The main reason for the production of pores in stainless steel castings

In the stainless steel casting process, the pore problem often occurs, which causes a lot of troubles for the stainless steel casting processing. The pore is the bubble defect formed by the deposited gas remaining in the ingot during the cooling and solidification of the metal liquid. Let's analyze the main reasons for the generation of pores: 01. The permeability of the coating is poor or the negative pressure is insufficient. The gas permeability of the filling sand is poor, and the gas and residue in the cavity cannot be discharged in time, and the pores are formed under the filling pressure. 02. The pouring speed is too slow to fill the sprue cup, expose the sprue, entrap the air, inhale the slag, and form the venting hole and the slag hole. 03. Foam model gasification decomposition generates a large amount of gas and residue can not be discharged into the mold in time, foam, paint layer filled dry sand is poor drying, surrounded by high temperature of liquid alloy, cracking a large amount of hydrogen and oxygen into the casting is formed The main cause of stomata. 04. Due to the unreasonable design of the pouring system, the filling speed of the molten metal is greater than the foaming gasification and gas discharge speed, causing the filling front to enclose the gasification residue in the metal liquid and vaporize again to form the decomposition black hole of the inner wall smoke black. . 05. The connection between the sprue cup and the sprue and the pouring system is not well sealed, especially the connection between the sprue and the sprue cup is not good, and the sand and the air hole are easily formed under the action of the negative pressure. This phenomenon can be calculated and explained by the Bernoulli equation. 06. The particle size of the molding sand is too fine, the dust content is high, the gas permeability is poor, and the internal pressure of the negative pressure pipe causes the negative pressure distortion, so that the negative pressure value around the cavity is far lower than the indicated negative pressure, and the vapor can not discharge the coating in time. Forming pores or wrinkles. 07. The pouring temperature is low, the filling front metal liquid can not fully vaporize the foam, and the undecomposed residual material can not be floated to the riser to solidify and form pores in the casting. 08. Poor deoxidation of molten steel, uncleaning of slag in the furnace, furnace and package, the sedation time is too short, the slag blocking is not strong during the pouring process, and the pouring process is unreasonable to cause slag holes. 09. The position of the sprue is unreasonable. When filling, the dead zone is formed. Due to the gas pressure in the cavity, the gasification residue accumulates at the dead corner to form pores. The cross-sectional area of ​​the gate is too large, so that the filling speed is greater than The foam gasification rate is reduced, the foam is swallowed, and the gas is decomposed and vaporized inside the alloy, and the gas cannot be discharged to form pores. 10. The capacity of the gate cup is too small, and the molten metal forms a vortex, which invades the air to form pores. https://janspijkers.nl/sitemap1.xml

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