Stirring Parameters Research Articles

The Effects of Electromagnetic Stirring on Solidification Structure and Macrosegregation of Pb-Sn Alloy

The effects of different electromagnetic field and technological parameters on the microstructure and composition segregation of Pb-80%Sn alloy were studied. The results show that, both rotating and spiral magnetic field can improve the composition segregation ,refine grains of alloy. Moreover,the spiral magnetic field is more effective on improving composition homogenization and grain refining. The electromagnetic force distribution of spiral magnetic field is more helpful to form a well stirring in a larger zone and promote the formation of equiaxed grains, and the direction of the grain arrangement is much smaller. The technical parameters of spiral magnetic field have been optimized. It is found that, under the spiral magnetic field condition, when stirring time and exciting current exceeded a critical value, the size of the primary phase became larger. Therefore, there existed an optimum value of magnetic stirring parameters for the homogenization of component and refinement of grains.

Numerical Simulation on A356 Aluminum Alloy Semi-solid Slurry Preparation with Electromagnetic Stirring

A two-dimensional model coupling of the electromagnetic field,temperature field and flow field of A356 alloy semi-solid slurry preparation by electromagnetic stirring(EMS) method is established.The power law cut-off(PLCO) semi-solid model is used to model the slurry.The effects of EMS parameters such as stirring frequency and stirring current on the electromagnetic field,temperature field and flow field are investigated by finite element code ANSYS combined with secondary development INTEL FORTRAN software.The results show that,electromagnetic field increases but non-uniformly distributes as stirring frequency and stirring current increase,as a result,flow field increases but non-uniformly distributes.The reasonable stirring parameters for A356 alloy semi-solid slurry preparation by EMS are obtained.The simulation results are verified with corresponding experiments.

Synthesis of Au-Cu Nano-Alloy from Monometallic Colloids by Simultaneous Pulsed Laser Targeting and Stirring

Abstract Experimental work has been focused on the formation of alloyed Au-Cu nanoparticles under simultaneous laser exposure and mechanical stirring of mixed monometallic colloids, here referred to as dual procedure. As a feed for the dual procedure, Au and Cu monometallic nanoparticle colloids have been using a laser ablation technique. To accomplish this, bulk targets were ablated with 1064 nm wavelength Nd:YAG laser in a pure acetone (99.99%) environment. Ultraviolet-visible optical absorption spectrometry, transmission electron microscopy, X-ray diffraction and X-ray fluorescence technique have been used to characterize the nanoparticles. It has been found that experimental conditions such as stirring and laser parameters strongly affect the synthesized particle properties, including the size, shape, composition and stability of the nanoparticles. Alloy nanoparticles containing 39% Au - 61% Cu have also been prepared in the same process, but in two forms of a homogeneous alloy and a core-shell structure.

An investigation on semi-solid forming of A360 aluminium alloy by mechanical stirring

Aluminium alloys produced by semi-solid forming processes are widely used instead of conventional die casting and forging processes. Uniform micro-structure, superior mechanical properties and the ability of producing near net shape parts are advantages of semi-solid forming processes. In this research by using a mechanical stirrer slurry maker constructed by the authors, the effects of mechanical stirring parameters such as: stirring time, stirring temperature and stirring speed on micro-structure, and mechanical properties of A360 aluminium alloy in semi-solid forming, are investigated. It is determined that a stirring temperature of 585°C, stirring time of 20 min, and stirring speed of 425 r/min lead to better micro-structure and mechanical properties. Also it is determined that the mould temperature and holding time of part in temperature of 580°C have a great effect on micro-structure and mechanical properties. By optimizing the forming parameters, dendrite microstructure changes to globular and mechanical properties improves. This is because of breaking and globularizing dendrites of primary α-AL.

Probe into the Thinning Effect of Natural Bamboo Fibre

To probe into an effective method for thinning the natural bamboo fibre, the natural bamboo fibres were refined by using alkali，laccase, and degumming enzyme, respectively, and then the parameters of stirring, concentration and time are selected by means of orthogonal test method to obtain optimal changing rate of fineness, strength and the content of lignin. The results show that the effect of degumming enzyme is better than that of alkali and laccase. the content of lignin was decreased from 18.98% to 7.27%, and the strength has little loss.

Research on the Road Concrete Mixing Uniformity Control Technology

In this paper, chaos theory principle is applied in studying the concrete mixing process.Using piecewise linear mapping model describes the stirred mixture mixing and separation process.A chaotic model is established for particle movement in mixing process.In order to determine the reasonable stir parameters , the solving mixed movement method and the number of periodic windows is also given out. Suggested using chaos model determine the reasonably mixing time, proposed pre-mixed aggregate method, aggregate pre-wet method and admixture batch feeding ways to improve productivity and mixing uniformity.

