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An arc sprayed aluminum (Al) coating on S355 steel was processed using a laser remelting (LR). The microstructures, chemical element composition, and phases of the obtained Al coating were analyzed using a field mission scanning electronic microscope (FESEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively, and the residual stresses were measured using an X-ray diffraction stress tester. The immersion corrosion tests and potentiodynamic polarization of Al coating in 3.5% NaCl solution were performed to investigate the effects of LR on its immersion corrosion behaviors, and the corrosion mechanism of Al coating was also discussed. The results show that the arc sprayed Al coating is composed of Al phase, while that by LR is composed of Al-Fe and AlO 4 FeO 6 phases, and the porosities and cracks in the arc sprayed Al coating are eliminated by LR, The residual stress of arc sprayed Al coating is −5.6 ± 18 MPa, while that after LR is 137.9 ± 12 MPa, which deduces the immersion corrosion resistance of Al coating. The corrosion mechanism of arc sprayed Al coating is pitting corrosion and crevice corrosion, while that by LR is uniform corrosion and pitting corrosion. The corrosion potential of arc sprayed Al coating by LR shifts positively, which improves its immersion corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, the optimization of pulsed Nd:YAG laser welding parameters was done on the lap-joint of a 316L stainless steel foil with the aim of reducing weld defects through response surface methodology. For this purpose, the effects of peak power, pulse-duration, and frequency were investigated. The most important weld defects seen in this method include underfill and undercut. By presenting a second-order polynomial, the above-mentioned statistical method was managed to be well employed to balance the welding parameters. The results showed that underfill increased with the increased power and reduced frequency, it first increased and then decreased with the increased pulse-duration; and the most important parameter affecting it was the power, whose effect was 65%. The undercut increased with the increased power, pulse-duration, and frequency; and the most important parameter affecting it was the power, whose effect was 64%. Finally, by superimposing different responses, improved conditions were presented to attain a weld with no defects. [ABSTRACT FROM AUTHOR]

Laser bending is a process of bending of plates, small sized sheets, strips and tubes, in which a moving or stationary laser beam heats the workpiece to achieve the desired curvature due to thermal stresses. Researchers studied the effects of different process parameters related to the laser source, material and workpiece geometry on laser bending of metal sheets. The studies are focused on large sized sheets. The workpiece geometry parameters like sheet thickness, length and width also affect the bend angle considerably. In this work, the effects of width and thickness on multi-pass laser bending of AH36 steel strips were studied experimentally and numerically. Finite element model using ABAQUS® was developed to investigate the size effect on the prediction of the bend angle. Microhardness and flexure tests showed an increase in the flexural strength as well as microhardness in the scanned zone. The microstructures of the bent strips also supported the physical observations. [ABSTRACT FROM AUTHOR]

A Ni-Cr-Si-B alloy layer was produced on a type 304 stainless steel plate by laser cladding. In order to produce cladding layer with smooth surface and low dilution, influence of laser beam profile on cladding layer was investigated. A laser beam with a constant spatial intensity at the focus spot was used to suppress droplet formation during the cladding layer formation. This line spot, formed with a focussing unit designed by our group, suppressed droplet generation. The layer formed using this line spot with a constant spatial intensity had a much smoother surface compared to a layer formed using a line spot with a Gaussian-like beam. In addition, the dilution of the former layer was much smaller. These results indicated that a line spot with a constant spatial intensity was more effective in producing a cladding layer with smooth surface and low dilution because it suppressed droplet generation. [ABSTRACT FROM AUTHOR]

The article presents a detailed analysis of the degradation phenomena and mechanisms of selected forging punches made of UNIMAX tool steel. Analyzed punches are used in the manufacture of a constant velocity joint boot forging (CVJB) applied in motorcars with front axle drive. The thorough analysis concerned the punches used in the fourth forging operation after a multi-operational process of forging at elevated temperatures, due to the lowest durability equaling only 4000 forgings. A comparison was made of 5 variants of surface thermo-chemical treatment including 2 types of nitriding (with a low and high potential) and 2 different coatings: CrN and AlCrTiN as well as a punch with and without additional thermo-chemical treatment. The performed complex analysis included a macroscopic analysis combined with scanning of the working surfaces, numerical modeling, microstructural tests, SEM microscopic tests, and microhardness measurements. The obtained results make it possible to select of the optimal variant of thermo-chemical surface treatment which improves the durability of these tools. In particular, the analysis included the manner and areas of wear of the punches as well as their resistance to the particular degradation mechanisms. [ABSTRACT FROM AUTHOR]

This paper presents a numerical methodology based on Euler-Bernoulli theory to simulate the steel, reinforced concrete and composite structures 2D nonlinear behavior. The displacement-based numerical formulation uses the principles of the Refined Plastic Hinge Method (RPHM) to simulate the concentrated plasticity at the corotational finite element nodal points. In order to present a more realistic simulation of the axial and flexural stiffness degradation, the RPHM is coupled with the Strain Compatibility Method (SCM), where the materials constitutive relations are used explicitly. The SCM is also applied in determining the structural elements’ bearing capacity. Moreover, the present approach is not limited to a specific cross-sectional typology. Also addressed are residual stress models; these are introduced explicitly in subareas of steel profiles generated by a two-dimensional cross-sectional discretization. It should be emphasized that this study considers full interaction between the materials. Finally, the results obtained are compared with numerical and experimental findings available in the literature. [ABSTRACT FROM AUTHOR]

