. Finally, the fatigue fracture characteristics of the STHE welded joint specimen are shown through the experimental and numerical methods.

Numerical assessment of stainless steel starred rolled angle sections under compression

This paper shows a numerical investigation of short-to-intermediate austenitic and duplex stainless steel welded starred columns with fixed supports prone to failure by torsional buckling. A finite element model, developed by the same authors in prior work and validated against experimental results, was used (i) to assess the cross-section geometrical properties – secondary warping and torsion constants, (ii) austenitic and duplex stainless steel material mechanical properties, (iii) the elastic buckling behaviour, and (iv) the columns' ultimate resistance. A parametrical analysis was carried out through a broader coverage of cross-section dimensions and member lengths. Finally, the obtained ultimate strengths are used to evaluate if the Eurocode 3: Part 1.4 – column buckling curve “b” – can adequately predict the ultimate column strength. Comparisons between numerical failure load and predicted Eurocode buckling ultimate torsional load showed excessive conservatism. Given this, modifications were proposed in European code following the same methodology, i.e., changing the column buckling curve.

Effect of wire EDM process parameters on material removal rate of duplex stainless steel (S31803)

Machining of high-strength alloy is needed for special requirements requiring less wear, such as sliding objectives in applications like cams, gears etc. High-strength alloy material profile machining is challenging in conventional machining; Wire-EDM is one of the machining processes to fulfil the requirement with a good surface finish. The present work is an experimental study on material removal rate in Wire-EDM machining on S31803 Duplex Stainless Steel (DSS) material at different thicknesses. Thickness is considered as 5 mm, 10 mm, 15 mm and 20 mm where the nozzle distance altered as 19, 29, 39 and 49 with pulse off time 1,2,3,4 s. L16 orthogonal array from Taguchi method of experiments considered for the present study. Material of 10 mm thickness with 4 s pulse off time at 29 nozzle distance gives better material removal rate when compared with other samples.

Effects of low-temperature neutron irradiation on the microstructure and tensile properties of duplex 2304 stainless steel and its electron-beam welds

A lean duplex stainless steel material (2304-grade) in its base metal and electron beam (e-beam) welded conditions were studied microstructurally and mechanically as a function of irradiation conditions to evaluate its use as a structural material at low temperatures (60–100 °C). Neutron irradiation up to a fluence of 1.40 × 1019 n/cm2 (E > 0.1 MeV) or ~0.011 dpa decreased the total elongation of both base metal and e-beam welded samples. Overall, radiation hardening was observed in all the samples. The transversely cut irradiated samples showed some nonuniform quasi-cleavage and shearing in their fracture surfaces, indicating the variance of ductile nature of the two-phased (deformable austenite and harder ferrite) duplex structure. The e-beam welded samples also showed quasi-cleavage fracture, which is a characteristic of radiation-induced embrittlement. These observations of the e-beam welded samples were attributed to the formation of coarse ferrites, grain boundary and intragranular phases such as γ2 and γ3, and minor impurity phases such as CrN and Cr2N in the weld pool and/or heat-affected zone of the samples. Radiation-induced elemental segregation was also identified in the post-irradiated base metal.

PENGELASAN DISIMILAR MATERIAL (DUPLEX STAINLESS STEEL) 2205 DAN (HIGH STRENGTH STEEL) GRADE VL D36 UNTUK KAPAL OIL TANKER

The choice of Duplex Stainless Steel material for oil tanker ship construction is very appropriate because in addition to having good mechanical properties (high tensile and yield strength and toughness) as a ship construction structure, it is also resistant to loads of highly corrosive liquid chemicals. Unlike Mild Steel or Duplex Stainless Steel A, welding and treating Duplex Stainless Steel requires very strict procedures and care must be taken. The choice of welding process, namely a combination of (Flux Cored Arc Welding) and SAW (Submerged Arc Welding) is a welding process that is very suitable for welding ship construction. The welding process is categorized as a semi-automatic and automatic welding process that can increase productivity while speeding up welding work. This paper illustrates the welding of two materials with different specifications, namely Duplex Stainless Steel 2205 plate material and VL D36 plate material, along with practical instructions for welding it up to the things that must be considered regarding the handling procedure. In welding Duplex Stainless Steel 2205 plate material it is very important to keep the heat input in the range of 0.5-2.5 kj / mm.

