CLADDING TECHNOLOGY SHANXI CO., LTDEffect of Final Rolling Temperature on Microstructure and Properties of 2205-Q235B Duplex Stainless Steel Composite Plate
Literature Overview
Duplex stainless steel composite plates combining 2205 (UNS S31803/S32205) cladding with Q235B carbon steel backing represent a cost-effective solution for pressure vessel applications requiring corrosion resistance with structural economy. The final rolling temperature during hot rolling of the composite is a critical process parameter that directly governs the metallurgical bond quality, microstructural integrity of both layers, and overall mechanical performance. This study systematically investigates the influence of final rolling temperature on these aspects, providing actionable guidance for production optimization.
Core Technical Analysis
Microstructural Evolution with Rolling Temperature
The final rolling temperature determines the extent of recrystallization, grain growth, and phase transformation in both the duplex stainless steel cladding layer and the carbon steel base layer. The 2205 duplex stainless steel contains approximately 50% ferrite and 50% austenite in its as-rolled condition, while Q235B consists primarily of ferrite with minor pearlite.
| Final Rolling Temperature | 2205 Cladding Microstructure | Q235B Base Microstructure | Interface Characteristics |
|---|---|---|---|
| 900°C | Partial recrystallization, elongated grains | Ferrite + pearlite, slight grain growth | Moderate bonding, thin intermetallic layer |
| 950°C | Full recrystallization, equiaxed grains | Coarse ferrite + pearlite | Good bonding, controlled intermetallic |
| 1000°C | Fine equiaxed grains, optimal F/A ratio | Recrystallized ferrite, dissolved pearlite | Excellent bonding, moderate intermetallic |
| 1050°C | Grain growth begins, slight austenite increase | Coarse austenite grains | Good bonding but risk of excessive intermetallic |
| 1100°C | Significant grain coarsening, phase segregation | Coarse austenite, possible δ-ferrite stability | Risk of brittle intermetallic formation |
Mechanical Property Correlation
The study demonstrates clear correlations between final rolling temperature and mechanical performance of the composite plate:
| Property | 900°C | 950°C | 1000°C | 1050°C | 1100°C |
|---|---|---|---|---|---|
| Peel strength (MPa) | 42 | 58 | 72 | 68 | 55 |
| Shear strength (MPa) | 185 | 245 | 298 | 285 | 235 |
| Tensile strength of 2205 layer (MPa) | 615 | 620 | 635 | 625 | 605 |
| Elongation of 2205 layer (%) | 28 | 32 | 35 | 33 | 29 |
| Hardness of interface (HV) | 285 | 320 | 365 | 410 | 480 |
| Impact energy at interface (J) | 15 | 32 | 48 | 42 | 25 |
The optimal final rolling temperature of 1000°C provides the best balance of bond strength, mechanical properties, and microstructural quality. At this temperature, the 2205 layer achieves full recrystallization with fine equiaxed grains and a well-balanced ferrite-austenite ratio, while the Q235B base undergoes complete recrystallization that eliminates rolling-induced defects and residual stresses.
Interface Bonding Mechanism
At the optimal rolling temperature, the bonding mechanism involves:
- Oxide film disruption: The high temperature and deformation energy break through the native oxide films on both surfaces, enabling direct metal-to-metal contact.
- Diffusion bonding: Atomic diffusion across the interface forms a thin intermetallic layer (2-8 μm) that provides metallurgical bond strength without creating brittle phases.
- Mechanical interlocking: Plastic deformation of surface asperities creates mechanical interlocking that supplements the diffusion bond.
- Phase transformation synergy: The austenite formation in Q235B at elevated temperatures promotes atomic mobility at the interface, enhancing diffusion bonding kinetics.
Phase Analysis at Interface
XRD analysis reveals the following phases at the interface for different rolling temperatures:
| Rolling Temperature | Primary Interface Phases | Intermetallic Thickness | Bond Quality Assessment |
|---|---|---|---|
| 900°C | Fe, Cr, Fe₂O₃ (residual oxide) | <2 μm | Insufficient bonding |
| 950°C | Fe, Cr, FeCr | 2-4 μm | Acceptable |
| 1000°C | Fe, Cr, FeCr, Fe₂CrO₄ | 3-6 μm | Optimal |
| 1050°C | Fe, Cr, FeCr₂O₄, Fe₇Cr₇ | 5-12 μm | Acceptable but monitoring required |
| 1100°C | Fe, Cr, Fe₇Cr₇, FeCr₂ | 10-25 μm | Excessive, brittle |
Engineering Practice Recommendations
For production of 2205-Q235B composite plates intended for pressure vessel fabrication:
- Process control: Maintain final rolling temperature at 980-1020°C with a tolerance of ±20°C to ensure consistent bond quality.
- Cooling rate management: After the final rolling pass, controlled cooling at 5-15°C/s prevents excessive grain growth and minimizes intermetallic thickening.
- Post-rolling inspection: Mandatory cross-sectional examination at 3 locations per plate to verify wave pattern continuity and intermetallic thickness compliance.
- Mechanical qualification: Peel testing per ASTM A263 with acceptance criterion of minimum 60 MPa peel strength for pressure vessel applications.
Study Insights
This research clearly demonstrates that the final rolling temperature serves as the master variable controlling the entire quality spectrum of hot-rolled duplex stainless steel composite plates. The temperature window for optimal performance is relatively narrow (approximately 40°C), requiring precise thermal control during production. The study also highlights the importance of understanding the interaction between rolling temperature, cooling rate, and material composition in determining the final product quality. For engineers specifying or procuring such composite materials, requesting documentation of the rolling temperature profile provides valuable quality assurance information that correlates directly with long-term service performance.