Rolling Steps Research Articles

Corrosion and mechanical properties of Al/Al2O3 composites fabricated via accumulative roll bonding process: Experimental and numerical simulation

With the advancement of science and technology and the construction of metal-based composites (MMC), it became possible to achieve improved properties that were not easily available in an alloy. In fact, with the emergence of such technology, manufacturers were able to adjust the resulting materials according to their needs in such a way as to provide mechanical strength, hardness, corrosion resistance, or other desired properties. These composites were used in various aerospace, automotive, construction, and production industries. Aluminum-based composites are among the structures that have taken an important place in the industry due to their lightweight and high strength. The present study produced bi-alloy aluminum-based 1060/5083 composites fabricated with alumina particles with a Hot ARBp at T = 380 °C. Also, the effect of rolling steps on the roll bonding mechanism is investigated using numerical simulation. As the novelty of this study and for the first time, a bi-alloy 1050/5083 composites reinforced Al2O3 particles via ARB process have been produced and then, potential dynamic polarization in 3.5 Wt% NaCl solution was used to study the corrosion properties of these composites. The corrosion behavior of these samples was compared and studied with that of the annealed aluminum. The study aimed to investigate the bonding behavior between the bi-alloy layers. So, as a result of enhancing influence on the number of ARBp, this experimental investigation revealed a significant enhancement in the main electrochemical parameters and the inert character of the Alumina particles. Reducing the active zones of the material surfaces could delay the corrosion process. Results showed that the corrosion resistance of the sample fabricated after six steps improved more than 100 % in comparison with the initial annealed Al alloy. Also, the average peeling force improved from 45 N to 94 N for the sample fabricated with six steps. Moreover, at a higher number of steps, the corrosion of MMC improved. Moreover, increasing the number of ARBsteps illustrated an improvement in the wear resistance of samples. Finally, the samples' bonding interface, corrosion surface, and peeled surface were investigated using scanning electron microscopy (SEM).

Effect of cold rolling route and annealing on the microstructure and mechanical properties of AISI 316 L stainless steel

Since cross rolling promotes the transformation of austenite to deformation-induced α΄-martensite and increases the dislocation density in the retained austenite, the reversion/recrystallization annealing after cross rolling might be more effective to achieve finer grain sizes in metastable austenitic stainless steels. Accordingly, the effect of cold rolling route and annealing for grain refinement and improvement of mechanical properties of AISI 316 L stainless steel was systematically investigated in the present work. It was found and formulated that by increasing strain, the grain refinement efficiency during annealing is improved, the effect being more pronounced if the cold rolling step is applied by cross rolling instead of unidirectional rolling. The evaluation of tensile properties revealed that all cold rolling and annealing routes lead to significant improvements of mechanical properties in terms of strength and plasticity, the influence of cross rolling being more prominent again. Moreover, the cross rolling and annealing route led to a remarkable strength-ductility balance, which revealed the opportunities that this route can offer for the improvement of mechanical properties of austenitic stainless steels. Accordingly, the results of the present work may shed light on the further utilization of cold rolling route and annealing treatment.

Manufacturing Oxide Dispersion Strengthened (ODS) steel plate via cold spray and friction stir processing

Oxide dispersion strengthened (ODS) steels, traditionally fabricated by ball milling and conventional powder metallurgy techniques to achieve bulk form, followed by intricate rolling and thermal treatment steps to achieve plate or sheet form. Here, we present a novel processing route that combines cold spray (CS) with friction stir processing (FSP) to manufacture ODS steel plate directly from gas atomization reaction synthesis (GARS)-prepared powder, thus no rolling steps involved. Microstructural and mechanical characterizations were performed to assess the quality and properties of the resulting ODS steel plate. Our findings demonstrate that the slightly porous CS deposited layer was fully consolidated after FSP, yielding a fully dense ODS steel plate that exhibited a favorable tradeoff between strength and ductility upon extraction from the substrate. Furthermore, through microstructural analysis, we revealed the presence of an appreciable density (∼1022/m3) of nano-sized oxide particles, with the majority being smaller than 5 nm via the combined CS + FSP fabrication route. This work serves as a first proof-of-concept demonstration of the manufacturing approach described herein, offering a possible alternative route for producing ODS steel plates.

