What is the difference between A2-70 and A4-80 grade U-bolts?

A2-70 Grade U-Bolt

Made from 304 austenitic stainless steel (06Cr19Ni10); features a tensile strength of 700 MPa and a yield strength of ≥450 MPa; complies with ISO 3506 and GB/T 3098.18 standards.

A4-80 Grade U-Bolt

Made from 316 austenitic stainless steel (06Cr17Ni12Mo2); features a tensile strength of 800 MPa and a yield strength of ≥600 MPa; contains 2–3% molybdenum, offering significantly enhanced resistance to chloride ion corrosion.

Applications for A2-70 Stainless U Bolts

Construction Projects: Steel-structure factory buildings, municipal bridges, standard building MEP (mechanical, electrical, and plumbing) piping, and cable trays.
Industrial Equipment: General machinery, sanitary-grade equipment (food, pharmaceutical, and medical), and non-corrosive chemical processing equipment.
New Energy: Inland photovoltaic mounting systems and wind turbine foundations.
General Applications: Agricultural machinery, home renovation, and securing light-duty equipment.

Application Scenarios for A4-80 Stainless U Bolts

Marine / Coastal: Marine vessels and offshore structures, coastal solar and wind power installations, port equipment, and seawater aquaculture facilities.
Chemical / Highly Corrosive: Environments with strong acids or alkalis, chemical reactors, storage tanks, and high-humidity/salt-spray workshops.
High-End Infrastructure: Cross-sea bridges, subway tunnels, nuclear power facilities, and deep-sea engineering projects.
Heavy-Duty Equipment: Large compressors, heavy machinery, and bases for high-vibration equipment.

How to choose between A2-70 Stainless U Bolts and A4-80 Stainless U Bolts?

1. Select based on environmental corrosivity
Standard environments (atmosphere / fresh water / weak acids): Choose A2-70; it offers the best value and meets the needs of 90% of applications.
Highly corrosive environments (seawater / salt spray / strong acids): Choose A4-80; the molybdenum content resists chloride ions, extending service life by over 50%.
2. Select based on load-bearing strength
Light to medium loads (≤15kN): A2-70 is sufficient; its 700 MPa tensile strength meets requirements.
Heavy loads / high vibration (≥18kN): Choose A4-80; with 800 MPa tensile strength and 600 MPa yield strength, it offers superior fatigue resistance.
3. Select based on budget and long-term value
Short-term projects / limited budget: A2-70; low cost while meeting basic requirements.
Long-term projects / harsh environments: A4-80; although the initial purchase price is higher, maintenance costs are reduced by 80%, resulting in a lower total cost of ownership over 10 years.