Effects of stirring parameters on microstructure and tensile properties of (ABO w+SiC p)/6061Al composites fabricated by semi-solid stirring technique

Aluminum borate whisker (ABO w) and silicon carbide particle (SiC p) hybrid reinforced 6061Al matrix composites ((ABO w+SiC p)/6061Al) were fabricated by semi-solid mechanical stirring technique with different stirring temperatures and different stirring time. The influence of stirring parameters on microstructure and mechanical properties of the composites was investigated using scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM) and tensile tests. The results reveal that the homogeneity of reinforcement and tensile properties increase with decreasing the stirring temperature and increasing the stirring time. The optimal stirring parameters of 640°C and 30 min are exploited based on the microstructure observation and tensile properties of the composites.

Research of Transverse Corner Crack and Optimization of Concasting Process for Bloom of Peritectic Steel Q235D

Q235D is one kind of peritectic steel, so the casting production inevitably encounter the universality defects of peritectic steel casting. The bloom(250mm×280mm) of Q235D is produced by 60t consteel EBT—LF(VD)—CC process at Xining Special Steel. The main problem in the production is the transverse corner crack, finally lead to occur the cracks and “triangular gaps” at surface of round bar（Φ130mm）after rolled. In order to eliminate the defects caused by transverse corner crack of bloom, the morphology and microstructure and principle of crack formation is researched. The results showed that the crack is caused by stress along the intergranular, and no obvious segregation and particles founded around the defects. The following parameters on the continuous casting process are optimized: steel composition, superheat, the choice of a various slag, the cooling water of different section, casting speed and the electromagnetic stirring parameters. Finally the cracking defects of the bloom is eliminated, and the quality of the bar is optimized.

Numerical Simulation of Electromagnetic Stirring Effect on Flow Pattern of Metal Melt

In this study, a mathematical model was developed to simulate 2-D axisymmetric melt flow under magnetic field in a cylindrical container. The modeling of this process required the simultaneous solution of the turbulent Navier-Stokes equations together with Maxwell equations. The flow pattern in liquid bath was obtained using a two-equation κ-є turbulent flow model, which was further used to obtain the solute distribution. The governing differential equations were solved numerically using finite volume based finite difference method. The computed results, were found to be in good agreement with the measurements reported in the literature. The effect of stirring parameters on temperature homogeneity of the melt have been discussed and presented.

The Kinetics Model Study of Al-Fe <i>In Situ</i> Composites and Applications

Through the reaction model of Fe powder in liquid Al melt, constructed the dynamic model of Al-Fe reaction and analyzed it’s forming kinetics of in-situ Al composites manufactured by reaction synthesis. The results showed that the time of Fe and Al complete response to forming strengthening phase has a square relation with the Fe powder original size in Al melt. According the kinetics model to improve the powder add method, and decrease the initial group size of Fe powder in the melt, can significantly accelerate the reaction. Then optimize stirring equipments and parameters to improve the microstructure and mechanical properties of composites.

Effects of SiC particle pretreatment and stirring parameters on the microstructure and mechanical properties of SiCp/Al–6.8Mg composites fabricated by semi-solid stirring technique

Al–6.8Mg aluminum composites reinforced by 10 vol.% SiC particle (10 vol.% SiCp/Al–6.8Mg) with homogeneous particle distribution and superior mechanical properties were successfully fabricated by semi-solid stirring technique. The effects of SiC particle pretreatment and stirring parameters on microstructure and mechanical properties of the composites were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and tensile tests. The results show that SiC particle pretreatment significantly improves the wettability and interfacial bonding strength between SiCp and Al–6.8Mg matrix, which further improves the homogeneity of SiC particle distribution and tensile properties of the composites. The optimal stirring parameters of 612 °C/500 rpm/30 min are exploited based on the SEM microstructure and tensile properties of the composites. The tensile strength of the composite fabricated by the optimal parameters is 344 MPa, which is 43.3% higher than that of the monolithic Al–6.8Mg alloy (240 MPa).

