Cross Section Of Billet Research Articles

Friction stir consolidation for recycling AA6061 chips with its metal flow investigation for billet production

This study aims to produce a billet from AA6061 chips recycling by adopting friction stir consolidation (FSC) technique. AA6061 was used to form different shapes of chips with a thickness of 1 mm. The billet was produced by stacking and forming the chips inside the cylindrical die adopting the friction stir consolidation technique with a rotating tool. Three parameters were considered: preheating time, rotating speed of tool, and depth of plunging, with three levels for each parameter. A Taguchi strategy was implemented to design the experiments (DOE) and analyse the billet properties. The billet cross-section was examined by the optical and scanning electron microscope examinations. The billet was successfully produced by recycling the AA6061 chips. The production mechanism occurred by grains elongating, metal flow, and welding the chip’s boundaries with the applied pressure and input heat. Minor defects such as cracks and porosities were found in the entire surfaces of the billets. The presence of the defects relied on the process variables. The billet's surface appearance or quality depended on the tool's depth of plunging. The tool's revolving speed and depth of plunge determined the process's temperature. The depth of plunging was the most influential parameter on the surface quality of the billets. Raising the depth of plunging and rotational speed generated higher heat input, which increased the weldability between the chip’s boundaries and reduced the surface defects. Regions of sufficient input heat during the stir forming process exhibited complete welding between the chip’s boundaries without defects. The best forming condition achieved among all runs was at (1800 rpm rotational speed, 1 min. preheating time, and 35 mm depth of plunging). For the first time, the friction stir consolidation process produced the billets by recycling the AA6061 chips without any material loss.

Modelling and Optimization of Process Parameters during Grooved Hot Rolling of SAE 1020 Steel

ABSTRACT The rolled SAE 1020 steel bars are widely used for production of mechanical components, such as, gears, spindles, camshafts, axles, fasteners, and gudgeon pins etc. Steel industries have been striving for productivity and better yield of hot rolled bar products. The roll separating force (RSF), driving torque (DT), end crop length (ECL), and drive energy (DE) are the important response parameters to be controlled for quality production, maximization of yield (i.e. minimization of rolled bar process scrap), safety of mill and reduction in energy consumption, etc. These response parameters depend on several process parameters – rolling speed, billet temperature, reduction ratio, billet cross-section area, roll diameter, etc. This paper presents a study on the effect of the process parameters on the response parameters during rolling of SAE 1020 steel. Simulation of the rolling process has been attempted using FORGE® NxT 1.1. The simulated results so obtained have been validated through experimental results obtained in a rolling mill, following statistical tests. Regression models showing relationship between the process parameters and the response parameters have been developed. Significant model terms have been obtained using ANOVA. The optimum rolling conditions for minimization of the response parameters have been obtained.

Неметалеві включення в металі котельних безперервнолитих заготовок

The article presents results of studies of contamination of metal of undeformed continuously cast billets (CCB) for boiler tubes from carbon steel supplied by various manufacturers with non-metallic inclusions. Contamination was investigated by metallographic means using methods of observation under a microscope in light and dark fields of vision in polarized light. Application of these methods has made it possible to determine the inclusion types (silicates, oxides, sulfides) with high probability based on optical properties (color, transparency, etc.). Shape, size and type of inclusions and the nature of their location along the billet cross-section were determined for the data set of actual level of contamination of the CCB metal with non-metallic inclusions. In addition, the methods Sh and L according to DSTU 8966 were used. To determine the number, dimensions and types of inclusions, an automated control method using the VIDEOTEST-METAL 1.0 software was also used for the Axiovert 200MAT microscope. Composition of some non-metallic inclusions was studied by means of X-ray spectral microanalysis using the MS-46 microprobe of the Cameca Co. (France). It was established that irregular and rounded silicates of both homogeneous and heterogeneous composition (including individual large ones up to 150 μm in size) are main types of inclusions in metal of continuously cast billets. In most cases, these inclusions are located in axial and peripheral zones along the CCB section. Intermittent film precipitation of non-metallic inclusions of varying degrees of dispersion (mainly of small size) which can have a negative effect on service characteristics of tubes made from such CCB was also detected. The study results have important scientific and practical significance in conditions of wide use of such CCB in the production of tubes of responsible purpose. The obtained study results will make it possible to further develop an advanced methodology of assessing the contamination of non-deformed continuously cast billets (with scale) with non-metallic inclusions in their metal and introduce them in regulatory documents on the CCB. The results of studies of metal contamination with non-metallic inclusions will also be useful for improving the CCB production technology with the aim of producing boiler tubes of high operational reliability. Keywords: undeformed continuous cast tube billet, non-metallic inclusions, silicates, film precipitation of non-metallic inclusions.