The fiber coating is the key part of the solid-phase microextraction (SPME) technique, and it determines the sensitivity, selectivity, and repeatability of the analytical method. In this work, amine (NH)-functionalized material of Institute Lavoisier (MIL)-53(Al) nanoparticles were successfully synthesized, characterized, and applied as the SPME fiber coating for efficient sample pretreatment owing to their unique structures and excellent adsorption properties. Under optimized conditions, the NH-MIL-53(Al)-coated fiber showed good precision, low limits of detection (LODs) [0.025-0.83 ng L for synthetic musks (SMs) and 0.051-0.97 ng L for organochlorine pesticides (OCPs)], and good linearity. Experimental results showed that the NH-MIL-53(Al) SPME coating was solvent resistant and thermostable. In addition, the extraction efficiencies of the NH-MIL-53(Al) coating for SMs and OCPs were higher than those of commercially available SPME fiber coatings such as polydimethylsiloxane, polydimethylsiloxane-divinylbenzene, and polyacrylate. The reasons may be that the analytes are adsorbed on NH-MIL-53(Al) primarily through π- π interactions, electron donor-electron acceptor interactions, and hydrogen bonds between the analytes and organic linkers of the material. Direct immersion (DI) SPME-gas chromatography-mass spectrometry methods based on NH-MIL-53(Al) were successfully applied for the analysis of tap and river water samples. The recoveries were 80.3-115% for SMs and 77.4-117% for OCPs. These results indicate that the NH-MIL-53(Al) coating may be a promising alternative to SPME coatings for the enrichment of SMs and OCPs. [ABSTRACT FROM AUTHOR]

Cold-formed steel hollow flange sections are structurally efficient compared to the conventional open channel sections. They can be of different forms including hollow flange I- and channel sections, which are generally fabricated by first cold-forming a single sheet to form the desired shape and then connecting their flange and web elements by continuous welding. Instead of welding, intermittently screw/rivet fastened or spot welded connection can also be used. A detailed investigation is currently under way on the structural performance characteristics of such intermittently screw/rivet fastened steel hollow flange sections. This paper presents the details of an experimental study performed to investigate the behaviour of built-up cold-formed steel hollow flange sections in compression, where more than 45 stub columns were tested. Both hollow flange I- and channel sections built-up using either single steel sheet or three steel elements were tested. Tests also included built-up hollow flange channel sections with stiffened web elements. Test results including the failure loads, load versus axial deformation plots and failure characteristics are presented in this paper. Test failure loads are compared with the predictions based on both effective width and direct strength methods to verify their adequacy in predicting the section compression capacity of built-up hollow flange sections. This paper has shown that although hollow flange I-sections made of three elements with a 100 mm fastener spacing can perform similar to continuously welded sections, hollow flange channel sections undergo premature failures even with a 50 mm fastener spacing, and the reasons are discussed. [ABSTRACT FROM AUTHOR]

This work reports the influences of helix angle on tool performances of titanium aluminum nitride (TiAlN)- and diamond-like carbon (DLC)-coated carbide end mills for dry side milling of 304L stainless steel. The study results revealed that the number of axis contact points and effective cutting length increased with increasing helix angle, leading to less tool wear and thinner milled chips but higher workpiece temperature. In addition, DLC-coated tools exhibited relatively high workpiece temperature, rapid chipping wear due to thermally induced graphitization, and chip-built-up on side edge while TiAlN-coated end mills displayed less severe abrasive wear on cutting and side edges. Moreover, the DLC-coated end mill with a high helix angle of 60° gave the lowest surface roughness of 0.26 μm within the cutting length of 20 m while the corresponding TiAlN-coated tools offered longer tool cutting length of more than 50 m with comparable surface finish. Consequently, the TiAlN-coated end mill with a high helix angle of 60° offered high-quality surface finish with long tool life time and would be more useful for dry milling of stainless steels. [ABSTRACT FROM AUTHOR]

Currently, it is widely acknowledged that ridging is caused by different plastic deformations from grains with different textures. In this study, a simplified model was used to predict the ridging height with different elongation values based on crystal plasticity (CP) and EBSD information with the purpose of understanding well the effect of texture and average grain size on the ridging generation and reduction of undesirable surface defects of ferritic stainless steel (FSS) 430 during the formation process. The results indicate that the reduction of average grain is effective to improve ridging generation in FSS along tensile directions. The numerical simulation results obtained using the crystal plasticity finite element model (CPFEM) match well with experimental values, which demonstrates that the CPFEM could be employed to analyse the ridging phenomenon under different elongation conditions of FSS. Based on the established models, the ridging modes of colonies with different crystal orientations ({001} <110>, {112} <110> and {114} <110>) are discussed to evaluate the effect of texture structure on ridging generation. [ABSTRACT FROM AUTHOR]

The 9Cr-1Mo steel (ASTM P91) was hot-dip aluminized, and its microstructural changes during oxidation were studied. Before oxidation, the coating consisted of (Al-rich topcoat containing a small amount of Al5Fe2 and Al13Fe4)/(Al13Fe4-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer containing a small amount of Al9Cr4precipitates), from the surface. During oxidation at 700-900 ±C for 20-100 h, Al diffused inward and the substrate elements migrated outward to broaden and soften the coating, and also to transform (high Al)-Fe intermetallics to (low Al)-Fe intermetallics. The phases in the coating progressively transformed during oxidation as follows; (Al-rich topcoat)/(Al5Fe2-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer)→(α-Al2O3 scale)/(Al13Fe4-rich, Al5Fe2-containing layer)/(Al5Fe2 layer)/(AlFe interlayer)→(α-Al2O3 scale)/(AlFe-rich, Al5Fe2-containing layer)/(AlFe layer)/(AlFe3 layer))→((α-Al2O3, Fe2O3)-mixed scale)/(AlFe3 layer)/(Fe(Al) layer) from the surface. As the oxidation progressed, the scale changed from α-Al2O3 to the (α-Al2O3, Fe2O3)-mixture, which provided the necessary oxidation resistance. [ABSTRACT FROM AUTHOR]

