Clad Plate Research Articles

Thermomechanical Coupling Model for a Stainless Steel-Clad Plate on Heat Treatment

Quick and correct prediction of the internal stress and deformation of stainless steel-clad plates on heat treatment is a problem of specific interest. A thermomechanical coupling model based on the engineering elastic-plastic theory is detailed. The discretization method and difference equations used simultaneously provide effective numerical calculations for the model. The generalized finite element model verifies relevant simplification conditions and efficiency of the numerical calculation logic. Heat treatment experiments of clad plates are also designed and presented, and the ability of the model to predict the stress and deformation behavior of the clad plate in the actual heat treatment process is evaluated. The calculation logic of the model is reasonable, and the prediction error of deformation and internal stress of the plate is ~15%. The model exhibits an extremely high computational efficiency and can meet the requirements of on-line analysis for heat treatment processes.

Effect of hot rolling on microstructure and properties of high-chromium cast iron hardfacing cladding plate

In this study, a high-chromium cast iron (HCCI) material hardfacing on a low-carbon steel (LCS) plate is fabricated into a symmetrical sandwich structure, which is subjected to multi-pass hot rolling on a rolling mill at a reduction of 15%, 25%, and 35%. The effects of different rolling reductions on the microstructure (interface and HCCI layer) and mechanical properties (bonding strength, hardness, and wear resistance) of the composite sheets are studied. Results show that the cracks in the hardfacing layer disappear. HCCI and LCS exhibit coordinated thermal deformation, and the shape of the composite plate after hot rolling is good without warpage. HCCI/LCS composite panels are successfully prepared. As the rolling reduction increases, the microstructure defects at the original bonding interface are eliminated. Moreover, a carbide-free zone and intergrowth are observed, and the bonding strength increases. Hot rolling results in the breakdown of a eutectic carbide chain network of hardfacing HCCI cast iron layer and the dispersion distribution of carbides. The precipitation of secondary carbides is observed in the HCCI layer after hot rolling at 35%, which results in increased hardness of HCCI.

Meso and microscale clad interface characteristics of hot-rolled stainless steel clad plate

Stainless steel clad plate containing corrosion-resistant 304 stainless steel cladding and Q235 carbon steel substrate has been successfully fabricated by vacuum hot rolling at 1150 °C. The interface characteristics, microstructure, alloy element distribution and precipitation phases of clad plate were investigated by SEM, EPMA and TEM analysis in detail. Due to the carbon element diffusion, a decarburized layer (60–80 μm) and a carburized layer (20–40 μm) were formed at the carbon steel substrate and stainless steel cladding beside the interface, respectively. The uphill diffusion and interface peak value of carbon element are attributed to the differences in the diffusion velocity and solubility of carbon element in the substrate and cladding. Concentration gradient and diffusion coefficient between Cr and Ni elements are different, leading to different diffusion distances. Meanwhile, the grain boundaries of carburized layer were surrounded by Cr23C6 particles. The interface with a thickness of 300–400 nm contains refined grains accompanying with many Cr23C6 and MnSi2O4, SiO2 particles. The sufficient alloy element diffusion behavior and interface oxides, precipitation phases lead to a high interface bonding shear strength (389 MPa).

Effect of hot rolling and cooling process on microstructure and properties of 2205/Q235 clad plate

The 2205/Q235 clad plate was fabricated by vacuum hot rolling with symmetrical assembling pattern of Q235/2205/2205/Q235. The flow stress behavior and processing map of 2205 duplex stainless steel (DSS) were investigated by hot compressive tests on a Gleeble-3800 simulator. Then, thermal–mechanical coupled nonlinear finite element models of vacuum hot rolling and subsequent cooling process were established. From the simulation results, the influence of rolling reduction and rolling speed on hot deformation state of 2205 DSS in the assembled slab was disclosed and the optimal rolling parameters were presented. Meanwhile, the cooling rate of 2205 DSS under different cooling conditions and thicknesses of the clad plate was obtained. According to the numerical simulation results, pilot experiments were successfully carried out on a laboratory scale. The material universal testing machine, optical microscope, scanning electron microscope and energy-dispersive spectrometer were used to evaluate the mechanical properties and microstructure of bonding interface and 2205 DSS matrix for different rolling reduction and cooling processes. The results showed that with symmetrical assembling pattern, the approximate thermodynamic conditions can be established for 2205 DSS to avoid cracks in hot rolling process. When the rolling reduction increased from 10 to 40%, the shear strength of the bonding interface is increased from 120 to 530 MPa, and the uniform two-phase microstructure of 2205 DSS and satisfactory mechanical properties can be obtained with cooling rate higher than 10 °C/s between 1050 and 500 °C after rolling.

