There are two types of degassing methods commonly used in industry 1 Into the inert gas helium nitrogen, spoon method: generally at 750-760 °C, into the melt into the atmosphere of 0.5% of the mass of the melt, the nitrogen content of the melt can be from 150-190cm 3 / Kg down to 100cm3 / kg o Ventilation speed should be appropriate to avoid melt splash, ventilation time is 30min, long ventilation time will lead to grain coarsening. 2 Into the active gas (chlorine spoon method: generally at 740-760 °C, the chlorine into the melt. When the melt temperature is lower than 740°C, the MgC12 formed by the reaction will be suspended on the surface of the alloy so that the surface cannot form a dense coating layer and magnesium combustion cannot be prevented. When the melt temperature is higher than 760°C, the reaction between the melt and chlorine is intensified, and a large amount of MgC12 is generated to form inclusions. The amount of chlorine gas introduced should be appropriate. Generally, the chlorine content in the melt should be controlled to be less than 3% by volume, preferably (2.5'-3) L / min. Carbonaceous materials such as CCl4. C2C16 and sic have a significant grain refinement effect on Mg-Al alloys. If degassing at a temperature of 690-710°C using a mixed gas of (1-1-5) % C12+0.25% CC14, the double effect of degasification and refinement can be achieved, and the degassing effect is better. , but it is easy to cause pollution. 2 removal of inclusions. The main inclusions in magnesium alloys are MgO' and MgF2 'MgC12, etc., MgO and MgF2's melting, b. are 26420C and 12630C, respectively, which are higher than the melting temperature of magnesium alloy and appear as solid state in magnesium alloy liquid. . The density of MgO is 3.5 8g/cm3, which is higher than the density of magnesium. Therefore, MgO will sink at the bottom of the alloy liquid as oxidized slag. Because magnesium is easily oxidized, a large amount of MgO is generated at high temperature, and it is impossible to be discharged completely. A portion of MgO slag remains in the magnesium alloy; the melting point of MgC12 is 7180C, which is within the smelting temperature range of the magnesium alloy. Therefore, MgC12 appears as a liquid in the magnesium alloy solution. In addition, the density of MgC12 in the liquid state and the density of magnesium. Closer, therefore, the probability of MgC12 remaining in the magnesium alloy fluid is greater, in addition, MgC12 also has a strong hygroscopicity, will accelerate the corrosion of magnesium alloys. The existence of these problems makes it necessary to refine the magnesium alloy when it is smelted. The refining treatment of magnesium alloys generally uses the addition of hexachloroethane (C2CQ, MgC03, and CaCO.) and other refining agents, which are mainly due to MgCO, and CaCO. They are easily decomposed to generate a large amount of CO: gas, and thus play the role of degassing and slagging. . The flux refining process uses a flux to wash the magnesium melt and wets the inclusions with sufficient contact between the flux and the magnesium melt and polymerizes them in the flux, which is deposited at the bottom of the site A along with the flux and the magnesium melt. The basis of this refining method is that the flux must have good wetting, adsorption and inclusion ability. The use of C2C16 as a refining agent for refining in production has a dual function of deterioration and refining. This method is particularly advantageous when fluxless refining is used. The mechanism of this method is that C2Ch rapidly decomposes C1.C and other elements in the magnesium melt. Since chlorine and magnesium can react to form MgC12, they can play a refining role, and carbon can play a role in grain refinement. In addition, the gas generated by the decomposition of C2C16 also has the effect of removing hydrogen. As the flux continues to spill onto the metal surface during the refining process, the flux melts into the metal. After the refining is completed, a covering agent is sprinkled onto the metal surface in order to prevent oxidative combustion of the surface metal. The covering agent is a mixture of 20% sulfur powder and 80% of a refining agent. After the surface refining agent melts, it gradually infiltrates into the metal. Even if the metal surface protective film in the oblique lifting package breaks during the casting process, the covering agent must be sprinkled onto the metal surface to be cast. These refined work have undoubtedly added extraneous impurities to the metal. Some manufacturers use nitrogen protection methods to prevent the entry of gaseous impurities, but it is effective to perform refining and casting in a more confined nitrogen environment, and nitrogen spraying on the surface of open containers prevents surface burning. In the case where the refining and casting temperatures are not too high, the use of sulfur powders to prevent the surface oxidation and combustion of the melt metal is better. A certain amount of air is blown into the box filled with sulphur powder with the outlet pipe facing the molten metal, and the sprayed sulphur powder rushes to the metal surface to burn, which reduces the surface oxidation of the metal and prevents the entry of foreign refining agents. The modifiers used in magnesium alloys readily form high-melting-point metal intermediate compounds with other high-melting-point impurities and settle to the bottom of the furnace. These refractory impurities and modifiers have a low solubility in magnesium alloys, a high melting point, and a larger specific gravity than magnesium. When they interact, and can remove the meltable impurities in the alloy, which is beneficial to the magnesium alloy, but it reduces the effect of the modifier, and even failure. Reducing the content of Fe, Ni. Si impurities in magnesium alloy can improve its corrosion resistance. Since Ti has a large solubility in magnesium at 800-850°C, the solubility sharply drops below 700°C and forms a high-melting-point intermetallic compound with Fe "Si. Therefore, it has begun industrially in recent years. The use of iron scrap and low-quality Chloride Chromium removes Fe "Si and some of the Ni in the melt to increase the corrosion resistance of the alloy. For example, when MB3 alloy is treated with low-quality TiC13+TiC1 and Mg-Ti master alloys, the content of Fe and Si can be reduced from Fe0.01% to SiO0.1% FeO. .002% "SiO.001% Magnesium alloys containing Zr, should strictly limit the content of Si.Al, Mn impurities. When the Al.Si.Mn content exceeds 0.1%, the alloy's fault content will be greatly reduced. Tv Cabinet,Modern Tv Stand,Black Tv Stand,Tv Lift Cabinet Ningbo Oulin Import&Export Co.,Ltd. , https://www.oulin-oversea.com