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ASTM A542 Steel Plate

ASTM A542 Type B Class 2 | A542-B Cl.2 Vessel Steel Plate

AI-generated illustration for ASTM A542 Type B Class 2 steel plate

ASTM A542 Type B Class 2, also written A542 Type B Class 2, A542-B Cl.2, and companion ASME SA542 Type B Class 2. This designation is quenched-and-tempered chromium-molybdenum pressure-vessel plate under ASTM A542/A542M. Type B sets the heat-analysis chemistry (2¼Cr-1Mo with restrictive residual limits relative to Type A). Class 2 sets the tensile line: yield strength min 100 ksi [690 MPa], tensile strength 115–135 ksi [795–930 MPa], elongation min 13% in 2 in. [50 mm]. A542/SA542 uses Type and Class only (no Grade number). Confirm the ASTM or ASME edition named on the purchase order before mill release. gangsteel produce and export this Type and Class cut to size; EN 10204 3.1 or 3.2 mill certificates and impact/PWHT/NDE supplements are supplied when written on the order.

ASTM A542 Type B Class 2 Chemical Composition

Heat-analysis limits for Type B. Product-analysis tolerances and footnotes follow the contracted edition of ASTM A542/A542M. Values below are heat analysis, %.

Element (heat analysis)	Type B, %
Carbon (C)	0.11–0.15
Manganese (Mn)	0.30–0.60
Phosphorus (P), max	0.015
Sulfur (S), max	0.015
Silicon (Si), max	0.50
Chromium (Cr)	2.00–2.50
Molybdenum (Mo)	0.90–1.10
Copper (Cu), max	0.25
Nickel (Ni), max	0.25
Vanadium (V), max	0.02

Type B is the second 2¼Cr-1Mo chemistry in A542/A542M. Relative to Type A, Type B carries more restrictive heat-analysis limits on carbon, phosphorus, sulfur, copper, nickel, and vanadium. Order Type B only when the vessel specification names it.

ASTM A542 Type B Class 2 Mechanical Properties

Property	Class 2
Tensile strength	115–135 ksi [795–930 MPa]
Yield strength, min	100 ksi [690 MPa]
Elongation in 2 in. [50 mm], min, %	13

Class tensile values are Class-based, not Type-specific, within the combinations permitted by ASTM A542/A542M. Apply ASTM A20/A20M elongation adjustment where thickness requires. Charpy impact (where not already Class-required), PWHT simulation, and NDE follow the purchase order and applicable ASME Section requirements when specified.

Application Areas

ASTM A542 Type B Class 2 is selected for welded pressure equipment that needs quenched-and-tempered 2¼Cr-1Mo (restricted residuals) plate at the Class 2 strength line. Typical engineered uses include:

Heavy-wall pressure vessels and reactors in refining and petrochemical service where the design specifies A542/SA542 Type B Class 2 (or dual-marked companion designation when Code-ordered).
Hydroprocessing and hydrotreating equipment shells, heads, and thick-section components that require this Cr-Mo or Cr-Mo-V alloy content with quenched-and-tempered mechanical properties rather than a normalized-and-tempered Cr-Mo specification alone.
High-integrity boilers and pressure vessels where the purchaser’s material specification names Type B chemistry and Class 2 tensile limits.
Repair, replacement, and project plate cut to size for fabricators working to ASME Section VIII or project vessel specifications that call out A542/SA542 Type B Class 2.

Final fitness for a given design temperature, hydrogen service, PWHT cycle, or sour-service supplement is project-specific. Order the exact Type, Class, edition, and test package required by the vessel drawing and Code.

Delivery Condition

Under ASTM A542/A542M, Type B Class 2 plate is normally furnished in the quenched-and-tempered (QT) condition so that Class 2 tensile and yield requirements are met at delivery. As-rolled or normalized-only shipment does not meet this Class unless the purchaser performs the full quench-and-temper cycle under the specification (see Heat Treatment Process).