The Determining Role of Nb Interlayer on Interfacial Microstructure and Mechanical Properties of Ti/Steel Clad Plate by Vacuum Rolling Cladding.

We elucidate here the determining role of Nb interlayer on mechanical properties of Ti/steel clad plate fabricated by vacuum rolling cladding (VRC) as a function of different heating temperatures. A critical analysis on the clad interface via electron probe micro-analyzer, X-ray diffractometer and shear testing were conducted to investigate the influence of TiC, Fe-Nb and TiFe compounds and Nb-Ti solid solution on microstructural evolution and shear properties of Ti/steel clad plate. The inter-diffusion between Ti, C and Fe was effectively restrained by adding the Nb interlayer at heating temperature of 800 °C, and average shear strength of 279 MPa was achieved. With increase of heating temperature, Nb-Ti solid solution was formed at the Ti/Nb interface, which reduced mechanical properties of clad plate at 900 °C. At 1000 °C, TiC and Nb-Fe compounds and Nb-Ti solid solution were formed at the interface, and minimum average shear strength of 152 MPa was achieved. The detailed analysis on the clad interface suggested that ideal shear strength can be obtained through the addition of Nb interlayer and selecting appropriate heating temperature.

High‐performance Cu/Al laminated composites fabricated by horizontal twin‐roll casting

AbstractHorizontal twin‐roll casting technology was successfully introduced to produce high‐performance copper/aluminum (Cu/Al) laminated composites. The interface morphology, electrical properties and peeling strength after different annealing and cold rolling processes were investigated and contrasted with Cu/Al clad plates fabricated by conventional methods. The results show that sound metallurgical bonding between the copper and aluminum matrix can be attained after the horizontal twin‐roll casting processes and Al2Cu is the only intermetallics at the interfacial region, the thickness of interfacial interlayer is about 0.7 μm. The peeling strength is 31.4 N/mm and can be further increased to 37.1 N/mm after annealing at 250 °C. However, higher temperature like 400 °C will cause the excessive growth of intermetallics so that peeling strength sharply decreases to 9.2 N/mm. Electrical conductivity of the clad plate is 51 MS/m. At the same electrical current intensity, the temperature‐rise of the composite plate is between the pure copper plate and the aluminum plate, and closer to the copper plate. All of the properties are outstanding than that of Cu/Al clad plate fabricated by conventional methods.

Study on the Microstructures and Properties of 904L Super Austenitic Stainless Steel Rolled Clad Plate

The microstructures and properties of 904L super austenitic stainless steel rolled clad plate were studied. The microstructures and properties of base metal and welding joint of 904L rolled clad plates were studied and analyzed by means of optical microscope, intergranular corrosion and electrochemical methods. The results showed that the clad plate had a good compound effect, and the tensile, bending, shear and impact properties of the base material and welding joint meet the standard requirements. Besides, the intergranular corrosion and electrochemical analysis showed that the base metal and welding joints of 904L had good corrosion resisting properties for the high self-corrosion potential and electrochemical impedance.

Production of Clad Metals Using the Melts-Kiss Method

The melts-kiss method is proposed for producing clad metals made of aluminum alloys via casting. In this method, a molten metal is solidified by another molten metal. AA1050 and A383 alloys were used in experiments. The interface between the two aluminum alloys was clear. The width of the diffusion area of Si was very narrow. The two aluminum alloys were strongly bonded. The melts-kiss method can be adapted for semi-continuous casters to cast clad plates.