Effects of whisker surface treatment on microstructure and properties of Al 18B 4O 33w/6061Al composites

6061Al matrix composites reinforced by ZnO-coated Al 18B 4O 33 whiskers were fabricated by a semi-solid mechanical stirring technique. The effects of ZnO coating on interfacial reaction between whiskers and matrix and the tensile properties of the composites were investigated. Tensile tests on composites were performed at room temperature, and microstructures were observed by scanning electron microscopy (SEM). The results show that the surface treatment of whiskers could reduce interfacial reaction effectively, improve the wettability between whiskers and matrix and enhance the tensile properties of the composites obviously. In addition, semi-solid stirring parameters were also under preliminary study. The stirring parameters were determined by the distribution of whiskers in the composites. The composites with homogeneously distributed whiskers were fabricated by semi-solid stirring at 610 °C for 30 min.

Effect of electromagnetic stirring in mold on the macroscopic quality of high carbon steel billet

An industrial plant trial for optimizing the process parameters in a round billet continuous casting mold with electromagnetic stirring (M-EMS) was performed, in which the influences of stirring parameters with M-EMS on the solidification macrostructure of high carbon steel were investigated. The results show that the billet quality is not well controlled under the condition of working current and frequency with EMS, in which the subsurface crack of grade 1.0–2.0 ups to 38.09%, the central pipe of grade 1.0–1.5 reaches to 14.28%, and the central porosity of grade 1.5 is 14.29%. The parameters of current 260 A and frequency 8 Hz as the final optimum scheme has a remarkable effect for improving the macroscopic quality of billet, in which the subsurface crack, central pipe and skin blowhole are all disappeared, and the central porosity and carbon segregation are also well improved.

Rational argon stirring for a 150-t ladle furnace

Based on the principle of similarity, water modeling experiments were carried out for a 150-t ladle furnace. The rational parameters of argon stirring were determined as the optimized positions of nozzles, top area of the porous brick, and gas flow rate. The following results are obtained: 1) the optimized positions of two nozzles are at 0.333 R ( R refers to the radius of the ladle at bottom) with an angle of 135°; 2) the top diameter of the porous brick should be 130 mm; 3) the flow rate of gas should be 25.0-30.6 m 3/h. The plant trial shows that the improved process is effective in enhancing the cleanliness of round billets. The total oxygen content, microinclusions, and macroinclusions in round billets are reduced by 12.5%, 8.2%, and 20%, respectively.

Enzyme immobilization. Part 4. Immobilization of alkaline phosphatase on Na-sepiolite and modified sepiolite

Alkaline phosphatase from calf intestinal mucous membrane was immobilized on the modified and unmodified Na-sepiolite. The effects of various factors such as concentration of enzyme solution, pH and temperature of immobilization medium, magnetic stirring and various thermodynamic parameters on the immobilization rate of alkaline phosphatase (APh) were evaluated. pH = 10 was optimal for enzyme activity for both the free enzyme and the sepiolite. Sepiolite with bilayer surfactant coverage (SBS) had high ability for immobilization of APh. APh immobilized on SBS showed approximately similar V max and K m in comparison with the free enzyme. By immobilization of APh on Na-sepiolite without surfactant (SWS) and sepiolite with monolayer surfactant coverage (SMS), V max decreased and K m increased.

Enzyme immobilization: Part 2: Immobilization of alkaline phosphatase on Na-bentonite and modified bentonite

Alkaline phosphatase from calf intestinal mucous membrane was immobilized on unmodified and modified bentonites. The activity of the immobilized enzyme was examined under varying experimental conditions. The effects of various factors such as concentration of enzyme solution, pH and temperature, stirring and various thermodynamic parameters were evaluated. The highest enzyme activity, for free and immobilized enzyme, was obtained in 0.1 M phosphate buffer at pH 7. Optimal enzyme activity of both free and adsorbed enzyme was reached at pH = 10. The best time period of magnetic stirring was 2 h at 4 °C. The adsorption isotherm was modeled by Langmuir equation. The effect of substrate concentration on enzymatic activity of the free and immobilized enzymes showed a good fit to the Michaelis–Menten plots. The immobilized enzyme exhibited activity comparable to the soluble enzyme after storage at 30 °C. Thermal stability and resistance against proteolytic attack were also evaluated.