Microstructural and textural evolution of double stage cold rolled non-grain oriented electrical steel

Non-grain oriented electrical steels (NGOES) are typically used in electric applications with rotating magnetic fields and thus essential for the production of electric motors. The increasing number of electric vehicles results in a growing demand for electrical steel sheets used in the stacked laminations of rotor and stator components. E-mobility applications require the best possible magnetic properties for optimum performance and efficiency, especially at high frequencies. In addition, increased mechanical strength is necessary to withstand the centrifugal forces resulting from high revolution speeds. Chemical composition, microstructure and crystallographic texture strongly influence the magnetic properties, whereas the mechanical properties are mainly affected by the chemical composition and grain size. Optimizing the texture is a possible method for improving the magnetic properties without significantly compromising the mechanical strength. In this work a special processing route for the production of 3.25% Si NGOES sample material has been studied, using laboratory cold rolling and annealing facilities. Compared to the classical processing route of single stage cold rolling and annealing, this alternative method involves two cold rolling steps with an intermediate annealing treatment between the first and second rolling sequence and a final annealing treatment after the second rolling step. The samples were produced with different intermediate thicknesses, changing the amount of cold rolling deformation of each sample variation. The degree of deformation affects the recrystallization and grain growth behavior and thus the resulting microstructure and texture. The microstructural and textural evolution was investigated in the hot rolled, intermediate annealed and final annealed state using electron backscatter diffraction (EBSD). Finished samples were additionally examined using magnetic testing and tensile testing. The results indicate a correlation between the intermediate thickness and the final grain size of the steel samples. Furthermore, the highly grain size dependent mechanical strength and magnetic losses are influenced. EBSD-data were used to interpret the texture and to calculate a parameter describing the magnetic quality of the texture. The results show a strong improvement of magnetically favorable texture components along with increasing intermediate thickness, enabling significantly better polarization values in rolling direction and transversal direction. However, anisotropy of the magnetic properties increases as well due to the textural changes.

Impact of rolling processes in the production of aluminum packaging assessed through LCA

PurposeThe environmental impact of aluminum cans and aluminum food packaging has been extensively studied in the last years; most of the researchers focused their attention on the whole lifecycle: from the aluminum extraction to the end-of-life management, while there are no dedicated studies devoted to the detailed analysis of the rolling phase. The aim of this paper is to present an LCA analysis focused on the fabrication of the thin plates to be used for can and tray production; the work has been carried out by studying the “Laminazione Sottile” plant with a cradle-to-gate approach, considering as functional unit thin plates of two different alloys.Materials and methodsInventory data were collected from the “Laminazione Sottile S.p.A.” plant, and off-plant emissions from external goods and fuels were accounted for based on existent LCA databases. Gabi has been used as software to model the process and calculate the impacts, while the CML method has been used. Most of the data have been directly measured in the plant during 1 year of work.Results and discussionThe results showed that the most impactful phase is the extraction of aluminum or the use of primary aluminum. Focusing the attention on the manufacturing process, the foundry is the most impacting stage, and the high energy required to melt the aluminum leads to most of the emissions. Moreover, this contribution is probably underestimated in this work because the impacts related to the manufacturing of the facilities used (furnaces and so on) are not considered. Another interesting finding is that both the supply chain and the general consumption have a non-negligible impact, highlighting the necessity to optimize these two aspects by implementing new policies for purchasing and work organization.ConclusionsThe study highlighted that the production of primary aluminum is the most impacting step, followed by the foundry and the hot rolling. Production of thin aluminum plates by rolling requires a lot of energy, so the carbon footprint of these processes is quite high. The chemicals used in the rolling steps play also a role in the general impact of the whole process. The company continuously promotes improvements of the process to reduce the footprint and puts a lot of money and effort to introduce new sensors and technologies to monitor the consumptions and improve the processes.

