Production Of Thin Sheets Research Articles

Feasibility Study of Single-Point Incremental Forming for Discontinuous-Fiber CFRP Using Oil-Bath Heating

Although, three-dimensional printing has several advantages, however there are currently many limitations. In particular, printed products using composite materials such as fiber-reinforced plastic have yet to achieve the same mechanical properties as those obtained from conventional manufacturing methods. In addition, fabricating thin plates or thin shell shapes with sufficient strength is challenging. Incremental forming enables high-mix, low-volume production of thin sheets. This method applies incremental deformation to thin sheets, the desired shape is obtained by accumulating the deformation, and no dies are required. Carbon-fiber-reinforced plastic (CFRP) materials have high specific strength. Discontinuous-fiber CFRP is capable of large plastic deformation under appropriate conditions due to the discontinuity of the reinforcement, and its mechanical properties are nearly isotropic due to the random fiber arrangement. The authors focused on this property and studied the application of single-point incremental forming to discontinuous carbon-fiber-reinforced polyamides. In this study, the workpiece was formed by heating it locally to a deformable temperature by the frictional heat between the rotating tool and the workpiece. The forming experiment was also conducted in an oil bath to keep the entire material at a suitable forming temperature. The results showed that the spindle speed affected forming results even in an oil bath and that heating using an oil bath suppressed deviations from the sine law for thickness and wall angle due to elastic deformation.

PRODUCTION AND CHARACTERIZATION OF 2024 ALUMINUM ALLOYS

This study aims to give theoretical information about the production and characterization of mechanical properties of 2024 aluminum alloys. AA2024 alloy; It consists of components such as aluminum, copper, magnesium and manganese, and the production of the alloy is usually carried out by different methods such as casting, rolling, extrusion and powder metallurgy. The choice between production methods should be made by considering the purpose and properties of the alloy. While the casting method is used for the production of large-sized parts, the rolling method is suitable for the production of thin sheets and strips, and the extrusion method is suitable for the production of profiles and pipes of various shapes. The powder metallurgy method, on the other hand, is carried out by shaping the powdered components of the alloy with a special pressing process and then sintering at high temperature. Alloys produced by this method exhibit high strength properties with their high density and homogeneous microstructures. The mechanical properties of AA2024 alloy are generally determined using various characterization methods such as tensile test, hardness measurement and fatigue life tests. The tensile test is used to determine the tensile strength, tensile elongation ratio and elastic tension properties of the alloy. The hardness measurement is used to determine the surface hardness of the alloy. Surface hardness can be performed using Brinell, Vickers and Rockwell hardness measurement methods. The fatigue life test is used to determine the fatigue strength of the alloy. In this test, the fatigue life of the specimen under repetitive loads is determined. The mechanical properties of AA2024 alloy may vary depending on production methods, alloy components, temperature and environmental conditions. Therefore, the mechanical properties of the alloy must be optimized for a particular application. 2024 aluminum alloys produced by powder metallurgy method are expected to exhibit high density, homogeneous microstructure and high strength properties as a result of hardness, tensile and fatigue tests.

Study of stress-strain state of thin-sheet billet during its deformation by new composite working tool

The results for solving of the finite element problem of thin-sheet billet deformation by composite and simple elastic working tool based on SKU-7L polyurethane are presented. Comparative analysis of the obtained results is performed. The technological improvement for obtaining process of the thin-sheet products— elements of flat heat exchangers, decorative panels and similar thin-sheet products is presented.

