First, homework preparation:
1. The temperature of molten magnesium is controlled at 670-695℃, and the final rolling temperature is controlled at 680-740℃.
2.N2 pipeline switch confirms that the inflation pipeline is in good condition, and bake the inflation pipe first.
3. Weigh fluorite powder and manganese powder or manganese chloride, mix them evenly, and confirm the batch number of fluorite powder, manganese powder or manganese chloride.
2. Primary refining process:
1. When the temperature of magnesium alloy liquid reaches 670-695℃, primary refining is started.
2. Put the baked mechanical stirrer into the crucible, turn on the power supply to start stirring, open the nitrogen valve, then turn on the pipeline switch, and the gas begins to flow out. Insert the baked blowpipe into the magnesium liquid from the nitrogen hole on the mechanical stirrer cover, and then adjust the nitrogen flow rate.
3. Mix the fluorite powder and manganese powder (or manganese chloride) evenly, and add them by artificial colander (to ensure that the fluorite powder and manganese powder fully enter the melt and do not sinter into lumps). Nitrogen blowing time is 40 minutes (AM series is not less than 25 minutes), and the time can be appropriately extended if there is any abnormality.
4. After refining, take out the nitrogen pipe first, and then close it.
5. The alloy liquid does not stick to the nitrogen tube, and the surface of the alloy liquid is pure and silvery white, that is, the refining is completed.
6. The final refining temperature is 680-740℃.
Three. Sampling analysis and composition adjustment:
1. Take a sample with a sampling spoon, push aside the alloy liquid level, shake it back and forth about 50mm below the alloy liquid level, take out the first sample, and then take the second sample as an analysis sample.
2. Turn the sample into a smooth plane, send it to spectral analysis, and then carry out secondary refining if it is qualified.
3. If there is a certain gap between AL, Mn and Zn and the product, fine-tune the components; If copper, silicon and nickel are unqualified, secondary refining is generally not carried out. Pour out the alloy liquid, check the chemical composition of raw materials and find out the reason.