Vacuum brazing furnace has several types, what are the characteristics?
1) hot fireplace
Brazing furnace adopts the form of the vacuum chamber is separated from the heater, commonly known as hot fireplace. Its characteristic is when the room temperature will be first pulled out, the air in the containers of brazing pieces and then push the container in furnace, heating in furnace brazing artifacts, vacuum and heating temperature simultaneously. Containers can be released out of cooling after brazing, shorten the production cycle, and can prevent the parent metal grain growth. Most hot fireplace inside the vacuum brazing for vacuum pump in the consecutive work in the thermal cycle. To remove the work load release of gases. In terms of size and the highest heating temperature, the hot wall vacuum furnace in the brazing temperature withstand high pressure capability limits.
The use of this type brazing furnace temperature can be as high as 1150 ℃, in most of them are limited to 870 ℃ or lower. Can use ordinary industrial furnace heating furnace. The vacuum inside the container without original heating and thermal insulation materials, not only has simple structure, easy to operate, and heat release less gas, is helpful to maintain the vacuum. In order to improve the productivity, at the same time with a few brazing container, alternate entry, retreat from bile for brazing and cooling. Due to the less investment in equipment and high productivity. But the container under the condition of high temperature, vacuum by outside the role of atmospheric pressure, easy to deformation, so is suitable for small small amount production. Large hot fireplace are often adopts double container structure. The outer shell of the heating furnace is also designed to low vacuum container, but the structure of the complicated limit its application.
2) cold fireplace
Vacuum chamber based on the indoor heating, the heating furnace and vacuum brazing chamber, commonly known as the cold of the fireplace. In this type of brazing furnace brazing brazing after a must with furnace cooling, limits the productivity. Thermal insulation materials and its electric heating element. Vacuum chamber is usually water cooled. For the radiant heat focused on the workpiece and prevent heat loss to the wall. In the heating element with appropriate between the furnace wall heat insulation screen (commonly used layers of molybdenum, tungsten, silver, graphite or other high temperature materials). The temperature can be as high as 2200 ℃, pressure can be lower than 1.35 x 10-4 pa.
Another cold wall for double water-cooled furnace wall structure of the vacuum furnace. The built-in thermal reflective screen, it consists of a thin metal plate layers of smooth surface. According to the furnace temperature is different, molybdenum sheet or stainless steel material selection. Its role is to prevent the heat radiated outward, reduce heat and improve the efficiency of heating furnace shell. Based on the distribution of the reflective screen inside the element, according to the rated temperature of the furnace and choose different heating element.
Cold working fireplace, furnace shell, because water and is reflective screen shielding, temperature is not high. Can withstand external atmospheric pressure, it is suitable for high temperature brazing of large weldment. Its heating efficiency is also high, but when used to heating vacuum first, then, after the brazing welding only with furnace cooling, with low temperature stage of furnace temperature falling slowly, so the productivity is low. But such as continuous cold fireplace adopts double rooms or more room, don’t destroy the vacuum heating chamber, weldment furnace charging, brazing, cooling and released can continuous operation, productivity can be improved.