Papers by Keyword: Carbon Steel

Abstract: This study investigates the microstructural and mechanical integrity of the interface between Wire Arc Additive Manufactured (WAAM) carbon steel (CS) and an S355 structural steel (Wrought CS) plate, with emphasis on the suitability of WAAM for repair and reinforcement of structural components. A wall structure was deposited on a Wrought CS plate using a Cold Metal Transfer (CMT) process and subsequently characterized through microstructural analysis, hardness measurements, tensile testing, and bending fatigue testing. The microstructural observations revealed a smooth and defect-free transition across the interface, consisting of a fine-grained heat-affected zone (HAZ) formed by partial recrystallization. The hardness profile exhibited a continuous gradient, with slightly elevated values near the interface (~210 HV), indicating grain refinement and the absence of softening effects. The tensile results showed that the WAAM-deposited CS possessed higher strength and ductility than the Wrought CS, while the hybrid WAAM CS–Wrought CS specimens displayed intermediate properties. Fracture consistently occurred within the Wrought CS plate rather than at the interface, confirming a metallurgically sound and mechanically robust bond. Under bending fatigue loading, the WAAM CS demonstrated the highest fatigue limit (~250 MPa), followed by the hybrid (~205 MPa) and Wrought CS (~162 MPa). All hybrid specimens fractured on the Wrought CS side, indicating that the interface remained intact under cyclic stress.

Abstract: Welding process is widely used as a metal assembly technique in various industries, including construction, automotive manufacturing, pressurization, and shipbuilding. In ship repair and fabrication, dissimilar welding between carbon steel and cast iron is often required, for example, in assembling appendages such as propeller shafts, yokes, and other equipment. Although cast iron offers high strength about 700 MPa and weight reduction benefits, its poor weldability due to high carbon content often leads to cracking when joined to carbon steel. Previous studies have found that preheating before welding mitigates rapid cooling and martensite formation, while buttering with Ni-based filler reduces carbon diffusion and carbide precipitation at the fusion boundary. This research has been carried out to investigate various procedures for dissimilar welding ductile cast iron A536 and carbon steel A36, as follows: (1) no preheat or buttering (Control), (2) preheating only (PH), (3) buttering only (BT), and (4) combined preheat and buttering (PHBT) to evaluate their effects on tensile strength, hardness, and microstructural evolution. Successful study of dissimilar welding between carbon steel and cast iron will reduce the cost of ship maintenance, increase its service life, and provide a path for more sustainable development.

Abstract: Food-grade piping and water transportation systems extensively use dissimilar welding between stainless steel and carbon steel, where cost-effectiveness and corrosion resistance are essential consideration. However, the fusion zone of dissimilar welds often observed microstructural inhomogeneities and hardness changes, thus compromising mechanical qualities and corrosion resistance. This study was seperated in two phases to investigate and optimize dissimilar welding between carbon steel and stainless steel in both plate and pipe applications. Phase 1 studied welding A36 carbon steel plate and A304 stainless steel using gas tungsten arc welding (GTAW) with ER308L filler metal, the effect of post-weld heat treatment (PWHT) holding time on the mechanical and microstructural propertie. PWHT was performed at 650 °C for 20 and 60 minutes. The 20-minute condition yielded an optimal combination of mechanical strength and microstructural refinement, while the 60-minute condition led to grain coarsening and reduced strength. Phase 2 extended the findings to pipe welding applications, adopting the 20-minute PWHT condition. Welding was performed on dissimilar joints between A106-B carbon steel pipe and A312 TP304L stainless steel pipe (2-inch OD) using ER308L and ER309L filler metals under 99.99% argon shielding. Tensile and hardness testing indicated that welds with ER309L offered superior mechanical performance. Microstructural analysis revealed delta-ferrite and stabilized austenite in the fusion zone, with enhanced Cr and Ni concentrations contributing to improved corrosion resistance, as confirmed by electrochemical testing.

Abstract: Nowadays, the application of hydrogen as an energy carrier has become important as a result of decreasing availability of oil and gas fields as well as increasing demands on sustainable energy carriers. Providing an adequate hydrogen transportation infrastructure is a key step. During transportation, many different materials can interact with hydrogen, but in order to transport high quantities of hydrogen at higher pressures, the use of steels is preferred. However, hydrogen has many negative effects on steel, thus extensive research needs to be performed before hydrogen can be transported safely. Solubility of hydrogen in steel depends on the temperature, pressure, and the crystal structure of steel, so welding is also an important subject. Since most of the steel structures are welded, welded joints should also be examined for exposure to hydrogen. In the case of welding, a number of factors can decrease the hydrogen resistance of the welded joint and thus increase the risk of degradation by hydrogen. In this research work, hydrogen damage, and hydrogen traps will be reviewed. Possible ways to reduce the diffusible hydrogen content will also be summarized, as well as aspects of the filler material and shielding gas selection. In addition, an overview will be provided on welding technology aspects of carbon steels related to hydrogen, such as heat input, preheating, t_8/5 cooling time, heat-affected zone size, number of weld runs, effect of discontinuities, etc. In general, filler material with the lowest possible diffusible hydrogen content should be used; for electrode coatings and fluxes, special care should be taken to ensure proper baking; for wire electrodes, care should be taken to ensure surface cleanliness; in case of shielding gas the use of the purest possible shielding gas is recommended, and the use of shielding gas containing hydrogen is prohibited; and strict attention must also be paid to the purity of the base material. In addition, other important considerations for welding technology development will be outlined for carbon steels. Such as pipelines, where the most important technological aspects of welding will also be discussed, e.g. low heat input, multi-pass weld design, etc.

