Mechnical property for SA203 Grade D steel plate:
| Yield strength (≥Mpa) | Tensile strength (Mpa) | Elongation in ≥,% | |
| 255 | 450-585 | 200mm | 50mm |
| 19 | 23 | ||
Chemical composition for SA203 Grade D steel plate (Heat Analysis Max%)
| Main chemical elements composition of SA203 Grade D | ||||||
| Thickness(mm) | C | Si | Mn | P | S | Ni |
| T≤50 | 0.17 | 0.15-0.40 | 0.70 | 0.035 | 0.035 | 3.25-3.75 |
| 50<T | 0.20 | 0.80 | ||||
Q1: What is the minimum design metal temperature (MDMT) for SA203 Grade D, and how does its 5% nickel content enable this performance?
Certified Service Limits:
ASME Section VIII Div.1 approved for -170°C
Charpy V-notch: ≥54J at -170°C (base metal), ≥40J at -150°C (weld)
ISO 21009-3 compliant for full-containment LNG tanks
Metallurgical Mechanism:
4.75-5.25% Ni prevents martensite formation at cryogenic temps
Thermomechanical Controlled Processing (TMCP) refines grain to ASTM No. 8+
Q2: What advanced processes allow Grade D to achieve 200mm thickness while maintaining cryogenic toughness?
Production Breakthroughs:
Electroslag Remelting (ESR) for ultra-low inclusions (<0.5% oxide rating)
Direct Quenching from 820°C at 50°C/s cooling rate
Through-Thickness UT with 0.5mm FBH sensitivity
Mechanical Performance:
Z-direction reduction of area (ψ) ≥ 40%
Sulfur ≤0.003% + calcium treatment for lamellar tearing resistance
Q3: What welding procedures are mandatory for LH2 service applications?
Critical Welding Parameters:
Preheat: 150-200°C (thermography-verified)
Consumables: AWS A5.28 ER100S-Ni4 (7%Ni modified)
Interpass temp: ≤80°C with ≤12kJ/cm heat input
Post-Weld Treatments:
PWHT at 580-620°C + Deep Cryogenic Treatment (-196°C soak)
100% Automated UT + EB weld repair qualification
Q4: When should Grade D replace 9%Ni steel for cryogenic storage?
| Parameter | SA203 Grade D | ASTM A553 Type I |
|---|---|---|
| Nickel Content | 5% | 9% |
| MDMT | -170°C | -196°C |
| Cost (Index) | 120 | 200 |
| Weldability | Excellent (low heat input) | Challenging (PWHT critical) |
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