In order to facilitate the heating of large workpieces, a trolley furnace suitable for heating ingots and large billets is presented, and a well furnace is also presented for heating long rods. After the 1920s, various mechanized and active furnace types that can improve furnace productivity and improve working conditions were presented.
With the development of fuel resources and the progress of fuel conversion technology, the fuel of trolley annealing furnace has gradually changed from solid fuels such as lump coal, coke and pulverized coal to gas and liquid fuels such as generator gas, city gas, natural gas, diesel oil and fuel oil, and various incineration equipment suitable for the used fuel have been developed.
The structure, heating technology, temperature control and atmosphere of trolley annealing furnace will directly affect the product quality after processing. In the casting heating furnace, increasing the heating temperature of metal can reduce the deformation resistance, but too high temperature will cause grain growth, oxidation or overburning, which will seriously affect the quality of workpiece. In the process of heat treatment, if the steel is heated to a certain point above the critical temperature and then cooled suddenly, the hardness and strength of the steel can be improved; If it is heated to a certain point below the critical temperature and cooled slowly, the hardness of the steel can be reduced and the toughness can be improved.
In order to obtain workpieces with accurate scale and smooth appearance, or to reduce metal oxidation to protect molds and reduce machining allowance, various less and no oxidation heating furnaces can be selected. In the open flame less and non oxidation heating furnace, the incomplete incineration of fuel is used to produce restorative gas, in which the oxidation burning loss rate can be reduced to less than 0.3% by heating the workpiece.
Controlled atmosphere furnace is a manually prepared atmosphere, which can be introduced into the furnace for gas carburizing, carbonitriding, bright quenching, normalizing, annealing and other heat treatments, so as to change the metallographic arrangement and improve the mechanical properties of the workpiece. In the movable particle furnace, the burning gas of fuel or other fluidizing agent applied externally is used to forcibly flow through the graphite particle or other lazy particle layer on the furnace bed. The workpiece buried in the particle layer can complete enhanced heating, as well as various non oxidation heating such as carburizing and nitriding. In the salt bath furnace, the molten salt is used as the heating medium to prevent the workpiece from oxidation and decarburization. The smelting of cast iron in cupola is usually affected by coke quality, air supply method, furnace charge and air temperature, which makes the smelting process difficult to be stable and difficult to obtain high-quality molten iron. Hot blast cupola can effectively improve the temperature of molten iron, reduce alloy burning loss and reduce the oxidation rate of molten iron, so as to produce high-grade cast iron.
With the appearance of coreless induction furnace, cupola is gradually replaced. The smelting operation of this induction furnace is not restricted by any cast iron grade. It can quickly switch from smelting one grade of cast iron to smelting another grade of cast iron, which is conducive to improving the quality of molten iron. Some special alloy steels, such as ultra-low carbon stainless steel and steel for rollers and steam turbine rotors, need to further refine high-quality molten steel with high purity and large capacity by vacuum degassing and argon stirring in the refining furnace.
The fuel of the flame furnace has a wide origin and low price, which is convenient for tailoring and adopting a different structure, which is conducive to reducing the production cost. However, the flame furnace is difficult to complete accurate control, serious environmental pollution and low thermal efficiency. The electric furnace is characterized by uniform furnace temperature, easy to complete active control and good heating quality. According to the energy conversion method, electric furnace can be divided into resistance furnace, induction furnace and electric arc furnace. The furnace heating capacity calculated by unit time and unit furnace bottom area is called furnace yield. The faster the furnace temperature rises and the greater the furnace load, the higher the furnace yield. In general, the higher the furnace yield, the lower the unit heat consumption per kilogram of material. Therefore, in order to reduce energy consumption, we should produce at full capacity, improve the furnace production rate as much as possible, and jointly adjust the active share of fuel and combustion supporting air for incineration equipment, so as to prevent excess or lack of air. In addition, it is also necessary to reduce the heat storage and heat dissipation loss of furnace wall, heat loss of water-cooling components, radiant heat loss of various openings, heat loss taken away from furnace flue gas, etc.
The ratio of the heat absorbed by metal or material during heating to the heat supplied into the furnace is called furnace thermal efficiency. The thermal efficiency of continuous furnace is higher than that of intermittent furnace, because the continuous furnace has high production rate and uninterrupted operation, the furnace thermal system is in a stable state, and there is no periodic heat storage loss of furnace wall, and there is a section for preheating furnace charge in the furnace, and some residual heat of flue gas is because there is a section for preheating furnace charge in the furnace, Some waste heat of flue gas is absorbed by the cold workpiece entering the furnace, which reduces the temperature of flue gas leaving the furnace.
To complete the active control of furnace temperature, furnace atmosphere or furnace pressure.
Gas is liquefied gas, natural gas, coke oven gas, city gas, converter gas, mixed gas, generator gas, blast furnace gas, etc.