ASME SA-387/SA-387M
SA387 Grade 21 Pressure Vessel Steel Plate Product-Performance
Technical Datasheet
Chromium-molybdenum (3Cr-1Mo) pressure vessel steel plate, supplied in annealed or normalized and tempered condition, with excellent high-temperature strength, creep resistance, and hydrogen resistance. Suitable for elevated temperature and high-pressure hydrogen service in petrochemical and power generation applications.
1. SA387 Grade 21 Material Identification & ASTM ASME Standards
Standards
- ASTM A387 / ASME SA387
- ASTM A20/A20M (General Requirements)
- ASME BPVC Section II Part A
Alloy Type
3Cr-1Mo
Grade Classification
- SA387 Gr.2 (0.5Cr-0.5Mo)
- SA387 Gr.5 (5Cr-0.5Mo)
- SA387 Gr.9 (9Cr-1Mo)
- SA387 Gr.21 (3Cr-1Mo) ← This Spec
- SA387 Gr.22 (2.25Cr-1Mo)
- SA387 Gr.91 (9Cr-1Mo-V)
2. SA387 Gr.21 Chemical Composition & Ladle Analysis Requirements
2.1 SA387 Grade 21 Chemical Composition Limits
| Element | Smelting Analysis | Finished Product Analysis |
|---|---|---|
| C | 0.05-0.15① | 0.04-0.15① |
| Mn | 0.30-0.60 | 0.25-0.66 |
| P, ≤ | 0.025 | 0.025 |
| S, ≤ | 0.025 | 0.025 |
| Si | ≤0.50 | ≤0.50 |
| Cr | 2.75-3.25 | 2.63-3.37 |
| Mo | 0.90-1.10 | 0.85-1.15 |
| Ni | ... | |
| V | ... | |
| Nb② | ... | |
| B, ≤③ | ... | |
| N | ... | |
| N/Al | ... | |
| Al, ≤③ | ... | |
| Ti, ≤③ | ... | |
| Zr, ≤③ | ... | |
| W, ≤③ | ... | |
| Cu, ≤③ | ... | |
| Sb, ≤③ | ... | |
| As, ≤③ | ... | |
| Sn, ≤③ | ... | |
Carbon Equivalent (CE)
CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
Typical value: 0.80-1.10 (depending on actual composition)
Note: 3Cr-1Mo steel requires strict welding procedures due to high hardenability
- A For steel plates with a thickness greater than 5 inches (125 mm), the carbon content in the finished product analysis should not exceed 0.17%
- B Cb and Nb are interchangeable and commonly used names for the same element, and both names are applicable to the ASTM "A101" standard
- C Both smelting analysis and finished product analysis are applicable
3. SA387 Grade 21 Mechanical Properties & Tensile Strength Specification
3.1 SA387 Grade 21 Tensile Properties (Class I Steel Plates)
| Property | Standard Value | Test Method | Remarks |
|---|---|---|---|
| Tensile Strength Rm | 415-585 MPa | ASTM A370 | Transverse specimen |
| Yield Strength ReL or Rp0.2 | >=205 MPa | 0.2% Offset Method | Or 0.5% Extension |
| Elongation A (8in./200mm) | ... | ASTM A370 | Not specified |
| Elongation A (2in./50mm) | >=18% | ASTM A370 | Per A20/A20M |
| Reduction of Area Z | >=45% (round) >=40% (flat) |
— | Round / flat specimen |
3.2 SA387 Grade 21 Tensile Properties (Class II Steel Plates)
| Property | Standard Value | Test Method | Remarks |
|---|---|---|---|
| Tensile Strength Rm | 515-690 MPa | ASTM A370 | Transverse specimen |
| Yield Strength ReL or Rp0.2 | >=310 MPa | 0.2% Offset Method | Or 0.5% Extension |
| Elongation A (8in./200mm) | ... | ASTM A370 | Not specified |
| Elongation A (2in./50mm) | >=18% | ASTM A370 | Per A20/A20M |
| Reduction of Area Z | >=45% (round) >=40% (flat) |
— | Round / flat specimen |
3.3 Charpy Impact Test Requirements for SA387 Gr.21
Standard Grade
Impact testing not required by standard
High Temperature ServiceHigh Temperature Service
- 3Cr-1Mo provides excellent creep resistance and hydrogen resistance
- Service temperature: up to 600°C
- Impact testing: By agreement
3.4 SA387 Gr.21 Hardness & Brinell Hardness Limits
- As-supplied condition (annealed or N+T): Typically ≤250 HBW
