With the advancement of the construction industry, the use of High-Strength Steel has gradually increased. High-Strength Steels can withstand higher stresses compared to conventional Steels, yet they exhibit less ductility. Currently, due to their high cost, they are primarily utilized in specialized industries. Connecting two Steel pieces requires the use of Welding or bolts. Fillet Welding is the simplest and most commonly used type of Welding. Therefore, investigating this type of Weld in High-Strength Steel is of great importance. Fillet Welds can also have different angles in the direction of applied force, which itself affects their strength. In this study, the influence of the Welding angle on the axis of the applied force has been examined. First, an experimental model, considering the effect of defects in the Weld, was modeled and validated using ABAQUS software. Subsequently, specimens were analyzed at various angles. The maximum strength of the Weld and its ductility were investigated. Additionally, the recommended strength of the American Steel code for Welds at different angles was examined. The results showed a 14% average difference from the code. Unlike mild Steels, an increase in the Welding axis angle with the direction of the applied force increased the ductility of the Fillet Weld.

Results of an experimental investigation carried out to assess the effect of various concrete strength levels on behavior of Steel fiber reinforced lightweight concrete (SFRLWC) under pure torsion are reported. The variables of the testing program were: compressive strength of concrete, volume of Steel fibers, and the aspect ratio of Steel fibers. The concrete strengths investigated are 9, 12, 30 and 61 MPa. Fiber content ranges from zero to 3.0 percent by volume of matrix. Addition of approximately two percent of fibers led to maximum torsional strength and toughness enhancement of SFRLWC; however, the improvement in higher strength concrete was more pronounced than that in lower strength concrete. In general, the torsion strength gained was higher for high strength level specimens with higher percentages of fiber volume and larger fiber aspect ratio. A proposed torsional strength formulation provided good agreement with the test results.      

Due to high joint efficiency, Welding is widely used to join materials. Today, there are many types of Welding procedures in different manufacturing industries. Among Welding procedures, Gas Metal Arc Welding (GMAW) is a versatile process due to its high flexibility. In this process, arc voltage, Welding current, and Welding speed are the main variables which can strongly affect the mechanical properties of the Weld metal. Based on the available literature, many research works have been conducted on the GMAW process but there is still little experimental research on impact energy of the Weld metal specifically in medium-carbon Steels. Impact energy of the Weld metal is extremely important particulary for the structures subjected to impact loads. Hence, the present paper is conducted to reveal the effect of GMAW variables on impact energy of the Weld metal in CK45 carbon Steel. The results of this paper indicated that the heat input value and Weld bead size in different Welding conditions are main factors which affect the impact energy of the Weld metal.

In this study، the effect of hydrogen on the mechanical properties of pipeline Steel Weld metal was investigated. In pipelines، Weld metal is a significant part، and this part especially has been evaluated because of the presence of sour gas containing hydrogen atoms and other hazardous solutes which can harm base metal and Weld metal. In this research، hydrogen charging was carried out due to the diffusion of hydrogen atoms into the sample through electrochemical pre-charging and immersion in the solution method. According to the results obtained in this study، in the presence of hydrogen، the yield stress of Weld metal in Shielded Metal Arc Welding (SMAW) increased by 16%، and hardness in both direct and indirect charging method increased by an average of 10%. In the presence of hydrogen، elongation was reduced by 28%، and the percentage of ductile fracture decreased by 60% which indicate the brittle fracture. The content of diffused hydrogen was 1. 5E-06 mol/cm3 using the Electrochemical Oxidation of hydrogen method. This amount was higher than that of other microstructures. According to microstructures observation (which provided from Optical Microscope (OM)، Scanning Electron Microscope (SEM) photos)، previous information، and recent reports in this field، it can be inferred that hydrogen diffuses into Weld metal microstructure، which most of this is acicular ferrite by residing in dislocation tangles، grain boundaries، precipitations، and inclusions، causes hardening and decreases properties of Weld metal. Overlay، the results of this study indicate that hydrogen degrades mechanical properties of Weld metals and causes hydrogen defects. Also، Weld metal microstructure has a significant effect on materials degradation in the presence of hydrogen.

The importance of Welded connections on the behavior of Steel moment resisting frames was the reason of researchers focus on Welding details. In this paper result on 32 pilot tests indicate moment connection behavior are presented. In this experimental research, in order to connection strength evaluation, complete joint penetration (cjp) Weld strength with different Welding procedure, double side Fillet Weld out of plane strength, one side Fillet Weld out of plane strength and amperage intensity effect on Welding quality, have been studied. Also in order to connection rehabilitation, rib stiffener effect on connection strength, T-stiffener effect on connection strength, electrode toughness effect on Welding quality and grinding and rewarding effect on Welding quality have been studied. Maximum strength of cjp Weld is observed in Welding with backing. Out of plane strength of double side and on side Fillet Weld have been determined. Connection strength increase amount with stiffener strengthening of connection have been proposed. It has also been proposed constructional recommendations about electrode toughness, reWelding and amperage intensity.

