1. Core Mechanical Properties
| Parameter | Required value | illustrate |
|---|---|---|
| Tensile Strength(σb) | ≥455 MPa | Ensure structural integrity under extreme loads |
| Yield point(σs) | ≥310 MPa | Provides high deformation resistance, suitable for deep foundation bearing |
| Elongation after fracture(δ) | Control by wall thickness(13.5%~20%) | The thinner the wall thickness, the lower the required elongation (e.g. ≥14% when t=3.2mm, ≥20% when t≥7.9mm) |
2. Material and manufacturing characteristics
Chemical composition
Low-carbon design: carbon content ≤ 0.05%, sulfur and phosphorus impurities are controlled (P ≤ 0.05%), improving weldability and low-temperature toughness.
Strengthening elements: manganese (Mn) is the main strengthening element, and iron (Fe) is the matrix remainder.
Manufacturing process
Straight seam submerged arc welding (SAWL) or high-frequency resistance welding (ERW) can be used to ensure weld continuity and strength.
Seamless processes are also applicable and must meet the same mechanical properties.
Enhanced weather resistance
Optional 3PE anti-corrosion coating to resist soil/seawater corrosion and extend service life.
The material can match low-alloy steels such as ST42, ST52, and X42, taking into account both strength and corrosion resistance.
3. Scope of application of the project
Deep foundation of high-rise buildings: penetrating hard rock or dense sand to provide ultra-high vertical bearing capacity.
Bridge and port structures: resist water erosion, seismic loads and high-salt environments.
Concrete pile shell: acts as a permanent formwork for cast-in-place concrete piles to form a composite load-bearing system
4. Advantages compared with other levels
| Features | GR3 | GR1/GR2 |
|---|---|---|
| Tensile Strength | ≥455 MPa(max) | Lower than GR31 |
| Yield Strength | ≥310 MPa(max) | Lower than GR31 |
| Applicable scenarios | Extreme Geology/High Load Engineering | Conventional foundation |
