•Six full-scale specimens with cover-plate beam-to-column joints were cyclic loaded.•Q460 beams, Q460 columns and C730 columns were involved in the tests.•The failure modes, the seismic behaviors and ...the mechanical indexes of the specimens were reported.•The behaviors of the panel zone and the components of story drift angles were analyzed.•Design recommendations were proposed for cover-plate beam-to-column joints in high strength steel frames.
Improved configurations of beam-to-column joints are required to avoid brittle fractures in earthquakes in the design of high strength steel frames, and the cover-plate beam-to-column joints are expected to be effective to reinforce the welded flange-bolted web joints with negligible additional requirements for construction space and have potential for applications in seismic design of high strength steel frames. A total of 6 specimens of high strength steel double-sided cover-plate beam-to-column joints, considering three different combinations of 345 MPa or 460 MPa steel beams and 460 MPa or 730 MPa steel columns, were designed according to the Chinese code and tested subjected to cyclic loads with axial compressions in columns in consideration. The failure modes, the resistance, the stiffness and the ductility of the specimens were analyzed, and the influences of the panel zone thickness, cover-plate length, attached fillet weld in web connection and shape of the weld access whole were evaluated. According to the test results, continuity plates with sufficient thickness in high strength steel cover-plate joints were necessary to avoid unexpected failure modes, and the panel zone shear rotation would make a considerable contribution to the total story drift angle and the plastic story drift angle of the high strength steel frames. All the 6 specimens reach a story drift angle larger than 0.035 rad with 4 of them larger than 0.04 rad, indicating that the high strength steel cover-plate joint may develop considerable ductility. However, the evaluation methods of joint ductility in high strength steel frames should be further discussed because of the significantly increased elastic deformability of high strength steel members. Based on the test results, design recommendations were proposed for high strength steel cover-plate beam-to-column joints.
Fe-Mn-Al-C steels, previously developed in the 1950s for replacing Fe-Cr-Ni steels, are currently generating a lot of interest with potential applications for structural parts in the automotive ...industry because they are lighter. This paper provides a review on the physical metallurgy, processing strategies, strengthening mechanisms and mechanical properties of Fe-Mn-Al-C steels from the published literature over a period of many years, and suggests avenues for future applications of these alloys in the automotive sector. The addition of Al to Fe-C steels leads to a reduction in both density and Young's modulus. A 1.3% reduction in density and a 2% reduction in Young's modulus are obtained per 1 wt% addition of Al. Due to the addition of the high amounts of Al, together with Mn and C, the physical metallurgy, general processing, microstructural evolutions and deformation mechanisms of these steels are largely different from those of the conventional steels.
Ferroalloys have become increasingly important due to their indispensable role in steelmaking. In addition, the demand for improved steel qualities has increased considerably, which in turn ...highlights the quality of ferroalloys. This is due to the fact that the impurities in ferroalloys directly and significantly influence the quality of steel products. To gain a better understanding of the main trace elements and inclusions in ferroalloys (such as FeSi, FeMn, SiMn, FeTi, FeCr, FeMo, FeNb, FeV, FeB, some complex ferroalloys) and their behaviours in steel melt after the additions of these ferroalloys, information from a large number of previous results on this topic was extensively reviewed in this work. The applications of different ferroalloys and their production trends were discussed. In addition, the effects of some trace element impurities from ferroalloys on the inclusion characteristics in steel were also discussed. The possible harmful inclusions in different ferroalloys were identified. Overall, the results showed that the inclusions present in ferroalloys had the following influence on the final steel cleanliness: (1) MnO, MnS and MnO–SiO
2
–MnS inclusions from FeMn and SiMn alloys have a temporary influence on the steel quality; (2) the effect of large size SiO
2
inclusions (up to 200
μ
m) in FeSi and FeMo alloys on the steel cleanliness is not fully understood. The effect of Al, Ca contents should be considered before the addition of FeSi alloys. In addition, Al
2
O
3
inclusions and relatively high Al content are commonly found in FeTi, FeNb and FeV alloys due to their production process. This information should be paid more attention to when these ferroalloys are added to steel; (3) except for the existing inclusions in these alloys, the Ti-rich, Nb-rich, V-rich carbides and nitrides, which have important effects on the steel properties also should be studied further; and (4) specific alloys containing REM oxides, Cr–C–N, Cr–Mn–O, Al
2
O
3
, Al–Ti–O, TiS and Ti(C, N) have not been studied enough to enable a judgement on their influence on the steel cleanliness. Finally, some suggestions were given for further studies for the development of ferroalloy productions.
