Numerical simulation and result analysis of horizontal pouring scheme in Lost Foam Casting

The 3D drawing of horizontal pouring scheme is imported into ProCAST software. Firstly, the virtual sandbox is set up, and then the area mesh and volume mesh are divided. The mesh size is mainly based on the casting size. The mesh width of the mold in EPC should not be set too large, otherwise the mesh defects will easily appear and affect the simulation results, but it should not be set too small, otherwise the number of mesh generation will be huge, which will lead to the operation time too long or even the operation collapse. In addition, since sandbox is not the main research object of simulation analysis, the mesh width can be divided into larger pairs. In this design scheme, the mesh width of mold and pouring is set as 20 mm, and the mesh width of sand box is set as 50 mm. The automatically generated finite element model is shown in the figure.

First of all, the module parameters should be set. This scheme is for EPC, so the “lost foam casting” working section in ProCAST software is selected. In this work section, additional parameters of heat transfer analysis module and software analysis module need to be set. Heat transfer analysis mainly includes shrinkage porosity and hot spots, while software analysis mainly includes air entrainment, flow length, particle tracking, oxides, etc.

Secondly, material configuration and parameter setting are needed. Lost foam casting is different from cast-in-place cavity casting, and its interior is filled with foam pattern. The filling process is the gradual replacement of foam pattern by molten steel. The finite element model of steel steel bearing is made up of four parts. The gate cup and runner are set as cavity structure, filling degree is 0%, used for pouring molten metal (Alloy), the rest casting parts are solid foam (Foam), the density of the initial plan of foam pattern is 18g/L, the insulation layer at the top of the riser is set as thermal insulation material (Insulation), and the sand box part is made of breathable sand type (Sand). The permeability of dry sand is generally set between 1 × 10-6cm2 ~ 5 × 10-6cm2.

After setting the material properties, set the gravity direction to keep consistent with the pouring direction. Then the interface parameters are set, and the heat transfer interface between the foam pattern (Foam) and the gate (Alloy) is set as “EQUIV”, indicating that the temperature and soft fields between the two interfaces can be continuously transmitted. The other heat transfer interfaces are set as “coinc”, which means that there is a change of heat transfer between the two interfaces. In this scheme, the heat transfer pouring number of all heat exchange interfaces contacting mold is set as 500W / (M2 · K), and that of all heat exchange interfaces contacting with insulation is set as 10W / (M2 · K).

The setting of boundary conditions includes thermal boundary conditions and pressure boundary conditions. The thermal boundary condition is that the periphery of the sand box is set as air cooling; the pressure boundary condition needs to be set with two, one is set on the upper surface of the gate cup, and the other is set on the outer surface of the sand box. The former minus the pressure difference of the latter is the negative pressure degree. In this scheme, the negative pressure is preset as 0.05Mpa, that is, the upper surface of the gate cup is set as 1atm (about 0.1MPa), and the outer surface of the sand box is set as 0.5atm (about 0.05Mpa).

The operation parameters are the predetermined parameters of “lost foam” in ProCAST software, in which the number of operation steps can be modified according to the actual situation. If the actual operation steps exceed the set steps, the calculation results will be incomplete, which can be set larger. In addition, it is necessary to set the interface parameters of the lost foam mold. “FOAMHTC” indicates that the number of heat conduction of liquid metal and foam through the pyrolysis zone is generally set to 0.02. “FOAMHTCMAX” indicates that the number of heat exchange water when metal is in contact with the foam is generally set as 0.25, “BURNZONE” indicates the width of the pyrolysis zone, which is slightly larger than the mesh width of the foam pattern. This scheme is set to 2.5cm. “GASFRAC” indicates the percentage of foam volume converted to gas and is generally set to 0.1. When all parameters are set, you can click “data checks” to check. If the test is passed, the simulation calculation can be run.

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