Machinability, weldability and surface treatment studies of SDSS 2507 material-A review

Super duplex stainless steel 2507, is a difficult to machine material due to high chromium content. Knowledge on machinability, weldability and surface treatment of 2507 super duplex stainless steel material is necessary due to the increase in demand of this material in variety of application in engineering and medical fields. In this review, machinability studies on turning and milling of SDSS 2507 is discussed. Weldability of SDSS 2507 material is also reviewed in this paper. Effect of heat and chemical treatments on strength, ductility, resistance to corrosion, wear, crack propagation and pitting characteristics of this material are included. Machining with wet, minimal quantity lubrication and dry conditions are analyzed. From the review, it was found that machinability can be improved by machining at high cutting speed and low feed rate along with proper selection of tool. Welding of SDSS 2507 material with similar and dissimilar materials is also discussed. Literatures on the studies on machining of SDSS 2507 material, especially on milling of SDSS material is very less compared to turning operation. Review revealed that SDSS 2507 material possess better strength, ductility and corrosion resistance properties compared to Austenitic SS and Ferritic SS. The present paper recommends the usage of tougher insert grades for machining. From this review, it is clear that SDSS 2507 material can be used in corrosion prone environments due to its high resistance to corrosion and pitting characteristics. SDSS 2507 material can also replace duplex stainless steel in storage and transportation of petroleum products, piping, etc. due to its exceptional characteristics.

Finite element Analysis on Buckling Strength of Stainless Steel Circular Hollow Section Columns Under Concentric Axial Compression

Stainless steel has superior corrosion resistance, fire resistance, and maintenance compared to carbon steel as a structural material. Although austenitic stainless steel (STS304) has mainly been used as structural steel material, lean duplex stainless steel, STS329FLD with lower nickel component (reduced to 0.5–1.0% in KS) has recently been developed as a substitute for austenitic stainless steel. Since duplex stainless steel is less costly and has excellent corrosion resistance compared with austenitic stainless steel, its use is expected to increase in the field of industry and infrastructure. However, there have been little data to apply this duplex stainless steel member to structural use. This paper presents an experimental and numerical investigation on the structural behaviors of austenitic stainless steel (STS304 TKC) and lean duplex stainless steel (STS329FLD TKC) circular columns subjected to concentrically axial compression. Test specimens were fabricated with four types of column lengths and slender ratios and were tested with both fixed ends. Duplex stainless steel (STS329FLD TKC) material showed higher yield stress and tensile strength than those of austenitic stainless steel (STS304 TKC). The results such as buckling shapes (local and global buckling) and ultimate strengths through additional parametric analysis were investigated and were compared with those predicted by current design codes [American Society of Civil Engineers (ASCE) and Eurocode (EC 3)] and by design equations of previous studies. Modified buckling equations were recommended considering the initial imperfection factor and limiting slenderness of two types of stainless steel circular columns and the accuracy of buckling strength prediction was improved.

Flexural buckling of circular concrete-filled stainless steel tubular columns

Concrete-filled steel tubular (CFST) columns are currently used in offshore structures and oil and gas drilling platforms, from which the external steel tubes become at risk due to the aggressive ocean climate and/or sea water. Therefore, the CFST columns in corrosive environment lose their excellent mechanical performances and safety as the thicknesses of steel tubes decrease due to corrosion. This has recently led to the introduction of the concrete-filled stainless steel tubular (CFSST) columns, which benefit from the stainless steel as a superior metallic corrosion resistant material. Accordingly, CFSST short columns have recently attracted the scientific community. However, circular CFSST slender columns have received very little attention. Currently, this paper provides a nonlinear finite element (FE) inelastic analysis for the axially-loaded circular CFSST slender columns to substitute the lack in their behaviour; especially when the relative cheap lean duplex stainless steel material (EN 1.4162) is utilised. The FE models are firstly validated by using the available test results in literature. This validation stage is, then, followed by a parametric analysis to explore the fundamental behaviour of such columns considering the most important factors. The paper divides the slender columns into intermediate length and long columns based on the type of the overall buckling that takes place, and then the behavioural differences between both types are clearly addressed. The obtained FE axial strengths are additionally compared with those predicted by the European (EC4) and American (AISC) specifications. Based on these comparisons, a formula, based on Eurocode 4, is suggested for the routine compressive design practice of these columns, which is found to fit well with the axial strengths of current slender columns which utilise the lean duplex stainless steel material.

