Industrial Grade High-Temperature Electric Heating Rod Factory - Yangzhou Darui
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The creation and development of industrial kilns have played a very important role in human progress. In the Shang Dynasty of China, relatively complete copper smelting kilns appeared, with kiln temperatures reaching 1200°C and inner diameters of up to 0.8 meters. During the Spring and Autumn and Warring States periods, based on copper smelting kilns, people further mastered the technology to raise kiln temperatures, thereby producing cast iron.
In 1794, the world saw the emergence of the vertical cupola furnace for smelting cast iron. Later, in 1864, the Frenchman Martin, using the regenerative furnace principle of the Englishman Siemens, built the first steel-making open-hearth furnace heated by gas fuel. He used regenerators to preheat air and gas to high temperatures, thus ensuring the temperature above 1600°C required for steelmaking. Around 1900, as the electricity supply became increasingly sufficient, various resistance furnaces, arc furnaces, and core-type induction furnaces began to be used.
In the 1950s, coreless induction furnaces developed rapidly. Later, electron beam furnaces appeared, which use electron beams to impact solid fuel, capable of enhancing surface heating and melting high-melting-point materials.
The earliest furnace for forging heating was the hand forging furnace, whose working space was a concave groove filled with coal, with combustion air supplied from the lower part of the groove, and workpieces buried in the coal for heating. This type of furnace had very low thermal efficiency and poor heating quality, and could only heat small workpieces. Later, it developed into chamber furnaces with semi-enclosed or fully enclosed hearths built of refractory bricks, which could use coal, gas, or oil as fuel, or electricity as a heat source, with workpieces placed in the hearth for heating.
To facilitate heating large workpieces, car-bottom furnaces suitable for heating steel ingots and large billets appeared, and pit furnaces also appeared for heating long rods. After the 1920s, various mechanized and automated furnace types emerged that could increase furnace productivity and improve working conditions.
The fuels for industrial kilns have also gradually changed from solid fuels such as lump coal, coke, and pulverized coal to gaseous and liquid fuels such as producer gas, city gas, natural gas, diesel, and fuel oil, following the development of fuel resources and advances in fuel conversion technology, and various combustion devices suitable for the fuels used have been developed.
The structure, heating process, temperature control, and atmosphere inside industrial kilns all directly affect the quality of processed products. In forging heating furnaces, raising the heating temperature of metal can reduce deformation resistance, but excessively high temperatures can cause grain growth, oxidation, or overburning, seriously affecting workpiece quality. In heat treatment processes, if steel is heated to a point above the critical temperature and then suddenly cooled, its hardness and strength can be increased; if heated to a point below the critical temperature and then slowly cooled, its hardness can be reduced while toughness is increased.
To obtain workpieces with precise dimensions and smooth surfaces, or to reduce metal oxidation to protect molds and reduce machining allowances, various scale-free heating furnaces can be used. In open-flame scale-free heating furnaces, incomplete combustion of fuel produces a reducing atmosphere, in which heating workpieces can reduce oxidation loss rate to below 0.3%.
Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
