1. Solutions to “gap” casting defects
After many tests, we finally understand that we must systematically match the three process parameters of “pouring temperature”, “pouring speed” and “mold temperature” according to the specific conditions of castings and molds.
·Pouring temperature: on the premise of ensuring the degassing quality and service time of molten aluminum refining, adjust the molten aluminum temperature of holding furnace from 720 ± 10 ℃ to 745 ± 10 ℃;
·Pouring speed: the tilting time is adjusted from 9 seconds (3.20kg / s) to 15 seconds (1.93kg / s);
·Mold temperature: use the “machine side cooling station” (Chongqing Hongding technology company) whose cooling water is controlled by the mold temperature signal to realize the transformation from “long-term cooling water” to “intermittent cooling water”, and control the bottom mold temperature in the range of 300 ~ 400 ℃ (there are many influencing factors, and the measured parameter of infrared temperature measuring gun is not very accurate.)
Verification results: a total of more than 100 pieces were dissected and observed with a magnifying glass. There were no original “gap” casting defects and 345 leak detection results. There were only 6 pieces of water channel leakage, with a leakage rate of 1.74%. Leakage casting defects are basically closed.
2. Solutions to “porosity” casting defects on the machined surface
Process correction of the wall thickness of the casting filling channel:
·Feeding risers are added at local hot joints;
·Correction of sand core design error: narrow aluminum water channel;
Verification results: the hole casting defects of camshaft hole and tappet hole have been closed.
3. Solutions to out of tolerance of inlet geometry and size
·Using “anti deformation tooling”, after taking out the sand core, it can be cooled under pressure in the tooling, which can effectively prevent the deformation of the sand core, and the influencing factor is closed;
·Enable the “gas inspection” device to prevent errors, the clamping gap is out of tolerance, the core shooting machine does not work, and the influencing factor is closed;
·Repair the core shooting machine to improve the clamping accuracy (Chongqing Teddy casting machinery). The renovated core shooting machine has been started. The universal joint is adopted between the template and the guide shaft to compensate the clamping error. The parallelism of opening and clamping is less than 0.10. This influencing factor is closed.
·The special coated sand with finer particle size is used to reduce the gap between sand particles and improve the smoothness of the surface of the sand core. The exhaust channel is added locally in the core box to prevent the loose surface of the sand core due to the retention of compressed air in the sand core. This influencing factor is closed.
·The positioning gap between the hot air distribution channel core and the die is closed.
Verification results: of 345 products tested by three coordinates, only 8 pieces did not meet the requirements of position error less than 0.35. The problem of out of tolerance of airway position has been basically closed.