Study on Interface Structure of Cu/Al Clad Plates by Roll Casting

Large scale Atomic/Molecular dynamic Parallel Simulator (LAMMPS) molecular dynamics simulation software was used to simulate the copper and aluminum atom diffusion and changes of interface during heating and cooling process of copper and aluminum composite panels. The structures of the interface were characterized through scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM), and the mechanical properties were also tested. The simulation results show that the diffusion rate of copper atom is higher than that of aluminum atom, and that the CuAl2 radial distribution function of the interface at 300 K is consistent with that of pure CuAl2 at room temperature. At 930 K, t = 50 ps Cu atoms spread at a distance of approximately four Al lattice constants around the Al layer, and Al atoms spread to about half a lattice constant distance to the Cu layer. The experimental results show that the thickness of the interface in copper–aluminum composite plate is about 1 μm, and only one kind of CuAl2 with tetragonal phase structure is generated in the interface, which corresponds with the result of molecular dynamics simulation.

Fabrication of a thick copper-stainless steel clad plate for nuclear fusion equipment by explosive welding

TU1/316 l clad plates with a high thickness are used in nuclear fusion equipment as coil terminals. The technical specifications of clad plates for nuclear fusion equipment, such as the composite ratio, tensile strength, shear strength and scale of the interfacial wave, are significantly higher than those of clad plates for conventional applications. It is difficult to produce high-quality clad plates through explosive welding experiments alone. To manufacture high-quality TU1/316 L clad plates, the technical parameters of the explosive welding process were obtained and optimized by theoretical analysis and numerical calculations. A procedure for fabricating explosion bonded TU1/316 L clad plates was successfully determined through the combination of numerical calculations and experiments, and the bimetallic plates were used to manufacture international thermonuclear experimental reactor (ITER) components.

Effect of interfacial compounds on mechanical properties of titanium–steel vacuum roll-cladding plates

ABSTRACTThe titanium–steel clad plates were prepared by vacuum roll cladding. Ti–Fe compounds and TiC were observed at different cooling rates after rolling. Optical microscopy, electron microprobe analyser, X-ray diffraction and shear test studies were carried out to study the effect of Ti–Fe compounds and TiC on the ultimate microstructure and mechanical properties of titanium–steel clad plates. At a cooling rate of 6.2°C/min, TiC and Ti–Fe compounds seriously impacted the mechanical properties of the clad plate. At a cooling rate of 1.8°C/min, the thickness of the TiC layer was optimal much that the maximum shear strength of 296 MPa was obtained. At a cooling rate of 0.6°C/min, the thickness of the TiC layer was relatively thick, which affected the mechanical properties of clad plates.

Interface characteristics and fracture behavior of hot rolled stainless steel clad plates with different vacuum degrees

In order to investigate the effect of vacuum degree on the interface microstructure and mechanical properties of stainless steel clad plate, series of 316L/Q235 clad plates were successfully fabricated by hot rolling with different vacuum degrees of 105 Pa, 400 Pa, 10 Pa, 10−1 Pa and 10−2 Pa. Interestingly, with the increase of vacuum degree, the interface oxides distribution changed from continuous wall/film to dispersed refined particles, and the thicknesses of martensite layer, decarburized layer and carburized layer were gradually increased. Meanwhile, the interface bonding strength of clad plates can be effectively enhanced by improving the vacuum degree. Due to thin decarburized and carburized layers, the stainless steel clad plate with a low vacuum degree of 105 Pa reveals superior yield strength and ultimate strength, while a low fracture elongation was obtained due to severe interface delamination. However, the stainless steel clad plate with a high vacuum degree can obtain a superior tensile ductility, which is attributed to the strong interface and localized necking delaying effect.

The Impact of Surface Treatment and Degree of Vacuum on the Interface and Mechanical Properties of Stainless Steel Clad Plate.