Evaluation of efficiency of methods for drawing round wire with large diameters

Drawing in monolithic draw dies is the primary and often nonalternative pressure metal treatment (PMT) method used in the wire manufacture for various purposes both in our country and abroad. Its effectiveness largely depends on the wire diameter and properties. Thus, when drawing wire of large diameters (>8.0 mm) from high-carbon steels (high-tensile reinforcing wire, spring wire, etc.), the stability of the process and the probability of metal fraction decreases. The use of classic roller draw dies increases the strain uniformity along the wire cross-section, reduces the force and multiplicity of drawing. However, the «circle-shaped section-circle» roller gauge system used in this process leads to a more complicated process, and most importantly, to a significant increase in production costs. In this paper, a comparative analysis of the drawing efficiency of a round billet with a diameter of 16.00 mm from steel grade 80 into a wire with a diameter of 14.25 mm (strain degree 21%) in one step in the classic monolithic draw die and roller draw dies: three-roller draw die with a spatially closed round gauge and three-roller draw die of radial shear strain. The latter is comparable to the well-known radial-shear rolling. The difference is that the energy is introduced into the deformation zone by applying a front pulling force, and the idler rollers rotate around the wire with a special drive. The authors used finite element modeling in the Deform-3d software package. The deformed state in processes with linear tensile strain was estimated by the distribution of the accumulated strain degree in the billet cross-section, and in processes with torsion – by the change in the curvature of the line applied to the side surface of the billet. The power parameters were determined in Deform-3d in the coordinates: drawing force – time of billet movement. The stress state was determined by the hydrostatic stress on the wire axis and the Cockcroft-Latham fracture criterion. It is established that the wire strain in a monolithic draw die is characterized by a significant strain inhomogeneity across the cross-section, monotonous flow, high energy consumption, and the wire collapsibility, especially of the mid-layers. The use of draw dies with a spatially closed round gauge reduces the drawing force by about 40%, reduces the degree of strain inhomogeneity along the cross-section, and increases the degree of accumulated strain. The radial-shear strain drawing significantly increases the degree of accumulated strain and provides grain grinding, especially in the surface layers of the wire.

Strengthening of Materials by Equal Channel Angular Pressing Using ANSYS

Equal channel angular pressing (ECAP) is one of the popular severe plastic deformation processes used to produce bulk nano structured materials. It is well known that large deformation results in microstructures with small grains and extensive dislocation cells development, often leading to corresponding increases in strength. In order to design an equal channel angular pressing (ECAP) die that can be used to process a variety of materials, it is crucial to understand the effect of die design and material parameters on the deformation behaviour, strain distribution and load requirement. In this analysis, the effect of internal die angle (Φ) and number of passes (N) on the strain behaviour of engineering materials and alloys, during ECAP was investigated by using three dimensional finite element analyses. The benefits of ECAE come from its ability to impose intense simple shear deformation through innovative die design. Unlike conventional extrusion processes, the cross section of billets extruded via ECAE is not reduced. Entire work will be carried out with the help of SOLID WORKS, ANSYS. These ultra-fine grained materials can be used in the manufacturing of semi-finished products used in the power, aerospace, medical and automotive industries.

Microstructure Evolution in Cu–0.5 wt% Zr Alloy Processed by a Novel Severe Plastic Deformation Technique of Rotational Constrained Bending

In the present study, a coarse-grained Cu–0.5 wt% Zr alloy was repeatedly processed by a novel technique of rotational constrained bending (RCB). In this technique, the workpiece was deformed by bending in a channel with an angle of 90°, using a rotating roller. The influence of the number of passes (N) of RCB on strain distribution, microstructure evolution and mechanical properties of the alloy was investigated. The heterogeneous distribution of the microhardness in the billet cross-section after the first pass was transformed into a homogeneous one after twelve passes, due to the rotation of the sample by 90° clockwise between individual passes. In addition, the gradual refinement/homogenization of the microstructure and formation of strong (110) crystallographic texture were found with increasing N. The initial grain size of 180 μm decreased down to 3.4 μm after twelve passes. The dislocation density increased by two orders of magnitude after RCB processing. In accordance with the grain-size refinement and the strong increase of the dislocation density, RCB processing significantly enhanced the strength of the alloy, while the ductility considerably decreased. The yield stress increased from 63 to 524 MPa, while the elongation to failure decreased below 10% after twelve passes.

Statistical Research of Stainless Austenitic Steel Grain Size Distribution after Screw Rolling.

Screw rolling of austenitic stainless-steel billets was conducted in two- and three-high mills. Statistical research results showed that, compared to heated but not rolled conditions, both screw rolling techniques provided a decrease of grain size, variance, grain size distribution asymmetry, and excess in the billet cross-section at the stationary stage of screw rolling. At that stage, grain size distribution after two-high screw rolling is closer to normal in terms of asymmetry and excess values compared to grain-size distribution after three-high screw rolling. A strong negative correlation between strain effective values and grain-size values for the cross-section of the rolled billets at the stationary stage was revealed for both two- and three-high screw rolling.

Numerical simulation of macrosegregation in continuously cast gear steel 20CrMnTi with final electromagnetic stirring

A 3D/2D hybrid multi-physical-field mathematical model, which takes into consideration the thermosolutal buoyance, was developed to predict the macrosegregation of gear steel 20CrMnTi continuously cast by a curved billet caster with size of 160 mm × 160 mm, and investigated the effect of final electromagnetic stirring (F-EMS) on the fluid flow, heat transfer and solute distribution in the liquid core of continuously cast steel. The results show that the application of F-EMS eliminates the effect of thermosolutal buoyancy on the asymmetric distribution of carbon concentration in the cross section of billet and accelerates the final solidification of resident molten steel in the liquid core of strand, but promotes the negative carbon segregation near the billet center. When the gear steel 20CrMnTi is cast at the temperature of 1803 K and speed of 1.7 m/min, the solidification end advances forward from 9.84 to 9.72 m, and center carbon segregation ratio of billet decreases from 1.24 to 1.17 with the increase in current density of F-EMS from 0 to 350 A.

Study on Solidification Structure Evolution of Direct-Chill Casting High Purity Copper Billet Using Cellular Automaton-Finite Element Method

A heat transfer model and a cellular Automation-Finite Element (CAFE) coupling model were established to analyze the solid/liquid (S/L) interface and solidification structure evolution of high purity copper Direct-chill (DC) casting billet under different casting conditions. The simulation and actual experimental results of liquid sump shape and solidification structure were first compared to verify the accuracy of the model. It is proved that the model is effective for simulating the solidification structure of the actual DC casting high purity copper billet. After that, the model was used to predict the solidification structure under different casting temperatures, casting speeds, and heat transfer coefficients. It is shown that, with the increase of casting temperature, the grain size decreases first and then increases. There is a compromise between grain size and its uniformity, and the grain size is more uniform at higher casting temperature. With the increase of casting speed, the depth of liquid sump and the height of the S/L interface increase, but the total grain number of the billet cross-section decreases gradually. As the heat transfer coefficient increases, the depth of the casting liquid sump becomes shallow, but the height of the solid-liquid interface increases and the grain size increases gradually. For the preparation of high purity copper billets with large cross-sectional dimensions by DC casting, a fine solidified structure could be obtained by appropriately reducing the casting speed and cooling intensity.

