1. Influencing factors:
1.1 The influence of temperature: the higher the pouring temperature, the greater the magnesium burn loss and the thicker the ink layer. Therefore, while ensuring no cold insulation, the pouring temperature should be reduced as much as possible.
1.2 The higher the residual magnesium content, the thinner the ink layer. When the residual magnesium content is below 0.06%, the ink layer thickens and even small ink flakes appear inside the body; Overall, a residual magnesium content of 0.06-0.09% is more suitable. Excessive residual magnesium can cause other casting defects.
1.3 During casting, the liquid flow is not stable, and the magnesium is burned and the ink layer thickens in large areas.
1.4 The more dead corners there are in the casting, the thicker the ink layer at the dead corners.
1.5 The higher the S content in the molten iron, mold, and core, the thicker the ink layer.
1.6 During the melting process of molten iron, oxidation is severe, resulting in a thick layer of ink after casting.
1.7 The production rate of 1.7 high nickel austenitic ductile iron is low, with a large amount of recycled materials. The recycled materials are repeatedly used multiple times, and the iron liquid is severely oxidized, resulting in a thick layer of graphite.
In summary, to reduce the ink layer, the following measures can be taken:
2.1 Choose high-quality furnace materials, quickly melt, and prevent oxidation of molten iron.
2.2 Under the premise of not producing cold insulation, it is not advisable to choose excessively high overheating temperatures. The temperature of the furnace should be controlled at 1620 ℃ and fully scalded. Rapid casting.
2.3 Try to fill the molten iron as evenly as possible to reduce magnesium burning.
2.4 Adding high-quality coal powder appropriately during sand mixing can create a reducing atmosphere inside the mold during casting, reducing the burning loss of Mg.
2.5 The S content of raw materials, molds, and cores should be as low as possible, and the S content of molten iron is more suitable at 0.015%.
2.6 The moisture content of the molding sand should be kept as low as possible, controlled between 3.5-4.5.
2.7 High nickel austenitic ductile iron has a high sensitivity to Mg, and the residual magnesium content should take into account the size, thickness, and complexity of the casting.
2.8 The overflow method can also reduce the thin ink layer, but this method reduces the process yield.
