ASME SA-387/SA-387M

SA387 Grade 91 Type 2 Pressure Vessel Steel Plate Product-Performance

Technical Datasheet

Chromium-molybdenum-vanadium (9Cr-1Mo-V) pressure vessel steel plate, supplied in normalized and tempered condition, with excellent high-temperature strength and creep resistance. Suitable for elevated temperature service in petrochemical and power generation applications.

1. SA387 Grade 91 Type 2 Material Identification & ASTM ASME Standards

Standards

  • ASTM A387 / ASME SA387
  • ASTM A20/A20M (General Requirements)
  • ASME BPVC Section II Part A

Alloy Type

9Cr-1Mo-V

Grade Classification

  • SA387 Gr.2 (0.5Cr-0.5Mo)
  • SA387 Gr.11 (1.25Cr-0.5Mo)
  • SA387 Gr.22 (2.25Cr-1Mo)
  • SA387 Gr.91 (9Cr-1Mo-V) ← This Spec

2. SA387 Gr.91 Type 2 Chemical Composition & Ladle Analysis Requirements

2.1 SA387 Grade 91 Type 2 Chemical Composition Limits

Table 2.1: SA387 Gr.91 Type 2 Chemical Composition Requirements (ASTM A387/ASME SA387 Mass Percent)
Element Smelting Analysis Finished Product Analysis
C 0.08-0.12 0.06-0.15①
Mn 0.30-0.50 0.30-0.50
P, ≤ 0.02 0.02
S, ≤ 0.005 0.005
Si 0.20-0.40 0.20-0.40
Cr 8.00-9.50 8.00-9.50
Mo 0.85-1.05 0.80-1.05
Ni 0.2 0.2
V 0.18-0.25 0.16-0.27
Nb② 0.06-0.10 0.05-0.11
B, ≤③ 0.001
N 0.035-0.070 0.035-0.070
N/Al ≥4.0
Al, ≤③ 0.02
Ti, ≤③ 0.01
Zr, ≤③ 0.01
W, ≤③ 0.05
Cu, ≤③ 0.1
Sb, ≤③ 0.003
As, ≤③ 0.01
Sn, ≤③ 0.01

Carbon Equivalent (CE)

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

Typical value: 2.0-2.3 (high chromium content)

Note: 9Cr-1Mo-V 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 91 Type 2 Mechanical Properties & Tensile Strength Specification

3.1 SA387 Grade 91 Type 2 Tensile Properties (Class II Steel Plates)

Property Standard Value Test Method Remarks
Tensile Strength Rm 585-760 MPa ASTM A370 Transverse specimen
Yield Strength ReL or Rp0.2 >=415 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 ... — Not specified

3.2 Charpy Impact Test Requirements for SA387 Gr.91 Type 2

Standard Grade

Impact testing not required by standard

High Temperature Service

High Temperature Service

  • 9Cr-1Mo-V provides excellent creep resistance
  • Service temperature: up to 650°C
  • Impact testing: By agreement
By Agreement

3.3 SA387 Gr.91 Type 2 Hardness & Brinell Hardness Limits

  • As-supplied condition (normalized + tempered): Typically ≤250 HBW
  • NACE service environment: Weld & HAZ ≤250 HV10

4. SA387 Gr.91 Type 2 Normalized + Tempered: Heat Treatment Guide

1

As-Rolled (AR)

Not applicable for Grade 91

High hardenability requires N+T

→
2

Normalized + Tempered (N+T)

Normalizing: 1040-1080°C

Tempering: 730-780°C

Cooling: Air

→
3

Simulated PWHT (SPWHT)

730-780°C × 2-4h

For property verification

Critical Control Points:
  • Grade 91 requires normalizing at 1040-1080°C and tempering at 730-780°C
  • Tempering temperature must be carefully controlled to achieve optimal properties
  • Grain size after normalizing: >=ASTM 5 (fine grain steel)
  • Cooling rate after normalizing: Air cool or accelerated cooling as required

5. SA387 Gr.91 Type 2 Welding Procedure Specification (WPS/PQR)

5.1 SA387 Gr.91 Type 2 Welding Procedure Specification WPS

SMAW (Shielded Metal Arc) SAW (Submerged Arc) GTAW (Gas Tungsten Arc) FCAW (Flux Cored)

5.2 SA387 Gr.91 Type 2 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 91 Type 2

Process AWS Classification Strength Match Hydrogen Control
SMAW E9015-B9, E9015-B9H4 90 ksi Low Hydrogen (H4)
GTAW ER90S-B9 90 ksi Shielding: Ar
FCAW E91T1-B9 90 ksi Self/ Gas Shielded
SAW F9A2-B9, F9P2-B9 90 ksi Flux bake 300°C*2h

5.4 SA387 Gr.91 Type 2 PWHT Requirements & Post Weld Heat Treatment

Temperature Range 730-780°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 91 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.91 Type 2 High Temperature Service & Creep Resistance

6.1 SA387 Gr.91 Type 2 High Temperature Properties

High Temperature Capability

  • Excellent creep resistance up to 650°C
  • High thermal conductivity
  • Low thermal expansion coefficient
  • Superior oxidation resistance

Applications

  • Steam generators and headers
  • Petrochemical reactors
  • Power plant components
  • High-temperature heat exchangers

6.2 SA387 Gr.91 Type 2 Creep Rupture Properties

Grade 91 provides excellent creep rupture strength at elevated temperatures:

  • At 550°C: 100,000 hour creep rupture strength ~100 MPa
  • At 600°C: 100,000 hour creep rupture strength ~60 MPa
  • At 650°C: 100,000 hour creep rupture strength ~35 MPa

7. SA387 Grade 91 Type 2 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.91 Type 2 Physical Properties & Thermal Conductivity

Density

7.77

g/cm3 (20°C)

Melting Point

~1500

°C

Thermal Conductivity

26-30

W/(m*K) (20-100°C)

Linear Expansion

10.5

*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 91 Type 2 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.91 Type 2 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 91 Type 2 Equivalent Grades: 9Cr-1Mo-V Comparison

Grade Standard Country Yield
MPa		 Tensile
MPa		 Cr Content
%		 Key Differences
SA387 Gr.91 Type 2 ASME USA >=415 585-760 8.00-9.50 ASME BPVC, 9Cr-1Mo-V high temp steel
SA387 Gr.22 ASME USA >=310 515-690 2.00-2.50 Lower Cr, lower strength, lower temp capability
X10CrMoVNb9-1 EN 10028-2 Europe >=450 620-850 8.00-9.50 European equivalent, similar composition
10Cr9Mo1VNb GB/T 150 China >=415 585-760 8.00-9.50 Chinese equivalent, similar composition and properties
High Temperature Service Notes:
  • SA387 Gr.91 Type 2: Maximum service temperature up to 650°C, excellent creep resistance
  • SA387 Gr.22: Maximum service temperature up to 580°C, lower creep strength
  • X10CrMoVNb9-1: European equivalent with similar high-temperature capabilities
  • 9Cr-1Mo-V 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.91 Type 2 Design Considerations & Fabrication Guidelines

Design Considerations

  • High temperature creep: SA387 Gr.91 Type 2 suitable for long-term service up to 650°C
  • Low temperature brittle fracture: Not suitable for low-temperature service
  • 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 1040-1080°C, re-normalization 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

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