Pouring Temperature Research Articles

Taper barrel rheomoulding process for semi-solid slurry preparation and microstructure evolution of A356 aluminum alloy

The self-developed taper barrel rheomoulding (TBR) machine for light alloy semi-solid slurry preparation was introduced. The semi-solid slurry was obtained from the intense shearing turbulence of the alloy melt in the cause of solidification, which was further caused by the relative rotation of the internal and external taper barrel whose surface contained wale and groove. The heat transmission model of TBR process, the flow rules and the shearing model of the alloy melt were deduced. Taking A365 as experimental material, the microstructure evolution rules under different slurry preparation processes were analyzed. The results show that decreasing the pouring temperature of A365 alloy melt properly or increasing the shearing rate helps to obtain ideal semi-solid microstructure with the primary particle size of about 70 μm and the shape factor of above 0.8.

Simulation of semisolid diecasting process of four-way valve of HPb59-1 alloy for air-conditioner

There exist many problems in producing four-way valve of HPb59-1 alloy for an air-conditioner by traditional solid state hot forging, i.e. larger forming loads, lower material utilization, larger subsequent machining allowance and nonuniform microstructure. For this reason, based on the orthogonal test, the semisolid diecasting process of a certain type of four-way valve was simulated with FLOW-3D. The simulation results show that the optimized process parameters are: the pouring temperature of 897.25 °C, the shot velocity of 2.0 m/s and the preheated die temperature of 260 °C. The simulation results demonstrate that the cavity can be filled smoothly and completely, the surface defects are small, the temperature field and the pressure field are uniform, and the casting quality is satisfactory. The effectiveness and availability of applying this technology are well verified by the numerical simulation.

Semisolid Microstructure Evolution during Cooling Slope Casting under Vibration of A380 Aluminum Alloy

This study is concerned with the influence of the vibration at a specific frequency to the inclined plate during cooling slope casting. A380 aluminum alloy was employed in the present work. The alloy was poured from the inclined plate with an angle of 60°and a length of 500 mm at a pouring temperature of 630°C. The pouring was carried out on an inclined plate with and without vibration. Microstructures of specimens obtained from both conditions were examined. Grain size analysis of specimens was carried out. Experimental results showed that the application of vibration affected the microstructure. Hence, it was determined that the application of vibration increased the nucleation and led to more breaking of dendrite arms. In this study, the convection of melt by vibration played an important role on formation of non-dendritic primary Al-particles.

Fabrication of WC/Fe composite coating by centrifugal casting plus in-situ synthesis techniques

Using tungsten wires as a reactive source, an iron-based composite coating, reinforced by tungsten carbide (WC) particles, with a thickness of 3.0 mm, was fabricated on the surface of a gray cast iron substrate by centrifugal casting plus in-situ synthesis techniques. With the help of differential thermal analysis (DTA), an appropriate pouring temperature of the gray cast iron molten was determined to be 1300 °C. The experimental results show that the composite coating is dense and consists mainly of primary WC carbides, fine secondly WC carbides as the reinforcing phases and pearlite accompanied by negligible graphite flakes as the matrix. Wear resistance of the composite coating was determined with a pin-on-disc wear test technique, indicating that the composite coating, containing high volume fraction of hard WC carbides, present good wear resistance property compared with the un-reinforced gray cast iron, regardless of load level. Additionally, according to the Fe–W–C ternary phase, reaction paths between tungsten wires and molten, and in-situ synthesis of WC particles, were investigated.

Deformation Behavior of Semisolid A356 Alloy Prepared by Low Temperature Pouring

The deformation behaviors of A356 alloy with various initial grain structures, from a very coarse dendrite to a fine equiaxed structure, prepared at different pouring temperatures, from 625°C to 725°C, were investigated. Cylindrical specimens with 12 mm in diameter and 10 mm in height were compressed in the semisolid state to a height reduction of 6 mm at an initial strain rate of 1.39 × 10−3/s and then jumped to 1.39 × 10−2/s. The instantaneous strain rate sensitivity was calculated under iso-structure conditions. Three very different deformation behaviors have been observed, which are believed to have resulted from their different starting microstructures. The materials produced at low pouring temperatures evolve into a fine globular structure after isothermal holding at semisolid region and shows a very low compression stress, while the materials cast at high pouring temperatures remain as coarse and dendritic in its microstructure and have much higher compression stress. The macrostructural breakage and microstructural segregation of hot compressed samples were analyzed, and the deformation mechanisms were discussed. The low temperature poured material is not sensitive to an instantaneous change in strain rate, while the high temperature poured material is very sensitive.

