What is the nitriding process of the nitriding furnace?
According to the requirements of the workpiece material and the infiltration layer, it ranges from 3 to 90 hours, so that the surface of the nitriding workpiece can obtain a nitrogen-containing strengthening layer, which results in high hardness, high wear resistance, high fatigue limit and good wear resistance.
1. The mold before nitriding must be a workpiece that has been normalized or quenched and tempered first.
2. Scrub the surface of the workpiece with gasoline and alcohol first. There should be no rust spots, oil stains, or dirt.
3. After installing in the furnace, tighten the furnace cover compression bolts symmetrically.
4. Pass the cooling water to the water inlet of the furnace tank and furnace cover for circulating water cooling. The bottom end of the cooling pipe of the furnace cover is the water inlet and the upper end is the water outlet. The furnace tank is fed with water separately and drained separately. All the water pipes of the furnace cover can be connected in series according to the principle of low inlet and high outlet.
5. Nitrogen exhaust should be sent before warming up, and the flow rate during exhausting should be more than double that during use.
During ion nitridation, the quality of the nitrided layer and the nitridation cycle are directly affected by the operating temperature. And due to the influence of high voltage, glow and atmosphere, it makes it difficult to measure the temperature. Currently used for ions
The temperature measurement methods of nitriding furnace are as follows:
(1) Visual measurement
Turn off the high-voltage power supply and judge the temperature by looking at the color of the workpiece through the observation window (in a dark furnace cover, the metal is reddish at about 520 ° C and dark red at about 550 ° C). Obviously, this method varies from person to person, the temperature difference may be large, and the quality of nitriding is poorly controlled.
(2) Thermocouple temperature measurement
This method usually uses armored thermocouples to make a special temperature probe, which is closely attached to the workpiece, and the nitriding temperature is measured and controlled by the display instrument.
In order to avoid the negative high voltage of the thermocouple, there is usually insulation such as mica sheet or quartz tube between the thermocouple head and the workpiece, but this will cause the temperature indication to be low, and after long-term work, due to the cathode sputtering effect The surface of the insulator is contaminated with metal powder and becomes a conductor. As a result, the thermocouple will still be nitrided with negative high voltage, and the indication error will increase. Sometimes due to the poor contact between the insulator and the workpiece, the glow discharge will be unstable, causing arcing, and the nitriding furnace will affect normal work.
(3) Temperature measurement by photoelectric pyrometer or photoelectric colorimeter pyrometer
These two types of thermometers are a more advanced method to achieve continuous, rapid, non-contact temperature measurement and temperature control outside the nitriding furnace through the glass of the observation window on a closed container. When measuring temperature with a photoelectric pyrometer, it is necessary to consider the changes in the surface condition of the workpiece (surface finish and geometry), the emissivity of the workpiece surface, window pollution, ionized gas in the furnace, glow discharge, and cathode sputtering. influences. When using photoelectric colorimeter pyrometer to measure temperature, the influence of these factors is much smaller. Therefore, it is an ideal temperature measuring instrument for measuring the temperature of the workpiece of the ion nitriding furnace.