Papers by Keyword: Welding

Abstract: In several industrial applications wear resistance of structural steels is required. Also enhanced temperature can occur when handling hot materials, e.g. in steel industry. Within this study a low alloyed structural steel (carbon steel S355) and a high temperature (HT) 9 % Cr steel ASTM A332 P92 were chosen for investigation. Repair welds with flux cored wires which are often required in applications were investigated, aiming on the role of interpass temperatures, the resulting effect of cooling conditions on the microstructure and their HT abrasion resistance. The influence of different microstructural parameters such as phase content, processing and the resulting temperature-hardness coherence on the wear resistance are evaluated within a high temperature abrasion test and a hot hardness test rig. Results indicate a strong influence of interpass temperature and heat input on the hot hardness and wear behaviour of welded structural steels.

Abstract: The application of high strength steels in welded structures relies on easy to use quality assurance concepts for the welding process. For ferritic steels, one of the most common methods for estimating the mechanical properties of welded joints is the cooling time concept t8/5. Even without experimental determination, the calculation of cooling time with previously introduced formulas based on the welding parameters leads to good results. Because high strength structural steels and weld metals with a yield strength of 960 MPa contain higher quantities of alloying elements, the transformation start temperature Ar3 is found to be outside of the range of 800 °C to 500 °C. This leads to inadequate estimation results, as the thermal arrest caused by the microstructural transformation in this case is not considered. In this work the usage of the well-proven cooling time concept t8/5 is analyzed using high strength fine grained structural steels and suitable welding filler wires during gas metal arc and submerged arc welding processes. The results are discussed taking into account the microstructure and the transformation behavior. Based on the experimental work, an improved concept is presented.

Abstract: Electron beam (EB) welding has been used to realize the seams on 2 mm thick plates of directionally solidified (DS) IN792 superalloy. A grid of the samples has been prepared by varying the pass speed v from 1 to 2.5 m/min, while the other process parameters (power P = 1 kW, acceleration voltage T = 50 kV, beam current I = 20 mA) were kept constant. Experiments were carried out both at room temperature and with pre-heating at 200 °C or 300 °C.Once found the best process conditions (pre-heating at 300 °C; v = 2.5 m/min) the effect of post-welding heat treatments at 700 and 750 °C for increasing time up to 2 hours has been investigated.

Abstract: Until recently a lack of knowledge and understanding of the structural advantages of aluminium has limited the use of the material in building and construction. Today, advances in engineering and standardization have improved our knowledge of this versatile material and it is becoming more widely accepted in many industries.This paper contains examples of structural applications where aluminum has been selected for bridge construction in Europe: The first project was launched and supported by the E.U. and forms part of the European Cycle Route Network development. The second bridge structure is part of the tourist development program launched by the city of Vitre in France

Abstract: The development of the friction stir welding being a solid state welding has provided an improved way of manufacturing aluminum joints in a quicker and reliable manner. The heat treatable aluminum alloy AA7075 is used substantially in the aerospace industry because of its high strength to weight ratio and good ductility. The objective of our work is to research the parameters of welding on the mechanical properties of friction stir welded joints of AA7075-T651. The parameters namely rotational speeds (500 rpm, 700 rpm, 900 rpm, 1100 rpm, 1300 rpm and 1500 rpm) were thought-about and table transverse speed of 50 mm/min, axial force of 8 KN is constrained throughout the welding process. The result of these parameters on weld quality is analyzed by its mechanical properties namely micro hardness and tensile strength.

Abstract: Plasma arc welding is an arc welding process wherein coalescence is produced by the heat obtained from a constricted arc setup between a tungsten electrode and the workpiece material. In the present work, the 6 mm thick stainless steel 202 plates are welded using plasma transferred arc welding. The welding parameters such as powder feed rate, welding voltage and welding current were carefully selected. The effect of these parameters on mechanical properties such as tensile strength, impact strength and hardness of the joints were studied. As a result, the increase in tensile strength and impact strength was obtained for the high current, low voltage and powder feed rate. But the highest hardness was attained for the joints made at low current, low feed rate and low voltage.

Abstract: The use of structural steel in the industry is increasing every day, and the study of stress state after welding has been shown to be of great importance. Nondestructive techniques become quite appropriate to be performed before and during the service component of welded, and thus ensure its integrity. The magnetic technique to be nondestructive, and easy to apply in the field, has potential to be an inspection tool for measuring residual stresses and other microstructural parameters. In this work it was possible to analyze the state of residual stresses through nondestructive techniques, Magnetic Barkhausen Noise and X-ray Diffraction, as well as the semi-destructive technique, high speed hole drilling method, and thereby determine the residual stresses in ASTM A36 steel plate welded by MAG (Metal Active Gas) process.

Abstract: In this work a multipass welding procedure was carried out on a 2205 Duplex stainless steels (DDS) plate. Due to the reheating cycle caused by the adopted procedure, it has favored the precipitation of secondary austenite at the weldment microstructure, besides of encouraging the grain growth at the heat affected zone (HAZ).

Abstract: The simulation of cooling curves of the heat affected zones (HAZ) of API 5L X80 steel was based on the cooling rates of welds made by the process named FCAW-S (Flux Core Arc Welding Self-Protecting). The specimens were analyzed by macroscopy, light microscopy (LM) and scanning electronic microscopy (SEM) to investigate the effects of cooling conditions on the tensile test and Vickers hardness. A thermo-mechanical simulator showed be able to reproduce the different thermodynamics conditions of points in the HAZ and allowed the reproduction of the thermal cycle obtained by welds were applied to the specimens of API 5l X80 steel. The values of the yield strength, ultimate strength and hardness found in the specimens were lower than those presented by the material as received.

Abstract: The difficulties experienced in welding processes of martensitic stainless steel led to development of a new class of them, known as stainless mild martensitic steels. Also, due to the current high demand for energy and materials to oil extraction at great depths, scientists have being developing specific researches about mechanical resistance and corrosion of steels and how these properties are influenced by high temperature processes. This research studies the effect of welding process over the corrosion resistance of the 13Cr4Ni0.02C steel in a lithium chloride solution with a concentration of 120,000 PPM Cl^-. The corrosion tests were conducted by cyclic potentiodynamic polarization in the base metal, weld bead and heat affected zone (HAZ) areas of the steel, in average temperatures of 23°C (as reference) and 3°C. The results revealed that the weld bead and heat affected zones of the 13Cr4Ni0.02C steel in a temperature of 3°C are less resistant to corrosion in this environment than the base metal in the same conditions.