Melting process and maintenance of vacuum induction melting furnace
Melting process
Step 1. Feeding:
The materials must be carefully cleaned, removed surface contamination, oil, etc. and baked to remove moisture.
Some complex recycling materials must be cut off and removed surface scale, non-metallic materials, etc.
When feeding, you need to make sure the materials at the top of crucible is looser than the bottom. Use small piece of material to fill the gap. Place more regular shape material at the top to avoid scaffold bridging during the melting. In the direction of tapping hole can amass some granular materials.
Feeding movements should be light to avoid crucible damage and slags in the metallic liquid.
Step 2. Vacuum pumping:
Firstly, open the 2-stage rotary pump to vacuum the furnace. At the same time, open the diffusion pump power supply, start heating the diffusion pump oil.
When the vacuum of 2-stage rotary pump is 15Pa and diffusion pump have been heated for about 50 minutes, now you can close 2-stage rotary pump valve, open diffusion pump valve, vacuum the furnace to the required high vacuum.
Step 3. Melting:
Firstly, open the thyristor medium frequency power supply, increase working voltage sensors gradually. Normally, start with the small power to avoid sudden sharp rise in temperature and vacuum dropped significantly. So the general rate of power increase should not make the vacuum dropped significantly.
The max power of furnace is subject to the medium frequency voltage and max current.Step 4. Refining
Step 4. Refining:
After all materials melting, when need to add alloy, you can turn the handwheel, then the alloy will drop into the feeding tipping bucket. Gently turn the operation handle, the alloy will drop into the crucible at the speed you need.
It’s easy to cause sputtering when some alloy drop into the crucible. You need to pay attention to the speed of alloy’s adding. It can’t be too fast. Sometimes, you need to lower the power, make the liquid surface a bit harder, then adding the alloy to reduce sputtering.
Step 5. Casting:
When refining complete, no need to cut off the power, tilt crucible to pour metallic liquid into ingot mould. Notice, do not pour it out of the ingot mould.
Maintenance
Cooling water:
When melting, you should pay attention to cooling condition of each part. The temperature of cooling water should not over 50℃. If the water pressure is inadequate or some part over temperature, you should cut off the power, find the reason and fix it, then restart. The hardness of water should not be too high, should be clean. Cooling water pressure: 0.2Mpa, water consumption: 3000kg/h.
When stop using the furnace for a while, you need to use compressed air to blow out the remained water to prevent corrosion and extent service life.
Vacuum system:
Replace the oil of diffusion pump and 2-stage rotary pump regularly. Add diffusion pump oil as lubricating oil to the seal parts regularly.
Pay attention to the heater of diffusion pump regularly. You can check if the heating wire is broken by measuring current.
When vacuuming steam-containing gas, you should open the gas ballast valve on the 2 stage rotary pump, or it will contaminate the oil in 2 stage rotary pump and lower the max vacuum.
Furnace:
When stop using the furnace, you should clean the furnace inside and outside and vacuum it.
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