Crystallization of Electromagnetic Stirring

             Working principle

       Continuous casting electromagnetic stirring device can effectively improve the internal organization of the slab structure, improve surface quality, reduce center segregation and center loose, basically eliminate the center shrinkage and crack, and greatly increase the equiaxial crystal rate, and has been widely used in all kinds of square billet continuous casting machine. Continuous casting electromagnetic stirring device is a kind of work in high temperature, high humidity and high dust slag harsh environment such as electric equipment. In order to achieve the necessary electromagnetic thrust, at the same time, we should try to reduce the volume of the device, often designed to work in high current, low frequency state.

        

          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: