Precautions for maintenance of vacuum induction suspension furnace:
1. Vacuum must be maintained after the furnace is used, so as to accelerate the vacuum pumping speed in the next application. Furnace temperature shall not exceed rated temperature. It is forbidden to pour all kinds of liquid and dissolved metal directly into the furnace, and keep the furnace clean.
2. Regularly check whether the electrical connection of the control system is in good contact, and pay special attention to whether the connection points of the heating power supply and the induction coil are fastened.
3. The furnace is applicable to the following working conditions:
(1) The ambient temperature is between -10 ~ 75℃.
(2) The relative humidity of the surrounding environment shall not exceed 85%.
(3) There is no conductive dust, explosive gas or corrosive gas that seriously damages the metal and insulation materials around the furnace.
(4) There is no obvious tilt, oscillation or jolt.
Nitrogen is one of the common elements in steel, nitrogen atoms in steel has a solid solution strengthening effect, can improve the hardenability of steel, improve the creep strength, and with other elements in steel, there is precipitation hardening effect. In the vacuum induction furnace, nitrogen element is affected by the vacuum exercise, most of the nitrogen compounds will be separated out nitrogen in the liquid steel, which makes it difficult to increase nitrogen in the liquid steel. The effects of vacuum degree, temperature and nitride composition on the nitrogen solubility of steel were investigated, and three nitride - silicon nitride, manganese nitride and chromium nitride nitrogen increasing tests were carried out on alloy steel with different chemical composition (0.06 ~ 0.36C, ≤3.23Si, ≤2.20Al, ≤9.00Cr) in a 50kg vacuum induction furnace.
The results show that: 1) among the main factors affecting nitrogen solubility, vacuity and chemical composition, vacuity can have a great influence on nitrogen solubility, whose contribution rate can be greater than 60% for nitrogen solubility. 2) When the exercise temperature and vacuum degree are together, the elements in steel have a great influence on the nitrogen solubility and the nitride yield. Ti and Cr improved nitrogen solubility and nitride yield. C. Reduce nitrogen solubility and nitride yield; There is a certain amount of aluminum in steel, which can obviously improve the yield of nitride. 3) When 40kPa argon pressure is applied at 1600 ~ 1650℃, silicon steel, structural steel and 9 percent Cr steel are added with si3N4, manganese nitride and chromium nitride, and the nitride yield is 25 ~ 30 percent, 30 ~ 50 percent and 60 ~ 100 percent respectively. 4) Under the condition of vacuum exercise, nitrogen increasing process requirements of nitrides. Firstly, confirm that the nitrogen solubility in steel is greater than the guideline nitrogen content, select the appropriate type of nitrogen compounds, and comprehensively consider the influence of elements in steel on nitrogen solubility and nitrogen compounds yield.