Engineering and Technology Journal

In this work Corrosion buckling interaction behavior of AISI 304 stainless steel circular columns was investigated. Long and intermediate columns diameter of (6 mm) are tested in as received and corroded condition. Corroded columns are tested after embedded it in soil for different times. Rotating buckling machine test was used to evaluate the critical buckling load (pcr) under dynamic compression loads. By using Perry Robertson formula, experimental work results are compared. The results showed that increasing in corrosion time (embedding time), the reduction in critical buckling load increases also. Maximum reduction of buckling load value are (2.28%, 1.37%) for long and intermediate column respectively as compared with as received condition.

This study is an attempt to investigate the effect of cutting parameters on the cutting force and tool wear during turning of AISI 304 steel using tungsten carbide tool (WC). The first aim of present work was to employ the Response Surface Methodology (RSM) technique to obtain the influence of input machining parameters, such as cutting feed, cutting speed and cutting depth on the cutting force and wear of tool. Experiments were carried out in a 20 runs experimental matrix by a CNC machine according to the design matrices established by Design of Experiment (DOE) software 'version 8' with RSM technique. Cutting force was measured using a lathe dynamometer and tool wear with the help of an optical microscope. The relationships between parameters of machining and the responses (cutting tool wear and cutting force) were modeled and analyzed by RSM technique. ANOVA analysis was applied to study the impact of machining parameters on the outputs (responses) and to establish empirical equations for these responses in terms of input machining parameters. Significant quadratic models were developed with a probability (p-value ≤ 0.05) for both tool wear and cutting force. Results showed that the depth of cut is the most significant factor affecting the cutting force, closely followed by feed and cutting speed, whereas only the important parameter influencing the tool wear was appeared to be the cutting depth. Also, the results manifested that the optimum value for minimum tool wear and minimum cutting force was found at (80 m/min) cutting speed, (0.2 mm/rev) feed and (0.4 mm) cutting depth. A good agreement was found between the experimental and predicted results with a maximum error of 8%.

In the present study, the effects of laser surface melting (LSM) on chromium carbide of heat treated (AISI 304) austenitic stainless steels (ASS) was studied with the aim to suppress sensitization of 304SS. Austenitic stainless steels were heated (aging) up to (800) ºC at constant holding time for two hours. LSM was conducted by using a (600 W) Yb-YAG laser. The microstructure was characterized by using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results shows, refined and homogeneous microstructure which contains austenite (γ) as basically phase and delta ferrite (δ) as the secondary phase, however, chromium carbide (Cr23C6) phase are fully dissolved. Desensitization of heat treated ASS has been successfully achieved by LSM which reduced Cr depletion at the grain boundaries.

Stainless steel has excellent corrosion resistance due to formation oxides protective films in many environments. When steel exposed to temperature in the range of (500-900) ºC, the carbon in the structure will be effective to react with chromium in the structure , which is no less than 18.6% in the present used steel, to form chromium carbides in different types (M23C6, M7C3, M2.9C) in which M represent chromium. Therefore pitting corrosion will be initiated due to two reasi, the first was depleted zone and the second is galvanic effects between carbides and matrix. The present work was aimed to find relationships to predict the initiation of pitting corrosion depending on carbides in the microstructure of 304 stainless steel, which formed in heated specimens at (500 - 900) ºC. The potentiodynamic cyclic polarization (PCP) measurement was performed to investigate and analyze pitting corrosion resistance properties.

This research is devoted to study the effect of applying different pre-tensile stresses (255,305,355,405,455,505 555 and 605) MPa on the microstructure, hardness and corrosion behavior of 304 stainless steel in 1N H2SO4. The stress-strain curve was drawn for standard (304) stainless steel in laboratory environment. The curve was divided into three zones. At zone one the values of elastic pre-stresses vary between (σ0 - σpro.) MPa. The results showed; that the corrosion rate was very little increased compared with that of as received (304) stainless steel. The microstructure presented undeformed austenitic grains and the hardness value was (157.433) Hv. At zone two the value of plastic pre-stress varies between (σpro.- σ U.T.S) MPa. The corrosion rate increases after applying pre-stress between (σ255 - σ 455) MPa. The microstructure showed that the austenitic grains begin to deform in the direction of applied pre-stresses. The maximum hardness at this region was (229.2) Hv, but at higher pre-stress (σ455 – σ 605) MPa, the corrosion rate decreases. The microstructure inspection shows the deformed austenitic grain and ά-martensitic phase needle are appeared inside austenitic grains and the hardness reached the maximum value (332.433) Hv. At zone three the values of pre-stresses are between (σ605 - σf) MPa. The results showed that the corrosion rate increases. The investigation of microstructure showed that there are distortion in austenitic grains and ά- martensite phase observed inside austenitic grains. The hardness reached the maximum value at (354.3) Hv. The necking of gauge length of specimens occurs in specimens and this leads to deterioration in original properties

Chemical machining is a well-known nontraditional machining process and is the controlled chemical dissolution of the machined work piece material by contact with a strong acidic or alkaline chemical reagent. It is also called as chemical etching. The present work is aimed at studying the effect of machining time, machining temperature, etching solution concentration on the surface finish of stainless steel 304 using mixed of acids (HCL+HNO3+HF+ H2SO4+H2O). Alloy samples are of (33×33×6) mm dimensions. Three machining temperatures (45, 50 and 55 ºC) for each of which three machining times (3, 6, and 9 min) were used as machining conditions. Surface roughness increases with the machining temperature and machining time. An assessment of CHM was achieved by empirical models for selecting the appropriate machining conditions of the required surface finish. The models were designed based on multiple regression method via Mtb 16 software.

Specimens of the as-received stainless steel type 316, according to AISI standard, in form of sheet with 1.5 mm thickness were first spot welded and thenshot peened to obtain the influence of shot peening process on the residual stresses induced by spot welding process. X-Ray Diffraction (XRD) method was used to measure the residual stresses. Also, a finite element method (FEM) was employed by ANSYS software version 11 to achieve the simulations for transient thermal analysis and residual stresses analysis in all cases. In addition, the temperature dependency of materials properties was used to assess its effects on the final residual stress results. A comparison showed a very good agreement between the experimental and the numerical results due to the total elimination of tensile residual stresses and creating the compressive type instead.

In this paper, a stainless steel 316 was selected for this study and tested to obtain its chemical composition, mechanical properties and stress relieving. Then, two plates (55*55*1) mm were first joined by spot welding and later tested by X-Ray diffraction (XRD) machine to measure the tensile residual stresses formed due to thermal effect. In order to remove the tensile residual stresses, a shot peening process for these spot welded plates was made to create the compressive residual stresses which will improve the life of spot welded part during the service. The results of the x-ray diffraction tests exhibited that only compressive residual stresses formed in the shot peened spot welded plates.