Wear analysis of treated Duplex Stainless Steel material by carburizing process – A review

A review about the effect of carburizing on Duplex Stainless Steel are analysed in this paper. The focus is kept on the expanding the hardness and wear-ability without losing corrosion resistance could essentially widen its applications. These heat-treated materials were analysed under with respect to different metallographic tests and mechanical tests. The most widely used metallographic tests like X-Ray Diffraction, Scanning Electron Microscope, and mechanical tests like tensile & hardness tests. The paper explains structural and physical changes of Duplex Stainless Steel after heat treatment process.

Alloying the surface of AISI 2205 duplex stainless steel material by PTA welding method and making its thermomechanical investigation in ANSYS software

AISI 2205 steel is a duplex stainless steel plate containing 22% Cr, 3% Mo and 5–6% Ni and having the properties like high strength, impact toughness and corrosion resistance. In plasma transfer arc (PTA) welding method, the arc occurs between the tungsten electrode and the workpiece. In this study, the surface of AISI 2205 steel material was alloyed by PTA welding method using different combinations of TiC and B4C powders. The effect of B4C and TiC powders on AISI 2205 steel in coating process performed by PTA welding was investigated. The coating layer was investigated with the help of microhardness, optic microscope, SEM and XRD. As a result of optical microscope, microstructure examinations and microhardness values, it was determined that the coating layer and substrate were bonded to each other metallurgically, there was a significant increase in the hardness values in the presence of B4C and also metal carbide (MC) and metal boride (Me-B) phases formed in the structure. The highest increase in hardness was observed in the sample N4. TiC mixture decreased when B4C rate was 75% increased and the hardness values in the coating region by 330–457 HV. Finally, in the thermomechanical analysis results we found that axes-dependent thermal and residual stresses of the alloying layer increased along the welding. It is clear that the stress distribution along the weld line was the same. At both ends of the weld, there was only a small reduction in the stress size. It was determined that the highest stress concentration existed in the highest cross-sectional area.

Application of the Master Curve concept on the choice of duplex stainless steel to avoid brittle fracture

ABSTRACTDuplex stainless steel gets more and more common in structural applications even in steel bridges. For these cases, the choice of duplex stainless steel material to avoid brittle fracture is of great importance as e.g. steel bridges are exposed to low temperatures, generally down to −30 °C or even lower, and fatigue loads. EN 1993‐1‐4 also covers duplex stainless steel, but the given toughness requirements for duplex stainless steel are insufficient. Due to this fact, first investigations have been carried out on various duplex stainless steel base materials and welded specimens based on the fracture mechanic based concept of EN 1993‐1‐10 including the Wallin Master Curve concept. The objective was to achieve a first insight in the applicability of EN 1993‐1‐10 for structural applications with different types of duplex stainless steels in principle. In this frame, Charpy and fracture mechanics tests have been evaluated for 1.4462, 1.4362 and 1.4162 duplex stainless steels of 30 mm and 50 mm thick base materials and weldments. The results have been transformed into the general approach used in EN 1993‐1‐10 originally developed for ferritic structural steel considering the structural detail of a welded longitudinal attachment with a semi elliptical surface crack at the weld toe. The results demonstrate that the investigated duplex stainless steels and their weldments show a very good toughness behaviour and that the EN 1993‐1‐10 model can be transformed for application of duplex stainless steel. The paper presents these first results.

Finite element analysis of cold-formed lean duplex stainless steel columns at elevated temperatures

The behaviour of cold-formed lean duplex stainless steel columns at elevated temperatures was investigated. A numerical investigation on columns of square and rectangular hollow sections were performed at elevated temperatures ranged from 24 to 900 °C. A validated numerical model with material properties obtained from tensile coupon tests at elevated temperatures were used in the finite element analysis. A total of 180 numerical column strengths were compared with design column strengths predicted by existing design rules, which do not cover the lean duplex stainless steel material at elevated temperatures. Reliability analysis was carried out to assess the suitability of the existing design rules for lean duplex stainless steel columns at elevated temperatures. It is shown that the existing design rules are generally not suitable for predicting the column strengths, except for the American Specification and the modified direct strength method for stainless steel. The modified direct strength method for stainless steel provides accurate and reliable predictions with relatively simple calculation procedure. Therefore, it is recommended that the modified direct strength method for stainless steel be used for design of cold-formed lean duplex stainless steel columns at elevated temperatures.