Rheological characteristics of steel in continuous roll casting-rolling

Problems. In the process of obtaining a strip in a casting and rolling device, the question arises of combining the process of hot rolling of the solidified material and the process of crystallization of the liquid melt. This makes it possible to implement an efficient technology for producing thin-sheet products.
 Purpose of the study. Determination of rational parameters for performing mathematical modeling of material behavior during roll casting requires clearly defined recommendations. The material for the rolling process is steel. The starting material was used in solid, solid-liquid and liquid states.
 Implementation technique. The analysis of the properties of steel was carried out on the basis of the results of experiments obtained at the Physico-Technological Institute of Metals and Alloys of the National Academy of Sciences of Ukraine. To analyze the rheological properties of steel, the dependences of the yield stress for alloyed and carbon steels were used in a certain temperature range. The selected temperature range includes solidus and solid-liquid state of steel, located above 0.8 melting point.
 Research results. Based on the research results, the analysis of the rheological properties of steel in solid, solid-liquid and liquid states during continuous casting-rolling on rolls was carried out. The use of the obtained dependencies makes it possible to perform mathematical modeling of the deformation and hydrodynamics of the material during continuous casting-rolling of steel strips using roll casting-rolling devices.
 Conclusions. The constructed dependences, together with studies of the viscosity of steel in the liquid state and the resistance of steel to deformation in the solid state, most fully describe the rheological properties of steels during casting-deformation processes. The obtained dependences will make it possible to implement an ultra-efficient technology for producing thin-sheet rolled products.

Analysis of the Reasons for the Tearing of Strips of High-Strength Electrical Steels in Tandem Cold Rolling.

High-strength non-oriented electro-technical steels with a low thickness possess excellent isotropy of electromagnetic and mechanical properties which is highly required in the production of high-efficiency electric motors. The manufacturing process of this type of steel includes very important and technologically complex routes such as hot rolling, cold rolling, temper rolling, or final heat treatment. The final thickness is responsible for the decrease in eddy-current losses and is effectively achieved during cold rolling by the tandem rolling mill. Industrial production of thin sheets of high-strength silicon steels in high-speed tandem rolling mills is a rather demanding technological operation due to the increased material brittleness that is mainly caused by the intensive solid solution and deformation strengthening processes, making the dislocation motion more complex. The main objective of this work was to investigate the distribution of local mechanical strains through the thickness of high silicon steel hot bands, generated during the cold rolling. The experimental samples were analysed by means of electron back-scattered diffraction and scanning electron microscopy. From the performed analyses, the correlation between the material workability and the nucleation of cracks causing the observed steel strip failure during the tandem cold rolling was characterized. Specifically, the microstructural, textural, misorientation, and fractographic analyses clearly show that the investigated hot band was characterized by a bimodal distribution of ferrite grains and the formation of intergranular cracks took place only between the grains with recrystallized and deformed structures.

Development of a new stainless austenitic CrMnNi steel using TRIP/TWIP effect for a high cold formability

AbstractA new austenitic stainless CrMnNi steel with a high cold formability coupled with high strength was developed. The cold formability is based on the distinct transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP). Thereby a maximum of strain is reached nearby room temperature. Using the TRIP/TWIP effect of CrMnNi steel a cost‐ and energy‐efficient production of thin sheets is enabled by a reduced number of interstage annealing. Thin sheets with thicknesses from 0.1 mm till 1.25 mm were cold‐rolled industrially and there properties compared to conventional CrNi steel 1.4301 (AISI 304) and CrNiMo steel 1.4404 (AISI 316 L).Plate and lamellae heat exchangers of CrMnNi thin sheets were produced under industrial conditions. The form stability of the plate heat exchangers was increased by 47 % and the component failure pressure raised by 45 % at room temperature. Based on its high strength it is suggested to apply the new austenitic CrMnNi steel in lightweight constructions. Although the nickel content was reduced by 50 % to 65 % compared to conventional steels 1.4301 and 1.4404 the corrosion resistance of the CrMnNi steel is comparable with conventional CrNiMo steel 1.4404.

A new incremental in-plane bending of thin sheet metals for micro machine components by using a tiltable punch

This paper proposes an innovative incremental in-plane bending of thin metal sheets for manufacturing microscopic machine components. The unique feature of the process is that a tiltable punch having a beating face with trapezoidal profile is used. The beating face enables the punch to bend thin metal sheets in in-plane manner. Working conditions, including indentation and feeding pitch, can easily and flexibly control the bending radius and even the bending direction. The in-plane bent thin sheet products are expected to be used as springs, conical cylinders, bushes and other components of micro machines such as medical instruments.

