One Mold Four Pieces, Horizontal parting, Horizontal Pouring Bottom Pouring with Bearing Water Inlet
2. Production Problems
Problem
Details
Defect Location
Rear End Face Flange (Highest Point in Horizontal Pouring, Isolated Convex Point)
Defect Appearance
Holes with Smooth Inner Wall, No Sand Inclusion (See Fig. 4, 5)
Defect Analysis
Rich in O Element (from Foreign Gas), Small Amount of Al Element (from Dirty Iron Water), Judged as Porosity Defect (See Fig. 3, Table 1)
Defect Probability
About 3.51% (See Table 2)
3. Problem Solutions
3.1 Causes of Porosity Defects
Gas Source
Details
Metal
Absorbs Atmospheric Gas during Melting, Additives Bring in Gas
Molding and Core-making Materials
Gas from Mold and Core Enters Molten Iron
Atmosphere
Gas in Mold Cavity Enters Molten Iron during Pouring
3.2 Defect Analysis
Analysis
Details
Defect Location Feature
Thick and Isolated Flange at Highest Point of Rear End Face, Last to Solidify
Porosity Formation Process
Gas Precipitates and Aggregates after Filling, Moves to Liquid Surface under Pressure, Forms Oxide Film on Surface before Gas Escapes, Blocking Gas Discharge and Causing Porosity
3.3 Improvement Measures
Scheme
Details
Scheme 1
Increase Overflow Block Volume to (Original ), See Fig. 7
Scheme 2
Change Overflow Mode from Side to Top with Original Volume, See Fig. 8
Scheme 3
Increase Overflow Block Volume to and Change Overflow Mode to Top, See Fig. 9
3.4 Simulation Analysis
Scheme
Maximum Temperature (C)
Cooling to Liquidus Temperature Time (s)
Original
1333
18.9
Scheme 1
1336
19.5
Scheme 2
1340
20.1
Scheme 3
1341
20.9
3.5 Verification Results
Verification Scheme
Verification Content
Number of Verifications
Number of Defects
Defect Ratio
Verification Result
Scheme 1
Increase Overflow Block Volume
420
11
2.62%
Improved
Scheme 2
Change Overflow Mode
580
7
1.21%
Improved
Scheme 3
Increase Volume and Change Mode
3460
7
0.20%
OK
4. Conclusion
For porosity defects in the production of HT250 engine cylinder blocks, when the pouring system and temperature cannot be easily changed, changing the overflow mode from side to top and increasing the overflow block volume can effectively reduce porosity defects. The overflow port at the top helps gas escape, and the larger overflow block makes the molten iron purer and slows down cooling and oxide film formation, reducing the risk of porosity casting.
