ASME SA-542/SA-542M

SA542 Type A Class 4a Pressure Vessel Steel Plate Product-Performance

Technical Datasheet

Chromium-molybdenum (2.25Cr-1Mo) quenched and tempered pressure vessel steel plate, with high strength and good toughness. Suitable for elevated temperature pressure vessel service in petrochemical and power generation applications.

1. SA542 Type A Class 4a Material Identification & ASTM ASME Standards

Standards

  • ASTM A542 / ASME SA542
  • ASTM A20/A20M (General Requirements)
  • ASME BPVC Section II Part A

Alloy Type

2.25Cr-1Mo

Grade Classification

  • SA542 Type A Class 4a (2.25Cr-1Mo) ← This Spec
  • SA542 Type B Class 1 (2.25Cr-1Mo-V)
  • SA542 Type B Class 4 (2.25Cr-1Mo-V)
  • SA542 Type C Class 1 (3Cr-1Mo-V)
  • SA542 Type D Class 1 (2.25Cr-1Mo-V)
  • SA542 Type E (2.75Cr-1Mo-V)

2. SA542 Type A Class 4a Chemical Composition & Ladle Analysis Requirements

2.1 SA542 Type A Class 4a Chemical Composition Limits

Table 2.1: SA542 Type A Class 4a Chemical Composition Requirements (ASTM A542/ASME SA542 Mass Percent)
Element Smelting Analysis Finished Product Analysis
C, ≤ 0.15 0.18
Mn 0.30-0.60 0.25-0.66
Si, ≤ 0.50 0.50
S, ≤ 0.025 0.025
P, ≤ 0.025 0.025
Cr 2.00-2.50 1.88-2.62
Mo 0.90-1.10 0.85-1.15
Ni, ≤ 0.40 0.43
V, ≤ 0.03 0.04
B ...
Ti ...
Cu, ≤ 0.40 0.43
Nb ...
Zr ...
Others ...

Carbon Equivalent (CE)

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

Typical value: 0.60-0.85 (depending on actual composition)

Note: 2.25Cr-1Mo steel requires controlled welding procedures due to high hardenability; low hydrogen practice is mandatory.

3. SA542 Type A Class 4a Mechanical Properties & Tensile Strength Specification

3.1 SA542 Type A Class 4a Tensile Properties

Property Standard Value Test Method Remarks
Tensile Strength Rm 585-760 MPa ASTM A370 Transverse specimen
Yield Strength ReH >=415 MPa ASTM A370 Upper yield strength
Elongation A (2in./50mm) >=18% ASTM A370 Per A20/A20M
Charpy Impact KV₂ ... — By agreement

3.2 Charpy Impact Test Requirements for SA542 Type A Class 4a

Standard Grade

Impact testing not required by standard

High Strength Service

Low Temperature Service

  • Impact testing by agreement
  • Cr-Mo steel provides good toughness
  • Typical test temperature: 0°C to -20°C
By Agreement

3.3 SA542 Type A Class 4a Hardness & Brinell Hardness Limits

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

4. SA542 Type A Class 4a Quenched + Tempered: Heat Treatment Guide

1

As-Rolled (AR)

Not applicable for SA542

High hardenability requires Q+T

→
2

Quenched + Tempered (Q+T)

Austenitizing: 900-960°C

Quench: Water or Oil

Tempering: 650-720°C

→
3

Simulated PWHT (SPWHT)

650-720°C × 2-4h

For property verification

Critical Control Points:
  • SA542 must be supplied in quenched + tempered condition
  • Austenitizing temperature: 900-960°C, quench in water or oil
  • Tempering temperature: 650-720°C, air cool
  • Tempering temperature must be carefully controlled to achieve required strength and toughness balance

5. SA542 Type A Class 4a Welding Procedure Specification (WPS/PQR)

5.1 SA542 Type A Class 4a Welding Procedure Specification WPS

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

5.2 SA542 Type A Class 4a Preheat & Interpass Temperature Chart

Thickness Range Min Preheat Temp Recommended Preheat Max Interpass Temp
<=13mm 150°C 150-200°C 250-300°C
>13-38mm 150°C 150-250°C
>38mm 150°C 200-250°C