Enzyme immobilization: Part 1. Modified bentonite as a new and efficient support for immobilization of Candida rugosa lipase

Immobilization of Candida rugosa lipase onto modified and unmodified bentonites is described. The effect of hydrophilic or hydrophobic nature of the support, the reuse efficiency, and kinetic behavior of immobilized lipase were studied. The modified bentonite with monolayer surfactant (BMS), was the best support, for immobilization. The activity of the immobilized enzyme was examined under varying experimental conditions. The effect of various factors such as concentration of enzyme solution, pH and temperature, stirring and various thermodynamic parameters were also evaluated. The activity of lipase on Na-bentonite, on BMS and on bentonite with bilayer surfactant (BBS) at the optimum pH was 7.2%, 56.6% and 3.6%, respectively. The adsorption isotherm was modelled by the Langmuir equation. The amounts of immobilized lipase on Na-bentonite, BMS and BBS at the highest activity were 42.6%, 61.2% and 28.3%, respectively. The effect of substrate concentration on enzymatic activity of the free and immobilized enzymes showed a good fit to the Michaelis–Menten plots. The immobilized enzyme exhibited an activity comparable to the free enzyme after storage at 30 °C. The thermal stability of free and immobilized lipase were also studied.

Effect of electromagnetic stirring on melt pool free surface dynamics during vacuum arc remelting

The deformation of the free surface of the liquid pool in the VAR process may play a key role in explaining the apparition of surface defects on the ingot skin. In the present study, the deformation of the surface induced by electromagnetic stirring is investigated, for a simplified geometry, using CFD-based simulations, combining models for the turbulent fluid flow, heat transfer, free surface movements and electromagnetic forces. Particular attention is given to the implementation of thermal and electrical boundary conditions at the moving free surface. Verification of the developed model is carried out by comparison with the dedicated code SOLAR. The free surface dynamics of a liquid zirconium pool is then quantitatively analysed for different stirring procedures, and the effects of the stirring parameters (magnetic induction, reversal time) are predicted and discussed. The obtained results provide some insights into mechanisms by which surface deformation may influence the ingot skin solidification, leading to poor ingot surface quality.

Semi-solid rolling process of steel strips

Abstract Semi-solid metal forming (SSF) is recognized as a new forming technology, which has been paid more and more attention by the researchers all over the world. The semi-solid rolling process (Rheo-rolling) combines the fabrication of slurry with continuously rolling as an important neoteric means to achieve near-shape forming. In this paper, an original device of semi-solid rolling has been designed and manufactured to prepare the spring steel–60Si2Mn and stainless steel–1Cr18Ni9Ti. The semi-solid slurry is successfully fabricated by electromagnetic stirring and rolled into the strips with the thickness of 3–5 mm, the width of 70 mm and the length of 1000 mm. The effects of the stirring parameters, including stirring power and time, on the solid fraction and microstructure of steel, have been investigated through electromagnetic stirring process. The experimental results show that the semi-solid slurry with the solid phase diameter of 50–150 μm and the solid fraction (fs) of 5–65% can be obtained by electromagnetic stirring. The highest ultimate tensile strength and elongation obtained for 60Si2Mn strip with 60% solid fraction are 860 MPa and 13.4%, respectively. For 1Cr18Ni9Ti strip with 60% solid fraction, the highest ultimate tensile strength and elongation are 1022 MPa and 40.6%, respectively. With increasing the solid fraction, the properties of semi-solid rolled products become better. The method of grooved rolling can ameliorate the stress state at the edge of rolled strip, which is beneficial to improve the homogenization of microstructure.

Physical modelling of slag splashing in converter

Slag splashing, which is a new technology to increase converter lining life, has achieved significant economic and environmental results. Via a converter model of Steelmaking Plant no. 3 of An-Shan Iron and Steel Group Corp., physical model experimental research on slag splashing was carried out. The effects of top blowing parameters, bottom stirring parameters, slag properties and lance structure on slag splashing are discussed. The optimum slag amount is 11% under the experimental conditions investigated. The secondary nozzles of the lance have a detrimental effect on slag splashing. The nozzle angle of the lance has a significant effect: the 12° lance obviously achieves much better results than the 14·5° lance. Bottom stirring is not only beneficial, but also can effectively control overslag of the furnace bottom and increase the life of bottom tuyeres. It is also advantageous to increase the bottom stirring gas flow appropriately. When the optimum lance height from the physical model is applied in plant, the lance height must be modified. The modification factor is 0·85-0·95. The modification factor should be smaller for higher viscosity slag and greater for lower viscosity slag. There is a gestation time for slag splashing. In the gestation time, the temperature of the slag is decreased and the viscosity of the slag is increased; at the same time, the slag foams dramatically. The gestation time is 1/4-1/2 of the total slag splashing time. The results of the physical model have already been applied to plant operation. At Steelmaking Plant no. 3 of An-Shan Iron and Steel Group Corp., slag splashing has increased the average lining life of a converter from 1472 to 8915 heats, and steel yield has risen from 3·13 to 4·00 Mton/year with an annual economic benefit of about US$3·4. This would provide a theoretical basis for the extension and application of slag splashing.