Influence of intermediate annealing temperature on the microstructure and texture of double stage cold rolled non-grain oriented electrical steel

Non-grain oriented electrical steels (NGOES) are commonly used as stacked laminations of rotors and stators in electrical vehicles. In order to achieve the best performance and efficiency for the motor, NGOES need the best possible magnetic properties of high polarization and low magnetic losses. Two important aspects influencing these magnetic properties are the grain size and the crystallographic texture of the material. Grain size and texture of the finished steel strongly depend on the production route and the processing parameters. Another important aspect besides the magnetic properties is the mechanical strength, which is needed to withstand the centrifugal forces, accounted with high rotational speed in high frequency applications. In this work a special processing route for the production of 3.25% Si NGOES sample material has been studied, using laboratory cold rolling and annealing facilities. Compared to the classical processing route of cold rolling and annealing, this alternative method involves two cold rolling steps with an intermediate annealing treatment between the first and second rolling step and a final annealing treatment after the second rolling sequence. The samples were heat treated at different intermediate and final annealing temperatures, influencing the recrystallization and grain growth behavior and thus the resulting microstructure and texture. Finished samples were examined using magnetic testing, tensile testing, light imaging microscopy and by electron backscatter diffraction (EBSD). The results indicate a correlation between the two annealing treatments (intermediate and final) and the final grain size of the steel samples. Furthermore the highly grain size dependent magnetic losses are influenced. EBSD-data was used to interpret the texture and to calculate a parameter describing the magnetic quality of the texture. The results show a strong improvement of magnetically favorable texture components along with increasing intermediate annealing temperatures, enabling significantly better magnetic properties.

Hot Rolling of ZK60 Magnesium Alloy with Isotropic Tensile Properties from Tubing Made by Shear Assisted Processing and Extrusion (ShAPE)

In the present work, we utilized Shear Assisted Processing and Extrusion (ShAPE), a solid-phase processing technique, to extrude hollow tubes of ZK60 Mg alloy. Hot rolling was performed on these as-extruded tubes (after slitting them longitudinally) to thickness reductions of 37%, 68%, and 93% to investigate their viability as rolling feedstock material. EBSD analysis showed the formation of twinned grains in the ShAPE processed material and a gradual re-orientation of the basal texture parallel to the extrusion direction with each rolling step. Moreover, an equiaxed grain size of 5.15 ± 3.39 μm was obtained in the ShAPE extruded material, and the microstructure was retained even after 93% rolling reduction. The rolled sheets also showed excellent tensile strengths and no mechanical anisotropy, a critical characteristic for formability. The unique microstructures developed and their excellent mechanical properties, combined with the ease of scalability of the process, make ShAPE a promising alternative to existing methods for producing rolling feedstock material.

Effect of Lean Alloyed Al and Ca on the Texture Development of Cold Rolled Mg Sheets

Lean alloyed Mg-Al-Ca alloys reveal weakened basal-type texture intensities and increased room-temperature ductility when compared to pure Mg. Since the combined effects of the alloying elements Al and Ca on texture evolution are not yet fully understood, in this study, two binary and seven ternary Mg-Al-Ca alloys (ranging between 0–2 wt.-% Al and 0–0.5 wt.-% Ca) were subjected to cold rolling with texture measurement after each rolling step. These measurements showed that the basal-type texture of Mg is weakened by the addition of Ca, while the addition of Al leads to stronger basal-type textures compared to the samples containing Ca. The joint effect of Al and Ca can, for specific alloy compositions, lead to a steady-state basal texture intensity, which does not become stronger with further rolling. We expect that the solubility limit of Ca in Mg affects this behaviour. For comparison, mechanical properties were obtained by compression testing, showing high degrees of deformation, of 15–25%.

Comparison of K-doped and pure cold-rolled tungsten sheets: Microstructure restoration in different temperature regimes

For tungsten in divertor parts of future fusion reactors, a fine-grained microstructure is preferred to reduce its brittle-to-ductile transition temperature and minimize cracking events due to cyclic thermal and mechanical loading. In our ongoing study on tungsten sheets with different degree of deformation by warm- and cold-rolling, the potential of potassium-doping to stabilize the microstructure at high operation temperatures is assessed. Successful production of technically pure and equivalently rolled potassium-doped tungsten sheets up to very high logarithmic strains of 4.6 was already shown in the past with in-depth analysis of the evolution of microstructure and mechanical properties after rolling steps. Our current study investigates the microstructure changes in the same material batch by recovery, recrystallization and grain growth in temperature regimes between 600 °C and 2400 °C. Annealing studies with subsequent microhardness and SEM analysis reveal increased retardation of recrystallization in potassium-doped tungsten with higher rolling strain, but abnormal grain growth at high temperatures is also increased. However, potassium-doped tungsten with low rolling strain shows promising results with much less grain growth than its pure tungsten counterpart.

