Molybdenum glass melting electrodes

10
Temperature [˚C]
Application Information
Sealing by glassification
For the installation of the electrode it is recommended to first push it into the glass melt and then pull it back into the electrode
holder, while turning it continuously in a clockwise direction. Through cooling of the electrode holder, the glass layer solidifies,
thus providing protection against diffusion. Before inserting an extension electrode, the cooling of the holder should be slightly
reduced so as to promote melting of the solidified glass layer.
Sufficient cooling
Sufficient cooling of the electrode holder is of the utmost importance. At high temperatures certain atoms – e.g. iron and nickel
atoms – diffuse out of the electrode holder into the molybdenum of the electrode, forming brittle and low-melting phases. In
order to avoid such problems the electrode holder, and consequently the glass melting electrode as well, must be cooled
sufficiently, and the electrode must be completely immersed in the glass melt. Otherwise, there can occur a melting of the
solidified glass layer in the gap, and this can in turn affect the atom-diffusion process described above, by bringing about a direct
contact between the glass melting electrode and its holder. Frequent monitoring of the electrical values is important in order
to ensure punctual replenishment and thus avoid overheating. In addition, electrode-erosion is influenced by temperature: high
temperatures result in increased electrode-erosion and thus in reduced service-life.
0 0
2700 2700
Temperature [˚C]
2500 2500
2300 2300
2100 2100
1900 1900
1700 1700
1538 / 2800 1538 / 2800
1500 1500
1394 / 2541 1394 / 2541
1300 1300
1100 1100
900 912 900/
1674
700 700
912 /
1674
Atomic Atomic percent percent molybdenum molybdenum
10 10 20 20 30 3040 4050 50 60 60 70 80 70 90 80 100 90 100
4892 4892
2623 / 4753 2623 / 4753
4532 4532
1611 / 2932 1611 / 2932
1488 / 2710 1488 / 2710
1370 / 1370 /
1449 / 2640 1449 / 2640 2498 2498
1235 / 2255 1235 / 2255
1200 / 2192 1200 / 2192
927 / 1700 927 / 1700
0 010 1020 2030 3040 4050 5060 6070 7080 809090 100 100
Fe Fe Weight Weight percent percent molybdenum molybdenum
Mo Mo
Binary phase diagram of Mo/Fe
Temperature [˚F]
4172 4172
3812 3812
3452 3452
3092 3092
2732 2732
2372 2372
2012 2012
1652 1652
1292 1292
Temperature [˚F]
Temperature [˚C]
0 0
2700 2700
Temperature [˚C]
2500 2500
2300 2300
2100 2100
1900 1900
1700 1700
1500 1500 1455 / 2651 1455 / 2651
1300 1300
1100 1100
900
700
900
700
Atomic Atomic percent percent molybdenum molybdenum
10 10 20 20 30 3040 4050 50 60 60 70 80 70 90 80 100 90 100
4892 4892
2623 / 4753 2623 / 4753
4532 4532
870 / 1598 870 / 1598
1362 / 2484 1362 / 2484
1317 / 2403 1317 / 2403
910 / 1670 910 / 1670
0 010 1020 2030 3040 4050 5060 6070 7080 809090 100 100
Ni Ni Weight Weight percent percent molybdenum molybdenum
Mo Mo
Binary phase diagram of Mo/Ni
Temperature [˚F]
4172 4172
3812 3812
3452 3452
3092 3092
2732 2732
2372 2372
2012 2012
1652 1652
1292 1292
Reducing the current surface-density
A current surface-density of 1 to maximum 2 A/cm2 is acceptable for glass melting electrodes. Corrosion increases drastically in
step with increasing surface current-density. A good possibility to minimize this strain is to increase the surface itself by choosing
a greater diameter or changing, especially in the feeder section, to plate or block electrodes.
Temperature [˚F]