Key Engineering Materials Vol. 1030

Abstract: This case study focuses on the laboratory examination and material analysis of welded components in automotive production. The investigation included metallographic analyses, microstructural evaluations, and non-destructive testing methods to assess weld integrity. Key issues identified were the presence of thermal distortions, incomplete welds, and material defects such as micro-cracks and porosity. A detailed metallographic study revealed that improper cooling rates significantly affected the heat-affected zone (HAZ) and weld microstructure, leading to weaknesses in material strength and increased susceptibility to fatigue. Variations in cooling water flow during the welding process were examined, showing that an intermediate cooling flow rate produced the most consistent microstructural properties. The analysis also indicated the presence of stress concentrators at weld interfaces, which may lead to premature failure under operational stresses. Recommendations include optimizing cooling rates and post-weld heat treatment to enhance material resilience, ensuring long-term durability and performance of welded assemblies.

Abstract: Laser beam welding (LBW) is an advanced welding technique based on keyhole welding, which makes use of a laser in order to join metals or thermoplastics. LBW is employed mainly in high volume applications which require high precision using automation, such as the automotive industry. The weldability, welding speed and penetration depth is mostly dependent on the power supplied to the laser, but the material and thickness of the workpiece also influences these parameters. This paper will present how various welding parameters such as power, frequency, the shape and size of the focal point affect different types of aluminium alloys, in an attempt to find the ideal parameters for the 5083 and 6082 aluminium alloys.

Abstract: This study investigates the thermal field of S355J2+N steel plates for shipbuilding applications welded with automatic welding equipment. Real-time thermal profiles were captured and validated using infrared thermography against SolidWorks simulations. Experimental data revealed maximum weld pool temperatures of 528 °C and sharp thermal gradients in the heat-affected zone (HAZ). The numerical model, which predicts a peak temperature of 670°C, closely matched the experimental results. An empirical relationship between welding parameters and maximum welding temperature was derived, allowing optimization of heat input and welding speed to minimize thermal distortions and residual stresses. This integrated approach improves process control and weld quality in shipbuilding.

Abstract: Magnesium alloys are used more and more in automotive industry due to specific strength (ratio between tensile strength and density) of 158kNm/kg versus 46kNm/kg in case of structural steel [1]. Another advantage of magnesium alloys is machinability, aspect and automated caste/extrusion. With this last procedure is possible to achieve high rate of productivity for complicate pieces, needed in automotive sector. Technologically, a big issue of magnesium alloy is its reactivity in contact with carbon steel, accentuated by high temperature and pressure from extrusion chambers.

Abstract: The application of high strength structural steels in welded structures is growing steadily and intensively. Quenched and tempered (Q+T) as well as thermomechanically treated (TM) steel base materials are developing faster than the filler metals for fusion welding processes, and therefore the selection of filler metal deserves special attention. Welded structures made of high strength steel are often subjected to cyclic loading, which can cause initiation and propagation of fatigue cracks and can lead to fatigue fracture failure of the structural element or the structure. This characteristic must also be taken into account when selecting the filler metal. In order to study this issue, welded joints were made from base materials in the 700-1300 MPa strength category using gas metal arc welding (GMAW) process. The applied filler metals were of the undermatching, matching or overmatching type, depending on the strength of the base material. Fatigue crack propagation (FCP) tests were performed on specimens machined from the welded joints, in which notch locations and crack propagation directions were statistical in nature. Therefore, the fatigue crack propagation directions were parallel and perpendicular to the longitudinal axis of the welded joints and located in different zones of the heat affected zone (HAZ). From these investigations, the two parameters (C and n) of the Paris-Erdogan equation were determined for each specimen and statistical samples were formed from the base material-filler metal matching pairs. During the evaluation of the results, it was found that the matching phenomenon has significant effect on the fatigue crack propagation behavior of the welded joints and that this effect depends on the strength category of the base material. Based on these results, recommendations for the applicable base material-filler metal pairings were proposed.

Abstract: Lightweight steel structural systems like trusses or built-up beams, made of thin gage steel elements, are highly efficient, with ease of handling and construction. Self-drilling screws are commonly used for connecting thin-walled elements, but the time and manpower required for numerous connections necessitate an improved solution. One possible solution is to use welding technology, but the conventional methods are not suitable for joining thin sheets. Manufacturing defect-free, mechanically sound welding joints remains challenging due to defects like porosity and undesired microstructural phases in the heat-affected (HAZ) and fusion zones (FZ). Conventional welding processes increase heat input, causing difficult challenges. Brazing, a relatively new joining process, offers the advantages of lower heat input for thin and zinc-coated steel sheets. Therefore, the paper aims to present the effect of MIG brazing parameters on the macro-and microstructural properties of Cu-Al-based weld seams manufactured for joining thin sheets with thickens in the range of 0.8-2 mm. The weld seams were manually fabricated using a MEGAPULS FOCUS 330 compact equipped with TBI XP 363S/4m welding torch, focusing on optimal welding regimes. The macro-and microstructures of the joints were evaluated along with the mechanical properties in terms of hardness, confirming that MIG brazing is a promising method for manufacturing lightweight steel structural systems.

