Seznam abstraktů 2018: POSTEROVÁ SEKCE B
Datum: 24.5.2018
This article is focused on analysis of state formation which influences the tubes production process from austenitic stainless steels with diameter ⌀ 0.34 mm in a negative way. The problems have been concentrated on factors monitoring which affect the drawing process stability of seem tubes where the desired final dimensions – a diameter ⌀ 0.34 mm and a wall thickness 0.057 mm have been limited factors. The seem tube from steel 1.4306 and 1.4301 from producers KRUPP THYSSEN and ERGSTE WESTIG with longitudinal weld line created by TIG welding has been used as a blank for constituent drawing operations. By means of a weld analysis it has been determined that a thermal field creating during a weld formation can cause such material changes which influence to plasticity in a negative way during constituent drawing operations. There is a danger of chromium carbide precipitation along grain boundary in heat affected zone if a weld thermal field isn´t sufficiently cooled. These carbides cause plasticity degradation during technological operations with the most intense strain. It is desirable to provide intense inert gas circulation during a weld creation in air protective chamber.
Flashless forging is one of precise metal forming methods. The main advantages of this method include reduced flash allowance and shorter manufacturing time due to elimination of the flash trimming operation. The paper describes a single-operation forging process for a stepped aluminium shaft based on the use of two-segment dies. The forging was performed as a cold metal forming process. The forging process was analysed numerically in Deform-3D (ver. 11.0). The numerical analysis involved examination of the product geometry and determination of the strains, temperatures and normalized ductile fracture criterion as well as force parameters of the forging process. The numerical results were verified in real conditions using a device that was specially designed for this purpose.
The paper describes the mechanism of destruction of forging die used for plastic working processes by die forging on hammers. The test material was a matrix after exploitation for plastic processing using the hot forging method, made of WNLV grade material. Cyclical changes in temperature and stress in the matrix led to degradation of the structure to the extent that it ruptures during operation. The criterion determining in industrial conditions the degree of remaining operational usefulness is the assessment of material hardness performed by non-destructive methods of hardness measurement (Leeb method). Obtaining extended material characteristics after exploitation will allow to predict the time of safe work of the die, as well as to determine the moment in which the matrix can be repaired, e.g. by making a pad in the working layer or by machining the cavity. The research focused on the assessment of the structure and properties of the damaged matrix. The scope of the work included the assessment of the structure carried out by means of light microscopy, scanning electron microscopy and determination of mechanical properties in the impact test and static tensile test. The obtained results were referenced to the WNLV steel parameters given in the standard.
The influence of two variants of initial soaking at 1100°C/2 h and 1150°C/2 h and parameters of hot plastic deformation on the deformability of an A-286 type superalloy have been presented. The hot deformation characteristics of alloy were investigated by hot torsion tests using Setaram torsion plastometer. The tests were executed at constant strain rates of 0.1 s-1 and 1.0 s-1, and testing temperature in the range of 900°C to 1150°C and were conducted until total fracture of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of maximum flow stresses (σpp) and strain limits (εf). It was found that optimal values of flow stresses and strain limits were obtained for the alloy after its initial soaking at 1100°C/2 h and deformation in the temperature range of 1100÷1050°C at strain rate 0.1 s-1. The increase of maximum flow stresses, σpp, and decrease of strain limit of the alloy, εf, as the initial soaking temperature was rising up to 1150°C/2 h, with the strain rate increasing to 1.0 s-1, was associated with a growth of the initial grain size and the degree of austenite saturation with alloying elements. The relationship between the maximum flow stresses and the Zener-Hollomon parameter (Z) was described by σpp = A × Z exp n power function. Activation energy for hot working (Q) was assessed for the alloy after two variants of initial soaking, i.e. 1100°C/2 h and 1150°C/2 h and amounted - respectively - 442 kJ/mol and 519 kJ/mol.
The zinc coating both increases the corrosion resistance and acts as a lubricator to minimize the friction at subsequent diameter reduction steps. The course of the reaction between the steel surface and the molten zinc depends on the formation and growth of the iron-zinc alloy layers. The type and quantity of zinc coating layer produced depends on many factors particularly, immersion time, zinc temperature, steel wire composition, zinc composition and condition of the wire surface. Process speed change is an important factor as it will affect both the galvanizing time and the wiping of the coating. The as-fabricated galvanized steel wire needs to pass a number of quality tests before going on the market, concerning mechanical and corrosion properties. This paper presents data obtained from trials and production records on the effects of hot dip galvanising on wire properties. In this study, mechanical properties (tensile, elongation, elongation ratio, torsion) and microstructure of alloy layer for different process speeds on 0,83 carbon wires at 3,20 mm diameter were investigated.
