Hydrogen and oxygen flame temperature, sealing effect and analysis of molybdenum foil crushing Cause for lamps
The melting point of molybdenum is 2 610 C, the melting point temperature of quartz glass is about 1 700 C, and the temperature of hydrogen and oxygen flame is above 2600°C. Molybdenum foil is often cracked and broken when making halogen incandescent lamp and gas discharge lamp. Whether the temperature of hydrogen and oxygen flame is too high, resulting in cracking and crushing of molybdenum foil? The answer is no. This can be demonstrated in the sealing process of short-arc xenon lamps, which uses quartz glass and molybdenum foil, and the length of the sealing of molybdenum foil is much longer than that of halogen incandescent lamps. Once the molybdenum foil is sealed into the quartz glass, the two melt together, no matter how to heat, molybdenum foil in addition to red, hot, will not crack, broken.
When the short-arc xenon lamp is sealed, the processing time is long, the processing temperature is high, but there is no air into the atmosphere, which is the key to prevent cracking and crushing of molybdenum foil.
The size of the meshing clearance of the sealing die is determined by design. When pressing, the left pressing punch and the right pressing concave die are closed, and the glass tube and the filament mounting part are tightly sandwiched in the middle. When the meshing gap design of the sealing die is moderate, the quartz glass will be close together during the sealing, and the molybdenum foil will not be subjected to other forces except the left and right pressures. When the meshing clearance design of the sealing die is small, the glass will carry molybdenum foil to move up and down. At this time, molybdenum foil will be subjected to both left and right pressure and up and down tension. At high temperature sealing, the tensile strength of molybdenum foil is much lower than that at normal temperature. At this time, if the pulling force of molybdenum foil is too large, the molybdenum foil will be fractured and broken. If the meshing gap design of the sealing die is too large, the sealing die can hardly push the fused quartz glass, and the quartz glass tube and molybdenum foil can not be pressed together. The sealing part is not crushed, there is an air gap, and then there is air leakage.
The pressure of the sealing machine is too large, and the force acting on the sealing die will be very large. This situation is about the same as the design of the meshing clearance of the sealing die, and the pressure is one. Once applied on molybdenum foil, the upward and downward pulling forces will be large, and the molybdenum foil with low tensile strength will be fractured and crushed. Experienced pressure sealing master will test the pressure before opening the pressure. On a few, and then according to the machine pressure, appropriate adjustment.