Abstract: In the oil and gas industry, drilling fluid plays a critical role in ensuring the safety and efficiency of hydrocarbon extraction. It serves multiple purposes, including cooling and lubricating the drill bit, transporting rock cuttings for geological analysis, and optimizing drilling performance. However, water-based muds (WBM) face significant challenges during drilling operations, such as high fluid loss into permeable formations, inadequate sealing properties, and instability of the mud structure, which can lead to sagging and settling of solids. These issues can compromise the efficiency of drilling operations and pose environmental concerns. This study aims to evaluate the impact of additives extracted from fenugreek, commercial saponin polymer, Gemini surfactant (GS), and nanoparticles on the performance of WBM. Key properties examined include plastic viscosity, gel strength, yield point, mud density, fluid loss, mud cake thickness, and interfacial tension (IFT). Notably, IFT plays a pivotal role in improving the sealing capabilities of drilling fluids, reducing fluid loss into permeable formations. IFT indirectly influences sealing properties and fluid loss by interacting with the mud cake formation process, which is the primary barrier preventing fluid invasion into permeable formations. The study achieved an optimal IFT of 22.65 mN/m and the highest yield point of 65 lb/100ft² using 1.6 g of commercial saponin, an environmentally friendly additive suitable for Malaysia's drilling conditions. These results prevent sagging and settling of solids in the drilling mud, enhancing overall performance. The optimal IFT and high yield point combination demonstrated superior effectiveness, ensuring improved sealing properties, minimized fluid loss, and enhanced mud stability compared to other tested conditions.

Abstract: Maintaining the optimal properties of drilling fluids such as rheology, fluid loss, and mud cake thickness is crucial for wellbore stability, shale inhibition, and efficient drilling operations. However, the addition of shale swelling inhibitors can alter these properties either positively or negatively, necessitating a thorough investigation of their compatibility and effectiveness. In this study, polyethyleneimine (PEI) and potassium citrate (PC) were used as a shale swelling inhibitor, and their effect on water-based muds’ (WBM) compatibility and rheological properties were investigated and compared to the commercial inhibitor, potassium chloride (KCl). Compatibility tests were conducted to visually examine the water-based drilling fluid after the addition of the shale swelling inhibitors for over 24 hours. Mud density and pH were measured using a mud balance and a pH meter. The rheological properties were then determined using a rotational viscometer by taking readings at 600 rpm and 300 rpm. These are done to observe the flow behavior of the fluids and their abilities to maintain wellbore stability. Further, the fluid loss and mud cake thickness properties of the WBM formulations were determined using a dynamic fluid loss apparatus (HPHT API RP 13B-1) at a pressure of 1000 psi and 90°C. Based on this study, the PEI, PC, and KCl inhibitors were found to be compatible with the drilling fluid as their interactions affected the optical properties but not the physical state. Also, the rheological properties of the WBM were not highly compromised upon the addition of 1 v/v % KCl as a shale inhibitor. However, it was highly compromised upon the addition of 1 v/v % PEI and PC. It was found that cationic PEI interfered with the interactions and structures developed by the anionic components in the drilling fluid. This led to a 16% reduction in viscosity, a 21% reduction in yield point, and a 46% reduction in gel strength. The effects were also most adverse on the fluid loss characteristics of the fluids. In contrast, the use of 1 v/v % PC improved structural integrity and interactions and thus increased the viscosity and the yield point by 16 % and 68 %, respectively. The optimal balance was achieved with the formulation of 0.6 v/v % PEI: 0.4 v/v % PC, which effectively maintained and enhanced the desirable rheological properties of the WBM while maintaining favorable fluid loss control and mud cake formation. The PEI and PC interactions appear to have had a synergistic effect on the overall performance of the WBM.

Abstract: Traditional deflocculants containing chromium in high-temperature and high-pressure (HTHP) wells present health hazards due to chromium toxicity. This study aims to tackle this issue by creating a heat-resistant diluting ingredient for water-based drilling mud (WBM) produced from easily accessible natural resources. The synthesized compound demonstrated exceptional heat resistance by employing an organosolv extraction method using formic acid, followed by cross-linking with tannin. It maintained stability even at a high temperature of 150 °C. Adding the agent to mud formulations significantly resulted in superior rheological properties, as 0.6 w/w % agent ratios led to greater thinning and control of viscosity. The study found that increasing tannin-lignin content effectively reduced plastic viscosity at higher temperatures, mitigating viscosity buildup. Apparent viscosity was highest at 0.2 w/w % tannin-lignin but decreased with rising temperatures, improving mud circulation for deep-well applications. While tannin-lignin from oil palm biomass fiber exhibited the highest yield point at 100 °C, the yield points generally declined at 150 °C, reaching a moderate value beneficial for hole cleaning. A slight pH reduction with temperature-affected rheology, with an optimal pH range (8.0–10.5), is required for effective WBM performance. This environmentally conscious solution has a considerably diminished ecological impact compared to chrome-based alternatives, promoting safer and more sustainable drilling methods. It enhances resource efficiency by harnessing biomass resources, reduces the use of hazardous chemicals, and facilitates safer operations due to its non-toxic composition. Later research may concentrate on enhancing the utilization of agents and investigating alternate biomass sources to achieve broader applicability. This sustainable thinning agent represents a possible alternative for HTHP WBM applications, facilitating a more environmentally friendly and safer future in the drilling sector.