Intensity of structural changes during forging is usually determined in dependence on the forging ratio. Forging ratio at elongation is most often calculated with use of simple relations, which are based on the change of cross section of the forged pieces. The intensity of structure development is influenced not only by the simple change of cross sections, but also by relative length of the stroke, magnitude of deformation in individual passes, manner of edging, temperature, friction and shape of anvils. The paper gives an analysis of influence of the relative length of the stroke on the forging ratio.
The article presents results of investigation of structure and properties of low-carbon steel after application of Equal Channel Angular Pressing (ECAP) at the temperature of approx. 290°C. The ECAP method lead to significant improvement of strength of investigated material. Investigation of structure was made by combination of TEM and FEG SEM together with EBSD. It was proven that the ECAP method enables obtaining of ultra fine-grained ferritic structure formed by re-crystallised grains with very low dislocation density and a small fraction of spheroidised carbides, which occurred usually at the ferritic grain boundaries. It was established with use of the EBSD technique that after 8 passes through the ECAP die the sub-grains with misorientation angles smaller than 10° formed less than 20% of the final structure. Average size of ferrite grains with high-angle boundaries after 8 passes was approx. 0.32µm.
The sheet metal pressing structures produced by hydromechanical forming of nickel superalloys were analyzed to determine effect of plastic deformation on the structure and mechanical properties of finished products. The Inconel 625 nickel-alloy sheet metal was extruded with liquid in the form of cones. The drawcpieces were mechanically divided by cutting into main cross sections. An analysis of local deformation distributions, structure deformation level and distribution of alloy components on these sections were evaluated. It has been shown that the plastic deformation carried out by liquid forming (hydroforming) or by a liquid through an elastomeric membrane preserves the original structure and properties of the sheet metal input level, only with the effect of work hardening of tested alloys.
The tube-hydroforming technology has advantages in producing high strength and lightweight structural components used in the automotive industry. In the tube hydroforming process, fracture defect caused by localized expansion of tube cross section is commonly encountered. This study begins with the research on the effects of localized expansion on the formability of tube-hydroformed parts. Then, it focuses on the analysis of applying the tube- hydroforming technology to manufacture a defect-free front sub-frame trailing arm.
In order to understand the influence of localized expansion on the part formability, the localized expansion models were developed in this sutdy to analyze the deformation mechanism resulted by various tube geometry parameters, process parameters and material parameters. Besides, this study also discusses the influence of different rectangular cross-section designs on the accurrence of localized expansion. As for improving the localized expansion phenomenon, the low-pressure hydroforming technology and preformin design were employed in this study to examine the feasibility for avoiding the occurrence of localized expansion. In the future, the research results achieved in this study can be applied to the tube-hydroforming process design for manufacturing automotive components without the occurrence of localized expansion phenomenon.
Numerical simulations are used for process planning of various manufacturing technologies and methods. These simulations are also used in the automotive industry, where currently sharp edges and geometries of small dimensions are used on various carbody parts to fulfill a design function or a function of a specific character. This article deals with the problematics and evaluation of simulations of forming small, sharp geometries and the application and verification of one of the basic laws of plastic deformation - the law of similarity in AutoForm software, which is often used for the planning of carbody parts manufacturing.
The results of numerical calculations performed for selected alloys of titanium and nickel deformed in the Equal Channel Angular Pressing, Twist Extrusion and Cyclic Extrusion-Compression are presented. As representatives of the alloy groups: titanium (Ti-6Al-4V) and nickel (Inconel®718) were chosen respectively. For each variant (process and alloy) distributions of the temperature, mean stress, plastic deformation and load were obtained. Each process was conducted under isothermal conditions to determine the possibilities of deformation of these materials by using of the analyzed SPD processes.
