How to avoid casting pores?
The main way to the gas in Aluminum Alloy by refining degassing agent producing large amounts of gas (gas bubbles in the liquid aluminum may be internally generated by chemical reaction, but also the possibility is through partial refining degassing agent added directly into the), using the differential pressure principle, make hydrogen atoms dissolved in liquid aluminum to bubble diffusion (partial pressure at bubble is zero), because the proportion of light when the bubble bubble, float to the surface of aluminum liquid, the bubble burst, the hydrogen escaped into the atmosphere, and ultimately achieve the purpose of removing hydrogen. The most common way is to use chlorine and chloride in the melting process to remove gas, chlorine gas and nitrogen gas removal, vacuum degassing, ultrasonic removal of gas, filtration, degassing and other methods. In addition, the use of commonly used gas refining agent is shown in table 5. the chlorine salt and chloride degassing agent degassing, with bell will degasifier is pressed into the crucible bottom 100mm, along the crucible diameter at 1/3 (from the crucible wall) of the moving circle. In order not to splash a large amount of aluminum liquid, the degassing agent can be added in batches, and the slag is removed at the end of the gas, and the installation is carried out at the time specified in table 6. 5 increase in gas solubility in the alloy by rapid solidification or under high pressure, improve the solubility of gas in the gas Aluminum Alloy, promote too late or can not precipitate, so as to achieve the purpose of eliminating pinholes. The specific method is limited to the length of space.
The preparation of smelting and pouring shall be done seriously; 1.1, the burden shall be properly handled according to the requirements of the technological procedures. Before using, use sand blowing or other methods to remove the rust, sediment and other dirt on the surface of the burden, and preheat the charge to keep 3H above, so as to prevent water and oil pollution. 1.2, melting crucible, mold tool before use should be clean oil stains, dirt etc.. And preheat to 120 degrees -250 degrees, coated with protective coatings. 1.3, new crucible, new building furnace, rusty old crucible, use sand blowing before other methods to clean the surface, and oven processing. Should generally be heated to 700 degrees -800 degrees C, 2H-4H insulation, to remove the water and other chemicals adsorbed by the crucible. Crucible, melting ingot mold, tool coating has 1.4 before use shall be preheated, the crucible should be preheated to dark red (500 DEG -600 DEG); melting tools should be preheated to 200 DEG -400 DEG, remain above 2H (in addition to the use of induction furnace for melting alloy, crucible without preheating.) 2 strict implementation of process planning, and strive to achieve rapid melting 3 to strengthen the preventive measures to the wet season 4 refining gas, removal of Aluminum Alloy in gas "under normal circumstances, the so-called" gas "(also called" gas ") is the gas removal in the alloy," refining "refers to the removal of inclusions in the alloy. In the process of smelting aluminum alloy, the two processes of degassing and refining are combined together, so in practice, these two processes are called refining. Because the main gas in aluminum alloy is hydrogen, degassing is the main removal of hydrogen.