Rectifying Process Problems in Production of Thin Sheets of Special Alloys

The paper deals with solutions to particular process problems in production of thin sheets of special nickel and iron-based alloys. Experiments were focused on trial operation of a new melting furnace, on hot rolling of feedstock from experimental heats and on fine-tuning hot and cold rolling processes with the aid of numerical modelling in DEFORM 3D software. The paper also gives description of results of FEM simulation of cold rolling of strips. A FEM model of the cold rolling process with front and back tension was developed. In order to describe the behaviour of nickel alloys in the FEM simulation, a specific material model was proposed. This material model combines the material data obtained from Rastegaev compression test and the results of thermodynamical calculation from JMatPro software.

Modern processes of production of thin sheets and strips by continuous casting

The history of the development of producing thin sheets and strips by continuous casting methods is considered. The mechanism of this sheet formation during casting of steel in a two-roll continuous caster is described. The advantages of this process over the corresponding traditional technologies are discussed.

Mechanical properties and formability of AZ31 magnesium alloy sheet produced by asymmetric rolling with thrust force

Magnesium alloys have the lowest density among metals in practical use and have properties such as high specific strength and good vibration damping. However, there has been little use of these materials in metal forming because of their poor plastic deformability at normal temperature and high cost of production. To promote sheet products manufactured by metal forming, rolling technologies enabling the production of thin sheets with good surface qualities, mechanical properties and sheet formability at normal temperature are strongly required. In this study, rolling experiments using cone-shaped rolls are conducted to investigate the effects of asymmetric rolling and the thrust force on the mechanical properties and sheet formability of AZ31 magnesium. Hot-rolled AZ31 magnesium sheets were experimentally warm-rolled and reduced a thickness from 2.5 mm to 0.6 mm (a total reduction of 76%) by 11 passes at a sheet temperature of 573 K and roll temperatures of 353 K. Rolling force and axial force were measured. The grain structures and orientations of the rolled materials were also examined. Their mechanical properties such as tensile strength, 0.2% proof stress, total elongation and Lankford value (r-value) were measured by tensile tests. To investigate the sheet formability at normal temperature, conical cup tests were conducted and the sheet formability by asymmetric rolling were compared with that by symmetric rolling. The material rolled by asymmetric rolling exhibits greater elongation than that rolled by symmetric rolling. Asymmetric rolling can improve the sheet formability. However, magnesium alloys rolled by asymmetric rolling have poor sheet formability compared with mild steel sheet.

Production of microfibrillated cellulose (MFC)-reinforced polylactic acid (PLA) nanocomposites from sheets obtained by a papermaking-like process

The fabrication of cellulose nanofiber-reinforced composites has been so far problematic due to difficulties in obtaining good dispersion of hydrophilic cellulose fibers in a hydrophobic polymer matrix. A new manufacturing process similar to papermaking, which enables the production of thin sheets made of uniformly dispersed microfibrillated cellulose (MFC) with polylactic acid (PLA) fibers was devised, and the composites were obtained by compression molding of the stacked sheets. The process is suitable for adoption at an industrial scale owing to the high yields and fast dewatering times. The measurement of tensile properties revealed that the modulus, strength, and strain at fracture increased linearly with the MFC content. The improvement in toughness was considered one of the key benefits brought by MFC reinforcement.

AZ31マグネシウム合金板の多パス温間圧延挙動と<br>圧延条件が機械的性質および成形性に及ぼす影響

There is limited application of magnesium alloys as metal-forming products because of their poor plastic deformability at normal temperatures and their high production cost. To promote products manufactured by metal forming, rolling technologies enabling the production of thin sheets with suitable mechanical properties and surface qualities are required. To investigate the optimum rolling condition, hot-rolled AZ31 sheets were experimentally rolled by four-pass warm rolling in a total reduction range of 76 % with or without lubrication states in the temperature range from 293 K to 573 K. Rolling behaviors such as rolling force, grain structures and grain orientations were investigated. Mechanical properties such as tensile strength, elongation and r value were measured by tensile tests. Then, bending tests and conical cup tests are conducted for sheet forming tests. Finally, the effect of warm rolling conditions on their mechanical properties and sheet formability are discussed.