Influence of Die Surface Topography and Lubrication on the Product Quality during Indirect Extrusion of Copper-Clad Aluminum Rods

Copper-clad aluminum rods are usually fabricated using hydrostatic extrusion, since during direct and indirect extrusion fracture of the copper sleeve is difficult to avoid. In this study, different die surface topographies and lubrication conditions were applied to improve the material flow during indirect extrusion of copper-clad aluminum rods. Thus, conic dies with different roughness (polished and sandblasted) and surfaces shapes (fine and coarse grooves) were tested. Additionally, the effects of a wax-graphite-based lubricant as well as a graphite-like carbon (GLC) coating of the die conic surfaces were investigated. The composite billets were made of aluminum EN AW-1080A cores and copper CW004A sleeves with an equivalent copper cross section of 0.24 of the total billet cross section. For all trials, an extrusion ratio of 14.8:1 and a conic die angle of 2α = 90° were chosen. Non-isothermal extrusion trials were carried out using a container at 330 °C and billet and tools at room temperature to reduce the flow stress ratio σCu/σAl. The extruded composite rods’ integrity, surface quality, interface integrity, and equivalent copper cross section were analyzed. In addition, a visual inspection of the sleeve-die contact surface was performed. The results showed that the GLC coating proved to be unsuitable due to a lack of lubrication, which causes accumulated sleeve fractures and longitudinal grooves on the extruded rods. The best results were achieved with the combination of the sandblasted die surface and the wax-graphite-based lubricant, observing a uniform material flow without sleeve fractures.

METALS HEAT TREATMENT MODEL

This paper considers the problem of developing a model of thermal metal processing by multiprocessor computing systems. The obtained metal is used for high-strength fasteners manufactured by cold forging method without final heat treatment. The model is based on the heat treatment method of a billet from low- and medium-carbon steels intended for cold heading. The model aims at improving technological properties of a billet by ensuring high dispersion and uniformity of a billet structure across the entire plane of its cross-section.Implementation of the proposed model ensures the technical result of high dispersion and uniformity of the structure of the billet. The technological process of steel heat treatment is characterized by high performance, low power consumption, and improved performance characteristics. The apparatus for implementation of the spheroidization annealing regime determines the uniform distribution of cementite globules in the ferrite matrix, which means that it provides the necessary mechanical properties of the metal for its further cold deformation. The multiprocessor computing system software allows controlling the temperature conditions, both on the entire plane of the billet section, and across its length. Such temperature conditions are controlled in the center of the plane of the billet cross-section.Experimental studies of the heat treatment of metal products were conducted. In order to test the functions of the proposed model, several experiments were performed when a 20 mm diameter wire from 20G2G steel was subjected to heat treatment. Experimental studies have shown that metal has the necessary elasticity properties, saving the required hardness.

Microstructure evolution in a CuZr alloy and CP Ti processed by a novel technique of free bending in rotating rollers

A novel technique referred to as free bending in rotating rollers was employed to refine the initial structure and to produce gradient fine-grained microstructures in the Cu0.5Zr alloy and commercially pure titanium (CP Ti). A newly designed die allowing a continuous and repetitive movement of a workpiece through a set of rollers in a channel bent by 90 degrees was employed to produce a series of billets after different numbers of passes resulting in different strains imposed on the billet. Microstructure evolution with increasing number of passes was characterized by precise measurements of microhardness (HV) distribution along the cross section of individual billets. The heterogeneous distribution of HV observed after a single pass was transformed to almost a uniform one in the whole cross section of the billets after 8 passes. EBSD analysis and TEM observations revealed a significant microstructure refinement in both materials after the final stage of processing. A homogeneous microstructure with an average grain size of about 300 nm was observed in CP Ti, whereas the microstructure of the Cu0.5Zr alloy was not fully refined and exhibited a bimodal grain size distribution. The experimental results were compared with the theoretical modelling of strain distribution by FEM.

Twisted Multi Channel Angular Pressing (TMCAP) as a Novel Severe Plastic Deformation Method

The Twist Multi Channel Angular Pressing (TMCAP) process is presented for the first time to investigate the mechanical properties of AL1050 numerically and experimentally. TMCAP that can be categorized as a SPD method is a process based on combining the Equal Channel Angular Pressing and Twist Extrusion processes. The process was simulated entirely using dynamic explicit solution of ABAQUS/software. Based on the simulation results as well as considering the hydrostatic pressure effect on die filling and strain distribution, the TMCAP die was designed in which the horizontal channel creates a required hydrostatic pressure during the process. This process can effectively impose large strains to a bulk material to enhance the mechanical properties. Upon on a single pass of routes, a value of nearly 2.4 total strain was obtained without having significant changes in the billet cross section. In addition, the load obtained from simulation of TMCAP process at the first pass was about 22 tons which has a good conformity with the value obtained from experimental study. The process was also repeated up to four passes to evaluate the subsequent mechanical properties such as the flow stress and the Vickers micro-hardness as well as microstructure after each pass.