In this study, the impact of different surface treatment and degree of vacuum on the interface and mechanical properties of 304/Q345 stainless steel clad plate was investigated. The study indicated that more continuous or aggregated Al2O3 and Si-Mn composite oxides were formed at the interface after brush grinding. However, less inclusions such as Al2O3, MnS and Ca-Mg-Al-Si composite oxides were formed at the interface after pickling treatment. For the vacuum degrees of 10−2 Pa, 1 Pa and 105 Pa, the oxidation reaction became more intense with the decrease in vacuum degree. The interface inclusions were gradually changed from Al2O3 and Si-Mn complex oxides to oxide scale and MnCr2O4 spinel oxide. The interfacial bonding strength of stainless steel clad plate was improved with the increase in degree of vacuum. The bonding strength was 55 MPa at vacuum of 105 Pa, but it was 484 MPa at vacuum of 10−2 Pa, which is far greater than that of the national standard, and an excellent performance was obtained.

Effect of Reduction on Bonding Interface of Hot-rolled Wear-resistant Steel BTW1/Q345R Cladding Plate

Wear-resistant cladding plates consisting of a substrate (Q345R) and a clad layer (BTW1) were bonded through hot rolling at the temperature of 1 200 °C and a rolling speed of 0.5 m/s. The microhardness of the cladding plate was also tested after being heat treated. The microstructure evolution on the interface of BTW1/Q345R sheets under various reduction rates was investigated with a scanning electron microscope (SEM) and EBSD. It is found that the micro-cracks and oxide films on the interface disappear when the reduction is 80%, whereas the maximum uniform diffusion distance reaches 10 μm. As a result, a wide range of metallurgical bonding layers forms, which indicates an improved combination between the BTW1 and the Q345R. Additionally, it is discovered that the unbroken oxide films on the interface are composed of Mn, Si or Cr at the reductions of 50% and 65%. The SEM fractography of tensile specimen demonstrates that the BTW1 has significant dimple characteristics and possesses lower-sized dimples with the increment in reduction, suggesting that the toughness and bonding strength of the cladding plates would be improved by the increase of reduction. The results reveal that a high rolling reduction causes the interfacial oxide film broken and further forms a higher-sized composite metallurgical bonding interface. The peak microhardness is achieved near the interface.

Interlayer engineering for titanium clad steel by hot roll bonding

Hot roll bonding was carried out between commercially pure titanium TA2 and high-strength low-alloy steel Q390 using pure Nb or Mo interlayer at 950 °C with a total reduction ratio of 86.7%. Interfacial microstructure and bonding properties of titanium clad steel plates were investigated by electron microscopy and mechanical tests. The results showed β-Ti, TiC and Fe2Ti reaction phases were generated at Ti/steel interface for the clad plates with no interlayer. Inserting Nb or Mo interlayer can effectively suppress the formation of brittle phases, while the weak bonding joint transferred to Nb/steel or Mo/steel interface. And some micro-voids were found at the interface of Nb/steel and Mo/steel. The improved shear strength of clad plates with Nb interlayer might be attributed to the elimination of brittle phases at bonding interface. The small size and little quantities of the micro-voids at Nb/steel interface had a relatively weak effect on shear strength. However, the large number and big size of micro-voids were responsible for the degradation of shear strength for the clad plates with Mo interlayer.

Effect of Rolling Reduction Rate on the Microstructure of Hot Rolling Stainless Steel Clad Plate

The macro-scale and meso-scale simulation models of stainless steel clad plate were established by DEFORM-3D. The multi-scale coupling simulations of clad plate with different rolling parameters were carried out. The seven pass hot rolling process of stainless steel clad plate was simulated by numerical simulation. By contrasting the vertical stress and the deformation resistance of cladding layer, the rolling reduction rate satisfying interface bonding was obtained. The grain distribution at the center of the substrate layer was analyzed and reasonable hot rolling reduction rates were selected considering their effects on the recrystallization volume percent and the grain size. The results show that the grain size decreases with the increase of reduction rate. However, too much reduction rate will decrease the rate of recrystallization volume percent and the refining effect of grain is not obvious. To ensure uniform grain size distribution, it is most reasonable to set the rolling temperature to 1150°C and the reduction rate to 50%.

