Comparison Between SA516 Gr. 70 and SA612 Pressure Vessel Steel Plate

2025-12-19 | More News

ASME SA516 Gr.70 and SA612 are two widely used carbon steel plates for pressure vessel applications, compliant with ASME/API standards and trusted globally in petrochemical, energy, and industrial sectors. While both are designed for pressure-bearing equipment, their core differences in strength, toughness, and cost make them suitable for distinct use cases.

SA516 Gr.70 is a medium-strength, cost-effective workhorse for general pressure vessel needs, while SA612 is a high-strength, low-temperature-tough steel tailored for demanding high-pressure/cryogenic environments. This guide compares key attributes to help you select the right material for your project

Overview of SA516 Gr.70 and SA612

SA612

SA612 is a high-strength carbon–manganese–silicon steel plate developed for pressure vessels requiring higher yield strength. Its key advantage is enabling thinner wall designs while meeting ASME code requirements.

SA612 is increasingly used in projects focused on weight reduction and cost optimization.

SA516 Grade 70

SA516 Gr.70 is a carbon steel pressure vessel plate designed primarily for moderate to low-temperature service. It is known for:

Good toughness
Stable welding performance
Wide global acceptance

It is often considered the standard choice for conventional pressure vessels.

Chemical Composition

SA516 Gr.70

Element	Content Limit (%)	Function
C	≤0.30	Balances strength and weldability
Mn	0.79-1.30	Enhances tensile strength
Si	0.15-0.40	Improves oxidation resistance
P	≤0.035	Minimizes brittleness
S	≤0.035	Reduces weld defects

SA612

Element	Content Limit (%)	Function
C	≤0.25	Lower than SA516 Gr.70 for better weldability
Mn	1.00-1.50	Higher manganese for enhanced strength/toughness
Si	0.15-0.50	Optimizes strength and ductility
P	≤0.035	Strict control for corrosion resistance
S	≤0.025	Lower than SA516 Gr.70 to prevent SCC
Cu/Ni/Cr	≤0.35/≤0.25/≤0.25	Controlled residual elements for consistency

Key Difference: SA612 has higher manganese and lower sulfur content, contributing to its superior strength and low-temperature performance.

Mechanical Properties Comparison

Property	SA516 Gr.70	SA612
Yield Strength	Lower	Significantly higher
Tensile Strength	Medium	Higher
Thickness Efficiency	Limited	Excellent
Structural Weight	Heavier	Lighter
Design Margin	Conservative	Optimized

Key takeaway:
SA612 allows designers to reduce plate thickness while maintaining the same pressure rating.

Heat Treatment & Delivery Conditions

SA516 Gr.70

Standard Delivery: Hot-rolled (AR) for thin plates (≤12.5mm); normalized (N) for thick plates (≥25mm) to improve toughness.
Optional Treatment: Normalized + Tempered (N+T) for extreme pressure applications.
Grain Size: Fine to medium grain structure (ASTM E112 ≥5).

SA612

Mandatory Treatment: Normalized (heated to 890-950℃, air-cooled) to refine austenitic grain size (ASTM E112 ≥6).
No Q&T Needed: Achieves high strength via chemistry and normalization—avoiding the high cost of quenching-tempering.
Dimensional Stability: Normalization ensures uniform mechanical properties across the plate.

Application Scenarios (Which to Choose?)

SA516 Gr.70: The “Workhorse” for General Pressure Vessels

Ideal For:
- Low-to-medium pressure boilers (operating pressure ≤10 MPa)
- Standard storage tanks (crude oil, water, chemicals)
- Heat exchangers and piping components
- Industrial furnaces and pressure vessels in ambient temperature environments
Key Industries: Food processing, pharmaceuticals, general manufacturing, and low-pressure petrochemical plants.

SA612: The “High-Performance” Choice for Demanding Environments

Ideal For:
- High-pressure reactors (hydrocracking, catalytic reforming, pressure ≤30 MPa)
- Cryogenic storage tanks (LPG, LNG, ethylene, -40℃ service)
- Offshore pressure vessels (cold oceans, corrosive media)
- Lightweight pressure equipment (where strength-to-weight ratio is critical)
Key Industries: Petrochemical, energy (power generation, renewable), offshore oil/gas, and cryogenic engineering.

Which One Should You Choose?

Choose SA516 Gr.70 if:

The design is conventional
Pressure levels are moderate
Budget focuses on material unit price
Thickness is not a concern

Choose SA612 if:

High pressure requires higher yield strength
Weight and thickness optimization are important
Welding cost and efficiency matter
Large pressure vessels are involved

Conclusion

Both SA516 Gr.70 and are reliable pressure vessel steels, but they serve different design priorities.
If your project emphasizes higher strength, reduced thickness, and overall cost optimization, SA612 is often the better choice.