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This study aims at investigating the effect of bolt hole-making processes on the post-fire behavior of S235 steel plates.

A total of nine steel plates with a single bolt hole are tested. The single bolt holes are fabricated using three different hole-making processes: drilling, waterjet and plasma. Among the nine steel plates, three fabricated specimens are control specimens and are tested at ambient temperature. The six remaining steel plates with a single bolt hole are subjected to a complete heating-cooling cycle and then monotonically loaded until failure. The six fabricated specimens are first heated up to two different temperatures 800 and 925 °C, and then cooled back to the ambient prior to loading.

The results show that after being exposed to post-fire temperatures (800 and 925 °C), the maximum decrease in strength of the S235 steel plate was 6% (at 925 °C), 14% (at 925 °C) and 22% (at 800 °C) when compared to the results of ambient specimens for waterjet, drilled and plasma bolt holes, respectively. For post-fire temperature tests, drilled and waterjet bolt hole-making processes result in having approximately the same load-displacement response, and both have larger strength and ductility than those obtained using plasma cutting.

This study provides preliminary data to guide the steel designers and fabricators in choosing the most suitable hole-making process for fire applications and to quantify the post-fire reduction in capacity of S235 plates.

This paper aims to investigate the effect of characteristic parameters of pits on the mechanical properties and fracture model of cable steel wires.

The tensile test and finite element analysis of steel wires with corrosion damage were carried out. The stress development of corroded steel wire under corrosion morphology was studied by the 3D reverse reconstruction technology. The internal relationship between the stress triaxiality, equivalent plastic strain and pit depth, depth-width ratio of corroded steel wire was discussed.

With the increase of corrosion degree, the neck shrinkage phenomenon of steel wire was not significant, and the crack originated near the pit bottom and expanded to the section inside of specimen. The fiber area of corroded steel wire decreased while the radiation area increased, and the ductile fracture gradually changed to brittle fracture. The pit size significantly changed the triaxial degree and distribution of stress and accelerated the initiation and propagation of internal cracks at the neck shrinkage stage.

The proposed fracture model based on the void growth model could accurately simulate the fracture behavior of steel wires with corrosion damage.

The combination of an Engineered Cementitious Composite (ECC) layer and steel plate to reinforce RC beams (ESRB) is a new strengthening method. The ESRB was proposed based on the steel plate at the bottom of RC beams, aiming to solve the problem of over-reinforced RC beams and improve the bearing capacity of RC beams without affecting their ductility.

In this paper, the finite element model of ESRB was established by ABAQUS. The results were compared with the experimental results of ESRB in previous studies and the reliability of the finite element model was verified. On this basis, parameters such as the width of the steel plate, thickness of the ECC layer, damage degree of the original beam and cross-sectional area of longitudinal tensile rebar were analyzed by the verified finite element model. Based on the load–deflection curve of ESRB, ESRB was discussed in terms of ultimate bearing capacity and ductility.

The results demonstrate that when the width of the steel plate increases, the ultimate load of ESRB increases to 133.22 kN by 11.58% as well as the ductility index increases to 2.39. With the increase of the damage degree of the original beam, the ultimate load of ESRB decreases by 23.7%–91.09 kN and the ductility index decreases to 1.90. With the enhancement of the cross-sectional area of longitudinal tensile rebar, the ultimate bearing capacity of ESRB increases to 126.75 kN by 6.2% and the ductility index elevates to 2.30. Finally, a calculation model for predicting the flexural capacity of ESRB is proposed. The calculated results of the model are in line with the experimental results.

Based on the comparative analysis of the test results and numerical simulation results of 11 test beams, this investigation verified the accuracy and reliability of the finite element simulation from the aspects of load–deflection curve, characteristic load and failure mode. Furthermore, based on load–deflection curve, the effects of steel plate width, ECC layer thickness, damage degree of the original beam and cross-sectional area of longitudinal tensile rebar on the ultimate bearing capacity and ductility of ESRB were discussed. Finally, a simplified method was put forward to further verify the effectiveness of ESRB through analytical calculation.

This study aims to report the oxidation behaviors of the T91 ferritic/martensitic steel (T91 steel) and 304 austenitic stainless steel (304 steel) in supercritical water (SCW) at 600°C.

The microstructure, elemental distribution and phase structure of the oxidation layers derived from the corrosion of the T91 steel and 304 steel were analyzed by scanning electron microscopy, Oxford Instrument X-ray spectroscopy, electron scattered diffraction and transmission electron microscopy.

