Sand casting steel rolling stand is a typical large steel casting widely used. It is one of the important components of rolling mill equipment. This piece is a key bearing casting in rolling equipment, which requires high mechanical strength and stiffness. Its quality is directly related to the production line capacity. Therefore, sand casting defects such as inclusion, shrinkage cavity, porosity, crack and stress deformation should be strictly limited in the actual sand casting production.
Combined with the rolling mill frame produced by a domestic heavy equipment manufacturing company, the temperature field and stress field of the frame during solidification and cooling are simulated and calculated by using the professional sand casting simulation software, and the corresponding analysis is made according to the simulation results to predict the possible sand casting defects in the sand casting, It provides a reliable theoretical basis for the formulation of actual production process.
Combined with the actual production of cast steel frame by sand casting in the factory, the correlation analysis of temperature field and stress field is carried out, and the rationality of riser size and position, cold iron position and setting are verified. The main contents are as follows:
- The general situation of sand casting production of frame is introduced, and the sand casting process scheme of frame is analyzed. The positions of chill and large and small risers in sand casting process are designed to provide basis for simulation analysis.
- The three-dimensional finite element model of the casting frame is divided and the three-dimensional finite element model is established by using the finite element method. The thermophysical parameters, initial conditions and boundary conditions for simulation pretreatment are introduced.
- The temperature field was analyzed, and the solidification sequence of sand mold casting frame was obtained; The outer protrusion and edge of the column are cooled at the beginning, and the center of the large riser is cooled at the end. The feeding channel between the large and small risers was cut off in about 8 hours. After solidification, there was no shrinkage cavity and loose defect in the main part of the sand casting frame. If the spot feeding riser process was adopted, the hot joint at the rear end beam was moved up to the riser, the defect could be avoided.
- The thermal stress field in the solidification process is analyzed. The thermal crack potential is used to analyze the root of large and small risers and transition fillets with concentrated hot joints. The yield strength ratio of equivalent stress is less than, and the trend of thermal crack is small, indicating that the sand casting process scheme is reasonable.
- The residual stress in the cooling process of sand mold casting frame is analyzed. It is determined that the box beating and sand falling time of sand mold casting frame is 12 days, and the equivalent stress before sand falling at the root of large riser is about 250Mpa. After sanding, the stress concentration at the root of large and small risers and transition fillet. It must be handled properly during handling and cutting.
- The stress and deformation before box beating and sand dropping are analyzed. The shrinkage state of each part on the sand mold frame is different. In the length direction, the deformation is large at the left and right ends of the beam. In the width direction, the middle part of the column is deformed greatly.