Hello friends, today I am going to tell you What is a Resistance Oven & Furnace, Construction and Working of Resistance Oven & Furnace: If you also want to know, then keep reading this article completely.
What is a Resistance Oven & Furnace
Resistance ovens have a heating chamber inside which a resistance heating element is installed. Generally, heating elements are in the form of wires or strips but in some resistance furnaces, heating elements are also in the form of electrodes.
Construction and Working of Resistance Oven & Furnace
Resistance walls are made inside the metal chamber by applying heat-resistant materials like fire-cum-bricks or heat insulating blankets. The shape and size of the ave are made as per the requirement and the resistance heating elements are installed in the roof: walls or floor of the ave or all over as required. While making the oven, the heat loss must be minimum and the object to be heated should attain a uniform temperature.
To achieve temperatures up to 1000 °C in the oven, an alloy of nickel, chromium, and iron is used in the form of a coil or strip, but to achieve higher temperatures up to 3000 °C, special heating elements of graphite are used.
65%Ni, 15%Cr, and 20% Fe alloy heating element are suitable for temperature up to 850°C and 78.5% Ni, 20% Cr, and 1.5 Si(80-20 nichrome V) for temperature up to 1000°C. ) is applicable. For temperatures up to 1000°C, 67% Fe, 25%Cr, and 5%AI(Fe-Cr-AI) alloys can also be used, but their lifespan is much shorter than that of nichrome V. Their resistance increases with time, and at high temperatures, they become brittle due to metallic changes. It is also very difficult to repair them when they are damaged. Silicon carbide can be used up to 1500°C and molybdenum disilicide up to 1700°C. Graphite can be used in inert gas up to 2200°C and special graphite resistive elements up to 3000°C. Graphite does not melt but it vaporizes at 3650°C to 3695°C.
- Read more: Principle Of CoreLess Induction Furnace
Two types of resistance ovens are used for heating purposes-
- Air circulation oven
- Bright annealing oven
1. Air Circulating Oven- This type of oven is also called convection type oven. Common resistance ovens in which heat is transferred by radiation but different parts of the charge are not heated equally. Therefore, air circulation ovens are suitable where uniform temperatures of different parts of the charge are desired and oven temperatures not exceeding 600°C are required. In these ovens, the air is heated by passing its overheated heating elements and then this hot air is circulated over the charge to provide uniform heating. The direction of air circulation is reversed to provide more uniform heating to the charge. Fans or blowers are used for air circulation. Air circulation ovens are used for steel hardening, stretching, aluminum coating, etc.
2. Bright TEMPERATURE Oven- In the normal process of annealing or annealing, the oxide layer on the job is formed in the form of a crust and it is necessary to remove it to get a shiny surface of the job. The oxide crust formed during annealing on the job can be prevented if the annealing process is carried out in an environment containing O.CO, and moisture. To obtain a flaky job, annealing is performed in a sealed oven with a one-way valve for expelling hot air that allows hot air to escape from the oven, but from outside as the oven cools. Does not allow air to enter the oven and the surface of the preheated job is shiny without any oxide layer.
- Read more: Vertical Core Type Induction Furnace
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