1. Preparations before commissioning of nitriding furnace
1) The electrical equipment is checked by an electrician and the current breaker (zone 1-5, insulation room) is opened. The manual cycle reset switch should be in the off position.
2) The fitter checks whether the furnace door, front and rear soft chains, main push rod, tray, conveyor belt, quenching table, fan and other components are operating normally and the lubrication points are normal.
3) Plumbers inspect and clean various gas pipelines.
4) Check whether the temperature controller, oxygen probe, thermocouple and protection tube are normal.
5) The operator should check whether the air valve is closed. The oil tank should ensure that the oil level of the main oil tank is higher than the oil level of the low alarm line. The top fan should work fine. Cooling water circulation is smooth and normal. The rotors and tube walls of various flow meters should be clean and normal. The hydraulic pump, mixer, and auxiliary tank are working properly. The selector switch on the program screen, button station and heating atmosphere control cabinet should be in the correct position. The process parameters of the workpiece running on the CRT display terminal should be correct. Various fixing devices and auxiliary materials should be prepared before starting.
2. Temperature rise adjustment of nitriding furnace
1) When the furnace head is installed or overhauled, when new bricks are placed in the furnace or the furnace is stopped for more than two weeks, the furnace should be heated according to the following process: the furnace door is half open, the quenching fuel tank is not refueled, and the sampling holes and front and rear explosion-proof caps are opened. When the temperature in each area rose to 200 ° C, the holding time exceeded 32 hours. Then 50 C / h was raised to 400 C and held for 32 hours, then 50 C / h was raised to 700 C and held for 8 hours. Then, at 50 C / h, increase the working temperature of each zone and keep it warm for more than 2 hours.
2) If the furnace is lowered to room temperature for less than two weeks without replacing the brickwork, the heating procedure is as follows: the furnace door is half open, the explosion-proof cover and sampling hole are opened, and the temperature in each area is raised to 200 degrees Celsius for 12 hours, then The temperature rises from 50 degrees Celsius / hour to 400 degrees Celsius for 8 hours, then the temperature rises from 50 degrees Celsius / hour to 700 degrees Celsius for 8 hours, and then reaches the working temperature and heat preservation for more than 2 hours.
3) During the warming process, each class should take two organizational actions, and all normal warming can continue. When the temperature rises to 200 degrees Celsius, all cooling water valves should be opened. When the furnace temperature rises to 400 ° C, the top fan should be started. When the 400C insulation is completed, the front and rear doors of the furnace should be closed, and the fuel tank should be filled. Silica sand will be added to the vault sand seal. Close the front and rear explosion-proof covers. Thermocouples and meters are calibrated after the furnace has reached operating temperature. After overhaul, the newly installed or newly built brick kiln should be subjected to full load temperature measurement to determine the process temperature.
3. Commissioning Open the valve of the discharge pipe next to the furnace, release it for 5 minutes, the ignition nozzle is burning normally, and the front and rear flange doors have flame detectors to alarm. Insert a welding torch under the furnace door and send it according to the following procedure
Open the raw gas valve, open the flow meter valve, and introduce the heat-absorbing air into the furnace to control the flow of the generator. Press the pressure switch. Close the protective pneumatic manual reset valve. Material pneumatic manual reset valve. Adjust the flow of each area according to the process. When the gas in the furnace door is burning steadily, remove the torch and close the furnace door.
4. Carburizing in the furnace, basket, and fixture, then add gas after pre-carburizing. The equipment is controlled by the carbon potential. The carbon potential of each zone meets the requirements of the process, and pre-carburization of the furnace hearth, furnace basket and fixture is started. The carbon potential of the furnace gas is the same as the process requirements of the product. The pre-carburizing time is not less than 12 hours. Place the workpiece after the furnace gas carbon potential is normal. After 12 hours, the carbon-free potential control device was analyzed through a three-zone air vent. When (co2) is less than 0.3%, the workpiece can be put into use. Before the workpiece is put into use, push 4-6 discs containing waste products. At the same time, place the sample on the tray.