The oxidation layers on the T91 steel and 304 steel have duplex structure. The two steels all suffer internal oxidation, and the phase of the internal oxidation layers are indexed as Fe-Cr spinel, although their morphologies are different. The formation of a continuous Cr-rich layer is not detected because of the relatively low Cr content of the steels, which is attributed to the corrosion property.

The accelerated corrosion and corrosion mechanism of the T91 steel and 304 steel with low Cr occurring in SCW at 600°C was clarified.

When the reinforced concrete beams are reinforced by bonding steel plates to the bottom, excessive use of steel plates will make the reinforced concrete beams become super-reinforced beams, and there are security risks in the actual use of super-reinforced beams. In order to avoid the occurrence of this situation, the purpose of this paper is to study the calculation method of the maximum number of bonded steel plates to reinforce reinforced concrete beams.

First of all, when establishing the limit failure state of the reinforced member, this paper comprehensively considers the role of the tensile steel bar and steel plate and takes the load effect before reinforcement as the negative contribution of the maximum number of bonded steel plates that can be used for reinforcement. Through the definition of the equivalent tensile strength, equivalent elastic modulus and equivalent yield strain of the tensile steel bar and steel plate, a method to determine the relative limit compression zone height of the reinforced member is obtained. Second, based on the maximum ratio of (reinforcement + steel plate), the relative limit compression zone height and the equivalent tensile strength of the tensile steel bar and steel plate of the reinforced member, the calculation method of the maximum number of bonded steel plates is derived. Then, the static load test of the test beam is carried out and the corresponding numerical model is established, and the reliability of the numerical model is verified by comparison. Finally, the accuracy of the calculation method of the maximum number of bonded steel plates is proved by the numerical model.

The numerical simulation results show that when the steel plate width is 800 mm and the thickness is 1–4 mm, the reinforced concrete beam has a delayed yield platform when it reaches the limit state, and the failure mode conforms to the basic stress characteristics of the balanced-reinforced beam. When the steel plate thickness is 5–8 mm, the sudden failure occurs without obvious warning when the reinforced concrete beam reaches the limit state. The failure mode conforms to the basic mechanical characteristics of the super-reinforced beam failure, and the bending moment of the beam failure depends only on the compressive strength of the concrete. The results of the calculation and analysis show that the maximum number of bonded steel plates for reinforced concrete beams in this experiment is 3,487 mm². When the width of the steel plate is 800 mm, the maximum thickness of the steel plate can be 4.36 mm. That is, when the thickness of the steel plate, the reinforced concrete beam is still the balanced-reinforced beam. When the thickness of the steel plate, the reinforced concrete beam will become a super-reinforced beam after reinforcement. The calculation results are in good agreement with the numerical simulation results, which proves the accuracy of the calculation method.

This paper presents a method for calculating the maximum number of steel plates attached to the bottom of reinforced concrete beams. First, based on the experimental research, the failure mode of reinforced concrete beams with different number of steel plates is simulated by the numerical model, and then the result of the calculation method is compared with the result of the numerical simulation to ensure the accuracy of the calculation method of the maximum number of bonded steel plates. And the study does not require a large number of experimental samples, which has a certain economy. The research result can be used to control the number of steel plates in similar reinforcement designs.

Polyurethane concrete (PUC), as a new type of steel bridge deck paving material, the bond-slip pattern at the interface with the steel plate is not yet clear. In this study, the mechanical properties of the PUC and steel plate interface under the coupled action of temperature, normal force and tangential force were explored through shear tests and numerical simulations. An analytical model for bond-slip at the PUC/steel plate interface and a predictive model for the shear strength of the PUC/steel plate interface were developed.

The new shear test device designed in this paper overcomes the defect that the traditional oblique shear test cannot test the interface shear performance under the condition of fixed normal force. The universal testing machine (UTM) test machine was used to adjust the test temperature conditions. Combined with the results of the bond-slip test, the finite element simulation of the interface is completed by using the COHENSIVE unit to analyze the local stress distribution characteristics of the interface. The use of variance-based uncertainty analysis guaranteed the validity of the simulation.

The shear strength (τ_f) at the PUC-plate interface was negatively correlated with temperature while it was positively correlated with normal stress. The effect of temperature on the shear properties was more significant than that of normal stress. The slip corresponding to the maximum shear (D₁) positively correlates with both temperature and normal stress. The interfacial shear ductility improves with increasing temperature.

Based on the PUC bond-slip measured curves, the relationship between bond stress and slip at different stages was analyzed, and the bond-slip analytical model at different stages was established; the model was defined by key parameters such as elastic ultimate shear stress τ₀, peak stress τ_f and interface fracture energy G_f.

Identification of the critical process conditions that enhance Cu diffusion in ferrite grain boundaries and promote precipitation of Cu-rich particles in the proximity of steel semi-finished products surface is crucial for every steel maker as it leads to the creation of hot shortness cracks in final products deteriorating surface condition. The purpose of this paper is to reveal the possible effect of Cu segregation in the metal/oxide interface, its role in surface crack initiation and, finally, to propose actions to prevent from hot shortness issues throughout the production chain of steel products.

The here presented study was based on S355 steel plate production starting from re-melting of scrap in an EAF, followed by metallurgical treatment in a Ladle Furnace, continuous casting, re-heating (RH) and thermo-mechanical rolling in a reversing mill. For the purposes of this study, more than ten heats, 100 t of steel each, were analyzed. Here presented are depicted steels in the high and low end of the permitted Cu-wt-% spectrum, 0.4 wt-% Cu (0.15 wt-% C, 1.1 wt-% Mn, VTi micro-alloyed steel) and 0.25 wt-% Cu (0.09 wt-% C, 1.2 wt-% Mn, NbTi micro alloyed steel), respectively.

Although Cu levels of 0.25-0.40 wt-% are well below the Cu solubility in austenite and ferrite (8 percent wt-% and 3 wt-% Cu, respectively) and within specifications, precipitation of Cu-rich particles is observed in industrial semi-finished and/or final products. Cu-rich precipitates and Cu segregation along grain boundaries near the steel surface lead to hot shortness cracks in industrial products.

Hot shortness surface defects related to Cu presence in steel having significantly lower Cu amounts than its maximum solubility in austenite and ferrite does not make sense in first place. Correctly, Cu is expected to remain in solid solution. Identification of Cu-rich particles is explained on the basis of the development of double diffusion actions: interstitial diffusion of carbon (decarburization) and substitution diffusion of copper. Root cause analysis and reliable countermeasures will save financial and material resources during steel production.

Automobile scrap re-melting results in noticeable Cu amounts in EAF produced steel. Presence of Cu-rich particles in grain boundaries near the surface of intermediate or final products deteriorates surface quality through relevant surface defects. Identification of Cu-rich particles is explained on the basis of the development of double diffusion actions: interstitial diffusion of carbon and substitution diffusion of copper. Pre condition for metallic Cu precipitation in ferrite is the Cu amount to be above 3 wt-%, which is ten times higher than the usual permitted Cu amount in such steel grades. This pre-condition is met through austenite oxidation during RH.

The purpose of this paper is to study the corrosion of the coupling of two different types of stainless steel, austenitic and ferritic, used in the fabrication of water reservoirs in the solar energy industry.

Potentiodynamic polarization and gravimetric immersion tests were used to evaluate corrosion of the coupling of two different types of stainless steel, austenitic and ferritic.

The galvanic corrosion was not significant in the case of the coupling of AISI 304 and 444 steels. The difference of the open circuit potentials obtained for the AISI 304 and AISI 444 steels was 28 mV for the polished samples. The galvanic current density (i_g) was 55 nA/cm². The corrosion observed in the stainless steel couple was in the weld area.

The methodology used is adequate to evaluate generalized galvanic corrosion. The problem of the corrosion in the coupling of the stainless steels is a problem of localized corrosion and the observed 28 mV potential difference was lower than the dispersion of results usually obtained from readings of corrosion potentials in electrochemical cells.

The use of two different types of steel in contact with each other may lead to galvanic corrosion, and the welding of steel pieces may lead to several corrosion problems. Since the boiler may be used in different countries, subject to a great diversity of water quality, corrosion may be a significant problem.

Literature data of the AISI 444 steel corrosion behaviour are still scarce. The coupling of two different stainless steels (AISI 304 and 444) in the water reservoir manufacturing was a necessary requirement of the solar energy industry. The manufacturers of boilers must evaluate and quantify the corrosion processes, which occur in the equipment used in the solar energy industry. As the solar energy industry has matured in the last ten years, the corrosion of this equipment may be a significant problem in due course.

States that duplex (austenitic/ferritic) stainless steels offer properties of interest and a cost‐effective material selection solution for plant and equipment in the pulp and paper industry. Reviews characteristics of duplex steels leading to successful long‐term applications of 22 Cr duplex and a copper containing 25 Cr super duplex stainless steel. Concludes that, applied correctly, two‐phase stainless steels can provide long‐term reliable maintenance‐free service in many pulp and paper plant environments.