How to guarantee the normal sealing of the molybdenum sheet?
Molybdenum, rare metal , element symbol Mo, atomic number 42, in the periodic table of elements is B group, atomic weight 95.94, body centered cubic lattice, melting point 2610 degrees Celsius.Metal molybdenum is a widely used refractory metal material. Molybdenum powder is the raw material for producing molybdenum material.Because of its high purity and high melting point, molybdenum is often used as molybdenum plate, molybdenum sheet and molybdenum and various molybdenum products in various departments of modern industry.
The normal sealing of molybdenum sheets at high temperature is the key to the success of molybdenum sheet processing. The key points of the technology for sealing molybdenum sheets are the following points from Baoji Yuan Da.
First, at high temperature molybdenum is very easy to oxidize in the air, so in the condition that there is no outer bubble shell, the temperature of the long life lamp - ---- quartz glass sealing part should not be more than 3500C.The excessive temperature will slowly oxidize the outer part of the sealing part to the air contact part, and finally lead to the damage of the sealing piece.Chromium plating on molybdenum sheets prevents oxidation and increases the working temperature to 5000C. However, studies have shown that the chemical adhesion of chromium to quartz glass is poor. To solve this contradiction, do not chrome the whole molybdenum piece, only chrome plating on the outer end of the molybdenum sheet contacting with air. Another disadvantage is that after chrome plating, the spot welding performance of molybdenum sheets becomes worse.
Secondly, we compare the sealing life of molybdenum sheet.
On the basis of the above principle, a life test is carried out after a variety of molybdenum sheet materials are made without an external bubble shell. At the same temperature, such as (1000T/T) =1.5 and T 3800C, the MR16 halogen lamp with yttrium oxide and cerium oxide coated MR16 halogen lamp has a life span of 1200 hours, and the pure molybdenum sheet is sealed only for only 650 hours. At high temperature, for example, T = 5000C, the sealing life of chrome plated molybdenum sheets is 2500 hours, while pure molybdenum sheets are sealed for only 30 hours.
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