Preparation of in situ-formed WC/Fe composite on gray cast iron substrate by a centrifugal casting process

An iron-based composite reinforced by in situ-formed tungsten carbide particles was fabricated on gray cast iron substrate by a centrifugal casting process. The as-prepared composite was characterized by X-ray diffraction, scanning electron microscopy, and microhardness and wear testers. An appropriate pouring temperature (1300 °C) of the gray cast iron melt was chosen considering the dissolution temperature of the tungsten wires determined by differential scanning calorimetry. The experimental results showed that the tungsten wires were dissolved partially by the cast iron melt. As a result, primary and secondary tungsten carbide particles and pearlite with a negligible amount of graphite flakes were formed as the reinforcing phase and the matrix, respectively. The composite with a thickness of about 3 mm was dense and metallurgically bonded to the gray cast iron substrate. Wear resistance was determined by a pin-on-disc wear test technique, indicating that the composite containing high volume fraction of hard tungsten carbides presented higher wear resistance compared with the unreinforced gray cast iron.

EFFECTS OF COOLING RATE AND POURING TEMPERATURE ON MICROSTRUCTURE AND FRACTURE TOUGHNESS OF THE INDUCTION MELTED Nb-16Si-22Ti-2Hf-2Cr-2Al ALLOY

The effects of cooling rate and pouring temperature on microstructure and fracture toughness of the induction melted Nb -16 Si -22 Ti -2 Hf -2 Cr -2 Al alloy were extensively investigated. The results revealed that with the decrease of cooling rates, the Nbss exhibits the dendrite-like morphology, the primary Nb 5 Si 3 blocks form and the mean sizes of Nb 5 Si 3, Nbss and eutectic colonies increase; with the increase of the pouring temperature, the microstructure shows columnar structure and the particles of Nb 5 Si 3 or Nbss become long and thin. Pouring temperature and cooling rate had little influence on the volume fractions of Nbss and Nb 5 Si 3 and their compositions. The Nb 3 Si phase eliminated in the case of high pouring temperature and slow cooling rate. Fracture toughness of the alloy prepared by induction melting is on the order of 13.7 to 15.3 MPa·m1/2. Similar fracture toughness value of each slab may be ascribes to the same volume fraction of the Nbss .

Simulation of solidification microstructure in twin-roll casting strip

The twin-roll strip casting is regarded as the most prospective technology of near-net-shape casting. The control of the grain structure is of primary importance in twin-roll strip casting because the solidification microstructure has great influence on the quality and mechanical properties of strips. In this paper, a three-dimensional cellular automation (CA) finite-element (FE) model within CALCSOFT3D package is used to simulate the microstructure of steel strip twin-roll casting. The Gaussian distribution of nucleation sites is adopted both at the mold surface and in the melt. The KGT model is used to describe the growth kinetics of dendrite tip. Then the influence of the casting conditions such as pouring temperature and heat transfer coefficient between the rolls and the solidified strip on the strip solidification microstructure is detailed investigated. The predictions show that the temperature profile and solidification microstructure are most sensitive to the pouring temperature. And with the increase of the pouring temperature, grain density obviously increases. However, the influence of three bottom cooling conditions on microstructure formation has little difference in this study.

THE OPTIMIZING CONDITIONS BY TAGUCHI METHOD FOR FABRICATING SEMI-SOLID Al–Zn–Mg ALLOY SLURRY BY COOLING PLATE METHOD

In order to optimize the condition for the semi-solid Al–Zn–Mg aluminium alloy fabricated by cooling plate method, the Taguchi design was used. The cooling plate method effectively separating the grains formed from the mold wall can be used to form a semi-solid material by flowing molten metal over an inclined Cu plate and casting in a mold for the near-net shape component. In Taguchi's design method, the higher signal vs noise (S/N) ratio the better. Therefore, the manufacturing conditions were arranged as a table of orthogonal arrays (L9(34)), and the influence of two factors, pouring temperature and cooling plate angle, was examined. From the observed microstructures, the grain size and aspect ratio were measured by image analyzer. The results indicated that the pouring temperature exerts the main effect on the spherical microstructures since the S/N ratio, which is the sensibility of the surrounding environment, was the highest. The optimum condition for the Al–Zn–Mg alloy was a cooling plate angle of 40° and a pouring temperature of 680°C. The grain size and aspect ratio were 70 μm and 1.3, respectively.

Longitudinal surface cracks of thin slabs

Based on the production practice of medium carbon thin slabs in the CSP plant, the reasons and influencing factors for the formation of longitudinal cracks were investigated, and some industrial measures were taken to eliminate the cracks. The results show that the efficient solutions to reduce longitudinal cracks are improving the performance of the mold powder, stabilizing the mold heat flux, and maintaining a proper taper of the mold during casting. Proper pouring temperature and secondary cooling also play important roles in preventing longitudinal surface cracks.

