Papers by Keyword: 304L Stainless Steel

Abstract: It is well known that the mechanical resistance of austenitic stainless steels can be increased considerably by cold rolling process.¶ The cold rolling effect on corrosion resistance of AISI 304L stainless steel in 3% Sodium Chloride solution was investigated by potentiodynamic polarisation and by Scanning Electronic Microscopy (SEM). The pitting corrosion in this environment is related to the rate of cold deformation. The cold rolling induces important changes in the microstructure and involves phase transformation (γ→a'). The AISI 304L developes martensitic structure after 16% cold working. The potentiodynamic results show a moderate variation of the passivity zone, a remarkable decrease in the pitting potential and a free potential. The results also show an increase in the current density. However, it seems that the critical deformation rate appears to start at approximately 50% of the rolling deformation where the passivation current is minimal. After the polarisation tests, metastable pits are observed using SEM and the most probable initiation causes are discussed

Abstract: The High Welding Residual Stress is the Main Factors Affecting the Service Life of Welded Structures. Post Weld Cool Treatment (PWCT) is a Novel Method by Introducing Reverse Process Welding Temperature Field to Eliminate the Residual Stress and to Obtain Compressive Stress Layer. the Major Factors Affecting the Effects of Post Weld Cool Treatment (PWCT) is Preheating Temperature, Cooling Time and Cooling Range. in this Paper, a Model to Calculate the Residual Stress was Built Using Finite Element Code ABAQUS, and Different PWCT Processes were Applied on 304L Stainless Steel Specimens. at the same Time, Impact Indentation Method (IIM) was Used to Measure the Residual Stress on the Specimens. the Results Show that the Longitudinal Stress and the Transverse Stress were Reduced Obviously and Compressive Stress was Generated after PWCT in both of the Simulation and the Experiment. the Proposal Preheating Temperature was 400°C and the Cooling Range was 2 Times of Weld Width. Besides, the Cooling Time had Little Effect on the Residual Stress.

Abstract: A slow strain rate tensile (SSRT) test was carried out to investigate the stress corrosion cracking (SCC) behavior of the sensitized 304L austenitic stainless steels (ASSs) in alkaline solution (0.5M NaOH). Mechanical properties and fracture morphology evolutions of the 304L ASSs were studied as a function of temperature through slow speed tensile tester and scanning electron microscopy (SEM). The results showed that the tensile strength and percentage elongation after fracture significantly reduced as the test temperature rose. Fractographic examination revealed both ductile and brittle fracture features for the specimens tested in different environments. However, the proportion of brittle fracture characteristics changed with the temperature.

Abstract: In this research work, thermo-elasto-plastic analysis using finite element modeling (FEM) was carried out to study the thermo mechanical behavior of AISI 304L stainless steel plate of 3 mm thick during the autogenous tungsten inert gas welding. Sysweld software has been employed for simulating the temperature distribution, residual stresses and distortion. Physical and mechanical properties of 304 L stainless steel required for simulation were obtained from the literature. Bead-on-plate experiment was carried out at 140 A and 120 mm/min for obtaining weld bead dimensions which are required for heat source fitting in the simulation. Heat source parameters in the simulation were frozen when the bead profile obtained in the simulation matched with the actual bead profile. Then thermal cycles were simulated with the frozen heat source parameters. The thermal cycles and the peak temperatures predicted by the model were compared with that of the experimentally measured values. There was good agreement between the predicted and measured values. The experimentally validated thermal model was further used for simulating residual stresses and distortion. The calculated residual stress profile was validated using experimentally measured residual stress profiles using an Ultrasonic technique. There was good agreement between the predicted and measured residual stress profiles. The simulated distortion values were compared with measured distortion values using height gauge. There was good agreement between the simulated and measured distortion values. The Finite Element model developed for simulating the TIG welding of 304 L stainless steel predicted the thermal cycles, residual stresses and distortion with minimum error.

Abstract: AISI 304L austenite stainless steel was irradiated by a high-current pulsed electron beam (HCPEB) source in different process. The microstructures were investigated in detail by electron microscopy. The changes of hardness and corrosion resistance induced by irradiation were also tested. The relationship between corrosion resistance and the microstructures has been explored. The experimental results demonstrate the potential of proper HCPEB processing for improving the hardness and corrosion resistance of metallic materials.

Abstract: A gradient nanostructured layer (GNsL) was generated on the two sides of bulk sample in 304L stainless steel by means of the surface mechanical attrition treatment. The microstructure of the GNsL was characterized via TEM observation. The prominent microstructural features involve the intersection of multi-system twin operation, subdividing the original grains into blocks, a martensite transformation mainly occurring at the interface of the twins as well, and the randomly orientated nanocrystallites at the top of surface. After annealing at 750°C for 10 min, recovery had occurred and the dislocation density was much reduced. The vast majority of the grains at the top surface were in the nanocrystalline/ultrafine range, with some recrystallization regions. The uniaxial tensile tests were performed to obtain the mechanical property of bulk samples with GNsL. The yield strength was about 2 times higher than that of the coarse-grained counterpart, but with a decrease in uniform elongation and elongation to failure as well. The relationship between the microstructure and mechanical property was discussed in detail.

Abstract: Stress corrosion cracking (SCC) of austenitic stainless steel serviced in aggressive environment often occurs in power, petrochemical industry, and leads to premature equipment failure and great economic loss. This paper focuses on the problem of the SCC on the 304L stainless steel nozzle of a hydrogenation reactor, which is caused due to on-line alkali cleaning. Susceptibility for SCC was evaluated by Slow Strain Rate Test (SSRT) for as-rolled and sensitized 304L stainless steel in low concentration sodium hydroxide solution with high temperature. The effects of different strain rates, different concentration of sodium hydroxide and different solution temperatures on SCC were investigated. On the basis of this, the contrast tests were also performed in high temperature pure water. After SSRT, fractograph of the fractured specimens was analyzed by using scanning electron microscopy (SEM).