Methods to Improve the Temperature Resistance of Induction Furnace Lining

Furnace lining refers to the furnace wall of induction furnace or other furnaces used to refine metal. It is a very important part of the working process of medium frequency furnace. The quality of furnace lining can directly affect the working efficiency of electric induction furnaces. As high-temperature smelting equipment, the temperature resistance of the furnace lining is certainly the main standard to judge the furnace lining. So how can we improve its temperature resistance? Today, the staff of the medium frequency electric furnace manufacturer will start a class to talk about the methods to improve the temperature resistance of the medium frequency furnace lining.

The temperature resistance of furnace lining mainly depends on the physical, chemical properties, and mineral composition of the refractory used for lining. On the premise of selecting raw and auxiliary materials, the sintering process is the key process to obtaining a good microstructure of furnace lining and giving full play to its high-temperature resistance. The densification degree of lining sintering is related to the chemical composition, particle size ratio, sintering process, and sintering temperature of refractories. After introducing the relevant factors, we will formally start to introduce the methods to improve the temperature resistance of the electrotherm induction furnace lining.

1. Remove Mica Paper During Furnace Building

One of the ways to improve the temperature resistance of the medium-frequency furnace lining is to remove the mica paper when building the furnace.

2. Treatment of Crystal Quartz Sand for Furnace Building

Manual selection: mainly remove lumps and other impurities;

Magnetic separation: magnetic impurities must be completely removed;

Dry ramming material: it must be dried slowly at a drying temperature of 200 ℃ -300 ℃ for more than 4 hours.

3. Selection of binder for induction melting furnace

Boron anhydride (B2O3) is used as a binder instead of boric acid (H3BO3), and the addition amount is 1.1%-1.5%.

4. Selection and Proportion of Appropriate Furnace Building Materials:

1) Selection of furnace building materials: it should be noted that not all quartz sands with SiO2 ≥ 99% can be used as furnace lining materials of induction furnaces. The important thing is the size of quartz grains. The coarser the grains, the fewer the lattice defects, the better. (for example, crystal quartz sands have high SiO2 purity, a white and transparent appearance.) The larger the furnace capacity, the higher the requirements for grains.

2) Proportion of furnace building materials: proportion of quartz sand for furnace lining: 6-8 mesh 10%-15%, 10-20 mesh 25%-30%, 20-40 mesh 25%-30%, 270 mesh 25%-30%.

5. The knotting of Furnace Lining

The quality of furnace lining knotting is directly related to the sintering quality. When knotting, the sand particle size is evenly distributed without segregation. After knotting, the density of the sand layer is high, and the probability of cracks after sintering is reduced, which is conducive to improving the service life of the induction furnace lining.

6. Knotting at Furnace Bottom

The furnace bottom is about 280mm thick and is filled with sand in four times. Uneven density is prevented during manual knotting, and the furnace lining after baking and sintering is not dense. Therefore, the feeding thickness must be strictly controlled. Generally, the sand filling thickness shall not be greater than 100mm/ time, and the furnace wall shall be controlled within 60mm. Multiple people shall work in shifts, with 4-6 people in each shift, and each time they tie knots for 30 minutes. They shall rotate and rotate around the furnace slowly with even force to avoid uneven density.

7. Knotting of Furnace Wall

The thickness of furnace lining is 110-120mm. Dry knotted materials are added in batches. The distribution is uniform. The thickness of filler is not more than 60 mm. Knot for 15 minutes (manually knot) until it is flush with the upper edge of the induction ring. After knotting, the crucible mold is not taken out, and it plays the role of induction heating during drying and sintering.

8. Observe Baking and Sintering Specifications

In order to obtain the three-layer structure of furnace lining, the baking and sintering process is roughly divided into three stages:

1) Baking stage: heat the crucible mold to 600 ℃ at the speed of 25 ℃ /h and 50 ℃ /h respectively for 4h, so as to completely remove the moisture in the furnace lining.

2) Semi sintering stage: raise the temperature to 900 ℃ at 50 ℃ /h for 3h, and raise the temperature to 1200 ℃ at 100 ℃ / h for 3h. The heating rate must be controlled to prevent cracks.

3) Complete sintering stage: during high-temperature sintering, the sintering structure of the medium frequency electric furnace crucible is the basis for improving its service life. With different sintering temperatures, the thickness of the sintering layer is insufficient, and the service life is obviously reduced.

The above is the method to improve the temperature resistance of the induction furnace lining. In addition, when the medium frequency furnace is cold started, it must be preheated at low temperature and then gradually increased, which can effectively improve the service life of the furnace lining.

If you are interested in our induction furnace, please mail at [email protected] or [email protected].

Kindly click on the article you may be interested in:

What is Metallurgical Equipment?

What Is the Ladle Refining Furnace?

Alkaline EAF Oxidation Smelting Process

Where Is Induction Furnace Used?

Leakage Detection of the Induction Furnace

Comparison of Electric Furnace, AOD furnace, LF furnace and VD Vacuum Furnace

Energy Saving and Emission Reduction in Steelmaking Production

Energy-Saving Technology for Heat Treatment of Induction Furnace

Walking Beam Reheating Furnace VS Push-steel Reheating Furnace

Cause Analysis and Solution of Induction Coil Blocking in Medium Frequency Smelting Furnace