Structure Of Billet Research Articles

Simulation and Experimental Study on the Effect of Superheat on Solidification Microstructure Evolution of Billet in Continuous Casting.

The control of the solidification structure of a casting billet is directly correlated with the quality of steel. Variations in superheat can influence the transition from columnar crystals to equiaxed crystals during the solidification process, subsequently impacting the final solidification structure of the billet. In this study, a model of microstructure evolution during billet solidification was established by combining simulation and experiment, and the dendrite growth microstructure evolution during billet solidification under different superheat was studied. The results show that when the superheat is 60 K, the complete solidification time of the casting billet from the end of the 50 mm section is 252 s, when the superheat is 40 K, the complete solidification time of the casting billet is 250 s, and when the superheat is 20 K, the complete solidification time of the casting billet is 245 s. When the superheat is 20 K, the proportion of the equiaxed crystal region is higher-the highest value is 53.35%-and the average grain radius is 0.84556 mm. The proportion of the equiaxed crystal region decreases with the increase of superheat. When the superheat is 60 K, the proportion of the equiaxed crystal region is the lowest-the lowest value is 46.27%-and the average grain radius is 1.07653 mm. Proper reduction of superheat can obviously reduce the size of equiaxed crystal, expand the area of equiaxed crystal and improve the quality of casting billet.

Effect of magnetic alternate stirring on solidification structure of the round billet

ABSTRACT In this study, a permanent magnet stirrer was constructed for the implementation of experiments on different magnetic field stirring modes. Through experiments, it can be observed that when the fixed speed of 200 rpm and the alternate stirring mode of magnetic field was adopted, the loose area in the core of ingots was reduced from about 72 mm2 to 21 mm2, which significantly improved the density and element uniformity of the ingot. A Φ220 mm SAE1527 round billet was selected as industrial trial steel. When the stirring current and frequency was 350 A and 3 HZ, the electromagnetic stirring of the mold was adjusted from continuous stirring to alternate stirring mode. The solidification structure of the billet has been improved to a certain extent. Furthermore, the number of spot segregation larger than 0.5mm2 was reduced from 43 to 26, thereby improving the uniformity of internal elements in the billet.

Drawing fracture behavior and mechanism analysis of ER50-6G welding wire steel

In this paper, we investigated the drawing fracture behavior of ER50-6G welding wire steel and analyzed the factors affecting the fracture, such as continuous casting slag and inclusion, billet structure segregation, Ti inclusion, surface defect inheritance, metallographic structure type, fracture morphology, and so on. OLYMPUS GX53 optical microscope was used to observe and analyze the macrostructure of the cross-section and longitudinal section of the continuous casting billet and the original quality state of the wire rod surface. The continuous cooling transformation curve (CCT curve) of the steel was measured using a DIL805A thermal dilatometer and a Gleeble-3500 thermal simulation test machine. The microstructures of the non-fracture area and drawing fracture of wire rod samples were observed through a ZEISS-ULTRA scanning electron microscope. The results show that the austenite starting transformation temperature (Ac1) and the austenite finishing transformation temperature (Ac3) of ER50-6G welding wire steel are 732 °C and 865 °C, respectively. Under the actual cooling conditions of online production, the strip structure is composed of ferrite (F), pearlite (P), and a small amount of bainite (B). There is a small amount of slag and inclusion in the continuous casting billet; in addition, Al2O3 inclusions and TiC (or Ti(C,N)) inclusions can be observed in the wire rod. The scratch depth of the wire rod surface is 24∼62 μm and the width is 31∼50 μm. With the increase in drawing cumulative deformation, the Al2O3 and TiC (or Ti(C,N)) inclusions that are not easy to deform lead to drawing fracture and brittle fracture. In addition, a small amount of bainite in the wire rod microstructure causes the fracture of the wire with a fine diameter, whereas, the limited-depth scratches on the steel surface do not have an obvious effect on the drawing fracture.

