In stainless steel cutting (such as laser cutting and plasma cutting), high temperature can easily cause oxidation of the cutting edge (forming oxide layers such as Fe ∝ O ₄ and Cr ₂ O ∝), which affects the quality of subsequent welding and coating.High purity nitrogen generatorBy providing high-purity protective gas (usually requiring purity ≥ 99.999%) to isolate oxygen, its anti oxidation effect needs to be verified through a three-step process of "purity monitoring cutting experiment oxidation evaluation" to ensure compliance with industrial production requirements (oxide layer thickness ≤ 5 μ m).

1、 Preparation before verification: Control variables and benchmark setting

1. Core equipment and materials

High purity nitrogen generator: set output pressure of 0.5-0.8MPa, purity monitoring adopts online oxygen analyzer (accuracy ± 0.1ppm);

Cutting equipment: Choose a 1000W fiber laser cutting machine (commonly used industrial model) with fixed cutting parameters (power 800W, speed 3m/min, focal position -1mm);

Stainless steel sample: 304 stainless steel plate (size 100mm × 100mm × 3mm), surface treated with ethanol degreasing to avoid oil contamination interfering with oxidation evaluation.

2. Comparison group design

Set up two parallel experiments to ensure consistency in all conditions except for nitrogen purity:

experimental groupHigh purity nitrogen generatorGas supply (purity ≥ 99.999%);

Control group: Compressed air supply (oxygen content 21%, simulating an unprotected gas scenario).

2、 Verification process: from purity monitoring to oxidation evaluation

1. Nitrogen purity confirmation (prerequisite verification)

Turn on the nitrogen generator and run it steadily for 30 minutes. Use an online oxygen analyzer to detect the purity of the nitrogen at the outlet of the cutting nozzle, and record it continuously for 5 times to ensure that the purity is ≥ 99.999% (oxygen content ≤ 10ppm);

If the purity does not meet the standard (such as oxygen content>20ppm), check the molecular sieve adsorption column of the generator (whether regeneration is required) and the sealing of the gas path (whether there is gas leakage) to eliminate interference from the purity of the gas source.

2. Cutting experiment operation

Both experiments used the same cutting path (straight cutting, length 80mm), with 3 stainless steel samples cut in each group to ensure data reproducibility;

During the cutting process, maintain a consistent flow rate of nitrogen/air (15L/min), and fix the distance between the nozzle and the sample at 1.5mm to avoid the stability of the airflow affecting the oxidation effect.

3. Quantitative evaluation of oxidation effect

(1) Appearance and macroscopic inspection

After cutting, observe the incision color of the two groups of samples: the control group usually appears dark brown or black due to oxidation, while the experimental group should appear silver white (without obvious oxidation color);

Measure the incision width with a vernier caliper (the oxide layer can cause the incision to widen): The incision width of the experimental group should be 0.1-0.2mm smaller than that of the control group, indicating a thinner oxide layer thickness.

(2) Microscopic oxide layer thickness detection (core indicator)

Take the cross-sections of the incisions from two sets of samples, and after embedding, polishing, and grinding, observe the oxide layer using a metallographic microscope (400x magnification);

Using image analysis method to measure the thickness of the oxide layer (measuring 3 different positions on each sample and taking the average): the thickness of the oxide layer in the experimental group should be ≤ 5 μ m, while the control group is usually>20 μ m. The larger the difference, the better the anti oxidation effect.

(3) Component analysis (auxiliary validation)

Using X-ray photoelectron spectroscopy (XPS) to detect the surface composition of the incision: the oxygen element content in the experimental group should be less than 5%, while the oxygen element content in the control group should be greater than 15%;

If the experimental group detects enrichment of Cr element (forming a Cr ₂ O3 passivation film on the surface instead of a thick oxide layer), it further proves that nitrogen protection effectively inhibits excessive oxidation.

3、 Verification result determination and optimization direction

1. Qualification criteria

Macroscopic: The incision of the experimental group was silver white with no obvious oxidation spots;

Microscopic: oxide layer thickness ≤ 5 μ m, oxygen element content<5%;

Repeatability: The RSD of the oxide layer thickness for 3 samples is less than 10%, ensuring the reliability of the results.

2. Handling of abnormal situations

If the thickness of the oxide layer in the experimental group is greater than 8 μ m (not up to standard), investigate whether the nitrogen purity has truly reached 99.999% (whether there is air leakage in the gas path mixed with air), and whether the airflow is insufficient (not effectively isolating oxygen);

Optimization direction: If the purity meets the standard but oxidation is still significant, the nitrogen flow rate can be appropriately increased (such as increasing to 20L/min), or the nozzle angle can be adjusted (to ensure nitrogen coverage of the cutting area).

4、 Application extension: Reproducing the effects in actual production

After passing the verification, it is necessary to conduct sampling and re inspection in batch production (10% of the cut parts are tested for oxide layer daily) to ensure long-term stable gas supply from the nitrogen generator (such as checking purity once a week); For cutting thick stainless steel plates (such as>10mm), the nitrogen purity can be appropriately increased (such as 99.9995%) to further enhance the anti oxidation effect.

In summary, the validation scheme can be accurately quantified through "purity control comparative experiment multidimensional evaluation"High purity nitrogen generatorThe anti oxidation effect provides data support for the quality control of stainless steel cutting, especially suitable for fields with high requirements for incision accuracy (such as medical equipment and food equipment manufacturing).