RQ Well Carburizing Furnace
RQ well type carburizing furnace is a periodic operation type electric furnace, mainly used for gas carburizing of carbon steel parts. Used in conjunction with the electric furnace control cabinet to automatically control and automatically record the temperature of the electric furnace
Ranben electric furnace structure is mainly composed of furnace body, heating element and temperature control system.
The furnace shell is welded by profile steel and steel plates, and the interior is built with ultra-lightweight high-alumina foam bricks. The insulation layer is made of aluminum silicate refractory fiber and diatomite (or vermiculite powder) bulk material to improve the furnace body. Thermal insulation performance.
The heating element is placed on the wire brick, and a small wire hook is used to position it.
The lifting and lowering of the furnace cover is completed by a hydraulic lifting mechanism, and its power is provided by a 10/25 hydraulic device.
When the furnace cover needs to be lifted, as long as the hydraulic device is activated, the furnace cover is slowly raised; if the furnace cover is lowered, as long as the internal thread stop valve in the hydraulic device is loosened, the furnace cover is slowly lowered. At the lifting shaft, there are two limit switches. When the lifting shaft rises, the lower limit switch automatically cuts off the power of the electric fan to avoid danger to the operation. When the furnace cover is raised, the upper limit automatically cuts off the power of the hydraulic device. To prevent accidents when the lifting shaft ejects the cylinder.
A water-cooled sample tube, air intake hole and exhaust hole are provided above the furnace cover. If it is combined with the infrared CO2 analyzer and modified, the carbon potential can be automatically controlled.
A heat-resistant plate is welded into the furnace to form the furnace tank and the basket, and the workpiece to be processed is placed in the basket.
In order to make the workpiece to be uniformly contacted with the carburizing gas, a ventilator is installed on the furnace shell to force the air circulation to make the temperature and gas in the furnace uniform. There is a sealing device on the fan shaft sleeve to prevent air leakage, and it is cooled by cooling water.
The liquid drip system of this electric furnace is equipped with a dropper that can simultaneously drip three liquids, and its flow rate can be controlled by a flow meter and a needle valve.
RQ well type carburizing furnace process operation:
1. Temperature rise: Ammonia exhaust should be passed before the temperature rise. The ammonia gas flow rate is more than twice the normal use flow rate. The deformation requirements are strict. Stepwise temperature rise is adopted. The temperature is maintained at 200 ~ 250ºC and 400 ~ 450ºC for 1 ~ 2h each. The speed is less than 50ºC / h. When approaching the holding time, the amount of ammonia should be increased to control the decomposition rate to the lower limit of the process requirements.
2. Exhaust: Generally exhaust while heating up, and evacuate within 150 ~ 200ºC. During the exhaust process, you can use pH test paper (soak the test paper with water, it will turn blue when met with ammonia gas) or glass rods (glass rods meet the salt with ammonia) White smoke is emitted from the gas) Method to check the sealing of the furnace tank and the pipeline
In the exhaust phase, ammonia gas is continuously introduced to make the furnace gas pressure reach 200 ~ 400Pa. Because ammonia gas is easily soluble in water, a U-shaped tube for measuring the ammonia decomposition rate is usually filled with oil. In the nitriding tank, the air is not clear, and the exhaust pipe cannot be ignited. The ammonia decomposition rate can reach 70% during the heating stage. When the ammonia volume fraction in the furnace gas is greater than 95%, the ammonia flow rate can be reduced and the positive temperature in the furnace can be maintained. Press
3． Insulation: When the temperature reaches the process specified temperature, adjust the ammonia flow rate to control the ammonia decomposition rate at 18% ~ 35%, and start to calculate the insulation time. At this time, the furnace pressure is 200 ~ 600Pa. During the nitriding process, the adjusted ammonia is used. The flow rate method is used to control the ammonia decomposition rate. Generally, the ammonia decomposition rate is measured every 15 to 30 minutes. During the insulation process, the upper and lower deviations of the furnace temperature should be less than 5ºC. When the insulation is near the end, the sample should be taken out of the sampling hole and necessary. Analysis
4． Denitrification cooling: After the entire nitriding phase is completed, the exhaust valve is closed to reduce the ammonia flow, and the heat is kept for 2 hours, so that the ammonia decomposition rate is greater than 70%, the nitrogen concentration on the surface of the part is reduced, and the surface brittleness is reduced. After that, the power supply was reduced to reduce the temperature, and a small amount of ammonia gas was continuously introduced into the furnace to keep the furnace at a positive pressure. The furnace temperature dropped below 150ºC to stop the ammonia supply, and parts should be avoided from collision.