Pay attention to three links to greatly improve the service life of medium frequency furnace

May 13, 2022

Improving the service life of induction furnace body is the goal pursued by every foundry worker, which will also be of great significance to the enterprise. The service life of electric furnace crucible is mainly affected by furnace lining refractory, furnace drying process and service process, which are introduced below.

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1、 Lining refractory

The quality and performance of lining refractory play a fundamental role in the service life of the furnace.

1) The refractory materials for furnace building shall have quite high fire resistance, resist the action of high-temperature heat load, and shall not soften or melt. At the same time, it also has high volume stability, resistance to high-temperature heat load, no volume shrinkage and only uniform expansion.

2) Composition of refractory. Impurities in refractories can form compounds with low melting point at high temperature, which reduces the refractoriness of refractories. Therefore, the content of quartz in furnace lining sand shall be ensured and the impurity composition shall be strictly controlled. The composition of furnace lining sand shall be controlled as follows: ω (SiO2)≥98.0%; ω (Al2O3)≤0.5%; ω (Fe2O3)≤0.5%; ω (TiO2)≤0.05%; ω (H2O)≤0.5%。

3) Refractory particle size ratio. The reasonable particle size ratio of refractory can easily form a refractory layer with high density in the process of furnace building, and it is not easy to have defects in the process of use. The following is a group of reasonable proportions: the proportions of 3.35mm ~ 5mm, 0.85mm ~ 1.70mm, 0.1mm ~ 0.85mm and less than 0.1mm are 17%, 33%, 20% and 30% respectively.

2、 Oven drying process

Oven drying is a process to obtain the sintering layer. The quality of the sintering layer directly affects the service life of the furnace. Oven drying is an important link. After the furnace cavity is built, the furnace shall be dried immediately; Before oven drying, check whether the electrical equipment and cooling water system are normal; The oven drying process shall be strictly followed. Oven drying process is the key factor in the oven drying process. The specific points are as follows:

① The heating speed should be controlled well, especially in the early stage of oven drying. If the heating speed is too fast and the water in the furnace lining is discharged too fast, it is easy to form cracks and greatly shorten the service life of the furnace.

② When the furnace lining is heated to 573 ℃, the rapid expansion of quartz in the process of phase transformation will easily cause cracks and even spalling. Therefore, when heating from 400 ℃ to 600 ℃, the heating speed should be slowed down, and when heating at 870 ℃, it should be kept warm for 1H ~ 2H, so that it can realize slow and complete phase transformation.

③ The final stage of furnace drying is sintering and heat preservation. The sintering temperature depends on the specific refractory materials. Generally, it is expected to obtain a sintering layer with a thickness of 30% of the furnace lining thickness. Therefore, the general sintering temperature is 50 ~ 100 ℃ higher than the tapping temperature.

3、 Furnace process

Various processes during the use of the furnace are also very important to the service life of the furnace, and various improper operations may reduce the service life of the furnace.