- NACE service environment: Weld & HAZ ≤250 HV10
4. SA387 Gr.21 Annealed or Normalized + Tempered: Heat Treatment Guide
1
As-Rolled (AR)
Not applicable for Grade 21
High hardenability requires heat treatment
→
2
Annealed or Normalized + Tempered
Annealing: 855-900°C
Or N: 900-950°C + T: 700-750°C
Cooling: Furnace or Air
→
3
Simulated PWHT (SPWHT)
700-750°C × 2-4h
For property verification
Critical Control Points:
- Grade 21 can be supplied in annealed or normalized + tempered condition
- Annealing temperature: 855-900°C, furnace cool
- Normalizing + tempering: 900-950°C + 700-750°C
- Cooling rate after normalizing: Air cool or accelerated cooling as required
5. SA387 Gr.21 Welding Procedure Specification (WPS/PQR)
5.1 SA387 Gr.21 Welding Procedure Specification WPS
SMAW (Shielded Metal Arc) SAW (Submerged Arc) GTAW (Gas Tungsten Arc) FCAW (Flux Cored)
5.2 SA387 Gr.21 Preheat & Interpass Temperature Chart
| Thickness Range | Min Preheat Temp | Recommended Preheat | Max Interpass Temp |
|---|---|---|---|
| <=13mm | 200°C | 200-250°C | 250-350°C |
| >13-38mm | 200°C | 200-250°C | |
| >38mm | 200°C | 200-300°C |
5.3 Recommended Welding Consumables for SA387 Grade 21
| Process | AWS Classification | Strength Match | Hydrogen Control |
|---|---|---|---|
| SMAW | E8015-B3, E8015-B3H4 | 80 ksi | Low Hydrogen (H4) |
| GTAW | ER80S-B3 | 80 ksi | Shielding: Ar |
| FCAW | E81T1-B3 | 80 ksi | Self/ Gas Shielded |
| SAW | F8A2-B3, F8P2-B3 | 80 ksi | Flux bake 300°C*2h |
5.4 SA387 Gr.21 PWHT Requirements & Post Weld Heat Treatment
Temperature Range 700-750°C
Holding Time 1h/25mm thickness (min 30min)
Heating Rate <=100°C/h
Cooling Rate <=100°C/h (to 300°C)
PWHT Notes:
- PWHT is mandatory for Grade 21 steel to achieve required mechanical properties
- Tempering temperature must be carefully controlled to avoid over-tempering
- Cooling rate should be controlled to prevent residual stresses
6. SA387 Gr.21 High Temperature Service & Hydrogen Resistance
6.1 SA387 Gr.21 High Temperature Properties
High Temperature Capability
- Excellent creep resistance up to 600°C
- Good hydrogen resistance at elevated temperatures
- Superior oxidation resistance (3% Cr)
- High thermal conductivity
Applications
- Hydroprocessing reactors
- Hydrocracking equipment
- High-temperature heat exchangers
- Petrochemical pressure vessels
6.2 SA387 Gr.21 Creep Rupture Properties
Grade 21 provides good creep rupture strength at elevated temperatures:
- At 500°C: 100,000 hour creep rupture strength ~100 MPa
- At 550°C: 100,000 hour creep rupture strength ~60 MPa
- At 600°C: 100,000 hour creep rupture strength ~35 MPa
7. SA387 Grade 21 Inspection & NDT Testing Methods
7.1 Non-Destructive Testing
UT ASTM A578/A578M Level C (Most Strict)
MT ASTM A275/A275M Surface Crack Detection
PT ASTM A165 Surface Open Defects
RT ASME V Article 2 Weld Internal Quality
7.2 Specimen Orientation & Location
Transverse (T)
Preferred for tensile & impact
Reflects transverse properties
Longitudinal (L)
Only when width insufficient
Higher strength, lower toughness
Thickness Position
1/4T or 1/2T
Represents worst location
7.3 Retest Procedures
- Tensile failure: Double retest from same plate; plate acceptable if both pass
- Impact failure: Additional 3 sets (9 specimens) from same plate; average must meet requirement with individual values >=70% of specified
- UT failure: Defect removal and re-inspection or rejection
8. SA387 Gr.21 Physical Properties & Thermal Conductivity
Density
7.80
