CLADDING TECHNOLOGY SHANXI CO., LTDSpark-Discharge Atomic Emission Spectroscopy Analysis of Seven Elements in Strip Clad Weld Deposit Metal
Literature Overview
This study presents a method for analyzing seven elements in the weld deposit metal of strip cladding (weld overlay) using spark-discharge atomic emission spectroscopy (Spark-AES). Strip cladding is a widely used process for producing bimetallic plates with a corrosion-resistant or wear-resistant overlay on a structural steel base. The chemical composition of the weld deposit metal is critical for ensuring that the overlay meets the required performance specifications. The study evaluates the accuracy, precision, and practical applicability of Spark-AES for rapid chemical analysis of strip clad weld deposits.
Core Technical Points
Spark-AES is a well-established technique for elemental analysis of metals, offering rapid results (typically 30–60 seconds per sample) with good accuracy for major and minor elements. The technique is particularly suitable for field and production environments where rapid analysis is required for quality control purposes.
Elements Analyzed and Their Significance
| Element | Role in Overlay | Typical Range (wt%) | Analytical Importance |
|---|---|---|---|
| Carbon (C) | Carbide formation, hardness | 0.2–1.5 | Critical for hardness and wear resistance |
| Chromium (Cr) | Corrosion resistance, carbide formation | 12–30 | Primary alloying element for stainless overlays |
| Nickel (Ni) | Matrix stability, toughness | 5–25 | Stabilizes austenite, improves ductility |
| Molybdenum (Mo) | Pitting resistance, high-temperature strength | 1–6 | Enhances resistance to chloride pitting |
| Manganese (Mn) | Deoxidation, strength | 0.5–2.0 | Affects weldability and hot cracking susceptibility |
| Silicon (Si) | Deoxidation, strength | 0.2–1.5 | Affects fluidity and oxidation resistance |
| Sulfur (S) | Inclusion formation, weldability | 0.01–0.05 | Must be controlled to prevent hot cracking |
The study demonstrates that Spark-AES can accurately measure all seven elements within the specified ranges, with uncertainties typically below 2 percent relative for major elements and below 5 percent relative for minor elements.
Methodology and Calibration
The Spark-AES analysis requires calibration using certified reference materials (CRMs) that match the matrix composition of the weld deposit metal. For stainless steel overlays, CRMs with compositions similar to 304, 316, or 321 stainless steels are used. The calibration curve is established by measuring a series of CRMs with known compositions and developing a mathematical relationship between signal intensity and concentration.
The sample preparation involves:
- Mounting the weld deposit metal sample on a sample holder.
- Polishing the analysis surface to a mirror finish using standard metallographic preparation procedures.
- Cleaning the surface with alcohol to remove polishing residue and contaminants.
- Positioning the sample on the spectrometer electrode and initiating the spark discharge.
The spark discharge creates a plasma that excites the atoms in the sample, causing them to emit characteristic wavelengths of light. The emitted light is dispersed by a diffraction grating and detected by an array of photomultiplier tubes or CCD detectors. The intensity of each wavelength is proportional to the concentration of the corresponding element.
Accuracy and Precision Evaluation
The study evaluates the accuracy and precision of the Spark-AES method through inter-laboratory comparisons and repeated measurements:
| Element | Relative Standard Deviation (n=10) | Bias vs. Reference Method |
|---|---|---|
| C | 1.2% | +0.5% |
| Cr | 0.8% | -0.3% |
| Ni | 0.6% | +0.2% |
| Mo | 2.5% | +1.0% |
| Mn | 1.0% | -0.4% |
| Si | 1.5% | +0.6% |
| S | 3.0% | +0.5% |
The results demonstrate that Spark-AES provides acceptable accuracy and precision for all seven elements, with the highest uncertainty observed for molybdenum and sulfur, which are present at lower concentrations. The slight positive bias for carbon, nickel, silicon, and sulfur is attributed to matrix effects and can be corrected through calibration with appropriate reference materials.
Process Standards and Quality Considerations
The chemical composition of strip clad weld deposits is governed by applicable product standards such as ASTM A263, A264, or A265, which specify the minimum and maximum limits for each alloying element.