Empty hat sections, single and double, made of steel are frequently encountered in automotive body structural components such as front rails, B-Pillar, and rockers of unitized-body cars. These closed-section thin-walled components can play a significant role in terms of impact energy absorption during collisions thereby protecting occupants of vehicles from potential or severe injury. With the need for higher fuel economy and due to stringent emission norms, auto manufacturers are aggressively looking for means to reduce a vehicle's weight either by employing materials lighter than steel (such as aluminum, fiber-reinforced composites, etc.) or by substituting traditional mild steel-based body parts with those made with high strength steel of lower gages, or through a combination of both the strategies mentioned. Reducing gages, however, may lead to structural instability due to early inelastic buckling. This phenomenon of instability provides an opportunity for using polyurethane (PU) foam in structural members. Once a hollow structural member is filled with PU foam, it delays the local buckling mechanism and leads to higher strength of the structure. The current study explores the effect of PU foam-based reinforcement of tubular structures. Here, both empty and PU foam-filled single-hat and double-hat components are tested under quasi-static axial loading in a UTM. The resulting load-displacement responses are compared. Higher energy absorption as well as mean load is observed for foam-filled hat sections. Moreover, for a given total folded length, more folds are observed in foam-filled hat sections as compared to empty hat sections. Experimentally obtained half fold lengths for double-hat sections are compared with analytical predictions of the same for square tubes. Furthermore, quasi-static axial crush behaviors of single- and double-hat section components are predicted through finite element modeling and analysis using the explicit non-linear LS-DYNA code. [ABSTRACT FROM AUTHOR]

Ballistic impact of typical armour steel plate of medium thickness by ogive-nosed projectiles travelling with ordnance velocities has been investigated through numerical simulations. Johnson-Cook material and failure models have been used to simulate the behavior and failure of the material under impact conditions. The model constants have been derived from an experimental work done by the authors published previously. Simulation has been done in Altair-HyperWorks FE package. The stages of penetration have been predicted. The residual velocities, ballistic limit velocity andperforation times have been determined from the simulation results and found to match with experimental data. [ABSTRACT FROM AUTHOR]

The majority of multistory steel framed buildings in the UK are designed such that the connections between the frame elements can be classified as ‘simple’ or ‘semi-rigid’. Current UK design provisions relating to structural integrity and robustness for these types of connections do not currently incorporate dynamic effects such as inertia or strain rate sensitivity. A numerical study has been carried out on a typical UK beam-column simple connection, in which the supported beam connects into the web of the supporting column. The connection has been subjected to a rapid rotation using the finite element software package LS-DYNA. Results and discussion of the numerical study are presented herein; experimental validation of these results is currently being carried out. [ABSTRACT FROM AUTHOR]

This work presents the results of a numerical and theoretical study on the cold-formed steel built-up sections under axial compression, to explore the buckling Behavior and ultimate capacity of built-up sections. The built-up sections have been formed by two identical lipped channels placed back to back connect by using spacers. The Finite element model is developed by using the ABAQUS software. The developed numerical model is verified against the experimental results published in the literature. After validation, the parametric study is conducted by varying the overall slenderness, depth, and number of spacers. The column strength obtained from numerical analysis are compared with the strength predicted by using the Direct Strength Method (DSM) and Effective Width Method (EWM) as per North American Specifications (AISI-S100:2007) for cold-formed steel members. [ABSTRACT FROM AUTHOR]

Bio-/environment-friendly cationic gemini surfactant, ethane-1,2-diyl bis( N, N-dimethyl- N-hexadecylammoniumacetoxy)dichloride, referred to as 16- E2-16, was synthesized and characterized. Corrosion inhibition effects of 16- E2-16 on mild steel (MS) surface in 1 M HCl solution at 30, 40, 50 and 60 °C were evaluated using gravimetric analysis, potentiodynamic polarisation and electrochemical impedance spectroscopy measurements. The nature of the protective inhibitor film formed on the MS surface was analysed by SEM, EDAX and FT-IR, while TGA was used to assure the thermal behaviour and stability of the film at high temperature. The formation of [inhibitor-Fe] on the surface of MS was confirmed by UV-visible spectroscopy. The inhibition efficiency of the studied inhibitor increased with increasing concentration and solution temperature. The compound behaved as a mixed type inhibitor and acted by blocking the electrode surface by means of adsorption obeying the Langmuir adsorption isotherm. Surface active properties and corrosion inhibition effects of 16- E2-16 in the presence of inorganic (NaI) and organic (NaSal) salts were also investigated and are discussed. Density functional theory calculations have been carried out to correlate the efficiency of the compound with its intrinsic molecular parameters. [ABSTRACT FROM AUTHOR]

Microstructures of new heat-resistant steel grade T23 welded joint without PWHT and its corresponding mechanical properties including creep were investigated to clarify its premature failure mechanisms in the large water wall panel of the advanced power plant boiler. The results show that the T23 steel GTAW welded joint in a wall thickness of 6.5 mm without PWHT exhibits high tensile strength, good ductility, and sufficient impact toughness, while the hardness of the WM is higher than the maximum permitted value of 350 HV due to the large amount of un-tempered martensite formed during the cooling process of welding. This WM in as-welded condition has higher creep rupture strength but poorer rupture ductility than the tempered BM. Poor rupture ductility taken place in the WM results from inter-granular cracking during creep exposure and is not related to the second hardening because no hardness rise occurs in the fractured WM compared with as-welded condition. The paper does not specifically investigate the effect of service exposure but simulates the failure of WM by a creep test. The main point is that the WM has low creep ductility, especially at a stress concentration. [ABSTRACT FROM AUTHOR]