The article concerns the development of a prototype fatigue bench for yoke type forge, with
particular emphasis on the archiving-measurement application that allows the determination
of characteristics (moment and rotation angle). These forgings are used for steering columns
and are a critical element of car safety. Due to the nature of the loads variability occurring in
the element, its high fatigue strength is very important, both in low and high frequency. For
this reason, they require special supervision during production process, development of
advanced techniques for their production and ensuring their repeatability. Unfortunately, in the
case of die forges, no strength tests are carried out for these forgings, which means that after
applying heat treatment, they may have different mechanical properties. The built-up
workstation is intended to enable the performance of fatigue strength tests. For its support,
was developed a web application in Python (with the use of Flask library and SQLite
database), which enables control, collection and analysis of data obtained during the process.
From this reason it is possible to execution of the set number of fatigue cycles, measurement
of the inflection angle, torque or detection of the cracking of the tested material. In the future,
it is planned to extend the workstation and use it to analyze the impact of the applied heat
treatment on fatigue strength, which will be an added value for the end customer.
Cutting is one of the most frequently carried out metal forming processes. One of the basic parameters of this process is the clearance value. The clearance is the difference between dimensions of the punch and the die, usually related to sheet thickness. The amount of clearance affects on geometry and quality of the material cut surface. The cut surface can be divided into the area of rollover, burnish, fracture and burr. Of these areas, only rollover and burr is visible on the sheet surface. In this paper, the authors proposed a method allowing to determine the clearance based on the rollover area measurement. By means of the camera and experimental lighting, it was possible to measure the size of the rollover area without making sheet cross-sections. Proposed vision system allows fast measurements of the rollover area and determine the associated clearance. The experimental measurements were carried out on a deep drawing steel DC04 with a thickness of 1 mm and 2 mm.
Grinding balls efficiency is an important goal to reach. Forged and cast balls are widely used as raw material grinding media in several industrial areas. They are used by various raw material preparation fields. A search for a better service life is a goal most desired by all manufacturers. To improve the performance and increase the service life of ball mill grinding, various approaches have been used among which addition of alloying elements, the use of appropriate heat treatment or the change in manufacturing process.
Since grinding balls are subjected to extreme abrasive and impact conditions; heat treatment must promote the desired properties. The scope of this work is to study the effect of heat treatment on the wear behavior of steel forged balls. Samples of law alloyed carbon steel were austenitized at different temperatures and are subsequently tempered at 250ºC then cooled in water. Samples were observed by optical and SEM microscopy. Hardness and friction tests were measured on all the samples. The obtained results showed the effect of the temperature austenitization variation on wear behavior and hardness values of the studied forged steel balls.
It is known that shear strain occurring in the asymmetric rolling process causes improving of the mechanical properties especially in the production of sheet metal. In this paper the influence of the deformation in asymmetric rolling process on the equivalent deformation distribution and austenite microstructure changes are presented. Numerical analysis of the C45 steel plate rolling process with reduction ε = 30 % in temperature 1000°C has been made by using Forge 3D computer program. The analyze of influence of different rolls speed ratio in range Av= 1,0 ÷ 1,5 were done. Based on austenite microstructure evolution model the austenite grain size as a result of asymmetric rolling processes with different coefficient of rolls speed ratio was determined. It was found that strain distribution was inhomogeneous. The zones of increased strain were observed, which affected the uneven distribution of austenite grain size. Increasing different coefficient of roll speed ratio caused a reduction in the uniform distribution of strains, and thus led to a more even distribution of the austenite grain size.
Deformation behavior of continuously cast steel with 0.43 % C, 1.01 % Cr and 0.19 % Mo was studied in the austenite region. Its solidus temperature was calculated as 1435 °C and the nil strength temperature at heating was determined as 1402 °C using a special testing method. Hot ductility was measured by means of the uniaxial tensile tests in wide range of mean strain rate (0.00073 – 63 s-1) and temperature (800 – 1375 °C). At medium strain rate of 0.65 s-1, formability steadily increased to a temperature of approx. 1335 °C and then sharply dropped as a result of overheating and burning of the steel. The nil ductility temperature was determined as 1365 °C in this case. Influence of strain rate on formability was evaluated at two temperature values corresponding to relatively poor and/or good plastic properties. At a temperature of 900 °C, ductility increased rather moderately with the increasing strain rate. At a temperature of 1280 °C, the growth of ductility at increasing strain rate was sharper and both dependencies intersected at a strain rate of approx. 0.008 s-1. Formability was improved by higher temperature at high strain rates and deteriorated at very low strain rates, which is a quite unique result. It was not possible to determine the value of the strain rate corresponding to the local maximum of ductility, even if applying the strain rate range of 6 orders. SEM analysis of the broken samples confirmed the expected influence of microstructure development on hot formability.
