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Three details to note in vacuum heat treatment of experimental vacuum furnace


Jun 06,2016

Three details to note in vacuum heat treatment of experimental vacuum furnace

I. What should I pay attention to when designing vacuum heat treatment for experimental industrial vacuum furnace?

The vacuum tempering furnace should have a quick cooling device. The pressure of cooling water should be greater than 0.2Mpa, the flow rate should be adjustable. Heating up: after putting in the workpiece, generally pre-pumping to 6.67Pa before heating up the heating process, the workpiece and the furnace material will be deflated, so that the vacuum level drops. Cooling gas: generally use 99.995% purity of nitrogen, high temperature alloys using 99.999% nitrogen or argon, titanium alloys using 99.995% argon. Vacuum furnace active connection part all use O-ring sealing connection, this part are through water cooling. Vacuum annealing, vacuum annealing, vacuum solution treatment and vacuum aging heating temperature is generally the same as the heating temperature of conventional treatment. Workpiece quenching under vacuum, should use vacuum quenching oil, this oil has a low saturated vapor pressure. Vacuum furnace maintenance should be in a vacuum or pure nitrogen state, to avoid the usual use of air absorption, moisture absorption. Domestic vacuum furnace pressure rise rate should not be greater than 1.33 Pa / h, the standard of some foreign companies for 0.67 Pa / h vacuum furnace treatment of titanium alloys, should not use nitrogen as a cooling gas, because titanium and nitrogen at high temperature reaction, the formation of golden yellow titanium nitride. The vacuum heating is based on radiation, and the workpiece should be kept spaced in the furnace.

II. How to use flue gas waste heat most effectively and apply to industrial vacuum furnace?

The high temperature gas generated by fuel combustion is discharged through the exhaust port after heat exchange between the furnace and the workpiece, and a large part of the heat is taken away by the flue gas due to the short heat exchange time. On the industrial furnace, the heat loss taken away by the flue gas accounts for more than 40%-60% of the heat supply of the furnace. Making full use of this part of waste heat is the key to improve the thermal efficiency of the furnace. The most effective way to lower the temperature of the flue gas leaving the furnace and reduce the heat loss carried away by the flue gas is to use the flue gas waste heat to preheat the gas, air and furnace charge. On a continuously heated furnace, by lengthening the length of the preheating section and extending the residence time of the flue gas in the furnace to allow sufficient heat exchange with the charge, the thermal efficiency of the furnace can be substantially improved and the furnace exhaust temperature reduced. But for continuous furnace, the high temperature flue gas in the furnace residence time is short, the exhaust temperature is close to the furnace temperature, the most effective and widely used measure to use the flue gas waste heat is to preheat the combustion air.

III. What are the safety hazards in the daily use of the experimental vacuum furnace?

The use of experimental furnace operation generated by the high temperature is prone to scalding, burns and burns and other accidents; high-temperature molten salt and molten metal encounter water will also produce explosions; gas and controlled atmosphere is also explosive gas, oil circuit, oil tanks and oil depots are flammable and explosive facilities, if not used with care, at any time may be explosive and poisoning accidents; electric furnace safety protection device if it fails, contact will be electrocuted; cyanide furnace cyanide is highly toxic; nitrate salt furnace will produce spontaneous combustion when heated above 550℃; nitrate salt will explode when combined with charcoal and carbon black.

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