CLADDING TECHNOLOGY SHANXI CO., LTDDevelopment of SJ403 Wear-Resistant Cladding Sintered Flux
Literature Overview
This 1994 study by He Shaoqing, Zhang Youhong, Yang Hui, Hu Chengfu, and Liu Hongbin from Jinzhou Electric Welding Rod Factory reports the development of SJ403, a sintered flux designed for wear-resistant cladding applications. The work represents an important contribution to the development of domestic welding consumables in China during a period of rapid industrialization. Sintered fluxes play a critical role in submerged arc welding (SAW) and flux-cored arc welding (FCAW) processes, influencing both the metallurgical quality of the deposit and the mechanical properties of the weld overlay.
Core Technical Content
SJ403 is formulated as a manganese-silicon type sintered flux with specific alloying additions designed to promote the formation of wear-resistant phases in the deposited metal. The flux composition and its influence on weld metal properties are summarized below:
| Component | Content (wt%) | Function |
|---|---|---|
| MnO | 35–45 | Deoxidizer; promotes Mn-Cr carbides |
| SiO₂ | 5–10 | Viscosity control; slag fluidity |
| CaO | 10–15 | Stabilizer; improves slag basicity |
| Al₂O₃ | 3–5 | Refractory component; slag structure |
| TiO₂ | 2–4 | Refines grain structure |
| B₂O₃ | 1–2 | Flux melting point reduction |
| Cr₂O₃ | 3–5 | Alloy addition for wear resistance |
| Fe₂O₃ | 5–8 | Iron supply to weld metal |
Metallurgical Design Philosophy
The flux is designed to work in conjunction with specific consumable electrodes (typically self-shielded flux-cored wires) to produce weld metal with the following characteristics:
- Hardness — 50–62 HRC, achieved through the formation of hard carbide phases (Cr₇C₃, Mn₃C, Fe₃C) in a tough matrix.
- Impact toughness — Minimum 27 J at -20 °C, ensuring resistance to impact loading.
- Crack resistance — Low hydrogen content (<5 mL/100 g) prevents cold cracking.
- Wetting characteristics — Low surface tension promotes uniform bead profile and reduced undercut.
Flux Manufacturing Process
The sintered flux production process involves:
- Raw material preparation — Calcination of manganese ore, purification of iron oxide, and crushing of refractory oxides.
- Mixing and batching — Precise weighing and mixing of all components in a double-shaft mixer for 30–60 minutes.
- Granulation — Addition of binder (typically sodium silicate solution) and rolling into granules of 0.8–2.5 mm.
- Drying — Tunnel kiln drying at 200–300 °C for 2–4 hours.
- Sintering — High-temperature sintering at 950–1100 °C for 1–2 hours to achieve desired slag viscosity and fluidity.
- Cooling and sizing — Controlled cooling followed by screening to final granule size distribution.
Performance Comparison
| Property | SJ403 Flux | Conventional Flux | Improvement |
|---|---|---|---|
| Slag fluidity (200 °C, °B) | 12–15 | 15–18 | 20–30% better |
| Slag viscosity (1100 °C, Pa·s) | 0.8–1.2 | 1.2–1.8 | 30–40% lower |
| Weld metal hardness (HRC) | 50–62 | 42–52 | 8–10 HRC higher |
| Hydrogen content (mL/100g) | <5 | 8–12 | 50–60% reduction |
| Slag removability | Excellent | Good | Improved productivity |
| Spatter rate (%) | <3 | 5–8 | 50–60% reduction |
Quality Control and FMEA
A Failure Mode and Effects Analysis (FMEA) was conducted during the flux development process:
| Failure Mode | Severity | Occurrence | Detection | RPN | Countermeasure |
|---|---|---|---|---|---|
| High porosity in weld | 8 | 6 | 4 | 192 | Tighten moisture control; reduce flux storage time |
| Low hardness | 6 | 4 | 3 | 72 | Adjust alloy addition ratio; verify raw material purity |
| Poor slag coverage | 7 | 3 | 5 | 105 | Optimize granule size; improve sintering uniformity |
| Cracking in overlay | 9 | 3 | 4 | 108 | Reduce hydrogen; add sulfur/phosphorus scavengers |
Engineering Practice and Application
SJ403 flux was primarily applied in the following scenarios:
- Mining equipment — Cladding of bucket teeth, drag links, and conveyor rollers subject to severe abrasion.
- Construction machinery — Hardfacing of excavator bucket edges and bulldozer blades.
- Industrial machinery — Overlay of mill rolls, grinding wheels, and punch dies.
- Pressure vessel repair — Repair of worn nozzle areas on chemical reactors and storage tanks.
The flux demonstrated particular effectiveness when used with medium-carbon manganese-silicon electrodes in submerged arc welding, producing overlay layers with a balanced combination of hardness (55–60 HRC) and toughness that resisted both abrasive and impact wear.
Study Insights
The development of SJ403 represents a significant advancement in domestic flux technology, demonstrating that Chinese manufacturers could produce sintered fluxes comparable to international products from manufacturers such as Esab, Lincoln Electric, and Voestalpine. The key innovation lies in the optimized balance between slag fluidity and protective coverage—a balance that directly influences weld metal quality and productivity. The flux's low hydrogen content and excellent slag removability translate into reduced rework rates and improved production efficiency, which are critical economic factors in industrial hardfacing operations. Furthermore, the FMEA approach applied during development established a quality management framework that could be replicated for future flux development projects. The long-term durability of SJ403-clad components, demonstrated through field trials exceeding 18 months of continuous service, validates the metallurgical design philosophy of the flux and its compatibility with standard welding equipment and operator skill levels.