Strength Stainless Steel Research Articles

Experimental investigation and optimization of IRB6700 ABB robot spot welding process parameters

In this study, the influence of robot spot welding parameters on the tensile shear strength of the weld joints was investigated. The experimentation was planned using Taguchi orthogonal array approach and the experiments were conducted on the IRB6700 Asea Brown Boveri (ABB) Robot Spot Welding machine. The important spot welding parameters studied in this work are electrode forces, welding currents, and welding times. The optimum IRB6700 ABB robot spot weld parameters were determined by using analysis of the Signal-to-Noise (S/N) ratio. The result shows that the parameter electrode force is having a maximum influence on the weld joint tensile shear strength in stainless steel and mild steel material, 58.51% and 70.95%, respectively. The confirmation experiment shows that the spot weld joint tensile shear strength can be improved by selecting a suitable range of spot weld parameters.

Enhancing the static and dynamic mechanical properties of laser powder bed fusion process built 15–5 precipitation hardening stainless steel specimens by laser shock peening

The Additive Manufacturing (AM) of high strength Stainless Steel (SS) metallic parts by Laser Powder Bed Fusion (L-PBF) process has been able to reduce cost and time significantly, leading to a successful adaption in various high technology industries. In this study, the static and dynamic mechanical properties of L-PBF 15–5 Precipitation Hardening (PH) SS in two different loading directions have been studied, and Laser Shock Peening (LSP) has been used as a post-processing tool to improve the part properties. Optimized parameters were chosen for the mechanical property evaluation based on the residual stress profile of the specimens subjected to LSP. Improvement in microhardness, uniaxial tensile properties and high cycle fatigue life due to LSP are reported. With LSP applied on vertically loaded L-PBF 15–5 PH SS specimens (loading axis parallel to building direction), the fatigue life has increased by more than four times, making it comparable to horizontally loaded L-PBF 15–5 PH SS base specimens. Thus, the viability of the LSP process as a post-processing technique to mitigate the fatigue life anisotropy due to loading direction has been established. The associated microstructure and phase analysis revealed an increased depth of plastic deformation with successive LSP shots without causing any phase changes. The central strengthening mechanisms for the enhancement of mechanical properties of L-PBF 15–5 PH SS due to LSP are reported.

Processing of IN718-SS316L bimetallic-structure using laser powder bed fusion technique

ABSTRACT A crack-free Inconel 718 – Stainless steel 316 L bimetallic structure has been fabricated using the laser powder bed fusion (LPBF) process. Firstly, an optimum process parameter set resulting in defect-free bonding of both materials has been predicted by carrying out a parametric study. Thereafter, microstructural and mechanical characterization such as optical microscopy, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, hardness and tensile testing have been carried out to investigate the characteristics of the bimetallic interface. The porosity quantification shows a density greater than 99.5% with no observable cracks or porosity at the transition zone. The secondary electron micrographs reveal a small inter-diffusion region at the interface. The interface and the nearby region consist of both cellular and columnar grains. The tensile strength of the bimetallic-structure approaches the strength of stainless steel 316 L. Even with the material discontinuity, the fracture happens at the weaker side (stainless steel 316 L) indicating the strong strength of the dissimilar interface. The fractography of the fractured surface displays a typical ductile cup and cone type of fracture. The results strongly suggest the suitability of the LPBF process for fabricating defect-free high-strength IN718-SS316L bimetallic structures.

Effect of Microshot Peening on Fatigue Strength of Austenite Stainless Steel

The effects of the peening conditions on the surface characteristics and fatigue strength of stainless steel were investigated by microshot peening (MSP). In recent years, MSP technology has attracted attention. The use of MSP technology with minute media has become more widespread in consideration of the reduction of the notch effect in the material surface. However, the effect of MSP technology on stainless steel has not been much studied. In the present study, an air-type machine was used. The media used was high-carbon cast steel (490 HV) and Fe-Cr-B alloy (1130 HV), with an average diameter of 0.1 mm. The peening time was in the range of 0 - 100 s. Four types of stainless steels, SUS304, SUS304L, SUS316, and SUS316L, were tested. The workpieces were annealed at 1100 K for 1.2 ks in air. In the measurement of fatigue strength, the workpieces were machined in hour-glass shape. As the results, surface roughness of the workpieces treated by MSP was small. Work hardening was evident to the depth of approximately 0.2 mm from the surface. This depth was about twice the diameter of shot media. However, the effect of the peening time on the hardness distribution was not large. The compressive residual stress was added in the surface vicinity. It is assumed that the fatigue limit had increased because the work hardened layer was formed near the workpiece surface.

