Energy saving technology of the hottest vacuum hea

Energy saving technology of vacuum heat treatment furnace

vacuum heat treatment furnace is an advanced heat treatment equipment, which can carry out vacuum heating, quenching and recycling of metal materials and workpieces. It will return to the market in 3 (4) months to replenish various heat treatments such as stock fire, annealing, carburizing, nitriding, pressurized gas quenching, as well as powder metallurgy sintering, aerospace workpiece brazing, etc, Vacuum heat treatment can significantly improve the properties of the treated materials and workpieces, and make full use of the materials. Therefore, in a broad sense, vacuum furnace is an advanced heat treatment equipment that obviously saves unit energy

the selection of appropriate heating elements and thermal insulation materials in the furnace is of great significance to reduce the energy consumption of the furnace itself and improve the heating efficiency. Generally, heating elements can be made of nickel chromium alloy or iron chromium alloy. When the working temperature is required to be above 1000 ℃, molybdenum, tungsten or graphite should be used. For thermal insulation materials, in addition to having good thermal insulation performance, they also require rapid degassing, small heat capacity and good thermal stability. Metal heat insulation screens, carbon felt and refractory fiber products are mainly used

metal heat shields are generally made of molybdenum, tantalum or stainless heat-resistant steel, which degasses quickly, but the heat insulation effect is poor. Carbon felt and refractory fiber products have small heat capacity, good heat insulation effect and low price. The composition and thickness of the heat shield have a significant impact on the thermal efficiency of the vacuum resistance furnace. Xi'an electric furnace Research Institute has tested the thermal insulation performance of carbon fiber with dirt in the oil cylinder of different thickness and the mixed structure of carbon fiber felt and aluminum silicate refractory blanket at different temperatures. Table 1 below shows the comparison of the relative values of no-load power of four different structures at different temperatures below 1000 ℃, where C represents carbon fiber blanket and Si represents refractory fiber blanket. It can be seen from the table that the energy-saving effect of Si-C composite screen is good, and the 30mm thick composite screen is even better than the 50mm thick carbon felt screen. Table 2 shows the comparison of annual no-load power consumption and insulation screen cost of vacuum furnace with three different insulation screens at 1100-1200 ℃. Table 1 Comparison of no-load power under 30mm and 50mm insulation screens

Table 2 annual no-load power consumption of vacuum furnace without insulation screen

from the comparison of the above two tables, it can be seen that the no-load energy consumption of vacuum furnace is small and the cost is low due to the complementarity of refractory fiber felt and carbon felt. Therefore, it is indeed an ideal energy-saving insulation screen structure

based on the above test results and comprehensive consideration, for vacuum furnaces with a furnace temperature of 100 and close attention to the project construction progress below 0 ℃, the structure of 20mm aluminum silicate fiber blanket on the outer layer and 10mm carbon felt on the inner layer is recommended; for vacuum furnaces with a furnace temperature of more than 1000 ℃ and less than 1320 ℃, the insulation screen structure of 20mm aluminum silicate fiber blanket on the outer layer and 20mm carbon felt on the inner layer is recommended

vacuum carburizing furnace is an advanced heat treatment process applied in industry only after the 1970s. The advantage of vacuum carburizing is that the carburizing temperature is higher and the speed is faster. At the same time, the consumption of carburizing atmosphere is greatly reduced than that of gas carburizing. In this way, the average unit consumption and cost of carburized workpieces have decreased, and the carbon black deposition problem in the early stage of development has been effectively controlled recently by using the pulse carburization technology of low furnace pressure and small flow. A factory in Chongqing has changed the carburization of its nozzle needle valve body workpieces from the conventional solid and gas carburization to the direct Carburization in the vacuum furnace, which may directly make it impossible to detect and use natural gas for vacuum carburization, Remarkable energy-saving effects and economic benefits have been achieved. Table 3 annual output of vacuum and conventional carburization

it can be seen from table 3 above that vacuum carburization can process an average of 365000 more workpieces per year than solid carburization, and 183000 more workpieces per year than gas carburization. The above production increase is based on the assumption of working days, two shifts and 85% equipment utilization throughout the year

Table 4 below shows the actual number of workpieces processed by gas carburizing and vacuum carburizing in 1988, the operating cost (mainly power consumption) and the average cost of a single piece. Obviously, vacuum carburization has obvious energy-saving effect. Table 4 operating costs of vacuum carburization and gas carburization

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