Papers by Keyword: AISI 304

Abstract: The utilization of hydrogen in the construction of a decarbonized society is expected to expand the application of austenitic stainless steels with high resistance to hydrogen embrittlement as structural materials. However, the residual stress generated during machining causes material deformation, leading to increased costs and decreased productivity. Therefore, cutting methods that can control residual stress are necessary, prompting numerous studies on residual stress. We proposed conditions to reduce deformation and clarify the relationship between the depth of cut and material deformation, as well as the relationship between residual stress and material thickness after machining. In this study, stainless steel (AISI 304) was face milled, and the relationship between the cutting temperature and material deformation after machining was evaluated, as in a previous study. In addition, electrolytic polishing was performed to measure the residual stress in the depth direction, and its relationship with material deformation was evaluated. The experimental results showed no correlation between the cutting temperature and deformation. However, the measurement of the residual stress in the depth direction suggests that the removal of the surface layer by electropolishing may affect material deformation and residual stress.

Abstract: Rotary friction welding (RFW) result is much affected by heating and joining stage parameters. Heating stage is the period where friction takes place to generate heat at the interface. Parameters that alter the heating are friction pressure, friction time and rotation speed. In this work, experiment of RFW AISI 1045 and AISI 304 under different friction pressure and friction time was carried out. The objective was to investigate the relation between those parameters with the welding strength. The experiments were performed using one-factor-at-a-time (OFAT) strategy. A polynomial model of relation between joint strength with friction pressure and friction time was developed. Welding efficiency of 81.7% from the AISI 304 base metal was attained. Optimum setting friction pressure of under constant friction time was 40 bar, whereas the optimum setting friction time under constant friction pressure was 5 seconds.

Abstract: AISI 304 is widely used as biomedical material due to its lower cost and availability, but low corrosion resistance. The shot peening method can increase the mechanical characteristics and corrosion resistance of a surface. The purpose of this study was to determine the effect of shot peening surface treatment with a combination of steel ball diameter variations and pressure on corrosion resistance of AISI 304 material. Shot peening treatment was carried out using variations of 0.2, 0.5, and 0.8 mm steel ball diameters with a hardness of around 40-50 HRC. Shot peening pressure varies from 7, 8, and 9 bar. Corrosion rate testing was carried out using bovine serum media. The results showed that the best increase in corrosion resistance was 0.117 mpy for a steel ball diameter of 0.5 mm with a pressure of 9 bar, 3 times lower than that of non-treated specimens, which was 0.378 mpy.

Abstract: Stainless steels are indispensable materials in many industrial fields. They can be easily shaped and joined by traditional welding methods. Some problematics such as possible decrease in corrosion resistance at the welding bead and in the heat-effected zone, residual stress, crack formation and distortions may take place after welding. Friction Stir Welding (FSW) may be used for joining stainless steels in a single pass and for optimising microstructure and mechanical properties of the processed region. The application of FSW to the widely used AISI304 stainless steel is investigated in food implants. The mechanical properties together with corrosion resistance and surface finishing are characterized. A high energy input is chosen for the welding (2000 rpm tool rotational speed and 50 mm/min advancing speed). The stirred zone (SZ) is characterized by optical microscopy. Vickers microhardness in the SZ results 37% higher than in the base material. Tensile tests highlight elongations up to 40% keeping maximum stress values at 600 MPa. All samples pass accelerated corrosion tests that simulate 20 years of cleaning cycles in a typical food implant.

Abstract: AISI 304 is a type of stainless steel used for load bearing implants due to relatively low cost. However, its mechanical properties and corrosion resistance must be improved to the level of AISI 316L, cobalt-based alloys, titanium and titanium alloy properties. Its fatigue characteristic is also one of the most important criteria have to be evaluated to achieve the overall service performance requirements, when this material subjected to dynamic load. High surface hardness may delay fatigue crack initiation and decrease corrosion rate because these two processes initiated at surface layer. The purpose of this research is to investigate the change in mechanical and corrosion characteristics of AISI 304 due to shot peening processes.Surface treatment with shot peening process were done by regulating the variation time for 0, 5, 10, 20, 30 and 40 minutes at the firing pressure of 7 bar; using 0,6 mm steel ball with hardness of 40-50 HRC. Firing distance between the nozzle with the specimen surface is 100 mm. Surface hardness was tested using indentation load of 10 grams for 10 seconds. Pitting corrosion test of treated AISI304 and non treated AISI316L was conducted in intravenous Otsu-RL brands as corrosion media. Pitting corrosion was performed using cyclic polarization methodThe hardness of surface layer increase with increasing shot-peening time. According to increase of length of shot-peening time from 0, 5, 10, 20, 30 and 40 minutes the hardness of these specimen increase to 241, 404, 418, 437, 481 and 496 VHN, respectively. The pitting corrosion rate tend to significantly decrease with increasing of shot peening time. According to increase of length of shot peening time from 0, 5, 10, 20, 30 and 40 minutes the pitting corrosion rate of these specimen also decrease to 0.853, 0.619, 0.086, 0.017, 0.116 and 0.036 mpy, respectively. Pitting corrosion rate of AISI316L is 0.042 mpy. Best pitting corrosion rate of treated AISI304 is 2.5 times smaller than that of non treated AISI316L. Therefore, shot-peening could be used to increase hardness number and reduce pitting corrosion rate, significanly.