Microstructures and Mechanical Properties of Dissimilar Metal Gas Tungsten Arc Welds of 15CDV6 Steel and AISI 304 Stainless Steel

The pressure pipeline applications demand high strength steels and stainless steels based on the requirement of strength and corrosion point of view, respectively. Welding is one of the widely practiced metal joining techniques in such kind of applications due to the high-pressure environment. The present work is primarily aimed at understanding the feasibility and producing X-ray radiography quality gas tungsten arc welds of dissimilar steels, particularly, 15CDV6 steel and AISI 304 stainless steel. The sound dissimilar GTA welds are subjected to evaluation of microstructures, mechanical properties such as microhardness across the weldment and tensile properties. The mechanical properties are further correlated to microstructures of dissimilar weld joints. The filler wire material has profound influence on the microstructures and mechanical properties (both tensile strength and hardness) of dissimilar steel weld joints. The dissimilar weld made with 8CD12 filler wire demonstrated higher tensile strength and joint efficiency as compared to the dissimilar weld made with ER 308L filler wire.

Using Stainless Steel and Titanium Alloy in Charcot Foot Reconstruction. FEA Simulation and Clinical Case

The aim of the study was to simulate a clinical case of Charcot foot reconstruction, using finite element analysis (FEA). Our work starts from a clinical failure case of Charcot arthrodesis, were one stainless steel Midfoot Fusion Bolt (MBF) prematurely failed. Starting from CT images a 3D model of the foot was reconstructed and together with the intramedullary bolts a virtual assembly was build. In addition, a second 3D model containing 3 MBF screws and one titanium locking compression plate (LCP) was constructed. The loading conditions used in FEA were extracted based on foot biomechanics according to the gait phases. The results are showing the critical sections of the bolts and also the stress shielding effect that appears on the bolts when the plate is used as supplementary fixation element. By comparing the stress values on bolts and plate with the yield strength of stainless steel and titanium alloy that are regularly used for manufacturing these implants, a valid reconstruction solution was found. This result can help surgeons in establishing the proper bolt insertion and plate positioning for minimizing the implant failure risk.

Effect of surface contamination on the durability and strength of stainless steel – polyisobutylene pressure-sensitive adhesive bonds

Cleaning of substrate's surface with a solvent is a standard step in a procedure of adhesive joints preparation while carrying out adhesion tests. However, is cleanliness of substrates really so important? The effect of contamination of substrate's surfaces with vegetable (sunflower) and mineral (naphthenic) oils on the strength and durability of adhesive joints formed by neat and organoclay-filled polyisobutylene-based PSAs with a stainless steel substrate was studied. For the filled composition, the strength of the adhesive joints was higher, even with the contaminated surface, than for the system with the neat PIB. Contamination of the surface leads to the formation of a weak layer of plasticized polymer, which contributes to decreasing of the adhesion strength and durability. These parameters, however, are restored over time, which could be connected with the absorption of the contaminants by the adhesive material, as a result of polymer swelling, and their migration to the bulk of the adhesive. The ability of contaminants that can be absorbed and removed from the surface into the bulk of the adhesive is determined by their solubility in the adhesive. It was demonstrated using laser microinterferometry method that PIB is miscible with naphthenic oil, whereas PIB − sunflower oil system exhibits upper-critical-solution-temperature behavior. These observations provide an explanation to the growth trends of durability and strength of the joints over time in the cases of sunflower and naphthenic oil contamination of the substrate's surface.

Behaviour of large fabricated stainless steel beam-to-tubular column joints with extended endplates

This paper presents the flexural behaviour of stainless steel beam-to-tubular column joints with extended endplates subjected to static loading. Moment-rotation relationships were investigated numerically by using Abaqus software with geometric and material nonlinearity considered. The prediction of damages among components was achieved through ductile damage models, and the influence of initial geometric imperfections and residual stresses was evaluated in large fabricated stainless steel joints involving hollow columns and concrete-filled columns. Parametric analysis was subsequently conducted to assess critical factors that could affect the flexural performance significantly in terms of the initial stiffness and moment resistance. A comparison between codes of practice and numerical results was thereafter made, and design recommendations were proposed for further applications. Results suggest that the finite element model can predict the structural behaviour reasonably well with the component damage consistent with test outcomes. Initial geometric imperfections and residual stresses are shown to have little effect on the moment-rotation responses. A series of parameters that can influence the joint behaviour remarkably include the strain-hardening exponents, stainless steel strength, diameter of bolts, thickness of endplates, position of bolts, section of beams and columns. AS/NZS 2327 is more reliable to predict the joint performance regarding the initial stiffness and moment capacity compared to EN 1993-1-8.