At the present time 9–12% Cr ferritic/martensitic (F/M) steels with target operating temperatures up to 650 °C and higher are being developed in order to further increase thermal efficiency so as to reduce coal consumption and air pollution. An 11% Cr F/M steel was prepared by reference to the nominal chemical composition of SAVE12 steel with an expected maximum use temperature of 650 °C. The precipitate phases of the 11% Cr F/M steel normalized at 1050 °C for 0.5 h and tempered at 780 °C for 1.5 h were investigated by transmission electron microscopy. Except for Cr-/Cr-Fe-Co-rich M 23 C 6 , Nb-/V-/Ta-Nb-/Nd-rich MX, Fe-rich M 5 C 2 , Co-rich M 3 C and Fe-Co-rich M 6 C phases previously identified in the steel, two types of sigma phases consisting of σ-FeCr and σ-FeCrW were found to be also present in the normalized and tempered steel. Identified σ-FeCr and σ-FeCrW phases have a simple tetragonal crystal structure with estimated lattice parameters a /c = 0.8713/0.4986 and 0.9119/0.5053 nm, respectively. The compositions in atomic pct of the observed sigma phases were determined to be approximately 50Fe-50Cr for the σ-FeCr, and 30Fe-55Cr-10W in addition to a small amount of Ta, Co and Mn for the σ-FeCrW. The sigma phases in the steel exhibit various blocky morphologies, and appear to have a smaller amount compared with the dominant phases Cr-rich M 23 C 6 and Nb-/V-/Ta-Nb-rich MX of the steel. The σ-FeCr phase in the steel was found to precipitate at δ-ferrite/martensite boundaries, suggesting that δ-ferrite may rapidly induce the formation of sigma phase at δ-ferrite/martensite boundaries in high Cr F/M steels containing δ-ferrite. The formation mechanism of sigma phases in the steel is also discussed in terms of the presence of δ-ferrite, M 23 C 6 precipitation, precipitation/dissolution of M 2 X, and steel composition. [ABSTRACT FROM AUTHOR]

Purpose: In a world where the population is expected to peak at around 9 billion people in the next 30 to 40 years, carefully managing our finite natural resources is becoming critical. We must abandon the outdated 'take, make, consume and dispose' mentality and move toward a circular economy model for optimal resource efficiency. Products must be designed for reuse and remanufacturing, which would reduce significant costs in terms of energy and natural resources. Methods: To measure progress in achieving a circular economy, we need a life cycle approach that measures the social, economic and environmental impact of a product throughout its full life cycle-from raw material extraction to end-of-life (EoL) recycling or disposal. Life cycle thinking must become a key requirement for all manufacturing decisions, ensuring that the most appropriate material is chosen for the specific application, considering all aspects of a products' life. The steel industry has been developing LCI data for 20 years. This is used to assess a product's environmental performance from steel production to steel recycling at end-of-life. The steel industry has developed a methodology to show the benefits of using recycled steel to make new products. Using recycled materials also carries an embodied burden that should be considered when undertaking a full LCA. Results and discussion: The recycling methodology is in accordance with ISO 14040/44:2006 and considers the environmental burden of using steel scrap and the benefit of scrap recycling from end-of-life products. It considers the recycling of scrap into new steel as closed material loop recycling, and thus, recycling steel scrap avoids the production of primary steel. The methodology developed shows that for every 1 kg of steel scrap that is recycled at the end of the products life, a saving of 1.5 kg CO-e emissions, 13.4 MJ primary energy and 1.4 kg iron ore can be achieved. This equates to 73, 64 and 90 %, respectively, when compared to 100 % primary production. Conclusions: Incorporating this recycling methodology into a full LCA demonstrates how the steel industry is an integral part of the circular economy model which promotes zero waste; a reduction in the amount of materials used and encourages the reuse and recycling of materials. [ABSTRACT FROM AUTHOR]

To improve mechanical properties and increasing useful life of metal pieces, different methods of welding are used for repairing surface crack of metal pieces. In this research, performance of flame welding method by spraying pure iron powder evaluated for repairing surface grooves of structural steel. First, four specimens including one control specimen and other three specimens grooved specimens in depth of 1mm and in length of 12.5mm and groove width in the sizes of 0.5, 0.75 and 1mm.were prepared then, powder melted using oxyacetylene reducing flame and spraying iron powder in the flame path and attached to the inner surface of the groove and finally, the specimen repaired. Results showed that after repairing surface groove, tensile strength of the repaired specimens were reached to the tensile strength of control specimen with the margin of 2.5%. [ABSTRACT FROM AUTHOR]

Though the mechanical properties of shape-memory alloys (SMAs) make them a promising material for reinforcement in concrete structures, their electrochemical behavior in concrete environments has not previously been studied. This study investigated the influence of galvanic coupling between a nickel-titanium (Ni-Ti)–based SMA and a low-carbon steel on their corrosion performance in simulated concrete pore solution. Three measurement cells were considered: SMA alone, low-carbon steel alone, and one with the coupled SMA and carbon steel. The specimens were immersed in the chloride-free pore solution for 20 days and then 3% by weight of NaCl was added to the solution. The specimens were then kept in the chloride-contaminated solution for 70 days. The corrosion resistances of the specimens were assessed by different electrochemical measurement techniques. The results of the electrochemical experiments showed a significant increase in corrosion activity of the coupled specimens compared with that for other measurement cells. [ABSTRACT FROM AUTHOR]

The present work employs the nanoindentation technique to investigate the effect of prior martensite formation on the mechanical stability of a retained austenite matrix. It is found that the small austenite grains that were surrounded by martensite laths have higher mechanical stability than the large austenite grains that were free of martensite laths. The higher mechanical stability of small austenite grains is due to its higher amount of defects resulting from the prior martensite formation. These defects act as barriers for the later martensite formation and therefore contribute to the higher mechanical stability of small austenite grains. As a result, the present work suggests that the formation of martensite tends to stabilize the surrounding austenite matrix. Therefore, it may explain the lower transformed amount of martensite after quenching as compared to the theoretical calculation using the Koistinen and Marburger (K-M) equation. [ABSTRACT FROM AUTHOR]