Abstract: Electro discharge machining (EDM) is a most commonly used machining process among all the non-conventional machining process which removes materials via electrical and thermal energy. The primary goal of EDM is to get more material removal rate (MRR) with lower radial overcut (ROC). Normally, the responses are predicted using empirical models which are limited to only machining parameters and they do not consider the effects of work material properties on the process performance. Therefore in this study, a model has been developed including machining parameter as well as thermo-physical property of work material. In this investigation, a semi-empirical model has been established for the material removal rate (MRR) and radial overcut (ROC) by adopting the dimensional analysis technique. Dimensional analysis is a technique of dimensions and a mathematical technique that deals with the physical quantities concerned with the experiments to formulate a model for the response in terms of response control parameters as well as some physical properties of the materials. Buckingham’s л theorem is a main theorem in dimensional analysis and it is a signification of Rayleigh’s method of dimensional analysis. The theory is applied to gather each and every variable presenting the problem in a number of the dimensionless products. For this study, the thermo-physical properties viz. density, thermal conductivity and coefficient of thermal expansion and machining parameters like peak current, pulse on time, gap voltage and duty cycle are considered as input factor. AISI 304 stainless steel used as work material and Tungsten carbide is used as tool material for this investigation.

Abstract: This paper deals with the investigation of the metallurgy of a dissimilar Ti-6Al-4V-stainless steel joint linear friction welded. In particular two different stainless steel were considered: AISI 304 and AISI 316. These two alloys differs in the Molybdemun content. Metallographic observations, EDS analysis and Vickers Microhardness measurements were carried out, particular attention was focused on the study of the intermetallic compounds and on the microstructures of the different zones produced by the process. As usual for solid state welding processes, three different zones can be identified: the parent material, the heat affected zone (HAZ) and the thermo-mechanical affected zone (TMAZ), furthermore a very thin joining line, rich of intermetallic compounds, was also observed. In this zone diffusive phenomena also occurred resulting in a variation of the alpha phase content on the titanium side.In the TMAZ, the bimodal microstructure of the parent material was deformed and the presence of elongated alpha grains with broken beta-phase particles was established. Moreover it was observed that in the weld region, exposure to supertransus temperatures (995°C) combined with hot-deformation working and rapid cooling after joining induced the recrystallization of a martensitic beta grain structure. Concerning the joint between Ti-6Al-4V and AISI 316 some cracks were observed within the weld line, this due to the presence of brittle intermetallics compounds in this zone. The formation of these intermetallics was promoted by the presence of Molybdenum.

Abstract: Plasma immersion ion implantation (PIII) method is often used to cleaning and enhancing mechanical properties of the surface of materials. In this work, the AISI 304 was treated in a PIII system to improve tribological and wear resistance properties. The new HV pulser was prepared to reach high average power (10 kW) using solid-state technology and a pulse transformer rather than using a conventional one based on hard-tube tetrodes with HV storage capacitors. For preliminary tests, low-density nitrogen plasma and pulses of 10 kV, 30μs width, and 1 kHz were used. A larger vacuum chamber used (600 liters) is very important for treating large area components and for batch processing. This is necessary in industrial applications and in cases that require high quality processing as in spatial or medical components. Stainless steel support was used to hold the samples in our case. XRD, SEM, and pin-on-disk surface diagnostics were used for investigation and characterization of the treated surfaces.

Abstract: This investigation concerns the influence of key parameters of laser welding on the geometry and microstructural properties of the weld bead. The study is intended to restrain the interval field of the welding parameters and to investigate the welded joints achieved through this technique. A 3,3 kW Nd:YAG laser together with a Rofin welding head and an ABB 6-axes robot were used for this investigation. The tests highlight the major influence of the laser spot diameter on the geometry of weld bead. The experiments were made on various samples of AISI 304 thin sheets. In depth characterization of the weld area was conducted by means of optic and electronic microscopy and EDS analyses.

Abstract: This work presents the development of an experimental study which aims to establish arelationship of temperature variations, deformation speeds and the possible microstructural changes in the AISI 304 stainless steel. For this, an IR thermographic camera recorded serveral tensile test with different deformation speeds.