Steel Clad Plate Research Articles

Microstructures and mechanical properties of stainless steel clad plate joint with diverse filler metals

Thick stainless steel clad plate is used widely in the petroleum and petrochemical industries because of its low cost and good corrosion resistance. It is generally welded by the multilayer and multipass welding process with stainless steel filler metal matched with the clad layer. In this research, the base metal of stainless steel clad plates was filled with carbon steel filler metal, and the microstructures and mechanical properties of joints with diverse filler metals were analysed and compared. The results indicate that a local hardening zone (LHZ) forms in the weld filled with the filler metals of stainless steel and carbon steel because of the formation of martensite phase in the first layer of weld with filler metal of carbon steel. The microhardness value in LHZ reaches up to 425 HV1, which is significantly higher than that of the base metal. However, the tensile strength value of joints filled with carbon steel filler metal is equivalent to that of the joints with stainless steel filler metal. The results of the side bending test indicate that the LHZ protrudes from the weld, and the crack occurs near the LHZ if the area of the LHZ on the cross section of joint is larger than 17 % of that of the whole cross section of the joint. The studied results show that it is feasible to use carbon steel filler metal to fill the base metal of carbon steel in welding of stainless steel clad plate.

Effect of Interlayers on Microstructure and Properties of 2205/Q235B Duplex Stainless Steel Clad Plate

In this research, 2205/Q235B clad plates were prepared by a vacuum hot rolling composite process. The effects of adding Fe, Ni, and Nb interlayers on the bonding interface structures and the shear strengths of the clad steel plates were studied. The results showed that 2205 duplex stainless steel and the three interlayers produced a large amount of plastic deformation and low-angle boundaries, and the main structures were the recrystallized and deformed grains. There were many recrystallized grains in the microstructure of the Q235B low-carbon steel due to the low deformation in the rolling process. The Fe interlayer had better wettability with the two kinds of steel, but the lower strength led to the reduction of shear strength by about 14 MPa compared with the original clad steel plate. The C element in the Q235B low-carbon steel easily diffused into the Fe interlayer, and the clad steel plate attained a poor corrosion resistance because a large decarburization area was formed. The Nb interlayer reacted with the Mo element in the 2205 duplex stainless steel to form an Nb–Mo binary alloy, which generated long-banded ferrite. The decarburization area was also produced because the Nb reacted with the C element in the Q235B to form hard and brittle NbCx. As a result, the shear strength was significantly reduced by about 282 MPa, and the corrosion resistance of the bonding surface was deteriorated. The Ni interlayer did not react with the alloy elements in both sides, and therefore effectively prevented element diffusion and improved the corrosion resistance of the bonding surface. Due to the low strength of the Ni interlayer and the increased number of bonding surfaces of the clad steel plates, the shear strength was reduced to some extent (about 40 MPa), but it still met the engineering application standards.

Interface layer deformation thickening analysis of hot rolling carbon steel–stainless steel clad plate

In this study, a stainless steel –carbon steel clad plate was rolled on a two-high mill. The microstructure and thickness of the bonding interface before and after the tensile test were observed through scanning electron microscopy. Results showed that the sample underwent plastic deformation via slipping in the static tension test, resulting in the rapid decrease in the Schmid factor (SF). However, the weighted average value of 1/SF increased from 2.1 to 2.2 after the tensile test. Consequently, the size of the grains with diameters between 12 and 120 μm decreased, whereas the percentage of grains with diameters of less than 5 μm sharply increased to 76.7%. The carbide layer in the bonding interface easily produced stress concentration and formed a fibrous region during the subsequent tensile test. The carbide particles in the bonding interface extended along the slip direction rather than the tensile direction, resulting in increased carbide thickness. The carbides hardly entered the SS but easily extended into the soft ferrite area of the CS surface. The deformation energy increased with a decreased in grain size, and the increase in the part size was the increment of the surface energy of the small grains.