Effect of Final Electromagnetic Stirring Parameters on Central Cross-Sectional Carbon Concentration Distribution of High-Carbon Square Billet

The effect of final electromagnetic stirring parameters, with current intensity increasing from 300 A to 400 A and frequency increasing from 4 Hz to 12 Hz, on the electromagnetic forces and carbon concentration distribution of the central cross section of a 70 steel square billet have been studied. Along the center line of the liquid core zone, current intensity of 400 A and frequency of 8 Hz achieve the maximum electromagnetic force at the position 48 mm away from the billet edge among the 10 groups of stirring parameters. Nevertheless, along diagonal of the liquid core zone, the electromagnetic force near the diagonal center is the greatest and the current intensity of 280 A and frequency of 12 Hz obtain the maximum electromagnetic force. The optimal final electromagnetic stirring (F-EMS) parameter to uniform the central cross-sectional carbon concentration and minimize the center carbon segregation of 70 steel billet was obtained with a current intensity of 280 A and frequency of 12 Hz. Under this stirring parameter, the area ratios of carbon concentrations of 0.66 wt%, 0.70 wt% and 0.74 wt% in the middle of the billet cross section reached 28.5%, 56.9% and 10.9%, respectively. Moreover, the carbon segregation indexes for all sampling points were in the range of 0.92–1.05.

Consequences of microphysical segregation of chemical elements in welded steels

Defects of metallurgy-originated steel (sub-cored bubbles, impurities, macro- and micro-segregations of chemical elements, nonmetallic inclusions) to a large extent determines the faultiness of metal rolled products. The processes of chemical elements segregation in steel macro- and micro volumes considerably influence its quality. Reasons of microphysical dendrite segregation originating in steels of welding purpose of Св-09Г2С and Св-08ГНМ type considered. Mechanism of dendrites formation studied as well as the segregation degree of chemical elements along the continuously casted billet cross section. To estimate the segregation degree a criteria was used – the segregation coefficient, determined as relation of chemical elements mass shares in different micro-areas (dendrites, inter-dendrite gaps) of continuously casted billet cross section to those elements content by a ladle analysis of a heat or one another in different micro-areas. A heredity of segregation transfer from CC billet to finished wire rod of Св-08Г2С and Св-08ГНМ steels studied. It was determined, that decrease of the number of bainite-martensite areas as a result of decrease of dendrite segregation of chemical elements takes place by minimization within grade chemical composition of both main alloying element and impurities ones. Besides an additional alloying of steel by boron takes place based on boron to nitrogen relation at the level of B/N = 0,8±0,15. It was shown that to decrease the inter-dendrite segregation it is necessary to elaborate and implement effective steel modifying by calcium and REMs regimes as well as electro-magnetic stirring during continuous casting.

Analytical and numerical modelling of open-die forging process for elliptical cross-section of billet

The present work proposes a novel analytical solution for open-die forging for the billet of elliptical cross-section. From design and evaluation, moreover, from industrial prospective, in order to overcome the limitations and complexities of mathematical modelling for complex shape billets, the numerical simulation technique has also been demonstrated to establish and exploit the potential of commercially available finite element analysis (FEA) software. To start with, testing of fundamental material properties such as tensile and compressive tests have been simulated and validated against experimental data of aluminum alloy such as AA6063-T7 and AA6061, respectively. In a similar manner, the FEA simulation for a closed-die forging process has been carried out and validated against experimental result. Subsequently, a mathematical model for open-die forging having elliptical cross-section of billet has been derived with certain predefined assumptions. The potentials of FEA simulation for different materials such as aluminum alloy (AA6063), mild steel and brass, have also been investigated to justify the proposed analytical solution, which has been noticed to have less than 5% error. The intricacies involved in the simulations along with mathematical modelling have been discussed in detail in the present article.

