After trial production for many times, a set of skills of white mold burning empty shell of stmma bridge shell is summarized, and basically every shell can be burned clean. In the process of empty burning, the probability of box collapse of process 1 accounts for 20%. Because the volute opening is upward, the negative pressure at the upper part of the sand box is low, and the sand core in the middle cavity is suspended as a whole after empty burning, so the support force is not enough. The probability of box collapse in process 2 is 5%. Improve the process and add a quasi 26 mm steel pipe in the cylinder to achieve the support of core bone. After the improvement, there is box collapse in process 1, and there is no box collapse in process 2, as shown in the figure.
After processing, the user conducted pressure test on the axle housing. The rigidity of full load vertical bending and the fatigue resistance of full load vertical bending reached the standard. The hot joints and key inspection parts of the axle housing were sliced, and no shrinkage was found.
After heat treatment, the mechanical properties of the cutting body are tested. The results are as follows: tensile strength 605 MPa, yield strength 436 MPa, elongation after fracture 19%, area shrinkage 38%, impact absorption energy 41 J, average hardness 215 Hb. Fully meet the technical requirements of users.
After repeated experiments, the problems of lost foam steel casting bridge shell are solved one by one: stmma bead foaming forming; White mold emptying process; High frequency vibration in the later stage of pouring process; Anti crack ring shall be added at the flange; Bottom leakage ladle pouring + argon blowing: Although the frame support is adopted for white mold drying and coating drying to prevent deformation, the stress shrinkage deformation after pouring can not be controlled. About 20% of the products still have deformation exceeding the user’s standard and need to be shaped by a press. However, in terms of material, mechanical properties, inclusion defects, leakage test, fatigue strength and other full load tests, it meets the acceptance standard of cast steel axle housing of heavy engineering vehicles.