Crystallization of electromagnetic stirrer @hebei 2016

              Crystallization of electromagnetic blender principle is to use the change of the current to produce strong magnetic field, through the medium of the multilayer cut off, make continuous casting slab of internal metal melting liquid produce flow, through the state of the flow control to improve casting internal organization, component distribution, melting liquid dramatically and surface quality on the purpose. Because the role of the electromagnetic field with the contact, the distribution characteristics of uniform, especially suitable for high temperature and other special occasions. The production practice shows that the electromagnetic stirring improve columnar crystal, bypass, pinhole, increase the equiaxial crystal area, reduce the composition segregation, reduce or eliminate center loose and center of shrinkage effect is very obvious. Therefore, in a certain process condition, the choice of reasonable installation blender position, appropriate stir intensity and mixing way, control the flow of liquid form and melt flow speed, to improve the quality of casting billet have obvious function.

          Working principle

          Crystallization of the principle of electromagnetic stirrer is powerful changes in the magnetic field generated by electric current, penetrating multilayer dielectric barrier, make the continuous casting billet internal flow of molten metal produced, through the control of the flow state to improve slab internal organization, the composition distribution, liquid and purity and surface quality, etc. Due to the role of the electromagnetic field had the characteristics of non-contact, uniform distribution, especially suitable for high temperature and other special occasions. Operating practice indicated that electromagnetic stirring in improving the columnar crystal, bypass, pinhole, increase crystal zone, reduce the composition segregation, to reduce or eliminate center loose and shrinkage cavity, etc. effect is very obvious. Therefore, under the certain process conditions, choose reasonable installation position of the stirrer, appropriate way of stirring intensity and stirring, control the flow of the molten form and flow speed, plays an obvious role in improve the quality of casting billet.

          Continuous casting and electromagnetic stirring device can effectively improve the internal organization structure of casting, improve the quality of the surface, reduce the center segregation and center loose, basic elimination of shrinkage cavity and crack, greatly increase the axis crystal rate, which has been widely used in all kinds of square billet continuous caster. Continuous casting and electromagnetic stirring device is a kind of work in high temperature, high humidity and high dust slag electrical equipment under the bad environment, etc. In order to achieve the necessary electromagnetic thrust, and to minimize the volume of device at the same time, often designed to work in the condition of high current and low frequency.

          Technical principle

          In the ordinary course of casting, Akira grew up in dendritic manner, when solid rate reached 0.2 or so, dendritic skeleton to form continuous network, loss of macro liquidity. If the liquid metal from liquid phase to solid phase of strong stirring during the cooling process, will make the casting which is easy to form the branch crystal network skeleton in normal be smashed and retains the dispersed particle morphology, suspended in the surplus liquid phase. This kind of granular non dendritic microstructure, in steady rheological aspect in 0.5-0.6 still has certain rheology, which can use conventional forming process, such as die casting, extrusion, metal forming die forging, etc.

         Technics predominance

         (1) Without any grain refining agent can obtain fine grain structure, eliminates the traditional rough casting of columnar crystals and dendrites.

        (2) Forming temperature is low (such as aluminum alloy can reduce more than 120 °C), can save energy.

        (3) Die is longevity. Solid and low temperature of semi-solid slurry forming shear stress, is smaller than traditional dendrite size three orders of magnitude, therefore, smooth filling, heat load is small, thermal fatigue strength degradation.

        (4) Reduce pollution and unsafe factors. For homework is getting rid of the high temperature liquid metal environment.

       (5) Deformation of small resistance, use small force can realize the homogeneous processing, for difficult-to-machine materials to the forming of easy.

       (6) Speed of solidification, increase in productivity, shorten the process cycle.

       (7) Suitable for using computer aided design and manufacturing, enhance the level of automation production.

        Product superiority

        (1) A high quality. Due to grain refinement and uniform distribution, reduce body contraction and the decrease of the thermal crack tendency, basically eliminated shrinkage tendency of the matrix, mechanical properties increase significantly.

        (2) Forming alloy is wide. Nonferrous alloy are aluminum, magnesium, zinc, tin, copper, nickel base alloy; Iron base alloys such as stainless steel, low alloy steel.

       (3) Manufacture of metal matrix composite materials. Use the high viscosity of semi-solid metal, to make the density difference, small solid solubility of metal alloys, also can effectively make mixing different materials, to make new composite materials.

           Application Effect

          (1) the existing process conditions, the use of mold electromagnetic stirring technology, chilled slab layer with fine equiaxed apparent effect.

          (2) Center equiaxed rate increased significantly, due columnar zone narrows in the middle crack basically eliminated.

         (3) Center shrinkage is weakened.

         (4) electromagnetic stirring in a certain extent, help to eliminate the adverse effects of high heat, similar to the low superheat casting.

         (5) elimination of the central segregation and porosity, resulting in reducing the residual shrinkage to prevent the core slab, the slab to improve the central segregation.

            Application effect of contrast: