How to prevent slag hole problem during casting
Cast iron china often appear a variety of sand casting defects, how to prevent these defects has become a major concern question for sand casting factory. Here is come to introduction some of the knowledge of slag prevention.
Measures to prevent slag holes:
1. Increasing the temperature of molten iron, vermicular iron and alloy cast iron. If time permits, rest for a period of time prior to casting to float the residue.
2. To prevent molten iron oxidation, iron foundry should strictly control the amount of nodularizer and modifier.
3. Design a reasonable gating system and set the filter into the chip to improve the ability of filter residue. When pouring, the best system is used on the casting slag package.
4. When we cast ductile iron, the molten iron flows in the cavity of the cast iron. Since the various elements in the molten iron oxidation or the molten iron react with the casting raw material and the sand core, slag is generated again. We often refer to it as “secondary slag” (as opposed to “primary slag”).
This defect is usually detected by magnetic particles only on the surface of the fractured surface of the finished sand casting. Such impurities mainly include oxides (magnesium oxide, silicon dioxide, iron oxide …) and sulfides (magnesium sulfide, iron sulfide, manganese sulfide …) and other impurities.
Measures for Preventing Secondary
1. Strictly control of the amount of magnesium in molten iron residue, (general mass fraction of 0.035% ~ 0.055%, if the wall is thin, it should be controlled at a minimum; otherwise controlled at the highest.)
2. Reduce the sulfur content of the original fused iron, if conditions permit, it is best to take some desulfurization methods to improve the processing temperature and pouring temperature. After the desulfurization of molten iron greatly reduced the sulfur content can effectively reduce the “secondary slag.
3. Increase the content of rare earth nodulizer, and reduce the magnesium content. It can help reduce the temperature of hot metal surface, and effectively reduce the “secondary slag hole.
Slag hole will reduce the effective load range, resulting in stress concentration around the hole and reduce casting fatigue resistance and impact resistance. Casting companies or individuals who wish to purchase sand casting parts should be carefully examined to avoid these defects.