Resistance furnace refers to the heating furnace with Joule heat generated by current passing through the conductor as the heat source. The commonly used heating elements include resistance wire, resistance belt, etc. Compared with the traditional flame furnace, the resistance furnace has the advantages of high thermal efficiency, easy heat control, uniform furnace temperature and long service life. The disadvantage is high power consumption. Resistance furnace can be used for sintering, dissolution and analysis of metals and ceramics; It can also be used for further analysis and determination of elements in the laboratory; Resistance furnace is also commonly used in mechanical industry to heat metal before forging, melt low melting point metal, dry sand mold and paint film, heat treatment and processing of small steel parts, etc.
According to the heating temperature, the resistance furnace with working temperature below 650 ℃ is a low-temperature furnace, 650 ~ 1000 ℃ is a medium temperature furnace, and above 1000 ℃ is a high-temperature furnace.
According to the heat transfer mode, the resistance furnace is divided into radiation resistance furnace and convection resistance furnace. Radiant resistance furnace is dominated by radiant heat transfer, and the effect of convective heat transfer is small; Convection resistance furnace is mainly convective heat transfer, which is usually called air circulation resistance furnace. It is mainly heated by radiation in high-temperature and medium temperature furnaces. In the low-temperature furnace, it is heated by convection heat transfer.
The basic purchase of resistance furnace is very simple. Just pay attention to two basic parameters: volume and temperature control range. However, in addition, the purchasing housekeeper of Soke believes that to choose a resistance furnace with high cost performance and long service life, you also need to consider the following matters:
1. Furnace grade and material
There will be some differences in heating effect and service life of resistance furnace with different furnace materials. The furnace of high temperature resistance furnace can be divided into four grades:
Ordinary refractory, low cost, limited heating;
High temperature aluminum furnace, suitable for carbon free test;
Silicon carbide furnace, slow heating rate and good heating comparison;
Ceramic fiber furnace has a fast heating rate, but sometimes the temperature is too high, which also has the risk of burning the furnace.
Generally speaking, when purchasing high-temperature resistance furnace in the laboratory, Soko recommends that you choose silicon carbide furnace.
2. High furnace temperature
Each resistance furnace has a nominal temperature range, but in practical application, you should distinguish the difference between instrument design temperature and service temperature.
Generally speaking, you should choose products that are slightly higher than your service temperature, because the nominal high design temperature of the furnace may not reach the high temperature due to various conditions.
3. Heating element
The heating elements of high-temperature resistance furnace generally include resistance wire, silicon carbide rod and silicon molybdenum rod. Generally speaking, resistance wire is used for 1000-1200 degrees and silicon carbide rod is used for 1300 degrees.
4. Furnace structure
There are two types of resistance furnace: integrated type and split type. The integrated resistance furnace integrates temperature control and furnace body design, and can be used directly without installation. The split resistance furnace needs to install the temperature controller on the furnace body first, and then carry out the installation and configuration in the next step, which is cumbersome. But split resistance furnaces are usually relatively cheap.
In addition, you can also learn about the furnace temperature control system of resistance furnace. The temperature control system is mainly composed of temperature sensing elements, matching temperature measuring circuits and temperature control instruments. The resistance furnace with uniform furnace temperature can perform better in the test.
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