Microstructure and mechanical properties of stainless steel clad plate joints produced by TIG and MAG hybrid welding

This paper investigated the microstructure and mechanical properties of Q235/304 stainless steel clad plate welding seam produced by hybrid welding of tungsten inert gas welding (TIG) and metal active gas arc welding (MAG). The results showed that the dual phases containing ferrite and austenite appeared in the stainless steel covering welding (SSCW), while the partial martensite phases appeared in the carbon steel backing welding (CSBW), which is attributed to the dilution behavior of Ni and Cr elements from stainless steel to the Q235 steel results into the movement of the CCT curve to the right side and the decrease of critical martensite formation cooling rate. The CSBW possesses the highest microhardness value in the weld metal due to the existence of the martensite zone. The impact tests were carried out and the results showed that the Charpy absorbed energy of weldments (81 J) is almost equal to that of base clad plate (83 J). The SSCW layer possesses the ductile fracture characteristics accompanying many dimples. However, in the CSBW layer, some cleavage fracture characteristics are presented in the radiation zone while many dimples are located in the fibrous zone, revealing a complex combination of brittle and ductile fracture behavior, which is due to the existence of martensite zone, different stress states and crack propagation velocity.HighlightsHybrid (TIG, MAG) welding is suitable for welding stainless steel clad plate;The martensite formation in CSBW is related to dilution and diffusion of Cr and Ni;Partial martensite transformation can strengthen and toughen the welding seam.

Hot roll bonding between commercially pure titanium and high-strength low-alloy steel using Fe interlayer

Hot roll bonding was carried out between commercially pure titanium TA2 and high-strength low-alloy steel Q390 using no interlayer and Fe interlayer at temperatures of 850, 900, 950 and 1000 °C with a total reduction ratio of 86.7%. Interfacial microstructure and bonding property of clad plates were investigated by electron microscopy and shear test. The results showed that with the increase in heating temperature, the shear strength of titanium clad steel plates decreases obviously. Compared with that of titanium clad steel plates with no interlayer, inserting Fe interlayer between titanium and steel can improve the shear strength at 850 and 900 °C but deteriorate the shear strength at 950 and 1000 °C. The reason for this consequence was that Fe interlayer prevented the reaction diffusion of C in titanium to form a thinner TiC layer at 850 and 900 °C, while Fe interlayer promoted the reaction diffusion of Fe in titanium to generate thicker Fe2Ti and FeTi intermetallic compound layers at 950 and 1000 °C.

Effect of Heating Process on Microstructure and Properties of 2205/Q235B Composite Interface

In this paper, the influence of heating process parameters on interface characteristics and mechanical properties of 2205/Q235B clad steel plate was systematically studied. The results showed that the interfacial gap of the 2205/Q235B composite blank was completely bonded by the mutual diffusion of elements under the action of temperature and metallurgical bonding is achieved. The shear strength of the air-cooled samples was only 114–132 MPa, which was far lower than that of water-quenched samples and rolling deformation samples and was unable to meet the requirements of engineering applications. With the increase in heating temperature and holding time, the diffusion distance of the Cr element gradually increased. After rolling deformation, the diffusion distance of the Cr element was significantly reduced to 4.1–10.2 μm. Rolling deformation of the specimen in the decarburization showed the lowest microhardness, and in combination with the microhardness of the interface is about 236–256 HV, which is between the hardness of Q235B and 2205. The 2205 stainless-steel shows the lowest corrosion rate and the best corrosion resistance when rolling at 1200 °C. It was found that the corrosion was the most significant in the side of Q235B near the bonding zone. The corrosion pit width increased gradually with increased heating temperature.

Interfacial fracture morphologies of stainless steel clad plates after uniaxial tension

The interfacial fracture morphologies of stainless steel clad plates, dividing into stainless steel layer, diffusion layer and carbon steel layer, after uniaxial tension loading are investigated. It is found that the fractures occur randomly along the interface line between the stainless steel and diffusion layers, which could be induced by the stress concentration effect. The relatively high ductility of the carbon steel reduces the stress concentration to avoid the possible generation of the interfacial fracture in its layer. Furthermore, the bonding forces between the stainless steel and diffusion layers determine the distribution of the fractures. High bonding force could retain the interface without fracture, while the fractures would occur in the domains with low bonding force. This work deepens the failure mechanism of the stainless steel clad plates and is useful in the safety evaluation in their applications.

