Papers by Keyword: Steel

Abstract: Oil-in-water emulsions (O/W-emulsions) are generally used to lubricate the cold rolling process of low-carbon steel. Besides the obvious advantages of efficient lubrication and cooling of the process, there are also some disadvantages mainly related to emulsion bath maintenance, subsequent production steps and waste disposal. In some application areas, Oil Free Lubricants (OFL’s) have shown to be at least equally effective in decreasing friction and wear as conventional lubricants, while resulting in benefits related to waste disposal. In 2018 a project (acronym ‘RollOilFree’) was started with funding from the Research Fund for Coal and Steel (RFCS). The objective of this project was to develop an OFL as a lubricant for the cold rolling process of low-carbon steel and hot rolling of aluminium. A cold rolling lubricant can be evaluated based on many criteria; for some criteria the OFL even outperformed the oil-based emulsion, but it was found that for some rolling conditions the coefficient of friction with the OFL was still too high. In September 2023 a follow-up project, “Transfer of aqueous oil free lubricants into steel cold rolling practice” (acronym ‘RollOilFreeII’) has begun, also in the RFCS-framework. This article briefly recapitulates the findings in the RollOilFree-project and describes the objectives and benefits of the RollOilFreeII-project. Furthermore, the main activities in the project will be discussed.

Abstract: One of the most important issues in the procurement of parts and products by the process of metallurgy is the design of the details of the press-mold. The design should be carried out in such a way that the additional mechanical processing of the purchased parts and products is minimal. The tooling and technological scheme of the press-mold should be selected as might it be economically viable and the mechanical processing stakes are small. For these purposes, in this present study, the valve part of the high-pressure drilling pump НП-720х105, which is widely used in the oil and gas complex, was selected for theoretical and experimental investigations. With the help of the software, in order to ensure equal distribution of residual porosity in the samples, the optimal size and configuration of the samples were determined, and the inner and outer conical walls of the asymmetric samples were subjected to dynamic hot pressing. "Valve seat" and "valve tray" of the НП-720х105 high-pressure three-plunger pump were used for the experimental studies. From the conducted tests, it became clear that during the preparation of abrasive steels with high impact-abrasive corrosion resistance, it is necessary to thoroughly study the chemical and granulometric composition, structure, and strengthening process. Theoretical and experimental results show that the technology of manufacturing parts resistant to impact-abrasive corrosion allows the obtained parts to work in conditions of high impact-hydroabrasive corrosion.

Abstract: The subject of the study presented in this paper is to quantify the effect of fiber content on the mechanical and mainly fatigue response of fine-grained cement-based composites. The reference cement-based composite was without fibers. Three types of fibers were used as dispersed reinforcement: tire cords (waste material), steel, and polypropylene. For each type of fiber, mixtures with varying reinforcement levels per volume were prepared: 0.0 % (reference composite), 0.5 %, 1.0 %, and 1.5 %. Prismatic specimens 40 mm × 40 mm × 160 mm were prepared and tested. A total of 10 composite variants were investigated. The ages of the specimens for the static three-point bending tests were 28 days, for the compression tests were 28, 120, and 275 days. While for the fatigue tests, it was approximately between 110 and 180 days. The obtained compressive strength values for the above-mentioned composite ages were approximated by a selected exponential function and the results of the fatigue tests were standardized to a nominal age of 28 days using them. All used types of reinforcement increase the strength values of the composites even from the lowest fiber doses. A positive effect of fiber dosage above 0.5 % on the fatigue behavior of composites was shown only in the case of reinforcement with commercial steel fibers.

Abstract: Blast performance of concrete and ultra-high performance fiber concrete (UHPFRC) has been subject to numerous publications in the past decades. The enhanced force-deflection diagram of fiber concrete and ultra-high performance fiber concrete provide massive increase on the protective function of these materials compared to regular concrete. Nevertheless, concrete spalling cannot be fully avoided even when using UHPFRC. The next step for harmful debris ejection prevention can be supplementing the concrete specimens with steel slabs. The steel slab will not just hold the debris, but can, if properly bonded with concrete, contribute to the load bearing capacity as steel-concrete composite structure. This paper presents an overview of recent experiments on blast resistance of steel-concrete composite slabs. In total 6 pairs of specimens (dimension 1.000/1.000/150mm) were prepared, 6 specimens using regular concrete and 6 specimens using UHPFRC. One pair of specimens was reinforced by a steel mesh at 30mm cover from the soffit, one pair was supplemented by a steel plate bonded with 4 studs in the corners, at the complementary specimen pair, the concrete was also covered with a steel plate at the side subjected to blast loading, in the case of the further pair of specimens, the steel plates were connected by steel bars arranged in a mesh 150/150mm. The final 2 pairs represented steel-concrete composite slabs, in the first case, the shear studs were supplemented with a steel mesh (according to provisions of the European standard for steel-concrete composite structures), in the last case, the shear studs were replaced by a shear plate. All specimens were subjected to the same contact blast loading. The paper presents the experimental arrangement, the achieved results and a brief discussion on the structural behavior.