Constant striving to reduce pollutant emissions, greenhouse gases and energy consumption, i.e., sustainable development, forces the development of new and improved materials, technologies and ...manufacturing processes. One of the areas of sustainable development of the global economy is also the development of laser devices and the spreading of laser technology applications.The book deals with important issues related to the development of science and technology in the field of application the laser beam for joining, surface treatment, coatings. However, the thematic scope is not limited only to mentioned issues. The scope of the book covers issues related to advances in computational modelling of heat sources in laser and arc processes, unique techniques of underwater welding or unique techniques of forced cooling the weld metal under solidification during arc welding or hybrid process of laser deposition under cryogenic conditions, microstructural and mechanical characterisation of coatings and joints produced by different welding technologies. The above book contains valuable information, both theoretical and practical research results in the field of advanced technologies of joining, surface treatment and coatings, quality control and assessment, as well as management of the technological processes. Therefore, I deeply believe that the book will be a valuable and helpful for young scientists, engineers, and students in the field of welding and surface engineering, materials science, and manufacturing engineering.
•Seven-type steel–concrete composite stub columns with the same steel ratio are tested under axial compression.•The newly proposed steel-tube-confined concrete-filled steel tube is included.•The ...influence of configurations on the mechanical properties of the composite column is determined and compared.•The confinement mechanism of various steel–concrete composite columns is illustrated systematically.•Current designing specifications are evaluated for different types of composite columns by the experimental results.
Steel-concrete composite columns are widely used in civil engineering structures for superior structural performance and economical cost. In response to the varying construction conditions, extensive types of composite columns have been developed nowadays, including concrete-filled steel tubes (CFST), CFST with steel bar (CFST-B) or steel section embedded (CFST-S), steel tubed concrete (T-C), steel tubed reinforced concrete (T-RC), steel tubed steel-reinforced concrete (T-SRC), and the newly proposed steel-tube-confined CFST (T-CFST), etc. A systematic and comparative experimental study was conducted for the seven types of steel–concrete composite stub columns with the same steel ratio, aiming to clarify their differences and facilitate an appropriate selection. Experimental results showed that all the conventional composite columns suffered from brittle failure, which was changed to ductile failure for T-CFST. Moreover, the employment of internal rebar or structural steel led to a variation of 13.3% in the ultimate load of CFST members; setting steel gap at the column ends for T-C columns increased the ultimate load by about 10% further; the addition of outer steel tube and sandwich material in T-CFST achieved up to 42.4% higher ultimate load. The enhanced mechanical properties of T-C and T-CFST were resulted from the increasing concrete confinement by the outer steel tube. The current design codes for different types of composite columns were examined by the experimental results, and a more suitable design method is needed for T-CFST.
The papers collected in this special issue clearly reflect the modern research trends in materials science. These fields of specific attention are high-Mn TWIP steels, high-Cr heat resistant steels, ...aluminum alloys, ultrafine grained materials including those developed by severe plastic deformation, and high-entropy alloys. The major portion of the collected papers is focused on the mechanisms of microstructure evolution and the mechanical properties of metallic materials subjected to various thermo-mechanical, deformation or heat treatments. Another large portion of the studies is aimed on the elaboration of alloying design of advanced steels and alloys. The changes in phase content, transformation and particle precipitation and their effect on the properties are also broadly presented in this collection, including the microstructure/property changes caused by irradiation.