Magnetic properties of spray-formed Fe–6.5%Si and Fe–6.5%Si–1.0%Al after rolling and heat treatment

The maximum silicon content in commercial Fe–Si steels is limited to about 3.5 wt%Si, since the ductility declines sharply as this maximum is exceeded, hindering the production of thin sheets by cold/hot rolling. However, the best magnetic properties are attained at about 6.5 wt%Si, a silicon content that renders magnetostriction practically null and minimizes magnetic losses. Using spray-forming, our research group has successfully produced this type of high silicon alloy in thin sheet form by carefully controlling the many variables of the process and subsequent rolling operations. In the present study, we investigated the magnetic properties and the microstructure of spray-formed Fe–6.5 wt%Si and Fe–6.5 wt%Si–1.0 wt%Al alloys after warm rolling and heat treatment. The main cause for the brittleness of Fe–6.5 wt%Si alloy has been attributed to the B2 phase long-range ordering, which leads to premature fractures. The presence of aluminum could avoid B2 formation and improve the alloy's ductility. The binary Fe–6.5 wt% Si alloy showed the best magnetic properties, which were ascribed to a recrystallized, coarse grain size (∼500 μm; and 340 μm for the Al-containing alloy). TEM analysis showed that a well-developed B2 domain structure (about 50–300 nm in size) was formed in the binary alloy when low cooling rates are prevailing after heat treatment. This structure contributed to improve additionally the magnetic properties, but its effect was not so strong as that of the grain size. The addition of Al to the binary alloy suppressed B2 formation, as indicated by Mossbauer spectroscopy, and apparently hindered excessive grain growth, which may explain the slightly poorer magnetic properties when compared with the binary alloy.

Influence of the atomization gas on the microstructure and magnetic properties of spray-formed Fe–3%Si–3.5%Al alloys

Despite, the homogeneous and refined microstructure, spray-formed deposits of binary Fe–Si alloys with high silicon content are still difficult to hot/cold roll due to A2-disordered/B2-ordered reactions. The addition of aluminum to Fe–Si alloys may be able to keep the A2-disordered phase metastable at temperatures below 973 K, allowing the deposits to be rolled without cracking while adequately maintaining their magnetic properties. This study is a first attempt to investigate the microstructure and the magnetic properties of spray-formed Fe–3 wt.%Si–3.5 wt.%Al alloy. Argon and nitrogen were used as atomization gases. The addition of aluminum to Fe–Si alloys led to the successful production of thin sheets (0.5 mm thickness) from spray-formed deposits when using argon as atomizing gas. In contrast, the use of nitrogen led to the formation of AlN particles, resulting in excessive brittleness of the spray-formed deposit, which fractured during cooling to room temperature. Otherwise, the magnetic properties of the Fe–3.0 wt.%Si–3.5 wt.%Al alloy performed very well when compared with binary Fe–6.5 wt.%Si, especially when spray formed with argon.

展延性マグネシウム合金AZ31板の機械的性質に及ぼす<br>温間圧延条件の影響

There is high demand for the use of magnesium alloys in automotive and electric parts, because that they have the lowest density among metals for practical use, and have excellent properties such as high specific strength, high vibration damping ratio and high electromagnetic interference shielding. However, there is a little application for magnesium alloys as metal-forming products because of their poor plastic deformability in the normal temperature range and their high production cost. To promote products manufactured by metal forming, rolling technologies enabling the production of thin sheets with suitable mechanical properties and surface qualities are required. For this purpose, hot-rolled AZ31 sheets are experimentally rolled with or without lubrication under temperatures ranging from 293K to 573K, and warm-rolled sheets are annealed for 1h at 523K. Grain structures are observed and their mechanical properties such as tensile strength, elongation and r value are investigated by tensile tests. Finally, the effect of warm-rolling conditions on their grain structures and mechanical properties are discussed for both as-rolled and annealed sheets.

