Methods for Determination of Multi-Element Content in Stainless Steel (Practical Version)
Main elements in stainless steel include: Cr, Ni, Mo, Mn, Si, P, S, C, Cu, N.Some high-end grades also contain: Ti, Nb, V, W, Co, Al. To meet different testing requirements, multi-element analysis of stainless steel generally adopts a combined approach: instrumental analysis as the primary method, supplemented by wet chemical analysis.
I. Optical Emission Spectrometry (OES) – Most Common & Fastest
Applicable to: Solid samples such as finished products, cast blanks, steel ingots, etc. Detectable elements:Cr, Ni, Mo, Mn, Si, P, S, Cu, Ti, Nb, V, W, etc. Advantages:
- Results available in 1 minute
- No sample dissolution required
- High precision and good repeatability
Disadvantages:
- Slightly lower accuracy for gaseous elements (C, S, N)
- Insufficient sensitivity for trace elements (<0.01%)
Standards: GB/T 4336, GB/T 11170
II. ICP‑OES (Inductively Coupled Plasma Optical Emission Spectrometry) – Simultaneous Multi-Element Determination
Applicable to: Liquid samples; especially suitable for elements such as Mo, Ti, Nb, V, W. Detectable elements: Almost all metallic elements Advantages:
- Simultaneous determination of multiple elements
- Low detection limit (ppm level)
- Wide linear range (0.0001% to several tens of percent)
Disadvantages:
- Sample dissolution required
- Cannot determine C, S, N
Standard: GB/T 20125
III. Carbon-Sulfur Analyzer (CS) – Dedicated Determination of C and S
Stainless steel is highly sensitive to carbon content (e.g., 304 requires ≤0.08%), so dedicated instruments are mandatory. Principle: High-frequency combustion → Infrared absorptionDetectable elements: C, S Advantages:
- Extremely high precision (especially for low sulfur)
- Fast (30–60 seconds)
Standards: GB/T 20123, GB/T 20124
IV. Oxygen-Nitrogen-Hydrogen Analyzer (ONH) – Determination of Nitrogen Content
Nitrogen is a critical alloying element in duplex stainless steels (2205, 2507) and must be accurately measured. Principle: Inert gas fusion → Infrared (O) / Thermal conductivity (N, H)Detectable elements: O, N, H Advantages:
- High precision for nitrogen
- Capable of measuring nitrogen as low as 0.001%
Standards: GB/T 20124, GB/T 11261
V. Wet Chemical Analysis – Reference / Arbitration Method
Used when highest accuracy is required or for dispute resolution. Common methods:
- Cr: Ammonium persulfate oxidation titration
- Ni: Dimethylglyoxime spectrophotometry or EDTA titration
- Mo: Thiocyanate spectrophotometry
- Si: Silicomolybdenum blue spectrophotometry
- Mn: Ammonium persulfate oxidation titration
- P: Molybdenum blue spectrophotometry
- Cu: Dicyclohexanone oxalyldihydrazone spectrophotometry
- Ti: Diantipyrylmethane spectrophotometry
- Nb: Mandelic acid gravimetry or spectrophotometry
Advantages:
- Highest accuracy
- National standard arbitration method
Disadvantages:
- Complex and time-consuming operation
VI. Typical Combined Schemes for Multi-Element Analysis of Stainless Steel
1. Routine factory analysis (fastest)
- OES (for metallic elements)
- CS analyzer (for C, S)
- ONH analyzer (for N)→ Full set of analysis completed within 5 minutes
2. Laboratory precision analysis
- ICP‑OES (for Mo, Ti, Nb, V, W, etc.)
- CS analyzer (for C, S)
- ONH analyzer (for N)→ Suitable for high-end stainless steels (e.g., 2205, 2507, 316L, 347)
3. Arbitration analysis
- Wet chemical analysis (for Cr, Ni, Mo, Ti, Nb, etc.)
- CS analyzer (for C, S)
- ONH analyzer (for N)