Effect of Heat Treatment on the Microstructure and Strength of Stainless Steel-Clad Plate

A 316L/Q345R stainless steel-clad plate after hot rolling was subjected to three heat treatments: rapid cooling, rapid cooling and tempering, high-temperature rapid cooling, and low-temperature slow cooling to improve its microstructure and properties. Its specimens were prepared by of an hot rolling evacuated package. Optical microscopy and energy dispersive spectroscopy were applied to examine the microstructure and constituents of the specimens. The mechanical properties under different treatments were evaluated in shear, tensile, and impact tests. The results demonstrate grain refinement and improved properties after heat treatment. After rapid cooling the microstructure of the specimen is mainly composed of martensite, strength increases, ductility is poor, and elongation is relatively low, only 12.7%. The microstructure and ductility are certainly at their optimum after rapid cooling and tempering, elongation tends to 16.7%, but performance still does not meet the practical requirements. After high-temperature rapid cooling plus low-temperature slow cooling, the microstructure mainly consists of bainite, fine ferrite, and a small amount of pearlite. The clad plate exhibits excellent performance due to the combined soft and hard phase structure, shear strength reaches 397 MPa, and elongation is 22.2%, both fulfill the requirements.

Relationship Between Corrosion Resistance and Microstructure Characteristic of Single-Pass Laser-Arc Hybrid Welded Stainless Clad Steel Plate

Superior weld corrosion resistance to base metal (BM) of stainless clad steel plate (SCSP) was achieved by laser-arc hybrid welding with only one pass. Under optimized parameters, the charge transfer resistance of the weld reached 2.3 times higher than the BM, and the corrosion current density decreased to 70 pct of the BM. Considering the inhomogeneity caused by dendrites, an equivalent Cr content, i.e., [Cr]E, was proposed to establish a new relationship between the corrosion resistance and the microstructure characteristic of the SCSP hybrid weld. It suggests better weld corrosion resistance than the BM is obtained when the [Cr]E ≥ 15.5 pct. The results would be suitable to predict the corrosion resistance of the SCSP weld, and promote its industrial application.

Interface formation and bonding mechanisms of hot-rolled stainless steel clad plate

Since the 1980s, vacuum hot rolling has been developed to fabricate the stainless steel clad plates by the Iron and Steel Institute of Japan. Herein, hot rolling is a widely used solid-state bonding process to join the carbon steel substrate and stainless steel cladding. In this paper, we provide a brief overview of the vacuum hot rolling process and effective parameters on the interface characteristics and shear strength of stainless steel clad plate. The effects of surface preparation condition, atmosphere condition, vacuum degree, rolling temperature, rolling reduction ratio, interlayer, heat treatment on the microstructure, interface characteristics and mechanical properties of stainless steel clad plate have been analyzed in detail. It is shown that the interface transition zone is formed due to the carbon diffusion, and the strong interface bonding is attributed to the sufficient alloy elements diffusion of Fe, Cr and Ni. Moreover, the interface shear strength and toughness are also affected by interfacial precipitation phase and multiple oxides. Finally, the present work concluded the bonding mechanism of hot-rolled stainless steel clad based on the oxide film theory, diffusion theory, recrystallization theory and three stage theory.

Interfacial microstructure and properties of a vacuum roll-cladding titanium-steel clad plate with a nickel interlayer

The titanium–steel clad plates with Ni interlayer were prepared by vacuum roll-cladding (VRC). Different compounds were observed at the interface at different heating temperatures. The effect of Ti2Ni, TiNi, TiNi3, α-Ti, β-Ti, TiC and TiFe on the mechanical properties and microstructure of titanium–steel clad plates were analyzed by electron probe micro-analyzer (EPMA), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and shear test. The study showed that TiC and TiFe brittle compounds were not formed at the clad interface at 800 °C and 900 °C, and the average shear strength of 310 MPa and 224 MPa were obtained, respectively. At 1000 °C, the diffusion between Ti and Fe was not restrained by Ni interlayer, and TiC and TiFe brittle compounds were formed at the interface, and the average shear strength of 151 MPa was obtained. With the increase of temperature, Ti2Ni in liquid phase was formed at the interface at 1000 °C, which seriously affected the mechanical properties of the clad plates.

