Vanadium-nitrogen alloy is a new type of alloy material used in the production of microalloyed steels, which can effectively reduce production costs by replacing ferrovanadium. The addition of vanadium nitride to steel can improve its comprehensive mechanical properties such as strength, toughness, ductility and thermal fatigue resistance, while endowing the steel with good weldability. Therefore, the accurate determination of nitrogen content is of great significance for the application of vanadium-nitrogen alloy in production sites.
1 Sample Preparation
Samples are taken and prepared in accordance with “Sampling and Preparation of Samples for Chemical Analysis of Ferroalloys” (GB/T 4010-2015). The particle size of the sample shall be less than 0.125 mm (120 mesh).
Weigh a sample of the required mass and place it into a nickel capsule or tin capsule. Pinch and seal the capsule opening tightly with thin-nose pliers to prevent sample spillage. Then gently squeeze the capsule toward the bottom to expel air while keeping the capsule flat. Fold the sealed end of the capsule inward slightly with thin-nose pliers, increasing the number of folds as much as possible down to the bottom of the capsule. This is intended to reduce the capsule volume, facilitate smooth loading into the instrument sample port, and avoid jamming.
2 Test Equipment and Reagents
Test Equipment: PENY‑X2 ONH Oxygen‑Nitrogen‑Hydrogen Analyzer, electronic balance (sensitivity 0.0001 g), graphite crucible, nickel capsule, tin capsule, nickel basket, tin granules.
Test Reagents: CO₂ absorbent, anhydrous magnesium perchlorate, copper oxide, copper wire, quartz wool, silicone grease.
3 Measurement Principle
The pulse heating inert gas fusion thermal conductivity method is suitable for the determination of nitrogen in steel and iron over the full range. The EMGA-830 Oxygen, Nitrogen and Hydrogen Analyzer can rapidly determine the contents of O, N and H in steel, iron and alloy samples and output results simultaneously without separate measurements.
Oxygen and nitrogen in the sample are extracted by high-temperature fusion under inert gas protection. A low voltage and high current is applied between the upper and lower electrodes of the pulse electrode furnace, heating the sample in the graphite crucible. Oxygen in the sample reacts with carbon in the graphite crucible to form CO. Depending on the concentration, oxygen is detected as CO or CO₂ (CO is oxidized to CO₂ by high-temperature copper oxide oxidant) with a Non-Dispersive Infrared Detector (NDIR). Nitrogen in the sample is detected by the Thermal Conductivity Detector (TCD).
The detected gas is converted into a signal corresponding to its concentration. The final measurement result is obtained through rectification, filtering, amplification and integral calculation of the signal.
