Dissimilar welding between Inconel 625 nickel base super alloy AND HIGH STRENGTH QUENCHED AND TEMPERED A 517 Gr.B STEEL was investigated by pulsed ND: YAG laser beam welding equipment. This joint has special application in submarine components. After welding, the optimized joint microstructure including the weld metal AND heat affected zones were characterized by optical AND scanning electron microscopy (SEM). The results showed a fine dendritic structure AND existence of large amount of Niobium carbide AND Laves eutectic phase in the weld metal. Energy-dispersive X-ray spectroscopy (EDS) analysis showed Nb AND Mo segregation to interdendritic zones at the weld metal. Grain growth in the heat affected zone of Inconel 625 did not occur, however, ultrafine precipitations were deposited at the heat affected zone. An approximately 65 mm wide transition zone was observed at the STEEL AND weld zone interface; consisting of a martensitic layer (10-20mm) along the weld interface AND the austenite phase region with a small amount of ferrite adjacent to the base metal. The tensile test AND micro hardness test of the optimized sample was investigated. The electrochemical behavior of the weld metal was investigated at room temperature in 3.5% NaCl solution using potentiodynamic polarization. The results show that the corrosion resistance of weld metal is more than that of Inconel 625 AND less than that of 517A Gr.B. It can be concluded that a proper selection of laser beam welding parameters provides sound, fully-penetrated welds.

A common process in auto-parts manufacturing consists of forging، normalizing، quenching AND tempering. Normalizing treatment is usually employed to improve machinability of STEEL, AND to homogenize AND refine the microstructure. For simple parts, production cost would be reduced if normalizing stage were eliminated. In this paper, the effect of normalizing treatment on fatigue life of a QUENCHED AND TEMPERED carbon STEEL has been studied. Samples were taken from forged، QUENCHED AND TEMPERED parts at industrial conditions. Sixty four fatigue specimens were tested using a rotary bending fatigue machine (R=-1) at four different stress amplitudes between 500 AND 600 MPa. Results showed minor effect of normalizing on microstructure, hardness AND tensile properties. However، specimens normalized after forging indicated improved fatigue life at the same stress amplitude. Average fatigue lives at 508, 516, 534 AND 583MPa were 261000, 194000, 119000 AND 54000 cycles respectively for normalized QUENCHED AND TEMPERED samples AND 209000، 138000، 101000 AND 46000 cycles for QUENCHED AND TEMPERED samples. Due to variation of fatigue life results, Student's t-test was employed to prove any meaningful difference of fatigue life for specimens with or without normalizing treatment. Student's t-test is often used to determine if the averages of two samples are significantly different. The test approved the difference with 95% confidence. Fatigue life of normalized samples was estimated at least 18% HIGHer than the life of samples without normalizing.

The aim of the present study was to investigate the effect of quenching AND tempering temperatures on the microstructure, mechanical properties AND the wear characteristics of medium carbon-HIGH chromium wear resistant STEEL. In addition, the dominant wear mechanisms were studied. For this purpose, austenitizing AND tempering temperatures were selected in the ranges of 900- 1000oC AND 300- 500oC, respectively. Mechanical properties were evaluated through hardness AND impact tests as well as wear test (by dry sAND/rubber wheel apparatus). Microstructure AND wear AND fracture surface appearances were investigated using scanning electron microscopy (SEM). Moreover, the measurement of retained austenite was done through X-Ray diffraction (XRD) analysis. The obtained results revealed that the best wear properties were achieved by tempering at 450oC due to the reduction of tendency to micro-cracking, the decrease in internal stresses, AND the improvement of the impact energy. Observing the wear surfaces showed that the wear mechanism for the specimen TEMPERED at 400 °C was a combination of abrasive, adhesive AND fatigue wear. However, abrasive wear was the only active wear mechanism for the specimen TEMPERED at 450oC.

A517 is a low alloy HIGH-STRENGTH STEELs that due to its HIGH STRENGTH, toughness AND weldability is used in ship building AND submarine hulks. The welded areas of this STEEL often require repairs. In this study, the effect of number of welding repair on microstructure AND mechanical properties of A517 STEEL is studied. Four samples (samples without repair, once repaired, twice repaired, AND three times repaired) were welded by SMAW welding. Microstructural studies were carried out by using optical AND scanning electron (SEM) microscopes. The effect of the number of repairs on mechanical properties of samples were investigated by using tensile, bending, impact AND hardness The profile of hardness illustrated that the hardness in the heat affected zone near the base metal increased by repeated repairs while the hardness of this zone reduced in the third repaired sample. By repeating the welding repair, tensile AND yield STRENGTHs of the welding areas were reduced AND fracture impact toughness of heat affected zone at-51○ C was increased. Generally, the results of tensile tests of second AND third repaired indicated that the STRENGTH of these samples were not meet the ASME IX stANDard requirements, so welding STEEL A517 in the second AND third repairs is not acceptable.

In this research, has been compared fatigue behavior of Mo 40 STEEL in ferrite-martensite dual phase condition AND QUENCHED-TEMPERED microstructure. The ferrite-martensite dual phase samples were prepared from intercritical annealing heat treatment process for 40 minute at ( α + γ ) dual phase region. The QUENCHED martensite samples after heating at 860 ° C AND QUENCHED in water, were tempering heat treatment at 600 ° C for 3 0 minute. The Hardness, tensile AND fatigue tests have been supplemented with optical AND electron microscopies. The result shown that hardness of ferrite-martensite dual phase is more than QUENCHED TEMPERED sample. Also, tensile STRENGTH of ferrite martensite dual phase samples is lower than QUENCHED-TEMPERED sample, while the fatigue STRENGTH of samples is more than QUENCHED-TEMPERED sample. These results are rationalized to STRENGTHening un TEMPERED martensite phase in ferrite martensite dual phase sample compared to TEMPERED martensite in QUENCHED TEMPERED sample.

