vacuum furnace development history

Industrial furnace in which the pressure in the vacuum furnace is lower than atmospheric pressure. Electric heating of vacuum furnace, no oxidation and decarburization outside the heated workpiece, small deformation, good mechanical properties. The melting of metal in vacuum furnace is conducive to the removal of impurities. The products have few pinholes, small segregation and good quality. Vacuum furnace is suitable for smelting and heating of high-quality, high-purity and refractory metals, such as tungsten, molybdenum, tantalum, niobium, titanium, heat-resistant alloy steel, electrical materials, high-strength steel, stainless steel, instrument steel, die steel and other smelting and magnetic materials.
In 1927, the United States made a vacuum annealing furnace for electronic materials.
In 1953, the vacuum consumable arc furnace was applied to the melting of titanium sponge in industry.
Vacuum induction furnace was widely used in industrial production in the 1950s, and oil quenching vacuum furnace was developed in the United States in 1960.

Vacuum furnace is generally composed of furnace, electric heating device, sealed furnace shell, vacuum system, power supply system and temperature control system. The sealing furnace shell shall be welded with carbon steel or stainless steel, and the joint surface of detachable parts shall be sealed with vacuum sealing material. In order to prevent the shell from deforming and the sealing material from deteriorating after heating, the shell is usually cooled by water cooling or air cooling. The furnace is located in a sealed enclosure. According to the purpose of the furnace, different types of heating elements such as resistance, induction coil, electrode and electron gun are installed in the furnace. Crucible is installed in the furnace of the vacuum furnace for smelting metal, and some are equipped with active pouring device and loading and unloading manipulator. The vacuum system is mainly composed of vacuum pump, vacuum valve and vacuum gauge.

In the 1950s, coreless induction furnaces grew rapidly. Then there is the electron beam furnace, which operates the electron beam to impact the solid fuel and can strengthen the external heating and melting of high melting point materials. The earliest furnace used for casting heating was manual casting furnace. Its working space is a concave groove full of coal. The air for combustion is supplied from the lower part of the tank, and the workpiece is buried in the coal for heating. This kind of furnace has low thermal efficiency and poor heating quality. It can only heat small parts. Later, it grew into a semi closed or fully closed firebrick chamber furnace. It can use coal, gas or oil as fuel or electricity as heat source. The workpiece is heated in the furnace.

In order to facilitate the heating of large workpieces, a trolley type heating furnace suitable for the heating of ingots and billets is developed, and a well type heating furnace suitable for the heating of long sections is developed. Since the 1920s, there have been various types of mechanized and active furnaces that can improve productivity and labor conditions. With the development of fuel resources and the improvement of fuel conversion technology, the fuel of industrial furnace has gradually changed from solid fuel such as lump coal, coke and coal powder to gas and liquid fuel such as producer gas, city gas, natural gas, diesel oil and fuel oil, and various combustion devices suitable for fuel have been developed.