In 1794, a straight cupola for melting cast iron appeared in the world. Later, in 1864, the Frenchman Martin used the principle of the regenerative furnace of the British Siemens to build the first steelmaking open hearth furnace heated by gas fuel. He used the regenerator to preheat the air and gas at high temperature, thus ensuring the temperature above 1600°C required for steelmaking. Around 1900, the supply of electric energy was gradually sufficient, and various resistance furnaces, electric arc furnaces and cored induction furnaces began to be used.Aluminum alloy and stainless steel vacuum brazing In the 1950s, coreless induction furnaces developed rapidly. Later, electron beam furnaces appeared, which use electron beams to impact solid fuels, which can enhance surface heating and melt materials with high melting points.Vacuum sintered powder metallurgy parts The furnace used for forging heating was the earliest hand forge. Its working space is a concave groove filled with coal, the air for combustion is supplied from the lower part of the groove, and the workpiece is buried in the coal for heating.316L stainless steel vacuum brazing process The thermal efficiency of this kind of furnace is very low, the heating quality is not good, and it can only heat small workpieces. Later, it will be developed into a chamber furnace with a semi-closed or fully closed hearth made of refractory bricks, and coal, gas or oil can be used as fuel. , Electricity can also be used as a heat source, and the workpiece is heated in the furnace.Vacuum heat treatment of aluminum alloy die castings