Effect of cooling rate on the order degree, residual stress, and room temperature mechanical properties of Fe-6.5wt.%Si alloy

The top side-pouring twin-roll casting (TSTRC) process was used to prepare a 100 × 1.7 mm non-oriented Fe-6.5 wt% Si alloy as-cast strip. The as-cast strip is directly rolled at 700 °C into 0.4 mm without the intermediate hot rolling step. This paper discusses the effects of different cooling rates in furnace cooling, air cooling, oil quenching, and water quenching on the order degree, residual stress, room temperature mechanical properties, and cold-rolled processing properties of Fe-6.5wt.%Si alloy after annealing of warm-rolled sheets are systematically investigated. Meanwhile, the effects of order degree, residual stress, and grain boundary element segregation on the mechanical properties were analyzed. The results show that as the cooling rate increases, the order degree of the Fe-6.5 wt% Si alloy decreases and the maximum residual tensile stress increases. The fracture modes of the furnace cooling, air cooling, and oil quenching samples are through-crystal disintegration fracture, and the fracture mode of the water quenching samples is an along-crystal fracture. The oil-quenched samples exhibit good room temperature plasticity due to the relatively low order degree and residual tensile stresses in the Fe-6.5wt.%Si alloy. Oil quenching improves the room temperature plasticity and cold rolling properties of Fe-6.5wt.%Si alloy warm rolled sheets, reduces edge cracks, and offers greater room temperature cold rolling processibility of the Fe-6.5wt.%Si alloy warm rolled sheets.

Fabrication and characterization of MgB2/SS 316L superconducting wire with amorphous boron prepared by sintering and cold rolling

Magnesium diboride (MgB2) is proposed to be a highly efficient wire with zero resistivity. In this research, Mg powder and amorphous-boron sheathed with a stainless steel (SS) 316L tube and powder-in-tube (PIT) technique were used in order to create a cheaper and potential superconductor that could eventually replace the currently expensive price crystalline boron. Mixed powder was put into SS 316L tube and compacted to avoid oxidation while being sintered at a temperature of 800 °C for one hour, prior to cold rolling with various size reduction. X-ray diffraction (XRD), scanning electron microscopy (SEM), and cryogenic magnet characterization were used to evaluate the crystal structures, surface morphology, and resistivity versus temperature and SQUID measurement for all samples. The XRD analysis revealed that the majority of the MgB2 phase was produced accompanied with a small quantity of MgO and Fe phases. The results of the SEM showed particle agglomeration in the sample’s morphology. It has been found that using the size reduction up to 60 % in the cold rolling step, the critical temperature (Tc) onset of the resulting MgB2 was calculated to be 39.25 and 39.44 K, respectively. This results reveal that the fabrication of the superconducting wire can be realized using a more economic raw material and process.

Microstructure and properties of a Cu-6Cr alloy with high friction and wear resistance

The microstructural evolution, electrical conductivity, and mechanical properties of a cast Cu-6Cr alloy were investigated after being homogenized at 900 °C for 4 h, hot-rolled by 80%, solid solution treated at 940 °C for 2 h, and subjected to two steps of cold rolling and aging treatment. After several thermomechanical processes (HR + SST + CR + AT + CR + AT), the microhardness (155.2 HV), yield strength (439.8 MPa), and ultimate tensile strength (473.7 MPa) are significantly improved, and maintained a good electrical conductivity of 87.0 %IACS. Furthermore, under a load of 50 N and speed of 200 r/min, the alloy demonstrates a good friction coefficient of 0.381 and a wear rate of 1.62 × 10−8 mm3/(N·m). The wear mechanisms of the experimental alloy were abrasive wear and oxidative wear under low loads and low speeds, and oxidative wear and adhesive wear under high loads and high speeds.