g/cm3 (20°C)
Melting Point
~1500
°C
Thermal Conductivity
35-40
W/(m*K) (20-100°C)
Linear Expansion
11.0
*10-6/°C (20-300°C)
Specific Heat
460-500
J/(kg*K) (20°C)
Elastic Modulus
200-210
GPa (20°C)
9. SA387 Grade 21 Dimensions & Thickness Tolerance ASTM A20
9.1 Available Dimensions
Thickness 6-400 mm (Standard 6-200mm)
Width 1500-4350 mm
Length 3000-27000 mm
Unit Weight Max 60 MT
9.2 Thickness Tolerances (ASTM A20)
| Nominal Thickness | Class A (Unrestricted) | Class B (Restricted) |
|---|---|---|
| 6-25mm | +1.20mm, -0.30mm | +/-0.60mm |
| >25-50mm | +1.50mm, -0.30mm | +/-0.80mm |
| >50-100mm | +2.40mm, -0.30mm | +/-1.20mm |
10. SA387 Gr.21 Mill Test Certificate & EN 10204 3.2 Documentation
EN 10204 3.1
Manufacturer Test Certificate
Based on non-specific inspection
EN 10204 3.2
Third Party Inspection Certificate
Witnessed by customer or third party
ASME Data Report
Form CM-1
For ASME stamped equipment
Mill Test Certificate must include:
- ✓Heat number, plate number, batch traceability
- ✓Chemical composition (ladle + product analysis)
- ✓Mechanical properties (tensile, impact)
- ✓Heat treatment records (temperature-time curves)
- ✓NDT reports (UT/MT etc.)
- ✓Dimensional inspection records
- ✓Creep test reports (if applicable)
11. SA387 Grade 21 Equivalent Grades: 3Cr-1Mo Comparison
| Grade | Standard | Country | Yield MPa |
Tensile MPa |
Cr Content % |
Key Differences |
|---|---|---|---|---|---|---|
| SA387 Gr.21 | ASME | USA | >=205 (CI) >=310 (CII) |
415-585 (CI) 515-690 (CII) |
2.75-3.25 | ASME BPVC, 3Cr-1Mo high temp steel |
| SA387 Gr.22 | ASME | USA | >=310 | 515-690 | 2.00-2.50 | Lower Cr, similar Mo content, different application |
| SA387 Gr.5 | ASME | USA | >=205 (CI) >=310 (CII) |
415-585 (CI) 515-690 (CII) |
4.00-6.00 | Higher Cr for better high-temp oxidation resistance |
| 1.7380 / 13CrMo4-5 | EN 10028-2 | Europe | >=275 | 440-590 | 0.70-1.15 | Lower Cr and Mo content, different grade family |
High Temperature Service Notes:
- SA387 Gr.21: Maximum service temperature up to 600°C, excellent hydrogen resistance
- SA387 Gr.22: 2.25Cr-1Mo for similar temperature range with different strength
- SA387 Gr.5: Higher Cr content (5Cr) for better high-temp oxidation resistance
- 3Cr-1Mo steel requires careful control of heat treatment and welding procedures
Warning: Equivalent grades are approximate. Project-specific Gap Analysis and PQR qualification required. Yield strength and creep rupture strength are critical for high-temperature pressure vessel design.
12. SA387 Gr.21 Design Considerations & Fabrication Guidelines
Design Considerations
- High temperature creep: SA387 Gr.21 suitable for long-term service up to 600°C
- Hydrogen service: Excellent resistance to hydrogen attack at elevated temperatures
- Thickness effect: As plate thickness increases, strength and toughness decrease; allowable design stress must be interpolated per ASME II-D Table 1A
Fabrication Considerations
- Cold forming: Bend radius recommended >=5t (t=plate thickness) to avoid surface cracking
- Hot forming: Forming temperature 855-900°C, re-annealing required after forming
- Grinding: Defect removal depth not to exceed 5% of plate thickness, PT/MT verification required
Common Failure Mode Prevention
- Type IV cracking: Avoid prolonged PWHT in 750-850°C range
- Hydrogen-induced cold cracking: Strict low-hydrogen practice, control diffusible hydrogen <=5 mL/100g
- Creep damage: Regular inspection for creep damage in high-temperature service