CLADDING TECHNOLOGY SHANXI CO., LTDFitting Analysis and Optimization of MIG Welding Current for Stainless Steel
Literature Overview
The paper authored by Quanyong Wang and Xiaojuan Wu from Shenyang Ligong University, published in China Welding in 2025 and supported by the National Natural Science Foundation of China (Grant No. 52301098), addresses the systematic fitting analysis and optimization of MIG welding current parameters specifically tailored for stainless steel substrates. This work is particularly relevant to the cladding and weld overlay community because stainless steel—especially austenitic grades such as 304, 316, and 321—is the most widely used cladding material in pressure vessel fabrication for corrosion resistance purposes. The precise control of welding current directly governs dilution rate, overlay layer composition, and bond strength, making this topic of critical importance to engineers designing clad-plate pressure vessels and weld-overlay equipment.
Core Technical Content
The study focuses on establishing quantitative relationships between welding current and key weld characteristics through mathematical fitting models. In MIG welding of stainless steel, the welding current is the primary parameter that determines:
- Heat input and thermal cycle severity
- Arc stability and transfer mode (short-circuit vs. spray transfer)
- Deposition rate and dilution of base metal into the overlay
- Microstructure evolution in the fusion zone and heat-affected zone
The authors developed fitting functions that correlate welding current with observable weld quality indicators, enabling engineers to predict and optimize process outcomes without relying exclusively on trial-and-error coupon testing.
Technical Parameter Analysis
| Parameter | Typical Range for Stainless Steel MIG | Influence on Cladding Quality |
|---|---|---|
| Welding Current (I) | 120–280 A | Primary driver of dilution and penetration |
| Voltage (U) | 18–28 V | Controls arc length and bead width |
| Wire Feed Speed (VWFS) | 3.5–9 m/min | Governs deposition rate |
| Shielding Gas Flow (Q) | 12–20 L/min | Protects molten pool from oxidation |
| Travel Speed (Vt) | 200–600 mm/min | Affects heat input and bead profile |
| Wire Diameter (d) | 1.0–1.6 mm | Influences arc stability and penetration |
Current Optimization Strategy
The fitting approach described in the literature enables the following engineering workflow:
- Establish baseline weld geometry and dilution data across a range of current settings.
- Apply regression or polynomial fitting to identify the current window that minimizes dilution while maintaining full bond strength.
- Validate the fitted model through independent coupon testing.
- Transfer optimized parameters to production welding procedures.
For stainless steel cladding on carbon steel substrates, the dilution rate must typically be controlled below 30% to ensure the overlay layer retains adequate corrosion resistance. The welding current is the single most influential parameter in this regard—excessive current increases penetration into the base metal, thereby increasing dilution and potentially compromising the corrosion performance of the clad surface.
Connection to Cladding Engineering Practice
In the fabrication of bimetal pressure vessels per GB/T 150 or ASME VIII Div.1, the weld overlay cladding layer must achieve both metallurgical bond strength (typically ≥ 1.25 times the lower of the base metal or overlay tensile strength) and acceptable corrosion resistance. The fitting analysis methodology presented in this paper provides a rational basis for procedure qualification under NB/T 47014 or ASME IX.
Practical Implications for Weld-Overlay Cladding
- When performing GMAW overlay of 304L or 316L on Q345R or SA-516 Gr.70 substrates, the current should be selected to produce spray transfer mode (typically above 180 A for 1.2 mm wire with Ar/CO₂ mixtures) to ensure stable deposition.
- For thin cladding layers (1–3 mm), lower currents reduce dilution but may compromise bond strength, requiring careful balancing.
- The fitting model approach allows systematic optimization for multi-pass overlay procedures where each pass has different thermal conditions.
Key Questions and Reflections
The fitting analysis methodology raises several important questions for cladding engineers:
- How does the mathematical model account for multi-pass effects where heat accumulation changes the effective thermal conditions for subsequent passes?
- Can the fitting relationships be extended to include the influence of interpass temperature and welding sequence?
- How sensitive are the fitted models to variations in base metal thickness and thermal conductivity?
These questions highlight the gap between single-pass laboratory optimization and the complex thermal history encountered in production cladding operations. The study provides a solid foundation, but engineers must supplement it with multi-pass simulation or experimental validation for production-critical applications.
Study Insights and Implications
This 2025 publication represents a methodologically rigorous approach to welding parameter optimization that goes beyond traditional empirical methods. For cladding engineers, the key takeaway is that quantitative fitting models can significantly reduce the number of qualification trials required for procedure development, thereby accelerating project timelines while maintaining quality assurance. The approach is particularly valuable when developing overlay procedures for exotic alloy combinations where material availability is limited and each test coupon represents significant cost. The systematic fitting methodology aligns well with modern quality management frameworks such as PDCA (Plan-Do-Check-Act), providing a structured pathway from parameter exploration through to validated production procedures.