Widely targeted metabolomics using UPLC-QTRAP-MS/MS reveals chemical changes during the processing of black tea from the cultivar Camellia sinensis (L.) O. Kuntze cv. Huangjinya

Huangjinya is a light-sensitive mutant tea cultivar that produces fresh leaves with a yellow phenotype, and the leaves also be used to produce black tea with special sensory characteristics. To thoroughly explore the chemical changes that occur during the processing of Huangjinya black tea, tea samples were collected from each processing step to perform quantitative and qualitative analyses by high-performance liquid chromatography and ultra-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS). Compared to fresh tea leaves, only approximately 20% of the catechins remained at the end of processing, while theaflavins levels peaked at the rolling step and were slightly reduced in the fermentation and drying processes. The levels of amino acids derived from protein hydrolysis increased significantly in the withering and rolling processes. Altogether, 620 differential metabolites were identified from 11 subclasses using widely targeted metabolomics based on UPLC-HRMS for the four steps used to process Huangjinya black tea. Flavonoids, phenolic acids, and lipids were the three major classes of differential metabolites, accounting for 52.4% of the differential compounds. The greatest changes in the metabolite profile occurred during the rolling step, with 292 metabolites showing increases or decreases. Two glycoconjugates of the amino acid were first identified in tea, which was sharply increased in the drying stage. The present study provides comprehensive information on the chemical changes during the processing of Huangjinya black tea, and this information is valuable for optimizing manufacturing process and utilization of the Huangjinya tea plant.

Proposing the employment of spring-wire turbulator for flat spiral tubes utilized in solar ponds, experimental study

Flat horizontal spiral-tube is an ideal sort of heat exchangers applicable in solar ponds as it is placed in the hottest zone (bottom of the pond) with the maximum coverage area to transfer the heat into the secondary fluid flow. Due to the curve nature of the flat spiral-tube, most types of turbulators, useable for straight tubes, are not applicable for spiral-tube. However, this paper shows how spring-wire can be employed as a turbulator for spiral-tube to enhance its thermal characteristics including Nu number and thermal performance. It is noted that, for a given spiral tube length, turbulator will increase the heat transfer rate. From another viewpoint, for a given expected heat transfer rate, the turbulator will reduce the required size/length of the spiral tube (which means lower material/weight and cost). Spring-wire with different geometries are utilized as the turbulator for spiral tube in this research to identify its thermal, frictional and performance features. It is noted that, spring-wire should be inserted into the spiral tube through its fabrication process prior to the rolling step (when it is still straight tube). Interesting results were obtained which are reported and discussed in this paper.

Processing Route Optimization and Characterization of Al6063–SiCp Metal-Matrix Composite Sheets

The target of this study is to develop routes for processing Al–SiCp (SiC particulate) sheets with improved microstructures; namely, the uniform distribution of SiCp and minimized porosity throughout the whole material, thereby improving its mechanical properties. Al–SiCp composites reinforced with 5, 10, and 15 vol.% SiC and having three average sizes of 29, 17, and 8.5 µm were produced using a semi-automated stir-casting machine; finally, the bars were hot rolled to get the final sheet dimensions. The rolling steps were performed based on the results of thermomechanical simulations performed on the cast blocks. The first rolling steps were applied according to a safe rolling schedule to avoid cracking via encouraging dynamic recrystallization. The last rolling steps were performed to improve the hardness and strength of the metal matrix composites (MMCs). A refinement in grain size from an average of 420 µm in the as-cast condition to an average of about 85 µm after rolling was observed. Some heterogeneity in grain size was observed where the regions with larger, elongated grains were associated with the zones depleted by SiCp reinforcement. Reinforcing with SiCp led to a small increase in tensile strength of 10–20 MPa, and this was further improved to about 60 MPa and 110 MPa for the 5 and 10 vol.% SiCp conditions, respectively, after a T6 heat treatment.

A four-prism tensegrity robot using a rolling gait for locomotion

Since the twenty-first century, research on tensegrity structures has been extended from the field of architecture to robotics, considering their promising environmental adaptability and safe human-machine interactivity. Tensegrity robots usually utilize strut-cable coupled dynamics to achieve crawling or rolling movement. Whereas, when it comes to a simple structure, e.g., the Four-Prism Tensegrity Robot (FPTR), its rolling locomotion has been challenging to realize. Therefore, this paper presents a design method utilizing the structural deformation of the FPTR to achieve steerable rolling locomotion. To investigate the parameter-selection process and the possible deformation of the FPTR, kinematic, static, and dynamic models are built and relevant simulations are implemented. Then this paper proposes four basic rolling steps of the FPTR and one specific control pattern allowing for going straight and turning left/right. A robotic prototype is further developed to validate the reliability of the model and the feasibility of the FPTR's steerable rolling gait. It eventually proves that even the prismatic single-unit tensegrity robot is qualified to make use of its structural deformation to achieve controllable and steerable rolling locomotion.