Вплив режимів роботи електромагнітного перемішувача на структуру сортової заготовки в умовах сучасних мікро-заводів

Вплив режимів роботи електромагнітного перемішувача на структуру сортової заготовки в умовах сучасних мікро-заводів

Influence of Thermal Limiters on the Formation of the Dendritic Structure of the Welded Stainless Steel Layer

In the work the influence of thermal limiters on the formation of a dendritic structure of the stainless steel AISI 304L layer deposited by electric arc welding in argon medium was investigated. The structure of the billets was investigated in the mode of differential interference contrast. The analysis of the obtained structures showed that the use of thermal limiters in the form of graphite skids allows to obtain a uniform structure in billets without sharp transitions between the deposited layers.

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.

Thixoforming and Rheo-Die-Casting of A356/SiC Composite

This research investigated the rheo-die-casting process and the production of an A356/silicon carbide (SiC) composite by a thixoforming. The composite contained 15 percent by weight SiC particles of around 15–37 µm in size as the reinforcing phase. The composite feedstock was produced by semi-solid stir-casting, where pretreated SiC powder was gradually added into the A356 alloy melt to form a continuously stirred slurry composite melt, which was then cast in a steel mold. For thixoforming, the feedstock was reheated to 583 °C (approximately 0.4 fraction liquid), and its viscosity was reduced with shear rate, implying that A356/SiC exhibits shear thinning or non-Newtonian behavior. This is caused by the characteristic billet structure obtained having relatively globular grains that accommodate the flow of the semisolid composite. In the rheo-die-casting process, the A356/SiC feedstock was re-melted at 610–615 °C (approximately 0.8–0.9 fraction liquid) prior to die-casting and the resulting slurry was injected into a die with injection speeds of 3 and 4 m/s and pressures of 11 and 12 MPa, respectively. Two work-pieces of 16 × 15.6 × 205 mm3 were produced in one shot, and the resulting samples were subjected to T6 solution treatment at 540 °C for 1 h, quenched, and aged at 135 °C for 12 h. The results show that both low speed and low pressure rheo-die-cast samples exhibit uneven filling at the end of the part, whilst both high pressure and high speed promote more uniform distribution of SiC particles throughout the part length. In the as-rheo-die-cast condition, the most uniform of microstructures and hardness obtained from a sample fabricated at 4 m/s speed and 12 MPa pressure.

Dynamic Crack Resistance and Steel 09G2S Tubular Billet Structure After Deformation and Heat Treatment

The structure and the dynamic crack resistance of steel 09G2S tubular billets are compared after a heat treatment and different versions of deformation and heat treatment, including cold plastic deformation by radial forging and subsequent annealing. Radial forging followed by annealing has a favorable effect on strength and dynamic crack resistance, which confirms the possibility of industrial use of tubular billets from steel 09G2S after cold radial forging.

Effect of Casting Temperature on Continuously-Cast Bearing Steel GCr15 Billet Structure Formation

Modeling is conducted for solidification and formation of a cast structure of continuously-cast blooms of steel GCr15 (Russian analog is steel ShKh15). A finite element method is used in order to model the formation of the crystal structure of continuously-cast blooms. Solidification is modelled for a bloom of steel GCr15 470 × 350 mm in cross section with different values of steel overheating above the liquidus line. Results of modeling are used for simulating continuously-cast billet macrostructure. It is shown that with a reduction in casting temperature the extent of the columnar crystal zone is reduced gradually within the structure, the extent of the skin and equiaxed zones is expanded, grain density increases gradually, and the maximum grain area and radius are significantly reduced. There are no small size fine dendritic crystals within the center of the equiaxed grain zone.

Effect of Crystal Structure Fineness for Charge Alloy AK6M2 on Its Flux Treatment Efficiency

The effect of charge billet structure and form of fluxes on structure, density, and gas content of alloy AK6M2 (Al – Si – Cu system) is studied. Alloys prepared from finely crystalline charge billet have smaller phase component sizes, lower gas content, and increased solid state density, and use of coarsely crystalline charge billets for alloy preparation necessitates an increase in flux preparation consumption in the stage of alloy preparation for casting.

