The generation of subcutaneous pores is a comprehensive reaction of improper operation of each link and process in the casting process. The reasons for the formation are complex, and there are many influencing factors. It involves everyone, and every process should arouse everyone's great attention.
1. Raw materials
1. Raw materials containing high titanium (Ti) and aluminum (AI), as well as high alloy steel and stainless steel, are prohibited from being used.
2. The raw materials with serious corrosion and oxidation, oil pollution, coal slime and waste sand should be cleaned and used.
3. Wet and watery raw materials should be used after drying.
4. Thin iron sheets (pipe fittings) less than 3mm are prohibited from being used.
5. The length of raw materials should be controlled at about 300-400mm.
2. Hot metal smelting
1. When the raw materials are loaded into the furnace, they should be relatively compact, and the space should be minimized to reduce the absorption and oxidation of molten iron.
2. During the melting process of molten iron in each furnace, thoroughly clean the slag for at least 2 to 3 times, and after the slag cleaning, cover the molten iron with slag and insulation materials in time to avoid the molten iron being inhaled and oxidized in contact with the air for a long time.
3. For melted molten iron, the waiting time at high temperature should not exceed 10 to 15 minutes, otherwise, the quality of molten iron will deteriorate seriously and become "dead water".
4. The tapping temperature should not be lower than 1540±10℃. After tapping, the slag should be removed in time, and the slag insulation agent should be covered at the same time to prevent the molten iron from cooling down and oxidizing.
5. The recarburizer that does not meet the standard is prohibited.
3. Inoculants
1. It should be baked at 300~400℃ before use to remove the adsorbed moisture and crystal water.
2. The particle size of the inoculant is 5～10mm.
3. The aluminum content of the inoculant is less than 1%
Fourth, pouring
1. The large and small bags should be dried and dried relatively. Wet bags are forbidden to be used. It is strictly forbidden to use hot iron scalding bags instead of drying.
2. Increase the pouring temperature and pour it quickly at high temperature. Pouring principle: slow-fast-slow. Practice has proved that increasing the pouring temperature by 30-50℃ can greatly reduce the incidence of pores. When pouring, let the molten iron fill the sprue, and flow continuously in the middle, so as to quickly build up the static pressure of the molten iron and resist the intrusion of the interface gas.
3. The temperature of the molten iron in the small package is lower than 1,350 ℃, which is prohibited. It should be used after returning to the furnace to raise the temperature.
4. Strengthen the slag blocking and slag shielding, and remove the oxide scale in time to prevent it from being brought into the cavity.
5. Sand mixing
1. Strictly control the moisture content of molding sand to be no more than 3.5%.
2. The air permeability of the molding sand is controlled at 130-180, the wet compressive strength is 120-140kPa, the compaction rate is 35%-38%, the surface hardness of the molding sand is >90.3, and high-quality bentonite and coal powder are selected.
4. Add new sand as required.
5. At the end of sand mixing every day, the excess molding sand should be recovered, and the sand mixer should be thoroughly cleaned and cleaned.
Six, mold and modeling
1. The parting surface of the mold should be equipped with an exhaust hole groove or an exhaust channel and a dark air chamber to reduce the gas pressure.
2. Add a dark air chamber on the mold to reduce the gas pressure.
3. Sprinkle cryolite powder on the runner or sand core (the amount is determined after the test).
7. Core making
1. The water content of silica sand is less than 0.2%, and the mud content is less than 0.3%.
2. Core making process: Before sand mixing, the silica sand needs to be heated to 25~35℃, first add component 1 to the sand, mix for 1~2 minutes, then add component 2, and continue mixing for 1~2 minutes. The addition amount of the two components is 0.75% of the mass fraction of sand.
3. Due to the high sensitivity of polyisocyanate to water, the storage time of the prepared sand core should not exceed 24 hours.
4. The concentration and residual amount of triethylamine are too high, which is easy to cause subcutaneous pores in the casting. (Source/Internet, Editor/Jing Liwen)
Henan Aoudi Casting Co., Ltd.
Add：No. 90, Industrial Road, Tiexi District,
Qi County, Hebi, Henan
Tel：+86-0392-7275525
Email：ryan_shi@aoudi.cn
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