The authors of this paper present assumptions and preliminary results of investigational and FEM numerical simulations laser-mechanical hybrid forming of thin-walled elements. According to establishments an experimental stand was designed and then manufactured. The equipment is intended for bending thin-walled tubes and conical diffusers used in the construction of aircraft engines. Method and experimental stand tested under laboratory conditions, as well as the results of the numerical analysis of the process show new possibilities thin-walled elements forming.
The paper presents the characteristics and possibilities of the rolling mill line based on a Duo D-300 rolling mill located at the Institute of Metal Forming and Safety Engineering at the Czestochowa University of Technology. Since 2012 has been started a new laboratory of semi-industrial rolling mill. Through the years, basic 2-high rolling mill with independent drives of each roll has been successively expanded by the innovative elements and equipment as: fully mechanized and automated roller tables with regulation of the position or active heat shields of the rolled feed. In parallel, the measurement and control system integrating all elements has been developed, based on programmable logic controllers. A full technical characteristic and research ability of this rolling mill system have been presented in this paper. A lot of advanced experimental works and scientific researches in area of plastic working processes of metals has been conducted using the system. The characteristic of a few most interesting works were described e.g. asymmetrical rolling of the plates, the rolling with heat treatment of special steel grade (X80 or X100) for pipeline installations, the rolling of preliminary explosively welded bimetals, including light weighted bimetals and tri-metals based on magnesium and aluminum alloys.
Over the last few years, the great attention was paid to materials with grain size of diameter smaller than 1 μm. These materials were classified as Ultra Fine Grained (UFG) materials with diameter of grains of the order of 100 to 1000 nm and nano-materials with mean diameters of grains smaller than 50 nm. This research concerned to the production of UFG materials, using Severe Plastic Deformation (SPD) process. One of the forming methods using the SPD process is the DRECE method. This method was used to achieve the UFG structure in brass strip sheet.
In the present paper, the brass CuZn37 strips sheets were processed by severe plastic deformation by DRECE method. The mechanical properties and structure achieved in individual passes by the forming device at room temperature were analyzed. Deformation route „C“ was applied, i. e., the sheets were rotated about 180° between subsequent forming passes. It was found that process SPD (Severe Plastic Deformation) has a significant influence on the increase mechanical properties of forming materials. The obtained results are detailed analyzed in the final part of this paper.
The paper presents computer modelling and experimental results of investigations on forcing through process of round bars. The calculations were carried out using the commercial code QFORM-2D, based on the Finite Element Method (FEM). The investigations involved the use of circular sectioned S355 (1.0577) steel segments of rods with diameter d0=9mm. Result of calculations of forcing through process were validated against experimental data in terms of changes in forces for different elongation factors (λ1= 1.24, λ2= 1.37, λ3= 1.57). The aim of the paper is to compare the experimental and computer modelling changes in forces for different degree of deformations. The results of investigations into forcing through process might be used as guidelines to develop a technological process for industrial practice.
The peak point coordinates (i.e. peak stress, peak strain) play a significant role in case of a flow curve description. These coordinates are strongly dependent on the temperature and strain rate, so they need to be related to these thermomechanical circumstances before use in the flow stress models. In this research, the experimental peak point coordinates of the C45 and 38MnVS6 steels were described in a wide range of thermomechanical conditions by use of two different methodologies. The first one was based on the ordinary predictive relationships utilizing the well-known Zener-Hollomon parameter. The second one was based on the artificial neural network approach. The aim was to compare appropriateness of these methods. The results have suggested better aptness in case of the assembled neural networks.
The paper investigates the influence of hot-working parameters on the course of thermally activated dynamic and static processes in HSLA (High Strength Low Alloy) constructional steel, containing 0.17% C, 1.37% Mn and microadditions of Nb, Ti, V in the amounts of 0.025 %, 0.004% and 0.019%, respectively. In order to determine the s-e curves and the kinetics of recrystallization of plastically deformed austenite, the Gleeble 3800 thermomechanical simulator was used. Specimens were tested in the temperature range from 900 to 1000°C, at the deformation rate of 3 s-1. Microstructure of primary austenite was revealed after two-stage compression of samples with given strain, with isothermal holding for the period of 0.2 to 120 s; the activation energy of plastic deformation process of examined steel was determined. Obtained research results will allow to develop the technology of HSLA type microalloyed steel metal plates with the method of thermomechanical treatment - recrystallization controlled rolling.