Modeling the structure formation during hot deforming the billets of the parts of gas-turbine engines made of heat-resistant nickel alloy

The results of finite-element and physical modeling of deformation heating and structure formation during high-temperature isothermal upset of a cylindrical billet according to various modes (continuous and fractional deformation) have been presented. The results of numerical modeling, which agree with the experimental modeling data, showed that, in order to minimize the deformation heating and formation of a homogeneous ultrafine-grain structure in bulk billets made of heat-resistant alloys, it is purposeful to perform the deformation fractionally (with a single degree no larger than 30–50%), which allows for the deformation rate and performance of post-deformation annealing. The formation of an ultrafine-grain structure in the billets made of nickel alloys (for example, EP742U) guarantees an increase in the quality of ready wares.

Numerical simulation of solidification structure of high carbon SWRH77B billet based on the CAFE method

Based on the coupled method of cellular automaton (CA) and finite element (FE), the solidification structure of 160×160 mm cast billet of high carbon SWRH77B steel was simulated. The nucleation density, kinetics of the dendrite tip growth, crystallographic orientation and coupling of CA and FE methods are discussed. In the current study, the influence of superheat on the solidification structure of the billet is researched in detail. The results show that for an increase in superheat extent from 20 to 30°C, the density of grain in billet decreased from 4·662×106 to 3·087×106 m−2, and the grain mean radius increased from 295·1 to 346·3 μm. The three-dimensional microstructure of high carbon SWRH77B steel was simulated by the CAFE method, and there was good agreement with the results from industrial billet.

Effects of U-Shape Inner Cooler on Flow and Solidification of Molten Steel in Slab Continuous Casting Mold

An inner-outer coupled cooling technology of molten steel for 1240×200mm slab continuous casting, that is to set an inner cooler—U shape pipes in the mold, is put forward in order to enhance the efficiency of transmitting heat and improve inner structure of billet. The flow status and solidification status of molten steel under coupling flow field and temperature field in inner-outer coupled cooling mold are simulated by using fluid dynamics software, and compare with those in traditional mold. It is found that setting inner cooler in the mold can make molten steel flow status even, which is favorable to floating up of the inclusion, quickening the solidification of steel liquid and improving the quality of billet.

Numerical Simulation of Filling and Solidification Process for Low Superheat Billet Continuous Casting

In view of the process of flowing steel before the establishment of strip casting, the low superheat forced pouring continuous casting technology, i.e. the molten steel is cooled by the rotating cooling rollers, then it is forced to flow into mold, has been put forward in order to reduce superheat of liquid steel, enhance the efficiency of heat transfer and improve inner structure of billet. The filling and solidification processes of low superheat casting and submerged entry nozzle(SEN) casting are numerical simulated using fluid dynamics software. It is gained that velocity distributing diagrams, temperature distributing diagrams and solidification distribution diagrams at different time in the filling process. Influences of twin-roller cooling pouring on velocity field, temperature field and solidification are analyzed. The results show that the superheat of liquid steel is decreased and the solidification rate of liquid steel is increased by low superheat casting of twin-roller cooling process, which is favorable to improving the quality of billet and enhancing pull speed.

Macrosegregation Mechanisms in Direct-Chill Casting of Aluminium Alloys

This review paper summarizes the results of recent studies on different mechanisms of macrosegregation upon direct-chill (DC) casting of aluminium alloys. In general, the main mechanisms of macrosegregation have been identified quite some time ago as thermo-solutal convection, free-moving crystals, shrinkage- and deformation-induced flow, and forced convection. Despite this general knowledge, the separation of the effects of these mechanisms on the overall macrosegregation pattern and the ratio of their contribution remained largely unexplored. With the advances in computer simulations and in experimental techniques it becomes possible to look at the impact of individual mechanisms in relation to the macroscopic parameters of the transition region of a DC cast billet and to the microscopic parameters of billet structure. Our systematic research helps in interpreting the apparently contradictory experimental macrosegregation profiles reported in literature. Paper is illustrated by own experimental and computer-simulation results.