Effect of Processing Parameters on Precipitation Reactions Occurring in a Ti-Bearing IF Steel

The investigation was focused on the detailed description of precipitation/formation processes of TiN, TixSy, Ti4C2S2, TiC, and (Fe,Ti)P particles occurring in the production of thin sheets of titanium-bearing interstitial-free steels. The knowledge concerning this reactions was gained based on the thermodynamic calculation and physical simulations conducted on Gleeble 3800 thermal – mechanical simulator. The formation process of titanium carbosufide of Ti4C2S2 is the crucial reaction for the thin sheets properties. The investigation confirmed the in-situ mechanism of this phase formation, involving carbon diffusion in the TiS and TixSy sulfides’ crystal lattice. Thus, the precipitation of the substantial fraction of these sulfides is a prerequisite for further intense carbosulfide formation. Titanium sulfides are formed at the rough rolling stage of the transfer bar rolling process. The most intense precipitation of the sulfides occurs at around 1000°C. Besides the effect on the carbosulfide formation, it was found out that the sulfides substantially retard the recrystallization and grain growth in the IF steels. The most favourable Ti4C2S2 formation conditions prevail in the temperature range of approximately 950 - 920°C, which corresponds to the plate finish rolling stage. Both reactions, i.e. sulfides and carbosulfide formation, are deformationinduced processes.

Global approach of 3rd octave chatter vibrations at Arcelor Mardyck cold rolling mill and analysis interactions

The 3rd octave chatter in cold rolling mills is a major issue for the industrial production of thin sheets with very tight tolerances, like packaging steels for instance. In this context, an experimental and theoretical approach, completed in partnership by Arcelor and VAI, afforded a precise analysis and innovative results, in the following fields : global on-line tandem mill instrumentation and efficient signal treatments implementation ; clear differentiation between brummer (non divergent mode) and chatter (divergent mode) ; modelling of interactions between chatter and technology (analytical and F.E. approaches) ; advanced chatter monitoring and industrial implementation.

Study of a hybrid joining method using TIG welding: Aluminium alloy (Report 2)

Summary The hybrid joining method has been proposed as a joining method which can be applied to the high precision assembly of thin sheet products. It has been confirmed that good joining results with 2–6 mm thick steel can be obtained consistently using this joining method. In this report, the plug joint and the hybrid joint welding of 1–6 mm thick aluminium alloy sheet were investigated. In plug welding, good results could be obtained only with a limited range of welding conditions using He-AC-TIG. Moreover, to get these results continuously was very difficult. However, by using a hybrid joint with a projection whose height was about 1/3 of the sheet thickness, consistent joining results could easily be achieved in short arc time. In the tensile test of hybrid welded joints, fracture occurred at the joint interface because of shearing forces and joint strength showed constant values.

Uniaxial tensile response of microfibre reinforced cement composites

Microfibre reinforced cement composites reinforced with high volume fractions of carbon, steel and polypropylene fibres were tested in uniaxial tension. Composites investigated included those with only one type of fibre (mono-fibre composites) and those with two or more types of fibres (hybrid-fibre composites) in the same mix. Considerable strengthening, toughening and stiffening of the host matrix due to microfibre reinforcement were observed. In the hybrid-fibre composites, different fibres appear to act as additive phases; i.e., they maintain their individual reinforcing capabilities. The composites were also impact tested in uniaxial tension using a newly designed instrumented impact machine. When compared with static test results, considerable sensitivity to stress rate was noted; composites were found to be stronger and tougher under impact and the improvements were more pronounced at higher fibre volume fractions. The potential of these composites for use in thin sheet products and other similar applications is recognized, and the need for continued research is stressed.

Fibre reinforcement in the cement and concrete industry

AbstractFibre reinforcement in the form of asbestos fibres has been used in the cement industry for nearly a hundred years. However, during the past twenty years a variety of new organic and inorganic fibres have been introduced into the construction industry, and the theoretical understanding of their behaviour at fibre volumes of between 0·1 and 10% in the composite has been comprehensively developed. The major uses of steel and polypropylene fibres are in massive concrete structures whereas carbon, cellulose, glass, natural, polypropylene, and polyvinyl alcohol fibres are used in thin sheet products. The theory and practice of these relatively new bulk marketsfor fibres are reviewed, together with examples of the most widely used products.MST/1950