Vacuum furnace graphite rod

---

1. Select the graphite rod with good red heat uniformity in the heating part. The poor uniformity of red heat of the rod will affect the furnace temperature uniformity and shorten the service life of the rod. In the process of using, the uniformity of red heat of the rod will gradually become poor, which will cause the rod to break seriously.

2. The longer the service life of the graphite rod is, especially after the surface temperature of the rod exceeds 1500 ° C, the faster the oxidation speed and the shorter the service life. During the use, pay attention not to let the surface temperature of the graphite rod be too high.

3. After the graphite rod is heated in the air, a dense silicon oxide film is formed on the surface, which becomes an anti-oxidation protective film, thus prolonging the service life. Intermittent use, with the temperature of the kiln changes, will lead to the surface of the protective film rupture, the protective role of weakened, accelerating the resistance of the bar become larger.

In order to ensure the furnace temperature stability and meet the needs of rapid temperature rise, the supporting electrical control system should have enough voltage adjustment margin – that is, when the new rod is used, it can meet the design and use power of the furnace at a lower voltage; as the use time continues, the resistance value of the rod becomes larger, at this time, it is necessary to increase the use voltage accordingly to meet the design and use power of the furnace.

Voltage margin value: the voltage of graphite rod at the later stage of use is generally 1.5-1.7 times of that of new rod. According to the different voltage regulation methods and wiring methods, the upper limit of the later voltage is generally 220V or 380V.

It is suggested to adjust the power by adjusting the voltage. It is recommended to select silicon controlled voltage regulation or voltage regulator for pressure regulation of graphite rod. Generally, it is not used to adjust the power regulator by changing the cycle number.

4. In general, the surface load density of graphite rod is obtained from the relationship between the temperature inside the furnace and the surface temperature of graphite rod. It is recommended to use the power with the maximum surface load density of 1 / 2-1 / 3 of graphite rod. The higher the current is, the higher the surface temperature is. A minimum surface load density (power) is recommended.

Please note that the values recorded at the cold end of the graphite rod are the current and voltage measured in the range of 1050 ℃ + – 50 ℃ in the air, which are not necessarily consistent with the actual use.

5. When the graphite rod is used continuously, it is expected to increase the voltage slowly to maintain long life.

6. The graphite rods shall be connected in parallel as much as possible. If the resistance value of the graphite rod is different, the load of the graphite rod with high resistance is concentrated in series, which leads to the rapid increase of the resistance of a certain graphite rod and the shortening of its service life.

At the same time, it is necessary to strengthen the combination of resistance values, that is, the resistance values of the same group of bars should be as close as possible. Generally, the resistance deviation of the same group of bars is within 10% – 15% in parallel and 5% – 10% in series. The higher the furnace temperature is, the smaller the resistance deviation is required.

Learn More: Vacuum Heat Treatment Furnace