The effect of final rolling temperature and cooling process on the microstructure of 1.0C-1.5Cr bearing steel was studied, and the relationship between the microstructure parameters and subsequent spheroidization annealing was analyzed. The results indicate that the increase of water-cooling rate after hot rolling and the decrease of final cooling temperature are beneficial to reducing both the pearlite interlamellar spacing and pearlite colony size. Prior austenite grain size can be reduced by decreasing the final rolling temperature and increasing the water-cooling rate. When the final rolling temperature was controlled around 1103 K (830 °C), the subsequent cooling rate was set to 10 K/s and final cooling temperature was 953 K (680 °C), the precipitation of grain boundary cementite was suppressed effectively and lots of rod-like cementite particles were observed in the microstructure. Interrupted quenching was employed to study the dissolution behavior of cementite during the austenitizing at 1073 K (800 °C). The decrease of both pearlite interlamellar spacing and pearlite colony size could facilitate the initial dissolution and fragmentation of cementite lamellae, which could shorten the spheroidization time. The fragmentation of grain boundary cementite tends to form large-size undissolved cementite particles. With the increase of austenitizing time from 20 to 300 minutes, mean diameter of undissolved cementite particles increases, indicating the cementite particle coarsening and cementite dissolution occuring simultaneously. Mean diameter of cementite particles in the final spheroidized microstructure is proportional to the mean diameter of undissolved cementite particles formed during partial austenitizing. [ABSTRACT FROM AUTHOR]

The mechanical behavior and microstructure characteristics of three high Mn austenitic steels prepared by directional solidification at withdrawal rates of 60, 120, and 240 μm s were investigated and compared with common TWIP steel with equiaxed grains. For each steel, the Hollomon analysis, differential C-J analysis, and modified C-J analysis as an alternative method to describe the work-hardening behavior were studied. The directionally solidified samples (DS samples) exhibited higher mechanical properties along the axis, five stages (A, B, C, D, and E) divided on the plot of stain hardening rate vs true strain, and a more stable and uniform deformation feature with larger strain-hardening coefficients when the true strain is over 0.25, in comparison with the common TWIP steel. The modified C-J analysis was found to be the best one for revealing the strain-hardening behavior characterized by several different stages with a definite work-hardening exponent n. In the case of DS samples, the dendrite spacings increase but the morphology becomes simple when decreasing the withdrawal rate. The larger volume fraction of twins and prevalent activation of twin systems, together with the fragmentations of the original grains in a sample solidified at a withdrawal rate of 120 μm s, lead to the best mechanical behavior in a medium-to-large strain range. [ABSTRACT FROM AUTHOR]

The effect of carbide distribution on the grain refinement in the steel for large-size bearing ring is investigated. It is observed that Ni-containing steel has an obvious grain refinement below 1050 °C, whereas its grain growth trend is steeper than that of Ni-free steel above 1050 °C. No evident segregation of Ni is observed, whereas the pinning effect of carbides distributed along grain boundaries is advantageous for the grain refinement. It is found that Ni addition could affect the type of carbides and contribute to decreasing the size of carbides via accelerating the diffusion of carbon. A stronger pinning effect with smaller carbides distributed along grain boundaries could be obtained, which is beneficial to grain refinement with Ni addition in small amounts. [ABSTRACT FROM AUTHOR]

Given that the modern world cannot be conceived without the existence of the steel and its use, the crude steel consumption may be considered as an indicator characterizing the economic development of a country. The purpose of this paper is to establish the evolution of the world, regional and state consumption of crude steel, both per total, as well as per inhabitant, but also the impact of the economic and financial crisis it had on the evolving evolution of using the crude steel. Data subject to the study are related to the period 2004 - 2014 and concern nine regions of development and ten countries. [ABSTRACT FROM AUTHOR]

In order to elucidate the impact of s phase on the oxidation film formation and stress corrosion cracking (SCC) resistance of 316L stainless steel, corrosion, SCC and three-point bending tests were conducted and the microstructures of the s phase in 316L safe-end pipes were characterized via optical microscopy, environmental scanning electron microscopy and scanning Kelvin probe force microscopy. The results indicated that the s phase was detrimental to the SCC resistance of 316L in high temperature and high pressure environments and the existence of inherently hard and brittle s phase could change the cracking mode. [ABSTRACT FROM AUTHOR]

Nano-sized SAPO-34 zeolites with high crystallinity are obtained in 10 minutes by fast heating the reaction gel in a stainless steel tubular reactor combined with the seed-assisted method, which show outstanding performance in methanol-to-olefin (MTO) reaction. [ABSTRACT FROM AUTHOR]

The paper describes experimental aspects for composite steel-concrete columns, with steel encased profile. In composite columns with HSC case, even if elastic displacement vy decreases, the value of the lateral force Hy corresponding to the vy displacement and the maximum lateral loading Hmax indicates a significant increase. Failure modes were different, characterized by sudden and violent concessions due to cracking developments through aggregate in columns with HSC, while columns with NSC shows a "slow" failure mode characterized by gradual decline of bearing capacity with the growth of the displacements. It is well known that the high strength concrete is more susceptible to fragile failure than the normal concrete, so it is, in a way, the presumed result. On the other hand, from the graphics and parameters analysis we can conclude that the columns with HSC have a higher energy absorption capacity, which can recommend this solution to the construction in seismic areas, even the failure mode was brittle. In structural terms, composite columns with concrete class C70/85 provide obvious better performances to structures, having significant increases to almost all analyzed parameters. The solution of fully encased composite column is a competitive solution for seismic and non-seismic zones, due to the excellent seismic performances (resulted from the presented experimental tests) and also because of improved fire protection. The results obtained on the columns made with high strength concrete showed improved performances, especially resistance. Due to the brittle fracture of the high strength concrete more experimental and numerical research must still be made. [ABSTRACT FROM AUTHOR]