Analytical behavior of carbon steel-concrete-stainless steel double-skin tube (DST) used in submarine pipeline structure

One type of submarine composite pipeline structure, with carbon steel-concrete-stainless steel (CCS) double-skin tube (DST), was introduced in this paper. This composite pipeline was expected to make optimal use of the three types of the materials, and provide significant structural and internal corrosion resistance. This study investigated the compressive and flexural behavior of the composite pipeline under internal content pressure and external hydrostatic pressure through finite element analysis (FEA). Finite element models were developed, where non-linear material properties of stainless steel and composite actions between constituent parts were considered. The models were verified through the comparisons between the numerically and experimentally determined results, in terms of load-deformation histories, failure modes and ultimate strength. Structural behaviors of the composite pipeline under pressures were compared with those without content and hydrostatic pressure. Parametric studies were carried out to investigate the effects of the outer carbon steel strength, inner stainless steel strength, concrete strength and hollow ratio on the compressive and flexural behaviors of the composite pipelines subjected to pressures.

3D printing doubles the strength of stainless steel

3D printing doubles the strength of stainless steel

Hybrid nanostructure stainless steel with super-high strength and toughness

Abstract The objective of the present study is to obtain the super-high strength and toughness stainless steel through hybrid nanostructure design. The hybrid nanostructured stainless steel was fabricated by two cold rolling and annealing processes. The second cold-rolled and annealing was carried out on bimodal microstructure which was obtained by the first cold-rolled and annealing on the original microstructure. The bimodal structure consisting of nanometer grains and a small amount of micrometer grains which were distributed in band. After the second cold-rolled and annealing, both the original coarse grain zone (micrometer grains) and fine grain zone (nanometer grains) formed their own finer bimodal microstructure and the bands of the grain distribution became narrower. In our investigations, the hybrid nanostructure obtained by two cold rolling and annealing processes had finer grains and narrower bands of the grain distribution. Meanwhile the results of tensile experiment showed that the yield strength (1221 MPa) and tensile strength (1376 MPa) of the hybrid nanostructure were greatly improved in the situation that the decrease of the toughness (et=45.3%) was not significant compared with the bimodal microstructure. It is obvious that the yield strength of the hybrid nanostructure increased by 2.7 times and the total elongation still remained at the level of 45.3% compared with the original microstructure. Mainly because we embed the soft micrometer grains into the hard nanometer grains to form the lamellar interphase structure. The back-stress hardening, dislocation hardening, TWP effect and TRIP effect produced by the hybrid nanostructure during tensile process contributed to high strength and toughness. And this contribution was more pronounced when the width of lamellar become narrower.

Enhancement of Fatigue Strength of Stainless Steel by Submerged Laser Peening Enhancing Bubble Collapse Impact

Enhancement of Fatigue Strength of Stainless Steel by Submerged Laser Peening Enhancing Bubble Collapse Impact

Dynamic Strength of Stainless Steel Subjected to Cyclic Impact Loading of Strong Motion

Dynamic Strength of Stainless Steel Subjected to Cyclic Impact Loading of Strong Motion

Bearing Strength of Stainless Steel Bolted Connections

The present investigation studies the load bearing performance of stainless steel bolted connections. The austenitic stainless steel developed in China containing approximately 17% of Cr, which could be graded as EN 1.4401, has been selected for this research. In order to study the bearing strength of stainless steel bolted connections, experimental tests on 5 specimens have been conducted. In addition, complementary finite element (FE) models, which have been validated by the test results, have been adopted to analyse the effect of the key factors for bearing strength of the stainless steel bolted connections. The key factors include end distance, thickness of connecting plate, diameter of stainless steel bolt and edge distance. According to the FEA results, the loading capacity increases with the increase of the thickness of the plate and the diameter of the bolt approximate linearly. However, the end distance and edge distance have a comparatively complicated influence on the loading capacity of the connection. Based on mathematical analysis of the experimental and FEA results, a calculation method as well as its simplified form for the bearing strength of stainless steel bolted connections has been proposed.