Microstructure Characterization and Mechanical Properties of Stainless Steel Clad Plate.

In this study the microstructure and mechanical properties of stainless steel clad plate are researched. Due to element diffusion (Fe, Cr, Ni, Mn), a 20 μm thick diffusion layer is formed between stainless steel and carbon steel clad plate. The diffusion layer has a stable mechanical performance without obvious grain microstructure, and its internal mechanical properties show a graded change in the thickness direction. This is beneficial to a strong bond between stainless steel and carbon steel and the stable transition of mechanical performance in the thickness direction, as well as further carbon diffusion changes in the microstructure and mechanical properties near the diffusion layer of clad plate. Carburization stainless steel with a thickness of 150 μm is formed in the stainless steel side and decarburization carbon steel with a thickness of 80 μm is formed in the carbon steel side.

Effect of interlayer material and rolling temperature on microstructures and mechanical properties of titanium/steel clad plates

Titanium (Ti)/steel clad plates with interlayer material of interstitial free (IF) steel, vanadium (V) and IF steel + V were successfully fabricated by hot roll bonding method at temperature of 850, 900 and 950 °C. Tensile shear test and tensile test were performed to evaluate the mechanical properties of the Ti/steel clad plates. The interfaces and the fracture surfaces of Ti/steel clad plates were carefully characterized by scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. The results reveal that the interlayer materials have influence on the compounds at the Ti/steel interfaces. Carbides are detected at the interfaces of Ti/steel with single IF steel or V interlayer. The formation of carbides impairs the shear strength of clad plates. σ phases instead of carbides are observed at the interface of Ti/steel clad plate with IF steel + V interlayer, which is beneficial for the tensile shear strength. Rolling temperature also has significant influence on mechanical properties of Ti/steel clad plates. The thickness of σ phase increases with the increase of rolling temperature. Thick σ phases impair the mechanical properties of the Ti/steel clad plate.

Process Analysis and Trial Tests for Hot-Rolled Stainless Steel/Carbon Steel Clad Plates

The trials of 304 stainless steel-clad plate made of plain Q345B carbon steel were performed on hot-rolling line of the Hesteel Group. After the two runs of pilot production, the key process parameters for the stainless steel/carbon steel clad plate were found to meet the GB/T 8165-2008 requirements. The interface shear strength of the clad plate was higher than 360 MPa, the yield strength of the final product was over 257 MPa, the clad plate tensile strength and elongation exceeded 351 MPa and 39.8%, respectively. The interpenetration of stainless steel and plain carbon steel layers was established to be complete, with the adequate composite interface. The tensile and shear properties of stainless steel-clad plates produced by the rolling process were at the same level as those obtained via the explosive method as an alternative, while their production cost were somewhat reduced.

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.

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).

Microstructures and properties of single-pass laser-arc hybrid welded stainless clad steel plate

The effects of wire Cr content on the microstructures and properties of single-pass laser-arc hybrid welded stainless clad steel plate (SCSP) were studied. Increasing Cr content strengthened the weld corrosion resistance, but it increased the average grain size of fusion zone (FZ), deteriorated the weld microstructure uniformity, and weakened the weld mechanical property. The variations of the weld properties were closely related to the microstructure changes. The solidification mode and microstructure transformation mechanism of the SCSP hybrid weld were clarified based on the quantitative calculation of the Cr and Ni equivalent contents (Creq and Nieq) after the mixing of the wire and base metal. The calculated ratio of the Creq and Nieq (θ) could effectively predict the solidification mode and microstructure of the SCSP weld, and then indicate its properties. The skeletal and acicular ferrites formed in the FZ when the θ was larger than 1.35, which benefited to strengthen the SCSP weld.

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.