Hardness of SA 516 Gr 70

SA 516 Gr 70 Hardness

The hardness of SA 516 Gr 70, a carbon steel plate grade under ASME SA-516/SA-516M (identical to ASTM A516 Grade 70), is a key property for engineers designing pressure vessels and boilers for moderate and lower-temperature service. Typically ranging from 150-190 HB (Brinell Hardness), the hardness of SA 516 Gr 70 reflects its balance of strength, toughness, and machinability, making it suitable for applications like petrochemical tanks and offshore structures.

This article details the hardness, its relation to chemical composition and mechanical properties, and comparisons with related grades like ASME SA 516 Gr 65, ASME SA 516 Gr 60, and ASME SA 516 Gr 55, addressing the core keyword hardness of sa 516 gr 70. For more details, visit our ASME SA 516 Gr 70 steel plate.

Hardness of SA 516 Gr 70

The hardness of SA 516 Gr 70 is typically 150-190 HB (Brinell Hardness), measured per ASTM E10 or equivalent standards. This range is influenced by its chemical composition, normalization (for >38 mm thickness), and heat treatment, ensuring:

• Machinability: Moderate hardness allows for easy cutting, drilling, and forming during fabrication.
• Wear Resistance: Sufficient hardness supports durability in pressure vessel applications under cyclic loads.
• Toughness: Balances hardness with impact toughness (≥27 J at -46°C), avoiding excessive brittleness.

For normalized plates (SA 516 Gr 70N), hardness may trend toward the higher end (170-190 HB) due to the refined microstructure. Non-normalized plates (≤38 mm) may be slightly softer (150-170 HB). Hardness is not directly specified in ASME SA-516 but is controlled through composition and processing to meet performance requirements.

Chemical Composition Supporting Hardness

The chemical composition of SA 516 Gr 70 contributes to its hardness:

Key Elements:

• Carbon (C): ≤0.27% (heat) / 0.31% (product) increases hardness but is kept low to maintain toughness and weldability.
• Manganese (Mn): 0.85-1.20% enhances strength and contributes to hardness, balancing machinability.
• Low Phosphorus (P) and Sulfur (S): ≤0.025% and ≤0.015% reduce inclusions, supporting uniform hardness and toughness.
• Silicon (Si): 0.15-0.40% aids deoxidation, indirectly stabilizing hardness.

Carbon Equivalent (CEV): Typically ≤0.43%, calculated as CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15, ensures weldability without excessive hardness increase.

Mechanical Properties Supporting Hardness

The mechanical properties of SA 516 Gr 70 complement its hardness:

• Yield Strength: ≥260 MPa (38 ksi) supports load-bearing capacity, correlating with moderate hardness.
• Tensile Strength: 485-620 MPa (70-90 ksi) aligns with hardness of 150-190 HB for durability.
• Elongation: ≥27% ensures ductility, preventing brittleness despite hardness.
• Impact Toughness: ≥27 J at -46°C ensures low-temperature performance, balancing hardness with toughness.

The hardness of SA 516 Gr 70 supports fabrication while maintaining structural integrity.

Comparison with Other SA 516 Grades

Key Difference: The hardness of SA 516 Gr 70 (150-190 HB) is higher than Gr 55 (120-160 HB), Gr 60 (130-170 HB), and Gr 65 (140-180 HB) due to its higher carbon content (0.27%) and strength, making it suitable for high-pressure applications while maintaining machinability.

Welding and Heat Treatment

The hardness of SA 516 Gr 70 supports weldability:

• Welding: Compatible with SMAW, GMAW, SAW per ASME Section IX. Preheating (149-204°C for >38 mm) prevents cracking due to hardness; PWHT (593-649°C) for stress relief in thick sections.
• Consumables: E7018 electrodes for SMAW; ER70S-6 wire for GMAW; EM12K flux with EH14 wire for SAW.
• Hardness Control: PWHT reduces weld zone hardness (typically <200 HB post-PWHT) to avoid brittleness, maintaining toughness at -46°C.

Applications

The hardness of SA 516 Gr 70 supports its use in:

• Pressure Vessels: High-pressure boilers and tanks for -46°C to 343°C service, where hardness ensures durability.
• Offshore Structures: Cold marine applications requiring toughness and moderate hardness.
• Petrochemical Tanks: Low-temperature storage for LNG, with hardness supporting structural integrity.

Explore ASME SA 516 Gr 65 for slightly lower strength needs.

Why Choose Gangsteel?

Gangsteel supplies SA 516 Gr 70:

• Inventory: Extensive stock in China.
• Sizes: Thickness 6-200 mm, widths up to 3000 mm, lengths up to 12,000 mm.
• Delivery: 7-30 days globally.
• Certifications: ASME SA-516, EN 10204 3.1/3.2, UT testing per SA-435/SA-578, ABS/LR/BV/DNV approvals.
• Processing: Cutting, rolling, bending, hardness testing available.

Contact us for ASME SA 516 Gr 70 steel plate.

FAQ

What is the hardness of SA 516 Gr 70?
The hardness of SA 516 Gr 70 is typically 150-190 HB (Brinell), balancing machinability, wear resistance, and toughness for pressure vessels.

How does the hardness of SA 516 Gr 70 compare to ASME SA 516 Gr 65?
SA 516 Gr 70 (150-190 HB) is slightly harder than Gr 65 (140-180 HB) due to higher carbon (0.27% vs 0.24%) and strength, suitable for higher-pressure applications.

Does hardness affect SA 516 Gr 70 weldability?
The moderate hardness (150-190 HB) of SA 516 Gr 70 supports weldability with low CEV (~0.43%), requiring preheating (149-204°C for >38 mm) to prevent cracking.

What applications rely on the hardness of SA 516 Gr 70?
The hardness of SA 516 Gr 70 supports pressure vessels, boilers, and petrochemical tanks for -46°C to 343°C, ensuring durability under cyclic loads.

How does the hardness of SA 516 Gr 70 compare to ASME SA 516 Gr 60?
SA 516 Gr 70 (150-190 HB) is harder than Gr 60 (130-170 HB) due to higher carbon (0.27% vs 0.21%) and strength, ideal for high-pressure vessels.

Does normalization affect the hardness of SA 516 Gr 70?
Yes, normalized SA 516 Gr 70 (Gr 70N) may have slightly higher hardness (170-190 HB) due to refined microstructure, enhancing toughness without compromising weldability.