Interactions Between Fibroblast Cells and Laser Beam Welded AISI 2205 Duplex Stainless Steel

Because of their high mechanical strength, excellent corrosion resistance and good weldability, duplex stainless steels are mostly used in industries such as oil, chemistry, petrochemistry, food and occasionally used in medical industry. These properties have enabled us to use duplex stainless steels in biomedical applications recently. Accordingly, duplex stainless steel material can be highly important to examine the toxic effect on the cells. In this study, the effect of the AISI 2205 duplex stainless steels which are joined by CO2 laser beam welding on viability of L929 fibroblast cells has been studied in vitro for the first time. For this aim, the cells were kept in DMEM/F-12 (Thermofisher Scientific 31331-028) medium for 7 days. The viability study was experimentally studied using the MTT (Thiazolyl Blue Tetrazolium Bromide) method for 7 days. The cell viability of the laser beam welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. According to the obtained results, it was revealed that laser beam welded and base metal AISI 2205 duplex stainless steel has been found suitable to study for biomedical applications. DOI: http://dx.doi.org/10.5755/j01.ms.24.2.18006

Optimization of cladding parameters for resisting corrosion on low carbon steels using simulated annealing algorithm

Low carbon steels used in chemical industries are frequently affected by corrosion. Cladding is a surfacing process used for depositing a thick layer of filler metal in a highly corrosive materials to achieve corrosion resistance. Flux cored arc welding (FCAW) is preferred in cladding process due to its augmented efficiency and higher deposition rate. In this cladding process, the effect of corrosion can be minimized by controlling the output responses such as minimizing dilution, penetration and maximizing bead width, reinforcement and ferrite number. This paper deals with the multi-objective optimization of flux cored arc welding responses by controlling the process parameters such as wire feed rate, welding speed, Nozzle to plate distance, welding gun angle for super duplex stainless steel material using simulated annealing technique. Regression equation has been developed and validated using ANOVA technique. The multi-objective optimization of weld bead parameters was carried out using simulated annealing to obtain optimum bead geometry for reducing corrosion. The potentiodynamic polarization test reveals the balanced formation of fine particles of ferrite and autenite content with desensitized nature of the microstructure in the optimized clad bead.

Overall buckling behaviour of circular concrete-filled dual steel tubular columns with stainless steel external tubes

Recently, a short composite column consisting of dual steel tubes (external and internal stainless and carbon steel tubes, respectively) with concrete filled in the entire tubular section has been introduced. This column, called as the concrete-filled dual steel tubular (CFDST) column, proved that a lower cost as well as weight can be achieved compared with the concrete-filled stainless steel tubular column (CFSST). This is mainly attributed to the increased strength of the concrete fill, inside the internal tube, that is surrounded by both the external and internal steel tubes. Based on the fact that the columns are generally slender in practice, this paper investigates numerically, by means of finite element (FE) analyses, the axial compressive behaviour of the CFDST slender columns, which has been rarely investigated in literature. The external tubes are currently made of the lean duplex stainless steel material recently attracted the structural community because of its relatively lower cost. The FE models carefully consider the compressive and tensile nonlinear behaviour of the concrete. The FE models are verified for their different material models. This is followed by examining the accurate overall buckling behaviour of the slender columns. This has been made through FE comparisons with tested columns of different cross-section types existing in literature. The fundamental behaviour of the CFDST slender columns under the effect of the slenderness ratio, the concrete confinement effect and the concrete compressive strength is then investigated. The study additionally addresses the differences in behaviour between the intermediate length and long CFDST columns. Moreover, the comparison between the design strengths calculated by Eurocode 4 from one side and the FE and experimental ultimate strengths from the other side shows generally that Eurocode 4 gives unsafe predictions. Accordingly, a modified European design model is suggested at the end to predict accurately the resistance of the CFDST slender columns under axial compression.

Magnetic Characterization of Selective Laser-Melted Saf 2507 Duplex Stainless Steel

Selective laser melting (SLM) is disruptive in terms of the sensitive balance between constituent phases of the biphasic duplex stainless steel material options. While adversely affecting the mechanical and corrosion properties, the predominantly ferritic structures resulting from the high thermal gradients were also noted to impart significant magnetic responses. Scientific attention is essential for ascertaining the material-process-magnetic response relationships to establish the underlying principles and critical responses. This is attempted here through magnetic characterization based on results from saturation hysteresis loops and evaluation of austenite–ferrite ratios allowing for identification of the structure–magnetic property relationships. Overall, the experimental results indicated strong process–property relationships, whereas the magnetic saturation levels of SLM samples are much higher compared with the wrought counterparts.