Superaustenitic stainless steel 654SMO was used as the experimental material to investigate the effect of heating temperatures and holding times on grain growth behavior in the temperature range of 1150-1250 °C and holding time ranging from 15 to 60 min. The contour maps of grain size and grain growth rate as a function of temperatures and times were plotted. The results of this study suggest that grains grow with parabolic trend. Grain size and its growth rate increase with increasing heating temperature, the former also increases with holding time, while the latter decreases with holding time. Both grain size and grain growth rate are more sensitive to holding time than solution temperature at temperatures below 1200 °C, which is contrary to that of at temperatures above 1200 °C. The growth behavior of grains in the tested steel is illustrated by a modified mathematical model deduced on the basis of previous empirical models, and this modified grain growth model can fit well with the experimental grain growth data obtained during solution treatment. [ABSTRACT FROM AUTHOR]

On the basis of hot rolling practice, the effects of thermomechanical control process parameters on the evolution of austenite grain size before the deformation at non-recrystallization zone were investigated in detail. The inflections in the strain hardening rate versus true stress curves show that the dynamic recrystallization (DRX) has initiated for different deformation conditions studied in the present work. But the volume fractions of the equiaxed grains in the specimens which were immediately water quenched to room temperature after deformation are different from each other. Moreover, the main refinement mechanisms for different deformation conditions have been differentiated. It is interesting to note that the austenite grain size can be refined significantly with increasing the strain from 0.0 to 0.5 for different deformation temperatures. However, when the strain increases to 0.8, the austenite grain size cannot be further refined for the higher deformation temperature range, while the austenite grain size can be further refined for the lower deformation temperature range. In addition, the effect of strain rate on the austenite grain refinement is vigorous for the higher deformation temperatures. Moreover, the empirical equation to estimate the austenite grain size for different deformation parameters was established. [ABSTRACT FROM AUTHOR]

In this paper, the material parameters of the Johnson Cook material model were determined and analyzed. Then, the flow curves were obtained by thermal simulation machine during the hot compression deformation process. The experimental data over a wide range of temperatures (1173 K-1373 K), strain (0.1-0.5) and strain rates (0.001-10 s-1) were employed to evaluate the material constants of Johnson Cook constitutive models. The flow stress predicted by the Johnson Cook equation was the same as the experimental result. Afterward, the new verification testing and 3D finite element compression model was established, which showed the reliability of the constitutive equation. The finite element simulation results show that the calculated deformed shape and the compressive stress-strain curves of the specimens were consistent with the experiment. The effectiveness and feasibility of the constitutive equations in the finite element calculations were proved. The equation supplied a flow stress model for rolling simulation calculation. Then, the 3-pass vertical-horizontal hot rolling model was established by Abaqus/Explicit. The simulation results agree with the measured values of the hot strip rolling. [ABSTRACT FROM AUTHOR]

The often-reported premature failures of expansion joints of long-span steel bridges call for a better understanding of their performance in service conditions. This paper presents the long-term monitoring and analysis of displacements of expansion joints, with emphasis on the influence of viscous dampers that were installed to mitigate seismic responses of the bridges. Data from the three long-span steel bridges in China--the Sutong Bridge, the Runyang Suspension Bridge, and the Jiangyin Bridge--are compared. Decomposition of displacement signals in various frequency bands reveals that temperature-induced movements contribute to only a small portion of the total cumulative displacements. Because of the small but rapid movements caused by vehicle/wind loads, the cumulative displacements of long-span steel bridges may far exceed those caused by temperature changes. According to the monitoring data, the existence of viscous dampers may reduce the vehicle/wind-induced displacements but have no significant influence on the temperature-induced movements. Finite-element analyses are conducted to further validate the influence of viscous dampers on displacements of expansion joints. [ABSTRACT FROM AUTHOR]

Long and torsionally slender H-shaped cross sections, often used as tension members in truss bridges, can exhibit wind-induced torsional motions. These motions have produced high-cycle fatigue damage for some bridges. There is limited information available to evaluate the torsional response on the fatigue performance of themembers and connections. An in-service bridge with a documented history of wind-induced torsional motions in the verticals was instrumented to capture the wind speed and direction that induced torsional motions in the verticals. Sensors also captured the rotation angle amplitudes and numbers of cycles. Laboratory tests were conducted on a full-size replica of a vertical-and-chord connection to establish the relationship between rotation and normal stresses in the cross section from warping restraint at the connection locations. Analytical methods were shown to accurately predict the rotations and warping stresses along the member length. Applying the experimental and analytical results, the stress ranges were determined for the field-measured torsional responses, and the fatigue potential was evaluated. The results showed the measured stress ranges are near the constant amplitude fatigue limit, but the large cycle counts and frequency of events in the historical wind record that could produce torsional response indicate the need for continued monitoring and a long-term mitigation strategy. [ABSTRACT FROM AUTHOR]

The present paper investigates a metastable austenitic stainless steel under different biaxial-planar load paths by using a cruciform specimen geometry. The material behavior was described by stress–strain curves and initial yield surface. Furthermore, the hardening behavior was determined by load sequence tests. To investigate the influence of the stress state on the martensite formation a ferrite sensor as well as electron backscatter diffraction measurements were used. Two cruciform specimen geometries were utilized and compared for the considered load cases. The stress state within the cruciform specimens was evaluated by an elastic unloading procedure with subsequent calculation of the stress components. Isotropic initial yielding and non-isotropic hardening were found. A recommendation for the use of the cruciform specimen geometry with respect to the load case is given. [ABSTRACT FROM AUTHOR]

