At present, China's construction steel structure industry has transitioned from a developmental phase to a mature one, with both steel production and consumption leading globally. In many steel structure projects, thick and high-strength steel is increasingly being used to meet the demands of complex architectural designs and structural load requirements.
**Key challenges and difficulties in welding high-strength steel:**
1. According to international standards, weldability testing for new steel grades should be conducted by manufacturers and research institutions. However, in China, there is no clear regulation on this process, and it is often left to the construction company. As a result, conducting proper weldability tests for new steel grades has become a major challenge in steel structure engineering.
2. The addition of alloying elements in the steel can significantly affect the hardening, softening, and cracking tendency of the welded joint. Therefore, preventing welding cracks and embrittlement in heat-affected zones remains a critical and challenging issue during the welding of high-strength steel.
3. Preventing lamellar tearing in thick-walled high-strength steel during welding is another key challenge that must be carefully managed to ensure quality and safety.
4. The design of the groove for slab high-strength steel directly impacts the construction timeline and the internal quality of the weld. Hence, optimizing the groove design is always a focal point in the welding process.
**To address these challenges, the following technical measures are commonly implemented:**
(1) Selecting welding materials that match the base metal is crucial. Low-hydrogen or ultra-low-hydrogen welding consumables are typically chosen to minimize defects such as cracks and porosity. Standards like GB8110—2008 for low-alloy gas-shielded arc welding and GB/T5293 for submerged arc welding provide guidance on material selection.
(2) Groove design plays a vital role in welding thick plates. Using a narrow and deep groove can lead to poor weld formation and increased risk of segregation and hot cracking. On the other hand, a wide groove increases welding volume and residual stress, which is not ideal for controlling structural stress. A 30°–35° groove angle is commonly used, with a gap of 6–10 mm. When the plate thickness exceeds 40 mm, a layered tearing groove is required. Bevels should be processed using a flame cutting machine to ensure quality and avoid manual cutting that may compromise the weld.
(3) To prevent welding cracks, preheating the weld area and its surrounding 100 mm is essential. The preheating temperature should follow guidelines from GB50661 “Code for Welding of Steel Structures.†During welding, maintaining an interlayer temperature above the preheating level is important. Using a lower current helps control heat input, reducing deformation and stress. Multi-layer multi-pass welding should be avoided.
After welding, post-heating and hydrogen removal treatments are necessary to allow any remaining hydrogen to escape, thus minimizing the risk of cold cracking.
For more detailed information, please refer to the attached documents or check the 18th issue of *Metalworking (Hot Processing)*.
DG Zhongxingshun Sealing Products Factory , https://www.zxs-seal.com