S690 steel features an ultra-high yield strength of 690MPa, approximately three times that of ordinary carbon steel, while possessing high toughness, excellent low-temperature performance and lightweight characteristics. Addressing common challenges in S690 steel welding, such as embrittlement in the heat-affected zone, residual stress concentration and crack formation, the research team conducted systematic process trials. Key parameters including pre-welding preheating, heat input control, low-hydrogen welding material matching and post-welding thermal insulation were optimised, establishing a stable, reliable and traceable welding process system for high-strength steel.
The application of this technology in the Tseung Kwan O Cross Bay Link Bridge offers remarkable benefits in the following aspects:
A. Structural Safety and Reliability
It effectively mitigates performance degradation in the welding heat-affected zone, ensuring the strength, toughness and fatigue performance of welded joints meet design requirements, and safeguarding the long-term stable operation of large steel arch structures.
B. Weight Reduction and Cost Savings
The twin arches of the main bridge utilise approximately 4,400 tonnes of S690 high-strength steel, achieving a weight reduction of over 20% compared to conventional structural steel. This saves around HK$100 million in construction costs and lowers the complexity of transportation and installation.
C. Low Carbon and Environmental Friendly
The reduction in material directly results in a reduction of approximately 12,000 tonnes of carbon footprint, aligning with Hong Kong’s goal of low-carbon construction and promoting sustainable development in the construction industry.
With leading welding techniques and rigorous quality control, this technology not only ensures stable quality and reliable performance of high-strength steel structures, but also successfully breaks through international technical barriers in high-strength steel welding. It marks that Hong Kong has entered the international advanced ranks in the research, development and engineering application of high-performance steel structures.