Pulse electromagnetic force microstructural control at continuous billet casting 7xxx Al-alloys

In this study, the original equipment and methods for the macro/microstructure managed formation in the crystallizers of continuous casting processes by the applying of the amplitude modulated (AM) pulsing magnetic fields (PMF) it the electromagnetic stirrer (EMS) has been developed and tested.Method has provide the complex electrodynamic, hydrodynamic and acoustic pulse-force processing of unsolidified casting product portion for providing equalizing of solidification front in the billet mushy zone. Resulted non-dendritic type of microstructure has been provide by the means applying: Pulse magnetic field with periodically changing in time amplitude (AM-PMF); Pulse amplitude-modulated rotating melt stirring (AM-PRMF); Pulse amplitude-modulated 3D-helicoidally rotating melt stirring.Study efficiency applying of unidirectional axial pulse magnetic field (AM-PMF) with pulse frequency in range 5~15Hz, carried frequency in range 22∼55Hz, at intensity of MF 0.05∼0.1T, for semi-continuous 7xxx alloys (analogue 7075 alloy) 7 ‘billet casting on micro- and macrostructure billet formation has been show reaching the stabile effect for non-dendrite state microstructure formation in all billet cross-section. As well-achieved uniform and homogeneity microstructure state with average grain size not more 100μm, and for middle and central billet part in range 60∼80μm, in 3∼5 times lowest instead grain sizes 200∼650μm at DC casting without EMS, or instead 150μm grain sizes as for conventional rotating EMS. As well, fully solved problems of axial and structural segregation, hot-crack ability or micro-cracks on grains edges and micro-porosity occurring.

Quantifying Crystallographic Texture Variation in a Titanium Billet

Ti-834 and other titanium alloy forgings can contain regions of similarly orientated primary alpha grains called macrozones that can have a deleterious effect on performance in-service. Understanding the origin of macrozones and how they change during processing is an important step in optimising process routes for these alloys. In this work a detailed characterisation of crystallographic texture variation was carried out on the cross-section of a 250 mm diameter Ti-834 billet using optical metallography, EBSD and neutron texture analysis. Results showed there was a variation in texture and macrozone size and shape through the billet with each macrozone composed of a single hcp component, with varying degrees of orientation spread. The texture of the majority of macrozones can be classed as either axial (c-axis parallel to the billet axis) or transverse (c-axis perpendicular to the billet axis). In the centre of the billet cross-section, the global texture was dominated by a fibre-like {10 1 0} texture due to a dominance of transverse macrozones. At the edge, there was a greater proportion of axial macrozones which gave rise to an additional {0002} component.

Predictive Mathematical Model of the Process of Metal Heating in Walking-Beam Furnaces

We propose a mathematical model for the analysis of the temperature distribution in the cross-section of billets heated in walking-beam furnaces and the determination of rational lengths of the zones of the furnace in the design stage. The influence of the size of the gap between the billets on the dynamics of their heating is investigated. We determine parameters affecting the output of the furnace and the volumes of fuel consumed for heating.

Study on the pre-shearing cropping process of steel bars

A new type of bar-cropping process, termed the pre-shearing cropping process, which can improve billet cross-section quality has been proposed in this study. The new cropping process was realized by using a servo-controlled press. A low-carbon steel 20Cr as-received and a medium-carbon steel SCM435 as-annealed were used to test the process. A group of pre-shearing cropping experiments was carried out with different pre-shearing values of 6.67, 13.33, 20.00, and 26.67% under a pre-shearing speed of 10 mm/s and a cropping speed of 600 mm/s, and conventional cropping experiments with different cropping speeds of 200, 400, and 600 mm/s were conducted for comparison. The quality of the cropped billets was evaluated quantitatively using the indices of surface flatness, ovality, and incline angle. The effect of cropping speed on the conventional process and the effect of pre-shearing on the pre-shear cropping process were investigated in detail. The experimental results showed that the pre-shearing cropping process could improve the quality of the cropped billets and reduce the maximum cropping load slightly compared with the conventional cropping process. Finally, the mechanism of the pre-shearing cropping process was furtherly analyzed by finite element simulation and tried to be summarized.