Effects of Three Different Types of Intracoronal Bleaching Agents on Shear Bond Strength of Stainless Steel and Sapphire Brackets Bonded to Endodontically Treated Teeth : An in Vitro Study

Effects of Three Different Types of Intracoronal Bleaching Agents on Shear Bond Strength of Stainless Steel and Sapphire Brackets Bonded to Endodontically Treated Teeth : An in Vitro Study

Lubricant Film Breakdown and Material Pick-Up in Sheet Forming of Advanced High Strength Steels and Stainless Steels when Using Environmental Friendly Lubricants

Increasing focus on environmental issues in industrial production has urged sheet metal stamping companies to look for new tribo-systems in order to substitute hazardous lubricants such as chlorinated paraffin oils. The efficiency of chlorinated paraffin is due to the fact that the lubricant reacts chemically with the tool and workpiece material forming thin films, which adhere strongly to the surfaces and reduce the tendency to metal-metal contact and material pick-up. Production tests of new, environmentally benign tribo-systems are, however, costly and laboratory tests are preferred as a preliminary simulative method to investigate alternative tribo-systems. The present paper presents a case study where an industrial process, consisting of deep drawing with two subsequent re-drawings, was selected and four potential new tribo-systems were tested including different workpiece materials, i.e. AHSSs and stainless steels. The performance of the tribo-systems was analyzed in the laboratory by means of a newly developed simulative test as well as in an industrial production process. The results obtained show a good agreement between the laboratory test and the industrial production process regarding the tribological performance, i.e. tendency to material pick-up and galling, of the evaluated tribo-systems. Moreover the SEM analysis shows that different workpiece materials result in different types of material pick-up.

Joint strength of friction stir welded AISI 304 austenitic stainless steels

Abstract In this study, AISI 304 (X5CrNi18-10) austenitic stainless steels were joined by means of friction stir welding. The welded joint strength of stainless steels was influenced by many factors, such as different tool rotational speeds, traverse speeds, compressive tool forces, and tool angles, etc. There is a strong interrelation among the friction stir welding design parameters. The effects of design parameters on the welded joint were analyzed using a genetic algorithm. Appropriate design parameter configurations led to fine-grained microstructures that resulted in higher tensile strength joints compared to the base material. The best design configuration that led to 1.16 times higher strength than the base material was achieved with 47.5 mm min−1 traverse speed, a rotational speed of 1 180 min−1, compressive tool force of 7 kN and tool tilt angle of 2.0°.

The Effect of Thermocycling and Debonding Time on the Shear Bond Strength of Different Orthodontic Brackets Bonded with Light - Emitting Diode Adhesive : In Vitro Study

Thermocycling simulates the temperature dynamics in the oral environment. This in vitro study done to measure and compare the effect of thermocycling on the shear bond strength of stainless steel and sapphire brackets bonded to human enamel teeth using light cured orthodontic adhesive and debonded at various time, and to measure adhesive remnant index after debonding. Materials and Methods: one-hundred-twenty extracted upper first premolars for orthodontic reason were used in this study; depending on weather thermocycled or not, the sample was divided into two main groups, then within each group 30 teeth were used for stainless-steel brackets (Bionic®) and for sapphire brackets (Pure®). Both groups were subdivided into three groups (n = 10) according to the debond times: I: debond after 24 hour, II: debond after 7 days and III: debond after 30 days. Within 24 hr, half of the sample was thermocycled manually for 500 complete cycles between 5/55°C and the remaining sample was stored in distilled water at room temperature and water was changed daily until debond time for each group was performed. The adhesive remnant index was tested under 20X magnification lens using stereomicroscope. Results and Conclusions: Both bracket types demonstrated high shear bond strength values before thermocycling (P≤0.05), whereas after 500 thermocycles, there were significant changes in shear bond strength resulted in marked reduction in the stainless steel brackets than in the sapphire brackets (P≤0.05). Shear bond strength values increased with time for both stainless steel and sapphire brackets with and without thermocycling (P≤0.05). The tendency of bond failure was increased at the bracket/adhesive interface rather than enamel/bracket interface in the stainless steel brackets whereas at the enamel/bracket interface rather than bracket/adhesive interface in the sapphire brackets.

The Research of Strengthening Mechanism on Ferritic Stainless Steel Under Impact Processing

This paper mainly studies the microstructure and strengthening mechanism of ferritic stainless under laser shock. the mechanical properties and microstructure were observed through the X-ray diffraction and TEM. The results showed that laser induced shock wave peak pressure is higher than the yield strength of stainless steel, the plastic deformation occus under the impact of the role of stress and high strain rate. when the laser power increases, ferritic stainless steel will have an obvious phase transition from the body-centered cubic into hexagonal system.

ファイバーレーザーによる超高張力鋼及びステンレス鋼の溶接

ファイバーレーザーによる超高張力鋼及びステンレス鋼の溶接