1. Defect analysis
(1) The stiffness of the base frame of the model is not enough, and the model is prone to warping deformation during modeling;
(2) The rigidity of sand core is not enough, and the upper arch of the middle part is deformed during pouring, resulting in the uneven wall thickness of the barrel;
(3) During the graphitization expansion of nodular iron castings, the mold wall migrates and the expansion box causes the deformation of castings;
(4) The barrel deformation caused by inclined pouring;
(5) Shrinkage stress and deformation.
2. Preventive measures
(1) The size of model plate frame is 120 mm × 60mm × The 5 mm mouth shaped steel is welded to ensure the stiffness and strength of the model structure, and the frame welding is completed on the platform to ensure the flatness of the frame;
(2) Before placing the sandbox, make sure that all the contact points at the bottom of the model are in contact with the site, and the non-contact points are supported by wedge blocks;
(3) Six long strip sand cores, cast iron core bone is put during core making to increase the deformation resistance of sand core, and core support is put in the middle of sand core to fix the position;
(4) The sand box with stiffened plate is adopted, and the width of the box belt is greater than or equal to 100 mm, so as to avoid the expansion caused by insufficient rigidity of the sand box;
(5) Before the lower core is matched with the mold, the lower mold should be leveled by the cross line to ensure the flatness of the box opening;
(6) In order to prevent the deformation caused by inclined pouring, the inclined 10 ° The frame is filled with dry sand and made into 10 ° Inclined sand bed;
(7) Ensure the reasonable time of heat preservation and unpacking, generally ≥ 24 h. Use infrared temperature measuring gun to control the open box temperature ≤ 250 ℃ to reduce the stress and deformation.