What is the difference between A516 GR 65 and 70?

ASTM A516 Grade 65 and Grade 70 are both carbon steel plates used for pressure vessels and boilers, designed for moderate- to low-temperature service. The primary difference between them is their mechanical properties, specifically tensile strength and yield strength.  

A516 Grade 70 has a higher tensile strength (485-625 MPa) compared to Grade 65 (450-585 MPa), making it slightly stronger and more suitable for higher-stress applications. Similarly, the yield strength of Grade 70 is 260 MPa, while Grade 65 has a yield strength of 240 MPa. This means Grade 70 can withstand higher pressures and stresses before permanent deformation occurs.  

Both grades have similar chemical compositions, with small variations in carbon, manganese, and silicon content, but these differences do not significantly affect weldability or corrosion resistance. Both grades are weldable and machinable, making them ideal for boiler and pressure vessel construction.  

In terms of applications, Grade 70 is preferred in higher-pressure environments and critical load-bearing structures, while Grade 65 is used where slightly lower strength is acceptable. Both grades meet the requirements for toughness at low temperatures, ensuring durability in oil refineries, power plants, and chemical processing facilities.  

If a project requires higher strength and durability, A516 Grade 70 is the better choice. However, if cost considerations or slightly lower strength requirements are factors, Grade 65 may be more suitable.