Item	Requirement	Order confirmation
Standard final condition	Quenched and tempered (QT) to Class 2 mechanical properties	State QT delivery on the PO unless another route is agreed in writing
Purchaser heat-treatment exception	Purchaser may perform final QT when permitted by ASTM A542/A542M; manufacturer pre-shipment temper still applies (see Heat Treatment Process)	Name who performs final QT and required mill temper before shipment
Marking	ASTM A542 (or ASME SA-542 when Code-ordered) with Type B and Class 2; dual marking by agreement when editions align	Confirm ASTM, ASME, or dual marking on the order
Certification	Mill test documentation for heat/product analysis and mechanical results as ordered	EN 10204 3.1 or 3.2, and any third-party witness, subject to enquiry and order confirmation
Supplementary tests	Impact, PWHT simulation, NDE, and other project extras when specified	List each supplement, acceptance, and temperature on the PO

Certificate form, analysis reporting, and supplements are not assumed as open guarantees: confirm them with the enquiry and order. Delivery marking must show Type B Class 2 as ordered.

Heat Treatment Process

Plate heat treatment for ASTM A542 Type B Class 2 is distinct from vessel post-weld heat treatment (PWHT). The plate route is austenitize, quench, and temper to Class 2. Fabrication PWHT follows the applicable ASME Section and the fabricator’s WPS and must be ordered separately when simulated or recorded on plate tests.

Step	Requirement	Order confirmation
Austenitize	Heating for quench as required to develop Class 2 properties after temper	No fixed temperature, hold time, or rate is stated here; confirm mill practice against the contracted edition if required on the PO
Quench	Cooling from austenitizing to produce the as-quenched structure for temper	Quench medium and parameters follow mill practice within the specification; name any purchaser limit on the order
Temper (final QT by manufacturer)	Minimum tempering temperature for Type B Class 2: 1050°F [565°C]	Confirm Class 2 temper requirement and any higher project minimum on the PO
Manufacturer temper when purchaser performs final QT	If the purchaser performs the quench-and-temper cycle, the manufacturer shall temper before shipment at not lower than 1050°F [565°C] for Types A, B, C, and D	State purchaser final QT and required pre-shipment temper on the order
Vessel PWHT (not plate delivery temper)	Separate from plate QT; governed by Code, drawing, and WPS	Order PWHT simulation or recorded cycles only when written on the PO

Only the minimum temper of 1050°F [565°C] for Type B Class 2 is given from the verified specification data used for this page. Austenitizing temperature (unless a Type minimum is listed above), quench medium, hold times, and heating/cooling rates are not fixed on this page and remain subject to mill practice and order confirmation. Impact test temperature and acceptance, when required, must be named on the order.

Size and Supply Range

ASTM A542/A542M states a minimum thickness of 3/16 in. [5 mm]. Maximum thickness is limited by the ability of the plate to meet the specified mechanical properties after quench and temper. Width and length are cut to the dimensions stated on the purchase order, within mill and processing capability for the order. Available thickness, width, length, lead time, certificate type (EN 10204 3.1 or 3.2), and any cutting or test extras are subject to enquiry and order confirmation. State thickness × width × length, Type B Class 2, edition, and required supplements on the RFQ.

Comparison with ASTM A533

Both ASTM A542 Type B Class 2 and ASTM A533 Grade A Class 1 (also written A533 Type A Class 1) are quenched-and-tempered alloy steel plates for welded pressure vessels, but they are not interchangeable.

Item	ASTM A542 Type B Class 2	ASTM A533 Grade A Class 1
Alloy family	Cr-Mo (Type B: 2¼Cr-1Mo, restricted residuals)	Mn-Mo (Type/Grade A: no specified nickel)
Naming	Type + Class (no Grade number)	Type/Grade + Class (commercial orders often say Grade A)
Heat treatment	Quenched and tempered	Quenched and tempered
This page Class 2 yield, min	100 ksi [690 MPa]	50 ksi [345 MPa] (A533 Class 1)
This page Class 2 tensile	115–135 ksi [795–930 MPa]	80–100 ksi [550–690 MPa] (A533 Class 1)
Elongation in 50 mm, min	13%	18% (A533 Class 1)

See the ASTM A533 Steel Plate hub for other A533 grades and classes. A533 Class numbers do not map one-to-one onto A542 Class numbers. Do not substitute A533 Grade A Class 1 for ASTM A542 Type B Class 2 (or the reverse) without a design and purchasing change.