5.3 Recommended Welding Consumables for SA542 Type A Class 4a

Process AWS Classification Strength Match Hydrogen Control
SMAW E9015-B3, E9015-B3H4 90 ksi Low Hydrogen (H4)
GTAW ER90S-B3 90 ksi Shielding: Ar
FCAW E91T1-B3 90 ksi Self/ Gas Shielded
SAW F9A2-B3, F9P2-B3 90 ksi Flux bake 300°C*2h

5.4 SA542 Type A Class 4a PWHT Requirements & Post Weld Heat Treatment

Temperature Range 650-720°C
Holding Time 1h/25mm thickness (min 30min)
Heating Rate <=150°C/h
Cooling Rate <=150°C/h (to 300°C)
PWHT Notes:
  • PWHT is mandatory for SA542 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. SA542 Type A Class 4a High Temperature Service & Creep Resistance

6.1 SA542 Type A Class 4a High Temperature Properties

High Temperature Capability

  • Good creep resistance up to 580°C
  • Good hydrogen resistance at elevated temperatures
  • Good oxidation resistance (2.25% Cr)
  • High thermal conductivity

Applications

  • Hydroprocessing reactors
  • Hydrocracking equipment
  • High-temperature heat exchangers
  • Petrochemical pressure vessels

6.2 SA542 Type A Class 4a Creep Rupture Properties

Grade SA542 Type A Class 4a provides good creep rupture strength at elevated temperatures:

  • At 450°C: 100,000 hour creep rupture strength ~170 MPa
  • At 500°C: 100,000 hour creep rupture strength ~120 MPa
  • At 550°C: 100,000 hour creep rupture strength ~72 MPa
  • At 580°C: 100,000 hour creep rupture strength ~48 MPa

7. SA542 Type A Class 4a 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. SA542 Type A Class 4a Physical Properties & Thermal Conductivity

Density

7.80

g/cm3 (20°C)

Melting Point

~1510

°C

Thermal Conductivity

35-40

W/(m*K) (20-100°C)

Linear Expansion

11.5

*10-6/°C (20-300°C)

Specific Heat

460-500

J/(kg*K) (20°C)

Elastic Modulus

200-210

GPa (20°C)

9. SA542 Type A Class 4a Dimensions & Thickness Tolerance ASTM A20

9.1 Available Dimensions

Thickness 6-200 mm (Standard 6-100mm)
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. SA542 Type A Class 4a 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

11. SA542 Type A Class 4a Equivalent Grades: Cr-Mo Steel Comparison

Grade Standard Country Yield
MPa		 Tensile
MPa		 Cr Content
%		 Key Differences
SA542 Type A Class 4a ASME USA >=415 585-760 2.00-2.50 ASME BPVC, 2.25Cr-1Mo high temp steel
SA542 Type B Class 4 ASME USA >=380 585-760 2.00-2.50 Contains V, similar Cr content
SA542 Type D Class 4a ASME USA >=415 585-760 2.00-2.50 Contains V, similar strength
SA387 Gr.22 ASME USA >=310 515-690 2.00-2.50 No V, no B, lower strength
High Temperature Service Notes:
  • SA542 Type A Class 4a: 2.25Cr-1Mo, yield ≥415 MPa
  • SA542 Type B Class 4: Contains V and B, lower yield (≥380 MPa)
  • SA542 Type D Class 4a: Contains V, similar strength
  • SA387 Gr.22: No V, no B, lower strength
  • Cr-Mo steel requires controlled 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. SA542 Type A Class 4a Design Considerations & Fabrication Guidelines

Design Considerations

  • High temperature creep: SA542 Type A Class 4a suitable for long-term service up to 580°C
  • Hydrogen service: Good 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 >=4t (t=plate thickness) to avoid surface cracking
  • Hot forming: Forming temperature 900-960°C, re-quenching and tempering required after forming
  • Grinding: Defect removal depth not to exceed 7% 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
  • Temper embrittlement: Avoid prolonged exposure to 350-550°C range

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