The paper describes an application of a new helical-wedge rolling (HWR) process for producing ball pins. The design of this technique and tools used in the process are described. The proposed rolling method was validated by numerical and physical modelling. The numerical analysis was performed using Forge NxT 1.1 and involved determining the distributions of the effective strain, tempe¬rature and damage function in the workpiece as well as variations in the forming forces and torque. The physical modelling was carried out in a standard rolling mill using plasticine as a material model, which allowed for examination of changes of the workpiece geometry and determination of the torque. The numerical results confirm that the proposed HWR process can be used for the mass production of ball pins.
Accumulative roll bonding (ARB) is one of the severe plastic deformation methods of producing ultrafine grained laminated metal composites (LMCs). This paper is focused on LMCs consisting of dissimilar bimetal system of aluminum alloys AA1050/AA6061. One difficulty of roll bonding two dissimilar materials is bending and rupturing caused by the difference in plastic flow behavior. Compared to conventional ARB the asymmetric accumulative roll bonding is more appropriate for the production of dissimilar bimetal composites. This paper presents the results of the finite element simulation and comparison of strain behavior during symmetric and asymmetric accumulative roll bonding of AA1050/AA6061 bimetal composites. The influence of thickness reductions, rolls speed ratios, friction conditions and layer thicknesses of AA1050 and AA6061 on the interface stress-strain state were analysed by FEM in details.
The method of determining the tendency to galling in microforming processes is introduced. The method consists in the drawing process of the strip with a width of 1-3 mm and a thickness of 0.3-1 mm using a cylindrical tool with a radius of 2.5 mm. The process force as a function of sliding distance is recorded. On the basis of the character of the force course, the coefficient of galling tendency is determined. The process is carried out in a specially designed device placed on the table of testing machine. The device is equipped with a piezoelectric vibrator that allows the tool to be vibrated in accordance with the tape drawing direction with adjustable frequency and amplitude. The stand has been tested statically and dynamically, achieving the assumed construction parameters, i.e. the vibration amplitude in the range of 0-10 um and the frequency 0-300 Hz. In the initial tests carried out, the effect of using vibrations with specific parameters on the tendency to galling and the surface condition of deformed materials was found.
Method DRECE (Dual Rolls Equal Channel Extrusion) belongs to a perspective group of technologies utilizing the process of severe plastic deformations (SPD). Used for forming of metallic materials. On the newly developed forming device, unlike the rolling technology, the material is significantly strengthening after the forming process, while maintaining the initial strip sheet dimensions. This is a special extrusion process. We want to achieve a significant increase in mechanical properties in as few passages as possible by the forming device, in particular increasing the yield strength Re and the ultimate tensile strength Rm, while maintaining good formability. The basic of the DRECE forming method: The sheet metal sheet is inserted into the forming device, the movement of the strip is provided by a feed roller and a pair of pressure rollers. With the optimum pressure setting of the pressure rollers, the resulting frictional force enables the extrusion process to be performed. The above-described forming method was used to extrude of low carbon steel (sheet strip). Overall, the effect of the individual passages on the increasing of mechanical properties of low carbon steel as tested in a total number of 1 to 7 passes through forming device. The forming tool, according to the pre-performed experiments, was chosen with an inclination of 108 ° in the deformation zone. The mechanical properties obtained after each pass through the forming device from the tensile tests and the influence of the anisotropy of steel on the mechanical properties (in the longitudinal, transversal direction and at the 30 ° deflection with respect to the rolling direction of the sheet) were analyzed and the microstructure of the strip sheet was evaluated.
The high-strength steels and tailor welded blanks (TWB) are applied in construction of cars parts to reduction of cars weight. The application of these materials brings possible complicatons during the forming because of different stress-strain characteristics of TWB individual parts what results in non-constant material flow and consequently a negative movement of the weld interface. One of the ways of elimination of this negative effect is to choose a suitable blankholder system with optimal distribution of blankholder forces by using elastic blankholder with adjustable distribution of blankholder forces. Within the frame of this study the experimental blankholder system with elastic blankholder with adjustable distribution of blankholder forces was used. The Finite element methods (FEM) simulation has unsubstitutable role in the study of TWB formability whereby it is possible to determine the values and points of application of the blankholder forces. The FEM simulation results carried out in simulative LS-Dyna software are presented in this article which is focused on achieving weld interface movement minimalization of tailor welded blanks from DP600 and BH220 materials by optimization of blankholder forces.
