Zhuojin Pipe Fitting Co., LtdMicrostructure and Properties of 3Cr13 Stainless Steel Overlay on Q235 Carbon Steel
Literature Overview
This study by Wu Zhisheng, Yun Hui, Liu Cuirong, Li Ke, and Quan Wanglin from Taiyuan University of Science and Technology, published in Welding Technology (2014, Vol. 43, No. 3, pp. 13–15), investigates the microstructure and hardness of 3Cr13 martensitic stainless steel overlay deposited on Q235 carbon steel using submerged arc welding (SAW). The research was supported by Shanxi Provincial Science and Technology Project (20100321084), Taiyuan City Science and Technology Star Special Fund (2011075), and Taiyuan University Student Innovation Fund (20121016). The work addresses the common engineering problem of upgrading low-cost carbon steel components with corrosion-resistant and wear-resistant surfaces.
Core Technical Findings
The key finding is that when the overlay is built up to three layers, the dilution effect from the Q235 base metal becomes negligible, and the overlay achieves a consistent surface hardness of approximately HRC 45.9 with a microstructure of needle-like martensite plus residual austenite. This establishes a practical guideline for minimum overlay thickness in engineering applications.
Process Parameters and Microstructural Analysis
The submerged arc welding process was selected for its high deposition rate and consistent weld quality, making it suitable for production-scale overlay applications. The following table summarizes the critical technical parameters:
| Parameter | Value |
|---|---|
| Base Metal | Q235 Carbon Steel |
| Overlay Material | 3Cr13 Martensitic Stainless Steel |
| Welding Process | Submerged Arc Welding (SAW) |
| Minimum Layers for Stable Properties | 3 |
| Surface Hardness (3 layers) | HRC 45.9 |
| Microstructure | Needle-like martensite + residual austenite |
| Dilution Effect at 3 Layers | Negligible |
The dilution phenomenon is a critical concern in overlay welding on dissimilar substrates. Carbon steel base metals introduce significant amounts of carbon and manganese into the first weld pass, which can alter the intended microstructure and properties of the overlay. The study confirms that three passes effectively overcome this dilution, as the subsequent layers are deposited primarily on previously welded overlay material rather than on the base metal.
Engineering Practice Integration
In pipeline and equipment repair, overlay welding is widely used to restore worn surfaces or add corrosion-resistant linings to carbon steel structures. The findings of this study have direct practical relevance:
- Overlay thickness design: For applications requiring consistent surface hardness and corrosion resistance, a minimum of three welding passes should be planned. The first two passes serve primarily to eliminate dilution effects, while the third and subsequent passes establish the final surface properties.
- Post-weld heat treatment: 3Cr13 is a martensitic stainless steel that typically requires tempering to achieve optimal toughness. Without tempering, the as-welded microstructure may contain excessive retained austenite or untempered martensite, leading to potential cracking during service. A tempering treatment at 500–550°C is recommended to achieve a balanced hardness-toughness combination.
- Base metal preparation: Surface preparation of the Q235 base metal is critical. Scale, rust, and contamination must be removed to ensure proper wetting and fusion of the first overlay pass.
Defect Analysis and Countermeasures
Common defects encountered in carbon steel to stainless steel overlay welding include:
| Defect Type | Cause | Countermeasure |
|---|---|---|
| Cracking at fusion line | High carbon dilution + hard martensite | Increase layers to 3+, use low-carbon transition layer |
| Porosity | Flux contamination or base metal moisture | Preheat to 150°C, use dry flux |
| Incomplete fusion | Insufficient heat input | Increase current, reduce travel speed |
| Hardness variation | Uneven dilution | Maintain consistent stringer bead width |
Key Questions and Reflections
The study reports HRC 45.9 hardness for the three-layer overlay, which is somewhat lower than the typical hardness of fully hardened 3Cr13 (HRC 48–52). This suggests that some residual austenite remains in the microstructure, likely due to the dilution effect not being completely eliminated even at three layers, or due to insufficient cooling rate during the SAW process. For applications requiring maximum hardness, additional passes or post-weld quenching may be necessary. Furthermore, the study does not address the interfacial bonding strength between the overlay and base metal, which is critical for applications involving impact loading or cyclic stress.
Study Insights and Implications
This research provides a straightforward and practical guideline for overlay welding engineers: three passes of 3Cr13 on Q235 carbon steel are sufficient to achieve stable surface properties independent of base metal dilution. The SAW process offers economic advantages for large-area overlay applications. However, engineers must recognize that hardness alone does not guarantee service performance. The combination of hardness, toughness, corrosion resistance, and interfacial strength must be evaluated holistically for each specific application. In pipeline engineering, where overlay systems are used for erosion protection at elbows and tees, the interfacial strength under cyclic bending loads is particularly critical and warrants further investigation.