In this study, the effects of Welding process interpass temperatures on the Weld metal corrosion behavior of Hadfield high carbon Steel Welding joints was investigated. For this purpose, initially 6 austenitized sheets with 2mm thickness prepared from Hadfield Steel. Then shielded metal arc Welding process with interpass temperature of 700, 850 and 1000oC was used for Welding. Then potentiodynamic polarization and electrochemical impedance spectroscopy methods were used to evaluate corrosion behavior of Welded joints’ Weld metal in the 3.5wt. %NaCl solution.Also, the evaluation of the microstructures of Weld metal in Welded joints were conducted by optical microscopy. X-ray diffraction was used for the analysis of phases formed in the Weld metal microstructure and the Weld metal corrosion mechanism was determined by scanning electron microscopy examination. Optical microscopy observations and patterns obtained from X-ray diffraction showed that increasing in interpass temperature resulted in increase in carbide precipitates and decrease in austenite grain size in the Weld metal microstructures of Hadfield Steel Welding joints. Corrosion test results showed that by increasing the interpass temperature in the Welding process, Weld metal of Hadfield Steel Welding joints showed decreese in corrosion resistance. Also, scanning electron microscopy images from corrosion morphology of Weld metals indicated that increasing in interpass temperature in the Welding process of Hadfield Steel, led to occurrence of micro-galvanic localized corrosion.

Fatigue failure is the most common type of failure in structures under oscillatory loading. Fatigue damage in Steel gas pipelines is very important due to internal pressure fluctuation. A large part of pipelines in oil and gas industry of Iran are made of thermomechanical Steel of grade API X65, made by spiral submerged arc Welding. In this study, the stress-life curve and fatigue limit of the spiral Weld seam of this Steel are determined by fatigue tests. For this purpose, 20 test specimens (12 specimens used in the limited fatigue life zone and 8 specimens used to estimate fatigue strength) according to ISO 1143 standard. All test samples were cut from an actual spirally Welded pipe with 1219mm outside diameter and 14. 3 mm wall thickness and were tested on a completely reverse rotating-bending fatigue machine. Statistical analysis of the results was performed by considering the normal logarithmic distribution. Mean curve, confidence interval, and characteristic curve of the results were obtained in the finite fatigue life range using Basquin fatigue model according to ISO 12107 and ASTM E-739 standards. In the fatigue resistance range ISO 12107 standard was used. The mean endurance limit of the seam Weld of the tested Steel was 258. 5 MPa which is located in the conventional range of 0. 4 to 0. 6 of the ultimate tensile strength of this Steel.

This paper aims at investigating the microstructure and failure behavior of dissimilar resistance spot Welds between low carbon Steel (st14) and ferrite-martensite dual phase Steel (DP600). The effects of Welding current in the range of 7.5 to 9.5 kA on the metallurgical and mechanical behavior of the Weld were investigated. Microstructural characterization, microhardness tests and the tensile shear tests were conducted. Mechanical properties of spot Welds were described in terms of failure mode, peak load and energy absorption. The fusion zone microstructure exhibited martensite, bainite, allotriomorphic ferrite and Widmanstätten ferrite, resulting in high hardness of fusion zone compared to base metals. Results showed that the mode of failure changed from interfacial fracture to pullout as the Welding current was increased. Fusion zone size proved to be the most important controlling factor for peak load and energy absorption of dissimilar DP600/St14 resistance spot Welds.

Surface mechanical attrition treatment (SMAT) was applied to the samples of a type AISI 304 stainless Steel in order to induce grain refinement as well as formation of twins. Transmission electron microscopy and X-ray diffraction analysis results showed that the average grain size at the surface of the SMATed sample was about 10 nm. The untreated and SMATed samples were then Welded using a one-pass gas tungsten arc procedure. The heat-affected zone (HAZ) of the samples was examined by optical microscopy and corrosion tests. Results of the double loop electrochemical potentiokinetic reactivation tests showed that the degree of sensitization in the HAZ for the SMATed sample was very low as compared to that of the untreated one. The pre-SMATed sample was resistant to intergranular corrosion. This is mainly due to the formation of high density of twins which are not prone to carbide precipitation because of their regular and coherent atomic structure and extreme low grain boundary energy as compared with those of other grain boundaries.

Ductility of High-Strength concrete (HSC) columns with rectangular sections was assessed in this study by reviewing experimental data from the available literature. Up to 112 normal weights concrete columns with strength in the range of 50–130 MPa were considered and presented as a database. The data included the results of column testes under axial and reversed lateral loading. Displacement ductility of HSC columns was evaluated in terms of their concrete and reinforcement strengths, bar arrangement, volumetric ratio of transverse reinforcement, and axial loading. The results indicated that the confinement requirements and displacement ductility in HSC columns are more sensitive than those in normal strength concrete columns. Moreover, ductility is descended by increasing concrete strength. However, it was possible to obtain ductile behavior in HSC columns through proper confinement. Furthermore, this study casts doubt about capability of P/Agf’c 0ratio that being inversely proportional to displacement ductility of HSC columns.