Limit values of the normalized Cocroft – Latham criterion for different values of temperature and strain rates may be determined by using the comparative method for the uniaxial tensile test of notched specimens. Uniaxial tension of notched specimens was performed on a multi-function metallurgical process simulator, Gleeble 3800, available at the Modelling and Automation of Plastic Working Processes of the Czestochowa University of Technology. In order to determine the actual values of the normalized Cockroft - Latham criterion, theoretical studies of the notched specimen tension process were. In order to determine the limiting value, the normalized Cockroft-Latham criterion values were summed for the finite elements existing in the notch axis, while preserving appropriate weights.
The ultra-fine grained austenitic AISI 304 stainless steel sheets were prepared using the asymmetric cryorolling (ACR) technique. The symmetric rolling (SR), the cryorolling (CR) and the asymmetric cryorolling technique were performed. Different rolling techniques were compared with regard to the resulting mechanical properties. Electron backscatter diffraction (EBSD) technique was used to explore both the structure and the texture evolution.
In comparison with the symmetric rolling (SR), the asymmetric rolling (ASR) process imposes additional shear strain to the normal plane strain on the conventional symmetrically rolled sheet. A large plastic strain has a direct influence on the process of the grain refinement. Many studies have shown that cooling the steel to the sub-zero temperatures supresses the dynamic recovery, thus improving the grain refinement process. A combination of high speed ratio ASR (1:2,3) and CR (liquid N2) gives rise to the stainless steel with exceptional values of the tensile strength and the ductility at the same time.
Reversible two-stand two-high laboratory mill TANDEM was used to study the effect of simulation parameters on the final properties of HSLA steel strip with 0.08 % C, 1.26 % Mn, 0.05 % Ti and 0.03 % Nb. The flat samples were heated at 1230 °C for 20 or 60 minutes and rolled from thickness 24.0 mm to 3.2 mm by 6 passes. After finishing at approx. 868 °C, three different regimes of cooling were applied: free air cooling only, accelerated water cooling down to 560 °C followed by 1-hour stay in furnace at this temperature (simulating the conditions in industrial strip coil), or water spray cooling followed by free air cooling to room temperature. Ductility of the laboratory rolled products was almost constant. Yield stress and strength was only little influenced by simulation complexity after accelerated cooling, but these values were much lower after simple free air cooling (minus 80 MPa in average). After free air cooling, final equiaxed ferrite grain size was rather greater in the case of longer heating (5.2 vs 4.5 µm), but the microstructure was quite different after accelerated cooling when accicular ferrite occurs and pearlite disappears. The obtained results are important from point of view of the physical simulations methodology.
Achieving a very high degree of deformation in sheet metal forming is a very complex problem. It is the main prerequisite for achieving an ultra-fine grain structure in the material. For the extrusion of the sheet of Cu with the DRECE method, at least 8 - 10 passes through the forming tool must be performed to achieve sufficient refinement of the structure. This is in contrast to a much smaller number of passages to achieve an equally high degree of deformation in the ECAP method when we use the passage type marked as "Bc" (only 2 to 3 passes). This method is used only for square or circular cross-section blanks. The paper analyzes the increase of mechanical properties and the refinement of the structure on the newly developed forming device (three-roll feed of the material combined with extrusion) for the Cu sheet metal strip, when choosing the "Bc" deformation path (rotation of the strip 90 ° after each pass). Furthermore, a mathematical simulation of the process was performed and the results were compared.
This paper presents numerical and experimental results of a study investigating a rolling method for producing balls for grinding mills from webs cut off scrap railway rails. The paper is divided into two parts. The first part describes the design of the proposed rolling technique for producing balls and the advantages of using billet obtained from scrap railway rails. In this paper a two-stage rolling method for producing balls is proposed. The first stage consists in shaping the web of a scrap railway rail into a round bar in two roll passes. Then, in the next stage, the semi-finished product is formed into balls using a skew rolling mill. The other part of the study presents a selection of numerical results obtained for the designed rolling technique for balls. The numerical analysis was performed by the finite element method with FORGE. Next, the FEM results are compared with findings of experiments conducted in longitudinal and skew rolling mills. The numerical and experimental results demonstrate that that the proposed longitudinal and skew rolling processes are an effective way of producing balls from webs of scrap railway rails. Produced balls have sufficient accuracy to use them as grinding media in ball mills.