The Influence of anisotropy on the vibration behaviour of S600Mc sheet metal

Sheet metal anisotropy is the directional dependence of mechanical properties. It is a critical factor that must be considered when using numerical simulation to predict any plastic deformation manufacturing process. Sheet metals prove anisotropic plastic behaves due to crystallographic texture caused by progressive rolling steps, Banabic D. et al. (2000). Cold bending of steel sheets is a widely used manufacturing process in the automotive industry due to its cost efficiency. By avoiding line heating, the oxidative process of steel is thus avoided. The automotive industry's primary application of sheet metal includes doors, fenders, bumpers, roof panels, and seat frames. In this paper, test specimens were laser cut at orientations θ = 0°, 45°, and 90° to the rolling direction. The specimens were subjected to forced vibration on an electromechanical shaker, and the frequency response amplitude was measured using accelerometers. Natural frequency and Q-factors were discussed. Experimental data are used for viscous damping coefficients (alpha and beta) for each direction of the specimen. The measured coefficients are then used to validate each type's finite element, numerical models. The results show the level of dependency between the structural damping and anisotropy of the laminated sheet metal and the influence on the high cycle fatigue performance.

Application of Big Data technologies in downstream steel process

In steel manufacturing, the rolling step defines the major properties of final products of the steel industry which are delivered to a wide range of different industrial sectors. Modern rolling mills, to reach high degree in process supervision and efficiency, installed sensor equipment that delivers masses of data and information about the process, the product and its quality at high sample rate and at high spatial resolution. But there is a misalignment between the applied high-tech equipment and the online exploitation of such measurements to describe their impact into the product properties. To make use of the high amount of online available data, on 2018 started the RFCS project NewTech4Steel aimed to enhance process stability and product quality in steel production by exploitation of break-through technologies for real-time monitoring, control and forecasting inspired by Big Data concepts. Within this project, on the basis of the strict correlation between the cold rolled strip flatness and downstream process productivity (HDG & painting line), it has been investigated at Marcegaglia Ravenna plant the case-study of managing the massive amount of production data and making them operational by leveraging machine learning algorithm in order to optimize the global productivity. The project allows fast and online data processing and in turn fulfills the plant line needs for: prediction of defect related to manifested coil flatness imperfections and real-time prediction of process parameters during the zinc coating to avoid break/sideslip on critical conditions. The solution created in New Tech4Steel is inspired by Lambda Architecture as the unified platform for data and analytics which is composed of three layers: batch processing layer for offline data, serving layer for preparing indexes and views and speed layer for real–time processing. The work compiled the necessary measures to integrate the new technologies into the existing IT systems especially under the aspects of brown-field implementation, the connection of newly developed systems to existing ones, and the requirements for HMIs for user interaction and visualization.

Structure, Texture, and Substructure of Foil in Sequential Rolling Steps of Cu–36.4 at % Pd Alloy

Structure, Texture, and Substructure of Foil in Sequential Rolling Steps of Cu–36.4 at % Pd Alloy

Dynamic distribution and transition of gluten proteins during noodle processing

In this study, dynamic distribution and molecular transition of gluten proteins during noodle processing as well as their relationship with texture changes were systematically investigated and quantified. Confocal laser scanning microscopy (CLSM) images and network analysis confirmed that the mixed dough and dough sheet showed higher gluten junctions (919.5, 815.0, respectively) and lower lacunarity (9.28, 8.64). Scanning electron microscopy (SEM) images revealed that the gluten network gradually became orderly and compact after different processing steps such as mixing, resting, rolling, and sheeting, except for the large gaps in the cooked noodles. The mechanical force of mixing (step 2) and rolling (step 4) caused partial depolymerization of gluten protein and promoted its repolymerization, thereby forming a well-developed gluten network structure. Each step of the noodle processing was accompanied by a reduction in the content of free –SH, which induced the SH/SS exchange. From resting (step 3) to rolling (step 4), the hydrogen bond interaction was strengthened. Heating induced the weakening of hydrogen bonds and hydrophobic interaction. Changes in texture properties were highly correlated with the dynamic morphology distribution and the molecular/structural transition of gluten protein.