Titanium plate of chemical industry tempered by vacuum induction furnace

The exercise question is an important factor that restricts the application of titanium plate containing chemical industry. Because nitrogen is a gas element, its solubility in titanium is relatively low. At present, the training of titanium plate in chemical industry generally uses the skills of pressurized electroslag remelting and back pressure casting to complete, and other methods such as hot isostatic pressure melting, pressurized induction melting and powder metallurgy. These training skills need special equipment with high cost.

How to adopt economic and useful methods to exercise chemical titanium plate has always been attached great importance. The Institute of metal science of Chinese Academy of Sciences has recently proposed to use vacuum induction furnace directly to train the technical skills of titanium plate in China’s chemical industry. With this skill, the chemical titanium plate with nitrogen content of about 0.5% can be trained without positive pressure, and the impurity element content in titanium can be effectively controlled. At present, various influencing factors in the process of chemical titanium plate tempering by vacuum induction furnace are further studied.

1、 The effect of alloy elements on nitrogen content.
The solubility of nitrogen in ferroalloy solution is greatly affected by other alloy components. Different alloys have different effect coefficients on the solubility of nitrogen in titanium. Cr, Mn, Mo, V, Nb and other elements increase the solubility of nitrogen, while Ni, Cu, Si, C and other elements decrease the solubility of nitrogen. The activity coefficient can be used to measure the effect of various elements on the solubility of nitrogen in titanium solution.

According to the current experimental results, chromium or manganese in titanium can effectively improve the solubility of nitrogen.

2、 Increase the influence of nitride varieties and methods.
Using vacuum induction furnace to train chemical titanium plate, the first step is to participate in nitrogen alloying. Because the training system of vacuum induction furnace is a low-pressure system, a lot of melting and dissolution of nitrides in titanium liquid will inevitably constitute the overflow of nitrogen on the surface of titanium liquid.
If we take part in the nitride too early, the nitrogen dissolved in the titanium liquid will continue to participate in the overflow reaction of the titanium liquid surface, so that the nitrogen dissolved in the titanium liquid is less and less.
If the melting temperature of nitride exceeds the temperature of titanium liquid, it will inevitably extend the melting time, and higher melting temperature will promote nitrogen to overflow from titanium liquid.
When the melting temperature of nitride is low (lower than the temperature of titanium liquid), the nitride will melt rapidly and be mixed evenly when it joins in the titanium liquid;
Because of the short time, a lot of supersaturated nitrogen dissolved in the titanium liquid was left in the titanium liquid before pouring into the titanium ingot, and then a higher nitrogen content was obtained.
As long as the melting temperature of MNN is low, it is about 1200 ℃, while the melting temperature of CrN and Si is above 1600 ℃.
Therefore, it is suitable to use MNN when using vacuum induction furnace to exercise titanium plate.

3、 The influence of exercise parameters.
The results show that the solubility of nitrogen in titanium decreases with the increase of temperature, which may be due to the interaction of alloying elements in titanium. Therefore, it is an important factor to control the temperature of titanium liquid and the temperature of titanium discharge during exercise to ensure the nitrogen content in titanium liquid.
Some standards and parameters of vacuum furnace (such as the volume of furnace cavity, the standard of crucible for exercise, etc.) all affect the content of nitrogen in titanium liquid to a certain extent.
The furnace cavity is small, and the dispersion of nitrogen to the furnace cavity can be reduced under the condition of constant pressure;
The smaller the inner diameter of the crucible, the smaller the specific surface product of the titanium liquid and the external touch, and the smaller the opportunity for nitrogen to participate in the spillover response, all of which are conducive to maintaining a higher nitrogen content in the titanium liquid.
In addition, when there is a lot of oxygen in titanium, the CO gas produced by carbon deoxidization can easily induce the nitrogen dissolved in titanium liquid to form bubbles and overflow, which is not conducive to obtaining high nitrogen content.

Learn More: Vacuum Induction Melting Furnace