ASME SA-516 Grade 70 (R-HIC) Steel Plate – Technical Overview

ASME SA-516 Grade 70 (R-HIC) Steel Plate – Technical Overview

SA-516 Grade 70 (R-HIC) is a normalized carbon steel plate designed for moderate and low-temperature pressure vessel applications, particularly in sour service environments where resistance to hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) is critical. This grade complies with the ASME Boiler and Pressure Vessel Code (BPVC) Section II and is widely used in oil & gas, petrochemical, and power industries.

The R-HIC (Resistant to Hydrogen-Induced Cracking) variant undergoes additional testing (per NACE TM0284) to ensure resistance to hydrogen blistering and stepwise cracking in wet H₂S environments.

Key Features
High toughness at low temperatures.

Excellent weldability and formability.

R-HIC tested with strict control of impurities (e.g., sulfur, phosphorus).

Normalized heat treatment for uniform microstructure.

Chemical Composition (Weight %)
The composition is optimized to minimize HIC susceptibility:

Element    SA-516 Gr.70 (R-HIC) Requirements    Typical Value
Carbon (C)    ≤ 0.27%    0.20–0.25%
Manganese (Mn)    0.85–1.20%    0.90–1.10%
Phosphorus (P)    ≤ 0.025%    ≤ 0.015%
Sulfur (S)    ≤ 0.010%    ≤ 0.002%
Silicon (Si)    0.15–0.40%    0.20–0.30%
Nickel (Ni)    –    ≤ 0.25%
Copper (Cu)    –    ≤ 0.35%
CE (Pcm)    ≤ 0.25% (Calculated per NACE MR0175)    0.18–0.22%
Notes:

Low S/P: Reduces HIC susceptibility.

CE (Carbon Equivalent): Ensures weldability.

Mechanical Properties
Property    SA-516 Gr.70 (R-HIC) Requirements    Typical Value
Tensile Strength (MPa)    485–620    520–580
Yield Strength (MPa)    ≥ 260    290–350
Elongation (% in 50 mm)    ≥ 21    22–28
Impact Test (Charpy V-notch)    ≥ 20 J @ -46°C (or specified temp.)    40–60 J
Hardness (HBW)    ≤ 200 (NACE MR0175 compliance)    160–190
Additional Tests for R-HIC:

HIC Test (NACE TM0284): Passes criteria (CLR ≤ 15%, CTR ≤ 5%, CSR ≤ 2%).

SSC Test (NACE TM0177): Optional for severe sour service.

Applications
Pressure vessels in refineries.

Storage tanks for H₂S-containing fluids.

Offshore platforms and pipelines.

ASME-certified boilers.

Standards & Certifications
ASME SA-516 / ASTM A516 (Grade 70).

NACE MR0175/ISO 15156 for sour service.

Supplementary Requirements: S1 (Vacuum-treated), S4 (Ultrasonic testing).