Tribological behaviour of microalloyed and conventional C–Mn rail steels in a pure sliding condition

This paper compares the tribological behaviour of microalloyed rail steel with conventional C–Mn rail steel under different test conditions (load, temperature and humidity). Pin-on-disc tribological tests were performed inside a climate chamber under different loads (20, 30 and 40 N), relative humidity (15, 55 and 70%) and temperatures (20 and 40 ℃). After the friction and wear tests, the worn surfaces were analysed using both confocal and scanning electron microscopies. The results obtained show that the use of microalloyed steel in railway applications under severe conditions (high loads and humidity) could lead to increased service life of the rails and could extend the time between maintenance operations

Influence of Martensite Volume Fraction on Ductile to Brittle Transition of Triple Phase Ferrite-Perlite-Martensite Steels Joined by GMAW and Electrical Arc Welding

In this study, the effect of martensite volume fraction on ductile to brittle transition of microalloyed steel joined by welding was investigated. Triple phase steel contains ferrite, perlite and martensite phases and was joined by two types of welding method as gas metal arc welding and the electric arc welding. Presence of three phases in adjacent to each other was confirmed by metallographic analysis and scanning electron microscopy studies. All welded samples were exposed to Charpy impact test at the temperature range of -30C to 30C in order to measure the fracture energies of samples having different amount of martensite volume fractions. The fracture surface micrographs of Charpy specimens, examined by scanning electron microscopy and optical microscopy, confirmed the reduction in ductility of ferrite-perlite-martensite steels with increasing martensite volume fraction

Investigation of Mechanical Properties of Microalloyed Steels Joined by GMAW and Electrical Arc Welding

In this study, micro-alloyed steel samples were exposed to gas metal arc welding process by two welding wires coded ER100 SG and SG 3. Protection gases compositions were selected as 100% argon (Ar), 15% $CO_2$ + 85% argon (MIG/MAG-1) and 25% $CO_2$ + 75% argon (MIG/MAG-2) in three different types in order to investigate the $CO_2$ effect on mechanical properties. In addition, an electric arc welding electrode coded Fox EV 85 was selected for arc welding applications to research the effect of welding method in mechanical properties. Welded joint were prepared at 130 A, 20 V; 150 A, 22 V and 170 A, 24 V welding parameters. All welded joint specimens were exposed to tensile tests, Charpy impact tests to evaluate the yields strength, maximum tensile stress, fracture stress, % elongation values and ductile-to-brittle transition temperatures values. Micro and macrostructure photos and scanning electron microscopy micrographs of specimens were obtained. The optimum parameters were advised to users at the end of this study

Investigation of Mechanical Properties of MIG-Brazed TRIP 800 Steel Joints Using Different Working Angles

In this study, TRIP 800 (Transformation Induced Plasticity) steel plates, 1.5 mm in thickness, were joined with copper-based (CuAl8) wire by the gas metal arc brazing technique. Specimens were prepared in butt joint form. Five different working angles 50° , 60° , 70° , 80° and 90° were selected for brazing operations. A copper based CuAl8 wire was used as the filler metal. After the metal inert gas brazing process, butt joined specimens were exposed to tensile test in order to characterize the mechanical properties. The microstructure of the joints was investigated by scanning electron microscope (SEM) and optical microscope to see the joinability of TRIP 800 steel by gas metal arc brazing technique

Influence of current intensity and heat input in MIG-brazed joints of DP 600 thin zinc coated steel plates

In this study, DP 600 (Dual-Phase) steel plates having 1 mm thickness were joined by copper-based CuAl8 wire in gas metal arc brazing technique. Specimens were prepared as butt joint. Brazing operations were done with ten different arc voltages and weld currents as 40, 45, 50, 55, 60, 65, 70, 75, 80 and 85 A. Tensile strength, bending force, microstructure of brazed materials, and their microhardness distribution throughout joining were determined. In macro and microstructure examinations, stereo optical microscope, scanning electron microscope (SEM) and energy dispersive spectroscopy were used. This study investigated the effects of current intensity on microstructure and microhardness distribution of transition zone between DP 600 steel and MIG-brazed joint. The tensile strength and bending resistance increase with increasing current intensity

Investigation of Mechanical Properties of Metal Inert Gas-Brazed TRIP800 Steel Joints Using Different Shielding Gas Flow Rate

In this study, TRIP 800 (transformation induced plasticity) steel plates having 1.5 mm thickness were joined by copper-based (CuAl8) wire in gas metal arc brazing technique. Specimens were prepared in joining forms as butt joint. Brazing operations were done with five different shielding gas flow rates of 8, 10, 12, 14, and 16 L/min. CuAl8 wire composed mostly of copper serves as the filler metal. Having accomplished the brazing operations, tensile properties of joints were detected, and micro- and macrostructures of joints were investigated in order to see the joinability of TRIP 800 steel by gas metal arc brazing technique

Investigation of Tensile Properties of Aluminum 6082-T6 Alloys Joined by Cold Metal Transfer Method by Using Different Working Time

In this study, Aluminium 6082-T6 plates having 1.0 mm thickness were joined by magnesium-based (AlMg5) wire in cold metal transfer technique. The specimens were prepared in butt joint form. Argon was used as shielding gas and joining operations were done at gas flow speed of 13 l/min. The joining operations were carried out during four different working times of 25, 30, 35, 40 and 45 seconds. Tensile properties of joints were determined and macro-structures of joints were investigated in order to evaluate the joinability of Aluminium 6082-T6 alloy by cold metal transfer technique. Finally, the micro-hardness values of specimens were measured

Effect of Welding Current on Mechanical Properties of Welding Joints in S235JR(Cu) Steel Sheets in Resistance Spot Welding

This paper presents an experimental study on resistance spot welding of S235JR(Cu) steel sheets used in side wall and roof in rail vehicles. S235JR(Cu) steel sheets having 2.0 mm thicknesses were joined by using resistance spot welding as lap joint. A timer and current controlled resistance spot welding machine having 120 kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 10, 15, 20, 25 and 30 cycles and also welding currents were increased from 6 kA up to 14 kA by rise of 1 kA. The electrode force was kept constant at 6 kN. The prepared welding specimens were exposed to tensile-shear and tensile-peel tests and the obtained results were supported by diagrams and, finally, appropriate welding parameters were advised to the users