Abstract: Metals are prone to wear through the separation of wear debris particles as well as the plastic displacement of surface and near-surface material. Particle sizes range from millimetres to nanometres. Erosion is the gradual, layer-by-layer destruction of a metallic object's surface brought on by mechanical pressure or electrical discharges. Metals erode as a result of surface friction, wear, cavitation, and the influence of powerful gas or liquid currents on a surface. Jet engines, nuclear reactors, steam turbines, and boilers might all suffer damage from erosion. By enhancing process technology or unit design, using better materials, and applying heat treatment, it is possible to strengthen the resistance of components against erosion. AlSi10Mg is a hypoeutectic alloy that may be additively manufactured due to its limited solidification range, which reduces hot cracking susceptibility during cooling. Complex bulk and open-cell structures with outstanding strength ratio (strength-to-weight ratio) and good formability may be created using additive manufacturing of aluminium alloys, particularly AlSi10Mg. Carbon, manganese, sulphur, silicon, phosphorus, chromium, nickel, copper, and niobium are all present in the pH grade of 17-4. This combination of high strength and corrosion resistance benefits a 17-4 PH stainless steel grade. It may be utilised effectively in a variety of applications due to its high tensile strength and exceptional corrosion resistance.Powder bed fusion is one of the most mature metal additive methods, and as such, it benefits from decades of industrial expertise. PBF can satisfy demands of creating a new component and need to iterate on ideas quickly or are searching for a more efficient procedure to produce sophisticated components. Material waste is reduced because building the part layer by layer reduces the majority of the waste associated with subtractive manufacturing processes. Any surplus powder is collected and recycled when the item is finished. This review researches about the wear and erosion behaviour of Al-Si Alloy and steels printed using additive manufacturing methods. Finally, the findings of this review are summarised, and recommendations are made for future research aimed at resolving current issues and advancing technology.

Abstract: The role of non-metallic inclusions is gaining increasing attention in steel research. Various inclusion characterisation techniques and methods are utilised in order to obtain reliable and accurate results. Automatic inclusion measurements carried out using field-emission scanning electron microscope with energy dispersive spectroscopy produces a large amount of data about detected inclusions in the scanned area. The data obtained must be processed and analysed in one way or another, for example, to classify the inclusions or construct size distributions. Until now, a Matlab script has been used to determine the phase composition of inclusions, and to classify them accordingly. The Matlab script has acted as the basis for the recently developed Karakterizer tool, written in Python. In addition to less restricted use, the recent advances include a graphical user interface. This paper demonstrates the use of Karakterizer tool in characterising inclusions with examples of direct-quenched martensitic steels with a yield strength of 1000 MPa.

Abstract: The consumption of steel for fasteners in China is about 9 million tons annually, accounting for approximately one-fifth of worldwide usage. High strengthening is the main development trend of high performance of fasteners. As strength increase, the sensitivity of both fatigue failure and delayed fracture increases, and the processing technology varies. These are the main problems need to be addressed. Fasteners of property classes 8.8-12.9 are currently the most widely used high-strength fasteners. The match between fatigue life with strength is commonly the paramount consideration. We have developed a series of steels involving (i) SCM435 steel wire for key fasteners of engine with ultra-narrow composition (ΔC≤0.01%), slight hardness variation (ΔHRC≤ 2) and a qualified fatigue performance of 1×10⁷ cycles; (ii) 10.9 and 12.9 fastener steels with large size, low cost and high hardenability for wind tower; (iii) A286 alloy wire with desirable 650 °C durability. In addition, we developed ML35 wire free of spheroidizing and microalloyed steels for slender bolts free of quenching & tempering process. The use of ultra-high strength fasteners ≥13.9 is necessary to achieve equipment light weighting. We have developed steels for 13.9 and 15.9 fasteners with an excellent resistance to delayed fracture. An austempering process was applied to 14.8-17.8 fasteners, which enables the reduction of the alloy content. A novel strengthening method needs to be introduced to develop fasteners in excess of class 19.8 fastener. We have developed 19.8 fastener steel with good fatigue and delayed fracture resistance. Secondary hardening plays a key role in the improvement of strength.

Abstract: Phase boundaries of the pseudo-binary Fe-C diagram are key inputs for the prediction and understanding of matrix phase transformation in steels. The mechanical properties, of such steels, however, are often not dictated by the individual phase fractions, accessible through CALPHAD calculations, but by the arrangement of the phases, i.e., the steel’s microstructure. The prediction of these microstructural constituents requires the application of additional models, which are reviewed in the present contribution. Additionally, the current use and limitations for industrial application are presented together with an outlook to future challenges and opportunities in this field of research.

Abstract: The Fe-0.44%C-1.8%Si-1.3%Mn-0.82%Cr-0.28%Mo steel treated by the quenching-partitioning process showed a product of strength and elongation of 30 GPa×% with the yield stress of 1150 MPa. The influence of the partitioning time on the structure and mechanical properties is discussed. It is shown that the volume fraction of retained austenite depends on carbon content in the solid solution of primary martensite. The formation of bainite leads to no deterioration of mechanical properties.

Abstract: A technique for fabricating structural joints by closed-die-type friction-stir forming (FSF) is introduced in this study. The process is as follows. First, a steel sheet with a prepared hole is placed on an aluminum alloy plate. A die with a through-hole cavity is then placed above it to press down the steel sheet tightly. Next, a rotating stepped cylindrical tool is inserted into the through-hole cavity. To enclose the die cavity, the upper side of the tool is then positioned such that it is nearly in full contact with the inner surface of the through-hole. Finally, the top part of the tool is allowed to penetrate into the aluminum alloy plate through the prepared hole of the steel sheet to cause the material to extrude backward. Consequently, the material fills the whole of the space between the tool and die to generate a hollow-rivet-like aluminum alloy structure fastening the steel sheet to the aluminum alloy plate. This technique enables easier alignment between the die and the prepared hole of the steel as compared with the conventional joining technique which uses FSF. In addition, the new technique uses a one-sided approach (i.e., from the side of the harder material with a higher melting temperature) to join dissimilar materials, a process which is difficult for conventional methods of friction-stir welding and forming.