Failure Analysis of Cast Lead–Antimony Battery Grids

This paper presents the failure investigation of lead-acid battery grids received from a local battery manufacturer. Distortion, cracking, and brittleness were observed in as-cast grids. These battery grids were gravity cast by re-melting of locally made Pb–Sb ingots. However, similar distortion and brittleness were not observed in grids of similar design cast by re-melting of imported Pb–Sb ingots. Spectroscopy, optical and scanning electron microscopy, SEM–EDS analysis, and microhardness measurements were carried out on both types of grids to find out the root cause of failure. It was concluded that the distortion and cracking were mainly caused because of coarse dendritic microstructure with interdendritic and intercellular segregation produced by either high pouring temperature or low cooling rates employed during casting. This conclusion suggests that the casting parameters may have differed for the two types of ingots used. However, another contributing factor was thermal stresses induced during solidification and the brittleness of the locally produced ingots which contained a high arsenic content.

Heat shock behavior of permanent die during non-solid near-net forming process

Heat shocks caused by alloy melt and coat spraying are the main reason of die plastic deformation and early fracture. Based on theoretical analysis of heat shock phenomenon, two characteristic parameters of die damage caused by heat shock were proposed, which are heat shock plastic deformation index (HSPI) and heat shock crack index (HSCI). The effect of heat shock on die plastic deformation and fracture behaviors was described quantitatively by these two parameters. HSPI represents approaching of heat shock stress to die yield stress. Plastic deformation will happen on a die if this index reaches 1. HSCI represents approaching of heat shock stress to die tensile strength. Die fracture will happen if this index reaches 1. According to theoretical analysis of heat transfer, theoretical models of HSPI and HSCI were established. It is found that, the smaller the interfacial thermal resistance (ITR) is, the higher the pouring temperature and die temperature are before heat shock, and the greater the HSPI and HSCI are, which can be fitted as exponential curves, linear and cubic curves.

Quality Improvement of Aluminum Alloy (LM-6) Casting Using Taguchi Method

There is no alternative to the intricacy; evidenced through sand casting as a production route, economical and poised for shorter runs. Quality of castings and parametric control thereof is more important than that of die casting. With increasing demand for high-quality castings at close tolerances, a need however was felt to study ways to get the optimal settings for main parameters to ensure better surface finish. The requirement in unison was hitherto attempted in case of LM-6 Aluminum alloys castings, developed through green sand casting route. Five main parameters namely Bentonite clay, AFS Grain Fineness Number, Moisture, Pouring temperature and Coal dust were duly identified. The effects of the selected process parameters on the surface finish and the subsequent optimal settings of the parameters were accomplished using Taguchi’s method. Using L8 (27) orthogonal arrays, experiments were conducted as per experimental plans given in this array. The results indicate that the selected parameters significantly affect the surface finish of LM-6 Aluminum alloys castings. The confirmatory experiments have also been carried out to verify the optimal settings of the parameters.

Semisolid A356 alloy feedstock poured through a serpentine channel

Fine spheroidal and equiaxed nondendritic microstructures required for semisolid casting can be formed through a serpentine pouring channel. Effects of the pouring temperature and the vertical section length of the serpentine pouring channel were studied. The results indicate that both favorable semisolid microstructures of A356 aluminum alloy can be generated by a serpentine pouring channel, and the solid shell inside the channel can be avoided when the pouring temperature is in the range from 660 to 680°C. It is also shown that the vertical section length of the serpentine pouring channel has a significant influence on the microstructure of the feedstock, namely both the microstructure of the feedstock and the microstructure uniformity in the radial direction get worse when the vertical section length is shortened; moreover, the pouring temperature for obtaining the feedstock with suitable microstructure decreases. The relevant mechanisms were discussed.

Annulus electromagnetic stirring for preparing semisolid A357 aluminum alloy slurry

The effects of pouring temperature and annulus gap width on the microstructure of the semi-solid A357 aluminum alloy slurry prepared by annulus electromagnetic stirring(AEMS) technology were investigated. The results show that low pouring temperature and narrow annulus gap are advantageous to obtaining the small spherical primary α(Al) phase. The lower the pouring temperature is and the smaller the annulus gap width is, the more uniform, the smaller and the more spherical the microstructure is. The microstructures obtained by the ordinary electromagnetic stirring and AEMS were compared. The results indicate that the primary α(Al) particles are globular, small and distribute homogeneously in the slurry obtained by AEMS. But in the slurry obtained by the ordinary electromagnetic stirring, the primary α(Al) particles are small dendrites in the edge of the slurry and they are large and rosette-like or dendritic in the inner of the slurry.