Semi-solid squeeze casting process of a ZL109 alloy

The structure evolution of the ZL109 alloy in the process of semi-solid squeeze casting and the mechanical properties of the components were investigated. The results show that (1) the eutectic silicon phase in original billets is refined in the low super-heat casting process; (2) the eutectic structure in billets starts to fuse and the crystals of the eutectic silicon phase are refined further and sphericized in the remelting process of billets; (3) in the semi-solid squeeze casting process, the sphericity of the α phase and the refining of the silicon phase occur, owing to the friction between solid and liquid; (4) in the process of heat treatment, the eutectic α phase aggregates with the primary α phase and the eutectic silicon pieces aggregate together. The elongation of the semi-solid component after heat treatment rises to 1.42%.

Size effects of the cavity dimension on the microforming ability during coining process

Abstract With the miniaturization of the parts, the size effects occur in microforming processes. To investigate the effect of die cavity dimension on the microforming ability of the billets, the coining tests have been carried out with pure aluminum using groove width from 40 to 120 μm at the temperature of 400 °C. The experimental results show that the microforming ability decreases with the increasing of ratio L/b when the ratio L/b is less than 0.5, and the microforming ability increases with increasing of the ratio L/b when the ratio L/b is larger than 0.5. These phenomena might be analyzed from the viewpoint of multi-grain structure of billet. Following that, the isothermal microforming processes of microgears are carried out, and the successful manufacture of the microgears indicates that the billet can fill a very small die cavity completely.

一方向貫通気孔を持つ多孔質アパタイトの製造と組織制御

By using molten wax colloidal process with graphite powders as combustible pore-forming agents, a method for controlling the porosity and pore size of porous hydroxapatite ceramics has been developed. Porous hydroxyapatite with unidirectionally aligned continuous pores were fabricated by multistage extrusion of green billets. Starting billet of this multistage extrusion was made from stacking hydoxyapatite green disks of outer diameter 50mm and inner diameter 25mm filled with 100% graphite green disks of 25mm. In order to make the porous matrix, the mixture of hyroxyapatite and graphite was used instead of hydroxyapatite. By the primary extrusion, hexagonal rods with the graphite in the central part were extruded. These extruded hexagonal rods were bundled to make composite billets for the next stage extrusion. This process was repeated for several stages. Finally, the extruded rods of proper stage were sintered. Size of the continuous pore can be controlled by total extrusion ratio. The pore diameter obtained in the present work was from 350μm to 8μm. The porosity can be controlled by the billet structure. The mean flexural strength of the porous hydroxyapatite ceramics obtained in this work was from 32MPa to 56MPa.

As-Cast Microstructure in VDC Cast AA 6082 Billet

The as-cast microstructure, in a cross-sectional slice of a 204-mm diameter vertical direct chill cast billet of AA 6082, was investigated with optical microscopy, backscattered electron microscopy, electron probe microanalysis and Thermo-Calc simulations. The major intermetallic phases present in the billet structure were found to be Al-15(FeMn)(3)Si-2 and Mg2Si. The pi-AlSiMgFe type intermetallic phase was also observed but its presence was limited. Except for the surface region, no obvious difference was found in the distribution of intermetallics across the billet section. For the surface segregation zone (less than or equal to 300 mum in depth), many coarse intermetallic colonies (similar to100 mum) were observed with a volume percentage of about 14.5%, compared with 2% in the centre.

Influence of billet structure of the quality of stamped heavy duty semifinished products fabricated from the Al?Zn?Mg?Cu?Zu system

Influence of billet structure of the quality of stamped heavy duty semifinished products fabricated from the Al?Zn?Mg?Cu?Zu system