The present investigation studies the load bearing performance of stainless steel bolted connections. The austenitic stainless steel developed in China containing approximately 17% of Cr, which could be graded as EN 1.4401, has been selected for this research. In order to study the bearing strength of stainless steel bolted connections, experimental tests on 5 specimens have been conducted. In addition, complementary finite element (FE) models, which have been validated by the test results, have been adopted to analyse the effect of the key factors for bearing strength of the stainless steel bolted connections. The key factors include end distance, thickness of connecting plate, diameter of stainless steel bolt and edge distance. According to the FEA results, the loading capacity increases with the increase of the thickness of the plate and the diameter of the bolt approximate linearly. However, the end distance and edge distance have a comparatively complicated influence on the loading capacity of the connection. Based on mathematical analysis of the experimental and FEA results, a calculation method as well as its simplified form for the bearing strength of stainless steel bolted connections has been proposed. [ABSTRACT FROM AUTHOR]

The use of capacity design method (CDM) in steel plate shear wall (SPSW) structures results in large vertical boundary elements (VBEs). One way to reduce the force demands on VBEs is to employ outrigger beams in the adjacent spans of SPSW. In this paper, twelve dual SPSW-moment resisting frames are designed and analyzed by FE method to investigate the effects of outrigger system on the behavior of SPSW structures. Results show that outrigger beams can transfer considerable amount of axial force and bending moment from VBEs to the outer spans columns; resulting in smaller sections for VBEs. In addition, the most effective stories to employ outrigger beams are shown to be the stories which undergo larger drifts. Outrigger system also results in a more uniform distribution of structural stiffness along the height of SPSW frames. Furthermore, a design procedure based on the direct analysis method is proposed for the design of SPSW-Outrigger system. The procedure eliminates the excessive capacities in CDM, while satisfying all CDM requirements. [ABSTRACT FROM AUTHOR]

This paper presents pin-ended compression tests on steel equal angles. Three nominal section sizes were tested. Detailed measurements of material properties, residual stresses, and geometrical imperfections were conducted. The pin ended specimens were tested with a minimal eccentricity ofL/1,000 applied about the minor axis to cause compression at the tips of the legs. The test data are compared with the Indian specifications for hot-rolled steel structures. The section capacities obtained from the column tests are found to be between 15 and 40% higher than those calculated according to the specifications. It is concluded that there is no need to include the additional eccentricity specified in the steel structures standards accounting for the shift of the effective centroid, and that the eccentricity ofL/1,000, specified for all section classes, should be applied to slender sections only. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of technological and composition factors on the structure and quality of ordinary and quality steels for processing forged crankshaft. It is known that influencing factors which determine the properties of ordinary steels are the carbon content and the microstructure. Beside the predominant effects due to the carbon content and the microstructure, the properties of ordinary steels can be modified by the effects of the residual elements (in addition to carbon, manganese, silicon, sulfur and phosphorus that are always present). The properties of steel can be influenced by the presence of gas, particularly oxygen, nitrogen and hydrogen, as well as by the reaction products thereof. These secondary elements usually penetrate the steel from the used scrap, deoxidants or furnace environment. The gas content depends largely on the method used to melt, on the deoxidation and casting, so that the final properties of these steels depend largely on the method used in their preparation. Thus, the factors that condition the steel properties are primarily the carbon content and its microstructure, which is largely determined by the chemical composition and the subsequent final processing of forging or by the heat treatment operations. Secondly, these properties depend on the residual elements of the alloy, non-metallic inclusions and gas content of the steel, which in turn depends on the steelmaking method. [ABSTRACT FROM AUTHOR]

For some powertrain components deep penetration laser welding is considered very advantageous and prospective joining technology. Presented article focuses on heterogeneous laser welds of two widely used materials, ductile iron with pearlitic matrix (e.g. differential carrier) and Cr-Mo low alloy steel (e.g. gears). When homogeneous welds without filler wire are done, both materials show poor laser weldability, because unacceptable welding defects, mainly cracks, are created in the weld. In ductile iron, almost under all welding conditions, cracks in WM and HAZ due to brittle phases (cementite and martensite) are created. Low alloy Cr-Mo steel creates under all welding conditions solidification cracks and microcracks, caused by solidification. Even though homogenous welds of both materials are unacceptable, for heterogeneous welds possibility to create sound welds was found. By mixing of materials approximately 1:1 substantial amount of retained austenite is present in the WM, helping to suppress creation of brittle cracks and also partially suppress solidification cracks. To supress solidification cracks completely, full penetration welds and welds with V shape were used. Also use of Ni filler wire proved successful to create sound welds. The weld joint strength for heterogeneous welds for both used solutions was about 450 N/mm², which is less than BM strength, yet acceptable. Occurring phenomena connected with ration of materials mixing and its influence on WM properties, structure and behaviour is explained. [ABSTRACT FROM AUTHOR]

A literature review was performed to assess the effects of inclusions in carbon and alloy steels on their mechanical properties. Inclusions, including brittle oxides and more ductile manganese sulfides (MnS), affect fatigue endurance limit, fatigue crack propagation rate, fracture toughness, notch toughness, transverse tensile properties, and anisotropy of these properties with respect to the rolling direction. Significant property anisotropy has been documented, which needs to be taken into account in the design phases. Typical fracture morphologies and metallographic appearances of MnS-containing materials that the failure analyst will encounter are illustrated. [ABSTRACT FROM AUTHOR]