In this study, wear behavior of the pearlitic ductile cast iron samples with the same hardness achieved by applying two different heat treatment cycles have been studied. A number of these samples after austenitzing at 900° C were QUENCHED into a molten salt bath of 290° C for holding time of 120 minutes followed by cooling in air. The rest of the samples after being austenitized under the same conditions were QUENCHED in oil AND then were TEMPERED in 505° C for 75 minutes. To compare wear behavior of the aforementioned cast irons, the “ pin on the disk” method based on the ASTM-G99 stANDard was used. In this method, the samples were prepared in the form of disks AND were worn by 52100 STEEL pins for a constant distance of 1000 meters AND the sliding speed of 0. 08 m/s at the applied loads of 25 N AND 75 N. Based on the results obtained from the wear surface observations, mass reduction AND friction coefficient measurements of the worn samples, it was revealed that at the lower applied load, the QUENCHED AND then TEMPERED samples exhibited a HIGHer wear resistance comparing to the ausTEMPERED samples. Whereas at the HIGHer applied load (75 N) the inverse result was achieved.

Stress relieving is a common practice among building codes for welded QUENCHED AND TEMPERED STEEL structures AND pressure vessels to reduce the magnitude of residual stresses. The present work analyzes the effect of stress relieving at 480, 560, 620 AND 680oC on microstructure AND mechanical properties of 20 mm ASTM A517 Gr. B STEEL plate weldments produced by shielded metal arc welding process. For this purpose metallographic analysis, hardness measurement, charpy V-notched impact test, guided bend test AND tensile test were performed AND the results were compared with the non-heat treated samples (A W). In order to evaluate effects of stress relieving on corrosion resistance, cyclic potentiodynamic polarization test have been used. According to the result of tests, stress relieving can reduces impact toughness of all base metals but in general, stress relieving at 560oC represents better mechanical properties.

This paper proposes a 2.4 GHz active mixer without passive inductor for the transceiver system. Taking into account the design requirements of the mixer, a double-balanced down-conversion structure with active inductor AND negative resistance is designed. The proposed mixer with 130 nm CMOS technology is designed AND simulated using Cadence software at 1.5 V supply voltage. Although we had to compromise conversion gain with linearity, we were able to achieve very HIGH conversion gain with average linearity. Based on the results of post-layout simulations, the conversion gain of 27.57 dB, IIP3 equal to -7.88 dBm, 1-dB compression point equal to -17.34 dBm AND IIP2 equal to 44.22 dBm with power consumption of 2.5 mW was obtained for the proposed mixer. The chip size without input AND output pads is 95.18 µm × 117.68 µm, which leads to a chip area of 0.0112mm2.

Progressive collapse studies generally assess the performance of the structure under gravity AND blast loads, while earthquakes may also lead to the progressive collapse of a damaged structure. In this study, the progressive collapse response of concentrically braced dual systems with STEEL moment-resisting frames was assessed under seismic loads through pushover analysis using triangular AND uniform lateral load patterns. Two different bracing types (X AND inverted V braces) were considered, AND their performances were compared under different lateral load patterns using the nonlinear static alternate path method recommended in the Unified Facilities Criteria (UFC) guideline. Eventually, the seismic progressive collapse resistance of models was compared to their progressive collapse response under gravity loads. These studies showed that models under the seismic progressive collapse loads satisfied UFC acceptance criteria AND limited rehabilitation objective. The structures had better performance under seismic progressive collapse than models under gravity loads because of more resistance, ductility, suitable load redistribution, AND more structural elements that participated in load redistribution. Furthermore, despite studies on progressive collapse under gravity loads, the dual system with X braces showed better progressive collapse performance (more resistance, residual reserve STRENGTH ratio AND ductility) under seismic loads than the model with inverted V braces.

In recent years, cryogenic-treatment is considered in order to improve of wear AND hardness resistance of tool STEELs. Cryo-treatment is performed on STEEL before AND after of tempering AND quenching treatment, respectively. In this research, the effect of deep cryogenic treatment is investigated on the GOS9HF-STEEL. In this regard, the QUENCHED-TEMPERED AND QUENCHED-Cryo-treated samples are prepared after tempering treatment for 2hrs. then, impact of Cryo-treatment on value of retained austenite, fine carbide precipitations are evaluated by XRD, SEM AND the amount of hardness, STRENGTH AND wear resistance are measured by micro-hardness, tensile AND wear tests. The wear test is conducted by pin-on-disc method. The results indicated that the amount of hardness AND properties of wear AND tensile in the Cryo-treated sample were rather than the QUENCHED-TEMPERED samples at all of tempering temperatures (i. e. from 150 to 650˚ C). Additionally, with increase of tempering temperature, the amount of hardness, wear behavior AND tensile property are decreased in both of Cryo-treated AND QUENCHED-TEMPERED samples. This can be attributed to the softening of microstructure AND the growing of grain sizes. Moreover, it was obvious that improving of Cryo-treated samples are related to the removing of retained austenite, precipitation of fine carbides AND more appropriate distribution of these carbides. It is cleared that the Cryo-treatment causes to decrease of value of retained austenite from 12% to below of 1% at QUENCHED-TEMPERED AND Cryo-treated samples, respectively. Finally, Cryo-treatment causes to increase of volume fracture of carbides to 52%.