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: Wire Arc Additive Manufacturing (WAAM) is an emerging technology for producing large scale metal components, offering significant advantages in material efficiency and reduced production time compared to conventional methods. This study investigates the microstructure and mechanical properties of carbon steel produced using two different WAAM systems: the Fronius TransPuls Syn ergic 2700 CMT and the Kemppi X5 500 Pulse+ systems. Both systems utilized similar operating parameters, yet exhibited subtle differences in microstructure, including grain size and phase distri bution. Due to slight microstructural variations, the mechanical properties, such as tensile strength, hardness, and fatigue performance, were nearly identical for both materials. The findings demonstrate the potential of WAAM to produce high-quality carbon steel components with consistent mechanical properties, highlighting its suitability for applications requiring large, custom metal parts.

Abstract: Superheater pipes in boilers generally experience failure due to extreme operating conditions, such as high temperatures and pressures, often leading to ruptures on the pipe surface. These failures reduce the boiler system’s efficiency and increase the risk of further, costly damage. Therefore, it is important to conduct a failure analysis on the ruptured pipe area to enhance the reliability and operational lifespan of the boiler superheater pipes. This study uses several methods to analyze superheater pipe failure, including visual observation and chemical composition testing, which showed a carbon content of 0.228%, classifying the material as low carbon steel. This was also confirmed by microstructure analysis. Hardness testing revealed an average hardness value of 140.9 HV, whereas the expected hardness should be around 180 HV. In the hardness test, there is a difference of 40 HV from the hardness value that meets the standard, which is an indication of material failure. Additionally, in the SEM test, fine defects were found along the grain, and the tested pipe that experienced rupture was already very thin, with many deposits found on the pipe walls.

Abstract: In this paper, the effect of printing parameters on the surface roughness and mechanical properties of wire arc additive manufactured (WAAM) carbon steel is evaluated. WAAM has become increasingly popular as an additive manufacturing method, particularly for producing large parts. Utilizing welding equipment with cold metal transfer (CMT) technology in WAAM production ensures high-quality parts. However, printing parameters play a crucial role in determining material properties. This study evaluates the impact of five different printing parameters on these properties. Microhardness measurements were conducted in the deposition direction of the printed walls, while optical microscopy was used to assess the surface roughness of the printed carbon steel. Tensile tests were performed to determine the mechanical properties of the WAAM-printed carbon steel. The results indicated uniform hardness across all printing parameters, with no observable defects such as pores. Significant differences in surface roughness were noted between the various printing parameters. Although the printing parameters did not significantly affect the tensile strength of the printed carbon steel, they did result in noticeable differences in elongation.

Abstract: Niobium is added to carbon steels in small amounts (< 0.1weight %), thus being called a microalloying element, to increase mechanical strength and toughness. When added to steel, niobium is partly soluble in the matrix and another part combines with carbon and nitrogen forming a family of Nb_xC_yN_z precipitates (niobium carbides, nitrides or carbonitrides), where the values ​​of x, y, z depend on the temperature and the chemical composition of the steel. The solubility equations for niobium in austenite available in the literature only provide the niobium content that could be solubilized at a given temperature. But when niobium is added above the solubility limit, the excess niobium will not only form the Nb_xC_yN_z family of precipitates. This is what the proposed model calculates. The proposed model is easy to apply and provided results are very close to those determined experimentally by different researchers, who used different techniques such as atom probe, or matrix dissolution with precipitate filtration, for example. Although the proposed model has been used to calculate niobium in solution in austenite, the same can be applied to any other precipitate, such as carbides, nitrides or carbonitrides of vanadium and titanium, for example.

Abstract: Steel has been one of the most widely used materials in land and sea construction due to its advantageous properties, especially carbon steel. This study focuses on molecular dynamics simulation to demonstrate carbon steel’s mechanical behavior. A uniaxial tensile test was conducted for body-centered cubic (bcc) structured carbon steel and pure iron to learn the effect of carbon presence. Both simulation cells were simulated under temperature variation to reveal its effects. It was found that carbon steel is stronger than pure iron based on their value on yield and tensile strength, namely up to 2.434 GPa and 1.368 GPa respectively, which are stronger at room temperature. This study also revealed that carbon steel exhibits better elastic properties with a Young’s modulus of 285.749 GPa, compared to that of pure iron 230.117 GPa. Additionally, this molecular dynamic study also identified another phenomenon, such as brittle-to-ductile temperature of carbon steel at 340 K. Structural explanation is provided in the form of bcc structure fraction during the strain progression and under temperature variation. These findings provide a comprehensive molecular perspective to unveil mechanical properties of carbon steel.