This article describes the findings of a detailed investigation into the failure of a final super heater tube in a 140 MW thermal power plant. Preliminary macroscopic examinations along with visual examination, dimensional measurement, chemical analysis, evaluation of mechanical properties, and oxide scale thickness measurement were carried out to deduce the probable cause of failure. In addition, optical microscopy was a necessary supplement to understand the cause of failure. It was concluded that the tube had failed due to stress rupture. The tube metal had been exposed to a temperature above the safe operating limit for a long duration. As a result the tube metal had lost its strength, suffered creep deformation and failed to support the working stress resulting in final rupture. The adherent scale, particularly on internal surface formed due to exposure at high temperature. It had acted as an insulating blanket in view of its much lower thermal conductivity than that of the tube metal. The progressive build-up of scale had greatly affected heat transfer and raised the tube metal temperature above A1 for a short duration before bursting of the tube. The overheating in this case may be due to poor circulation over the localized area. [ABSTRACT FROM AUTHOR]

Screw-thread steel bars made of high strength steel fractured after exposure to a constant pre-stress of 650 MPa for more than 10 h. Visual examination, chemical analysis, mechanical tests, metallographic analysis, and fractographic examination were carried out in order to determine the causes of this failure. The fracture surfaces consisted of three regions: the crack source or fracture origin region, steady-state crack growth, and unstable or final fracture region. The crack initiated at the center of the cross section and then propagated to the periphery. The fracture exhibited a brittle appearance, accompanied with secondary cracks, tear ridges, and micropores on the grain boundary. The results revealed that this failure was due to hydrogen embrittlement of the steel. [ABSTRACT FROM AUTHOR]

After approximately fifteen months of service, cracking was detected in the journal section of a 3-MW electric motor shaft used to drive a reciprocating gas compressor. A detailed failure analysis revealed sulfide inclusion and quench crack-initiated fatigue cracks. Two crack orientations were observed, axial and angular. The axial cracks are believed to be quench cracks which initiated along sulfide stringers; the angular cracks were found to be high-cycle fatigue cracks emanating from the axial cracks. Recommendations included the use of a reduced sulfur content shaft steel (0.010 wt.% max) and a pre-service non-destructive inspection to detect the presence of quench cracks or other surface imperfections. [ABSTRACT FROM AUTHOR]

In this paper, the deformation behaviors of elastic-plastic asperity on rough roll surface in a strip steel mill were simulated by a three-dimensional finite element (FE) model. The asperity characterized a sinusoidal profile and all objects in the FE model were elastic-plastic with linear strain hardening. The deformation behaviors including contact stresses, strains (including elastic and plastic strains), and contact radii of different rolling force densities and different geometrical shapes and sizes were calculated and analyzed. It revealed that the tall-thin type asperity caused larger plastic strain in the asperity itself and larger Von Mises stress in the mating roll subsurface. Long-term repeated effects of large cyclic strain and stress were liable to spark subsurface cracks and increased the risk of fatigue failure of rolls in strip rolling mills. [ABSTRACT FROM AUTHOR]

This paper describes the changes to design provisions for embedded steel reinforcement in the fib Model Code for Concrete Structures 2010. The changes introduce new coefficients for steel grade and clear spacing between bars, and extend the range of concrete strengths covered. The way in which the contribution of hooks or anchorages is calculated has been revised and the contribution of end bearing to laps and anchorages of compression bars is recognized. The revised rules represent a move away from a distinction between laps and anchorages per se towards a distinction based on the presence or absence of transverse pressure perpendicular to the bar axis within the bond length. The benefits of staggering laps with only a proportion of bars lapped at a section are also reviewed. Finally, the potential impact of lap and anchorage performance on structural robustness is discussed, and it is concluded that this can only be achieved if bar yield precedes splitting mode bond failures. [ABSTRACT FROM AUTHOR]

The material characterization of steel fibre-reinforced concrete (SFRC), which is required for its implementation in design codes, should be based on nominal properties that describe its post-cracking strength in tension. In the case of brittle and quasi-brittle materials, such as concrete, the tensile parameters are often derived indirectly. However, for materials with more ductility, such as SFRC, there is conjecture as to whether or not an indirect measure may be used to establish the stress versus crack opening displacement relationship, such as the use of a three- or four-point prism test combined with an inverse analysis. In this paper a simple and efficient inverse analysis technique is developed and shown to compare well with data obtained from direct tension tests. Furthermore, the methodology proposed by the fib Model Code for Concrete Structures 2010 has been investigated and recommendations made to improve its accuracy. [ABSTRACT FROM AUTHOR]

A Mo2NiB2 cermet coating on steel substrate was fabricated by laser cladding technique. The laser cladding samples were subjected to various microstructure examinations, hardness, and wear and corrosion tests. The results showed that a continuous, dense and adherent laser‐clad coating was formed on the steel substrate. The coating consisted of γ‐(Fe, Ni) as a metallic matrix binder and Mo2NiB2 particles as a reinforced phase distributed uniformly in the microstructure. Average hardness of the coating up to 700 HV was significantly higher than that of the matrix 150 HV. The coating exhibited a dry‐sliding wear resistance that was increased by about 6 times relative to the steel substrate. Extensive pits formation on the surface and through the inner part had taken place for 304 stainless steel, while it disappeared in the coating. A novel method to synthesize Mo2NiB2 boride cermet coating on Q235 steel substrate, consisting of Mo2NiB2‐type ternary boride as a reinforced phase and a γ‐(Fe, Ni) base binder, is realized with laser cladding technique. The wear resistance of the Q235 substrate is greatly improved. As compared to 304 stainless steel, lower corrosion rate is obtained for the coating and pitting corrosion disappeare in particular. [ABSTRACT FROM AUTHOR]