Structure and Characteristics of Well Furnace and Nitriding Furnace

1. Air circulation

The fan at the lower end of the furnace cover drives the furnace gas to flow around by the centrifugal force of the fan, stirring the penetrant dripping from the drip tube to bring the air flow. The air flow is blocked on the furnace tank wall, flows down the channel between the inner wall of the furnace tank and the material frame (or guide cylinder) to the furnace tank bottom, and then under the effect of the negative pressure of the fan, the air flow flows upward through the holes at the bottom of the material frame to the material frame, providing fresh penetrant to the workpiece. At the same time, the inactive gas layer stuck on the surface of the workpiece is broken, and then it is sucked into the negative pressure area of the fan core for re circulation. A wind deflector is often hung under the fan to prevent airflow from returning directly to the fan from above the material frame.

2. Furnace tank seal

There should be a good seal between the hood and the furnace tank. The outer edge of the vacuum nitriding furnace cover should be sealed with water-cooled rubber rings. It is difficult to seal the shaft dynamically in the carburizing furnace. The common methods are piston ring seal, labyrinth seal and closed motor seal. The motor seal is that the motor is connected to the fan shaft and directly pressed on the furnace cover to achieve complete sealing.

3. Furnace tank and components

The material basket, air duct, furnace tank, tank base, material basket chassis, etc. shall be made of heat-resistant steel, usually CrMnN cast steel. The use temperature of the steel is 950 ℃, which limits the working temperature of the furnace. Cr25Ni2O steel is also commonly used to make furnace tank and other components that will deform and expand when heated. Leave room for expansion.

The nitriding furnace tank is usually made of high nickel steel such as OCr18Ni 9Ti, and cannot be made of ordinary steel plate. Ordinary steel plates are easy to be nitrided, which can crack and peel the furnace tank surface, and play a catalytic role in ammonia decomposition, increasing ammonia consumption and making ammonia decomposition unstable, or even impossible to nitride.

4. Furnace atmosphere supply, measurement and control device

The furnace cover is equipped with air inlet pipe or fluid drip pipe, exhaust pipe, thermocouple lead pipe for measuring furnace temperature uniformity, carbon (nitrogen) potential sensor insertion hole or gas pipe, sample inspection hole, etc.

When the old well type furnace realizes carburizing computer control. The oxygen probe insertion pipe shall be added. There are generally three holes on the furnace cover, namely: sample hole and large exhaust hole, oxygen probe installation hole and small exhaust hole and drip hole.