How Does a Muffle Furnace Work?

What is muffle furnace?

Tube Furnace
Tube Furnace

The muffle furnace is a universal heating device. Its resistor wire hidden in the box, the wall of the box is thick, and there is an insulation material, the temperature can rise to 1200℃. It is often used in alkali melting of some insoluble metals and minerals, as well as in gravimetric analysis. It burns filter paper into flameless ash, burns to decompose organic matter, and drives out volatile components in inorganic matter. The muffle furnace is a new generation of energy-saving intelligent products for high performance machinery.

What is the purpose of using the muffle furnace?

Atmosphere Furnace
Atmosphere Furnace

The main purpose of using the muffle furnace is to prevent the workpiece from being affected by the combustion product. Another purpose is to eliminate the unevenness of the “combustion side” temperature of the industrial furnace.

How does a muffle furnace work?

Box Furnace
Box Furnace

The muffle furnace is an electric furnace that uses the Joule heat generated by the current passing through the conductor as the heat source. The muffle furnace uses electricity as a heat source, and converts electrical energy into heat energy through electric heating elements to heat the metal in the furnace.

The working principle of the muffle furnace is divided into the following steps:

①The principle of automatic control of muffle furnace temperature: According to the deviation of the furnace temperature to a given temperature, the heat source energy supplied to the furnace is automatically turned on or off, or the size of the heat source energy is continuously changed to stabilize the furnace temperature in a given temperature range, so as to meet the needs of the heat treatment process. Commonly used adjustment laws for temperature automatic control include two-position, three-position, proportional, proportional integral and proportional integral derivative. The temperature control of resistance furnace is such a feedback adjustment process, which compares the actual furnace temperature and the required furnace temperature to obtain the deviation, and obtains the control signal through the processing of the deviation to adjust the thermal power of the resistance furnace, thereby realizing the control of the furnace temperature. The control function (PID control) is generated according to the proportion, integral and derivative of the deviation, which is the most widely used control form in process control.

② When the muffle furnace starts to heat up, the brick masonry in the furnace absorbs a lot of heat to increase its own temperature, and this part of the heat is lost to the space when the furnace is shut down to cool down; This part forms the heat storage loss of the furnace body. An advanced electric furnace should have low empty furnace loss and high effective power. Less heat storage phase loss. The loss of an empty furnace is an important indicator to measure the efficiency of an electric furnace. An electric furnace with a small empty furnace loss can achieve high technical productivity and a low unit power consumption ratio.

③The main purpose of the industrial muffle furnace is for the mechanical industry to heat raw materials, blanks, and mechanical parts. Such as billet heating before plate rolling, heating of forgings. Heat treatment of mechanical parts and semi-finished products to improve their mechanical properties, such as rod quenching, tempering, annealing, normalizing, gas carburizing, nitriding, etc. It is also used for sintering, brazing, and some resistance furnaces are used for smelting low melting point metals and heating in the ceramic glass industry.

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