Microstructure, mechanical properties and interface bonding mechanism of hot-rolled stainless steel clad plates at different rolling reduction ratios

The microstructure, interfacial characteristics, shear behavior, tensile properties and fracture morphologies of stainless steel clad plates fabricated by vacuum hot rolling at different rolling reduction ratios of 20%, 40%, 70%, 90% and 93.75% are investigated using optical microscope (OM), ultra-depth microscope, scanning electron microscope (SEM), electron probe microanalysis (EPMA) and universal testing in detail. With the increasing rolling reduction ratio, the refinement degree of microstructure is increased, while the thicknesses of interface alloy element diffusion zones including the decarburized, carburized layers and martensite zone are decreased. Due to the different interface bonding status, the shear fracture of clad plate rolled at a low reduction ratio of 40% is located at interface, while clad plates with high reduction ratios of 70% and 90% fracture at the decarburized layers. Therefore, interface shear strength is sharply and then slightly increased. Moreover, the interface bonding strength, tensile strength and interface deformation coordination are increased, while fracture elongation is increased firstly and then decreased with the increasing rolling reduction ratio, which are attributed to the competing mechanisms of grain refinement, work hardening, interface strengthening and intergranular cracks of carburized layer. Overall, the interfacial bonding mechanism can be related to the Mn-Si oxide inclusions rupture, alloying elements diffusion, phase transition and severe plastic deformation at high rolling temperature.

Microstructures and properties of roll-bonded stainless /medium carbon steel clad plates

A 304 stainless steel/medium carbon steel clad plate was fabricated by hot-rolling in an argon atmosphere. The interfacial microstructures of the clad plates were observed by SEM, and the carbide phases were identified by XRD and TEM. The effect of the rolling parameters on the shear strength and composition diffusion was analyzed. The results show that a sensitization region appears in the stainless steel side and a decarburization region is present in the carbon steel side. The sensitization region is composed of a dual structure, ditch and full-depletion of chromium zones. The precipitates in the stainless steel side are Chromium-rich M23C6 carbides.

Interfacial microstructure and mechanical properties of stainless steel clad plate prepared by vacuum hot rolling

A stainless steel clad plate composed of stainless steel and carbon steel was prepared by vacuum hot rolling process, and its microstructure, especially the bonding interface, was evaluated using an optical microscope, a scanning electron microscope and a transmission electron microscope (TEM). The corresponding mechanical properties were also assessed by means of hardness and shear tests. The results showed a bonding interface formed between stainless steel and carbon steel, which was relatively straight in macroscope but serrated in microscope. Decarburization layer and carbon-enriched layer were distinguished at the side of carbon steel and stainless steel near the interface, respectively, which should be related to diffusion of carbon and alloying elements. The carbon-enriched layer could also be identified as a recombination region, whose microstructure was mainly recognized as martensite by TEM. Consequently, the hardness was the highest at this region. Furthermore, the result of shear test at the bonding interface showed that the shear strength was 395 MPa and the fracture mode was dominated as ductile fracture, indicating the bonding interface with good quality.

Microstructure and mechanical properties of hot rolled stainless steel clad plate by heat treatment

Series of stainless steel clad plates were heat treated at the quenching temperatures ranging from 900 °C to 1150 °C for holding time of 6min and 60min, respectively. It was observed that the ferrite and pearlite phases in the hot-rolled carbon steel substrate changed into lath martensite and needle-like ferrite through quenching treatment. The carburized layer thickness was gradually decreased till disappeared, and the interfacial shear strength was firstly increased and then decreased with the increasing quenching temperature, which was attributed to the sufficient alloy element diffusion and matrix softening at the high quenching temperature. At the quenching time of 6min, the shear fracture zone transmitted from the interface into the decarburized layer with the increasing quenching temperature, and the severe interfacial delamination cracks all existed at the clad interface. However, the main shear cracks were all presented at the decarburized layer for the quenching time of 60min, and there were no interfacial delamination cracks in the tensile samples, revealing that strong interface can be obtained by prolonging quenching time. The tensile behavior and fracture characteristics showed the ductile-brittle transition with the increasing quenching temperature.