Solidification microstructure and temperature field during direct chill casting of Al-16Si alloy

By properly controlling casting parameters such as pouring temperature, casting velocity and water flux, direct chill (DC) casting can be employed to produce refined microstructure in the hypereutectic Al-Si alloys without chemical modification. This refined microstructure is characterized of fine primary Si particles, fully developed dendritic Al halos and fine coupled eutectics. In this work, in situ measurements of temperature field in the mould during DC casting of Al-16Si alloy at casting velocity of 2.17 mm/s, 3.5 mm/s and 4.34 mm/s at a pouring temperature of 800°C were performed. The results show that the primary Si phase nucleated at considerable undercooling (about 27°C to 38°C) and the growth temperature of dendritic Al halos was 7°C to 8°C below the equilibrium eutectic temperature. In the center regions of the DC cast billet, halos are fully developed because the Gl/R value is low.

Vertical Indirect Squeeze Casting Process of an Al-Cu-Mn Alloy Frame Part

To decrease weight and increase fuel efficiency, an Al-Cu-Mn alloy frame part with vertical indirect squeeze casting process was fabricated to replace original parts with spheroidal graphite iron, which is used in a special vehicle. Mold filling of the frame with pouring temperature of 700°C and injection velocity of 0.03m/s was simulated. According to the results vents and overflows were designed and the dies were produced with H13 steel. Furthermore, the casting trial producing was conducted. Cross sections of the castings were checked. A number of specimens were obtained from different parts of the castings to evaluate microstructure, and both high dense and fine grain microstructures were found in the specimens. Mechanical properties of the tensile samples with T5 heat treatment were measured, and the average tensile strength and elongation were 387 MPa and 8.8%, respectively.

Centrifugal casting processes of manufacturing in situ functionally gradient composite materials of Al-19Si-5Mg alloy

Cylindrical components of in situ functionally gradient composite materials of Al-19Si-5Mg alloy were manufactured by centrifugal casting. Microstructure characteristics of the manufactured components were observed and the effects of the used process factors on these characteristics were analyzed. The results of observations shows that, in thickness, the components possess microstructures accumulating lots of Mg2Si particles and a portion of primary silicon particles in the inner layer, a little Mg2Si and primary silicon particles in the outer layer, and without any Mg2Si and primary silicon particle in the middle layer. The results of the analysis indicate that the rotation rate of centrifugal casting, mould temperature, and melt pouring temperature have evidently affected the accumulation of the second phase particles. Also, the higher the centrifugal rotation rate, mould temperature, and melt pouring temperature are, the more evident in the inner layer the degree of accumulation of Mg2Si and primary silicon particles is.

Comparison of rapid casting solutions for lead and brass alloys using three-dimensional printing

The purpose of the present investigation is to study and compare the feasibility of decreasing the shell wall thickness for rapid casting solution of brass and lead alloys using three-dimensional printing (3DP) technology. Starting from the identification of components/benchmarks, technological prototypes have been produced at different shell thicknesses using lead and brass alloys. Measurements on a coordinate measuring machine helped in calculating the dimensional tolerances of the castings produced. Some important mechanical properties are also compared to verify the suitability of the castings and further results are supported by microstructure analysis. The study suggested that the production of sound casting for minimum wall thickness depends on pouring temperature and weight density. It has been observed that IT grades comparable to machining can be obtained with 3DP for lower pouring temperature alloys. Further feasibility of obtaining minimum shell thickness is more dependent on pouring temperature than weight density. Based on improved dimensional accuracy and microstructure analysis, the saving of costs up to 45.75 per cent and time up to 43 per cent can be achieved over the recommended one in the case of lead alloy for the selected benchmark/component. For brass alloy casting saving of costs and time up to 40.05 and 32.84 per cent, respectively, has been achieved.

Effects of Process Parameters on the Macrostructure of a Squeeze-Cast Mg-2.5 mass%Nd Alloy

The effects of applied pressure, pouring and die temperatures on the macrostructure of a squeeze-cast Mg-2.5 mass%Nd alloy were investigated. The grain size of the Mg-2.5 mass%Nd alloy increased with increasing applied pressure from 60 to 180 MPa when the pouring and die temperatures were 725°C and 330°C. This was attributed to the melting temperature at the time when pressure was applied under the pouring temperature of 725°C, higher than the liquid temperature. Whilst, the pouring and die temperatures are 700°C and 330°C, the grain size of the alloy decreased with increasing applied pressure from 0 to 180 MPa. Lower die and pouring temperatures were favorable to refine grains, but the effects of the die temperature on the distribution and structure of grains were much smaller than those of the pouring temperature.