The kinetics of the growth of M.sub.23C.sub.6 carbide particles in 9% Cr martensitic steel with a high boron content is studied under conditions of long-term aging and creep. It is shown that the ...grain-boundary diffusion is a mechanism that controls the coarsening of these carbides during the aging. Deformation accelerates the coarsening of particles during creep, which can be explained by additional diffusion along dislocation lines.
AbstractCorrosion of metals is one of the primary factors leading to the deterioration of bridge structures in the US. Protective coatings applied to the surface of the metal have been widely used as ...a corrosion protection system for steel bridge components. Because the coating also can deteriorate over time, other strategies, such as using steels with better corrosion resistance (i.e., weathering steels), have also been adopted. A recently developed structural stainless steel has shown better performance than conventional weathering steels, particularly in harsh environments, but it comes with a high initial cost. The aim of this study is to compare the life-cycle costs (LCCs) of various corrosion management strategies for bridge steel structures, using either coated carbon steel or structural stainless steel. To evaluate the structural performance of the coated carbon steel structure, a new probabilistic corrosion model is developed for the first time that explicitly incorporates the coating degradation in the steel deterioration process. Using two case studies, this study compares the LCCs of cyclical- and condition-based maintenance strategies and investigates the impact of different coating systems on the LCC. The results show that the structural stainless steel may be more economically beneficial than coated carbon steel, but the payoff time depends on the parameters used in the LCC analysis, such as the maintenance strategies adopted for the coated carbon steel, the coating type, the discount factor, and the size of the structure considered.
Low-carbon steel pipelines are frequently used as transport pipelines for various media. As the pipeline transport industry continues to develop in extreme directions, such as high efficiency, long ...life, and large pipe diameters, the issue of pipeline reliability is becoming increasingly prominent. This study selected Q235 steel, a typical material for low-carbon steel pipelines, as the research object. In accordance with the pipeline service environment and the accelerated corrosion environment test spectrum, cyclic salt spray accelerated corrosion tests that simulated the effects of the marine atmosphere were designed and implemented. Corrosion properties, such as corrosion weight loss, morphology, and product composition of samples with different cycles, were characterized through appearance inspection, scanning electron microscopy analysis, and energy spectrum analysis. The corrosion behavior and mechanism of Q235 low-carbon steel in the enhanced corrosion environment were studied, and the corrosion weight loss kinetics of Q235 steel was verified to conform to the power function law. During the corrosion process, the passivation film on the surface of the low-carbon steel and the dense and stable α-FeOOH layer formed after the passivation film was peeled off played a role in corrosion resistance. The passivation effect, service life, and service limit of Q235 steel were studied and determined, and an evaluation model for quick evaluation of the corrosion life of Q235 low-carbon steel was established. This work provides technical support to improve the life and reliability of low-carbon steel pipelines. It also offers a theoretical basis for further research on the similitude and relevance of cyclic salt spray accelerated corrosion testing.
Certain species of sulfate-reducing bacteria (SRB) use cathodes as electron donors for metabolism, and this electron transfer process may influence the proper protection potential choice for ...structures. The interaction between SRB and polarized electrodes had been the focus of numerous investigations. In this paper, the impact of cathodic protection (CP) on Desulfovibrio caledoniens metabolic activity and its influence on highs trength steel EQ70 were studied by bacterial analyses and electrochemical measurements. The results showed that EQ70 under -0.85 VSCE CP had a higher corrosion rate than that without CP, while EQ70 with -1.05 VSCE had a lower corrosion rate. The enhanced SRB metabolic activity at -0.85 VSCE was most probably caused by the direct electron transfer from the electrode polarized at -0.85 VSCE. This direct electron transfer pathway was unavailable in -1.05 VSCE. In addition, the application of cathodic protection led to the transformation of sulfide rusts into carbonates rusts. These observations have been employed to provide updated recommendations for the optimum CP potential for steel structures in the presence of SRB.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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