Thin – walled box with cooling water pipe and intake holes
Casting Method
Furan resin sand three – part molding
Pouring System
$\phi$70 mm straight runner, 40 mm×38 mm cross runner, 20 mm×18 mm 8 internal runners
Sand Core
5 sand cores, two – stage connection for stability
2. Casting Defect Causes and Prevention Measures
2.1 Sand Holes (‘Sand Inclusion Defect’)
Causes
Prevention Measures
Residual sand in mold cavity and riser not cleaned before core setting
Control type (core) sand quality, adjust resin and curing agent addition amount
Uneven sand core joint and parting surfaces, damage during core setting and closing, causing sand to fall into cavity
Remove head and tail sand during molding and core making, fill sand carefully, and compact and level it
Incomplete inspection and incorrect sand blowing method before closing the box, leaving sand grains in the cavity
Strictly control mold and core removal and dewaxing time, ensure sufficient strength
Low strength of mold and sand core, unable to withstand external forces such as molten iron scouring
After mold removal, scrape off flash, clean surface sand, coat with alcohol – based graphite powder paint and dry
Insufficient inspection of sand mold (core) surface before core setting, potential damage and sand loss after core setting and closing
Check sand mold (core) surface before core setting, pre – assemble sand cores, and ensure tight joint
Residual sand on cavity and sand core surface not cleaned before formal core setting, incorrect sand blowing method, loose sand falling into cavity during closing
Blow clean residual sand with compressed air before core setting, set cores carefully and steadily
Incorrect sand blowing method before closing the box, sand falling into cavity during closing, improper handling of upper box’s pouring riser and vent holes
Blow clean cavity sand before closing the box, level and coat pouring riser and vent holes of upper box, close the box carefully
2.2 Gas Holes (‘Blowhole Defect’)
Causes
Prevention Measures
Poor connection of vent holes or molten iron entering vent holes during pouring, resulting in blocked gas exhaust channels
Embed a $\phi$10 mm vent pipe on each side of the cooling water pipe in the lower sand core, and drill 2 $\phi$15 mm vent holes above the pipe
Large amount of gas generated by the long and thin intermediate water pipe sand core during pouring, with long exhaust path and difficulty in exhausting
Apply casting glue around the lower sand core vent holes before core setting, and set corresponding vent holes in the upper box
Use a $\phi$40 mm steel pipe as the water pipe sand core core bar, drill several $\phi$6 mm holes for ventilation
Check the steel pipe before use, insert a $\phi$15 mm vent pipe at both ends of the core bar after core setting
Set 8 12 mm×50 mm gas outlet risers in the upper box
Ensure smooth gas exhaust through vent pipes, core holes, and gas outlet risers
2.3 Sand Adhesion
Causes
Prevention Measures
Loose structure of flange loose block, insufficient compaction of sand, and rough surface after template removal
Compact the thin – walled part at the bottom of the flange during sand filling
Difficult to coat the back of the flange at the bottom due to its structure, resulting in missed coating
Remove the template in parallel according to the loose block demolding sequence to ensure a smooth sand mold surface
Poor heat dissipation at the corner where the flange is connected to the side wall, large heat effect of molten metal, prone to sand adhesion
Select a suitable casting brush, brush the coating in the correct order, check for missed coating, and use pure alcohol to smooth and dry
2.4 Cold Shuts
Causes
Prevention Measures
Slow pouring speed, thin wall of water pipe, long length, and few connection parts with the box
Increase the pouring temperature of the molten metal, use a large – size pouring cup, and increase the pouring speed
Middle – injection pouring system, long flow distance of molten metal from bottom to top, resulting in temperature drop
Check the ceramic slag – stopping plate, do not use those with blocked or small – sized holes
Unreasonable hole size of ceramic slag – stopping plate
Ensure the straight runner is aligned with the center of the ceramic plate and maintain the cross – sectional area of the straight runner
2.5 Shrinkage Porosity
Causes
Prevention Measures
Thick wall part at the bottom of the casting, long solidification time, insufficient molten metal for feeding during solidification
Set chills at the parts prone to shrinkage porosity, such as the circular hole plane, to accelerate cooling speed
3. Conclusion
By improving the sand core exhaust system, core setting and cavity cleaning methods, and setting chills at thick – walled parts, casting defects such as sand holes, gas holes, and cold shuts in the pressure stabilizing box have been effectively reduced, improving product quality and economic benefits.