Mold design and sheet metal parts production are very important issues in terms of cost and time in vehicle development process in automotive industry. In Automotive ındustry, hydro formic process is especially preferred for the production of difficult, complex and narrow tolerance parts. However, hydroforming process has some drawbacks such as long process time and high pressure requirements, highly needed polished mold surface and hydraulic sealing problems. These drawbacks cause rising the unit price of produced parts. The fact remains that, knowledge and experience about this process and mold design in the sector is also limited. The production of closed non-linear parts is difficult with the traditional molding method due to their geometries, for this reason traditional molding methods generally not preferred by the companies. Hydroforming is the main process for the production of non-linear pipes and tube parts instead of molding. The objective of this study is about to produce nonlinear pipe sections (such as lower control arms) by conventional molding method instead of hydroforming. The production of nonlinear pipe sections by conventional molding is a method which is not very common in the world due to forming difficulties, tolerance and surface problems. But here, production of this nonlinear part is achieved with the curling method that have been have developed by our company so a new know-how accumulation has been created.
This paper deals with optimization of roll cooling during hot rolling of tubes in stretch reducing mill (SRW) in Železiarne Podbrezová. Temperature of the tube after rolling in SRW should be higher than Ar3 as much as 30 ÷ 50 °C. Current practice in SRW cooling system in Železiarne Podbrezová utilizes nozzles A with nominal flow rate of 10 l/min. These nozzles cannot maintain stable spray cone for lower flow rates that are necessary to pass the Ar3 rolling temperature limits. Prospective nozzles B with nominal flow rate of 5 l/min were tested and evaluated. Although the highest possible rolling temperature is of primary importance here, overheating of the rolls should be avoided at all costs. All our experiments were carried out with single temperature of the furnace in which hollows are preheated prior to rolling. Surface temperature of the rolls was measured by means of K-thermocouple contact measurement system.
Modern approaches and materials must be used to achieve mass reduction of car body parts. Important step is to depict processing of these materials in detail. This article deals with a comparison of deep drawing test of DP500 steel and results of numerical simulation. To achieve this a forming tool with simple shape was designed. The goal of this article is to evaluate prediction of defects (splits, wrinkling, necking and marking lines) in designed stamping.
The manufacturing of high quality steels is connected to high temperatures at which the material reacts with the surrounding atmosphere. A layer of iron oxides (scales) is formed on the surface of the steel. To assure a high quality product, the layer must be removed prior any metal forming operation. The mass production of steel requires quick and effective method of descaling. In the overwhelming majority, the descaling is performed by high pressure flat jet water nozzles placed in a row.
This article builds on the previous manuscripts of the process optimization and further studies the effect of offset angle of the nozzles on the uniformity of cooling impulse on the surface of the hot rolled steel strip. Current research has brought a significant improvement in the area of measuring of the heat transfer coefficient.
Article compares two configurations of nozzles and presents the impact pressure measurements and corresponding heat transfer coefficient measurements for both of them. The results so far showed that commonly used configuration is not optimal from a cooling point of view. New suggested configuration presents a new method how to make the cooling impulse more uniform along the width of the hot rolled steel strip and the cooling rate of the descaled surface.
The cold drawn wires are used to spring manufacturing in automotive and whiteware equipment. The most important mechanical properties of the wire used in spring production are tensile strength and minimum number of twists in the torsion test. In this study, the change of mechanical properties was examined by drawing wire with a diamater of 3,80 mm from wires with diameters of 7,00 and 8,00 mm diameter by cold wire drawing. The 3,80 mm wire was drawn from both the 7,00 mm wire at 6 steps with a diameter reduction of %70 and from 8,00 mm wire at 7 steps with a %77 diameter reduction. Following the production of the 3,80 mm wires, the values of tensile strength, elongation, elongation ratio, torsion, galvanizing thickness as micro, surface quality as macro were investigated by mechanical and microscobic analyzes.
Forming dished end-plates of tanks loaded vacuum must be a compromise between the ideal shape of the bottom in terms of load carrying and the shape of the dished end-plates which is easy to perform in the workshop. The article analyzes the output laden vacuum tank concept in terms of load transfer vacuum. Compared to the ideal effort of the tank shell to the container dished end-plate which was welded sheets.