Equivalent / Related Materials

The table lists companion designations and chemistry-family related materials. Rows marked “similar / related” are engineering cross-references only—not proven drop-in equivalents and not automatic Code interchangeability. Dual certification requires the stricter combined limits on the purchase order and MTC.

Standard / region	Designation	Relationship	Reference
American (ASME companion)	ASME SA542 Type B Class 2	Companion designation when editions align; dual marking by agreement	Order ASME SA542 Type B Class 2 when the vessel specification requires the ASME name
American (related Cr-Mo)	ASTM A387 / ASME SA387 Grade 22 Class 1 / Class 2	Similar 2¼Cr-1Mo chemistry family; typically normalized-and-tempered elevated-temperature material—not an A542 QT Class substitute	A387 Grade 22 Class 1 · A387 Grade 22 Class 2 · A387 hub
American (related QT)	ASTM A533 Grade A Class 1	Also quenched-and-tempered vessel plate; Mn-Mo chemistry—related product family only	A533 Grade A Class 1 · A533 hub
Chinese GB (similar / related)	GB/T 713 12Cr2Mo1R	2¼Cr-1Mo pressure-vessel grade family; not a proven one-to-one QT Class interchange with this A542 Type/Class	GB/T 713 12Cr2Mo1R · GB/T 713 hub
Chinese GB (V-bearing related)	GB/T 713 12Cr2Mo1VR	Related Cr-Mo-V vessel grade; different chemistry and route from A542 Type B	GB/T 713 12Cr2Mo1VR
Japanese JIS	No confirmed direct equivalent	Related Cr-Mo plate designation SCMV4 (JIS G4109) is a chemistry-family reference only and is not interchangeable with ASTM A542 Type B Class 2	—

No automatic one-to-one equivalent across EN/JIS/GB is claimed for ASTM A542 Type B Class 2. Order and certify the designation required by the vessel specification.

FAQ

1. What is ASTM A542 Type B Class 2?

It is quenched-and-tempered pressure-vessel plate under ASTM A542/A542M. Type B fixes the 2¼Cr-1Mo (restricted residuals) heat-analysis chemistry. Class 2 fixes strength: yield min 100 ksi [690 MPa], tensile 115–135 ksi [795–930 MPa], elongation 13% min in 50 mm. Plates are supplied to order with mill certificates when this Type and Class are named on the purchase order.

2. How does ASTM A542 Type B Class 2 relate to ASME SA542 Type B Class 2?

For the same Type and Class, ASTM A542 and ASME SA-542 are companion designations used for product versus Code ordering. Chemistry and Class tensile limits are intended to align when the contracted editions match. Order the name required by the vessel specification; dual marking is by agreement.

3. What mechanical values apply to Class 2?

Class 2 tensile strength is 115–135 ksi [795–930 MPa]; yield min 100 ksi [690 MPa]; elongation in 50 mm min 13%. These Class values apply to Types ordered to Class 2 under the permitted combinations in ASTM A542/A542M. Thickness-dependent elongation adjustment follows A20/A20M when required.

4. What distinguishes Type B / which Type–Class combinations are allowed?

Type B is the second 2¼Cr-1Mo chemistry, with more restrictive residual limits than Type A. Other Types use different Cr-Mo or Cr-Mo-V chemistries. Not every Type may be ordered to every Class; specify a permitted Type and Class combination from ASTM A542/A542M as named on the drawing and purchase order.

5. Is ASTM A542 Type B Class 2 interchangeable with A387 Grade 22 or A533 Grade A Class 1?

No automatic swap. A387 Grade 22 is a different Cr-Mo pressure-vessel heat-treatment specification. A533 Grade A Class 1 is a Mn-Mo quenched-and-tempered specification. ASTM A542 Type B Class 2 must be ordered and certified as A542/SA542 Type B Class 2.

6. What thickness and certificate options should be confirmed on the order?

Specification minimum thickness is 3/16 in. [5 mm]; maximum thickness depends on meeting Class 2 after quench and temper. Confirm thickness × width × length, edition, impact/PWHT/NDE, and EN 10204 3.1 or 3.2 by enquiry and order confirmation.

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