ASTM A302 Grade B Steel Plate | A302 Gr.B Mn-Mo Vessel Plate

As a professional China mill-Direct Supply and pressure-vessel plate exporter, SHH STEEL supplies ASTM A302 Grade B Steel Plate produced to ASTM A302/A302M.

On drawings, MTCs and RFQs this grade is written many ways: ASTM A302 Grade B, A302 Gr.B, A302 Gr B, A302GRB, A302 GR B, A-302 Grade B, A-302 Gr.B, ASME SA302 Grade B, SA302 Gr.B, SA302GRB, Mn-Mo vessel plate, manganese molybdenum boiler plate and A/SA302 Grade B. All of these names refer to the same manganese-molybdenum alloy plate. ASTM A302/A302M is the ASTM product specification; ASME SA-302/SA-302M is the Boiler and Pressure Vessel Code companion.

A302 Gr.B is the workhorse grade in ASTM A302. Grade A is the lower-strength Mn-Mo plate. Grade B raises manganese and strength. Grades C and D keep Grade B strength and add nickel. Minimum yield of Grade B is 345 MPa (50 ksi). Tensile strength is 550–690 MPa (80–100 ksi). Molybdenum heat analysis is 0.45–0.60%. Nickel is not specified for Grade B.

The plate is intended for welded boilers and other pressure vessels. For ASME Code work it is dual-certified to ASME SA-302 Grade B and used under ASME Section VIII. It is not a 2.25Ni / 3.5Ni low-temperature grade such as A203, and it is not a Cr-Mo elevated-temperature grade such as ASME SA387. Compared with carbon vessel steels such as ASTM A516 and ASME SA516, Grade B adds molybdenum for higher allowable strength in boiler and vessel service.

General requirements follow ASTM A20 / ASME SA-20. Steel is killed and produced to fine-grain practice. Plates 50 mm and under are normally supplied as-rolled unless normalizing or stress relieving is ordered. Plates over 50 mm shall be normalized.

SHH STEEL supplies A302 Gr.B as true China mill-Direct Supply. Dual marking ASTM A302 Grade B / ASME SA302 Grade B is available. Certificates can be EN 10204 3.1 or EN 10204 3.2.

If the project compares other coded vessel plates, SHH STEEL places A302 Gr.B next to ASTM A537, ASME SA537, ASME SA515 and ASTM A285.

This product belongs to the Pressure Vessel Steel Plates family. It is a Mn-Mo coded vessel plate under ASTM A302, not a structural Carbon Steel Plates grade.

A302 Grade B chemistry under ASTM A302/A302M is reported as heat analysis (ladle analysis) and, when specified, product analysis.

Heat Analysis (Ladle Analysis) — Grade B

Product Analysis — Grade B

Grade B uses a higher manganese band than Grade A so the 345 MPa yield in ASTM A302 can be met. Molybdenum stays 0.45–0.60% on heat analysis for all four grades. Nickel is the separator: Grade B has no Ni requirement; Grade C adds 0.40–0.70% Ni; Grade D adds 0.70–1.00% Ni. Tighter residuals or carbon equivalent limits are supplementary requirements.

SHH STEEL reports ladle analysis on every certificate. Product analysis is added when ASTM A20 product analysis or the vessel specification requires it.

Tensile Requirements — ASTM A302 Grade B per ASTM A302/A302M

These limits apply to A302 Gr.B at both thin and thick sizes. Density is 7.85 g/cm³. Hardness after the agreed heat treatment is typically in the 160–200 HB range unless a special window is ordered.

Compared with A302 Grade A, Grade B gives 35 MPa more yield and a higher tensile band. Compared with Grades C and D, strength is the same; only nickel changes. Specimens are prepared under ASTM A20. If simulated PWHT is specified, coupons are heat-treated to the vessel cycle before testing.

Order A302 Gr.B / A302GRB when the ASTM drawing needs Mn-Mo plate at 345 MPa yield and nickel is not required. If the same strength is needed with nickel for toughness, use Grade C or Grade D. If 310 MPa yield is enough, Grade A is sufficient. Carbon QT options include ASTM A537 and ASME SA537. HSLA Steel Plates are not a coded substitute for ASTM A302.

A302 Grade B is specified for welded boilers and pressure vessels, not for cryogenic 3.5Ni or 9% Ni service. Molybdenum in ASTM A302/A302M supports strength in boiler and process equipment. When dual certified to ASME SA-302 Grade B, allowable stress at temperature is taken from the applicable ASME Section II Part D table, not from a commercial datasheet.

Impact temperature, orientation and energy minimums are agreed on the order. They are not automatic on Grade B. When the vessel specification sets Charpy values, SHH STEEL produces A302 Gr.B Mn-Mo vessel plate with those sets and lists the results on the 3.1 or 3.2 certificate.

A302 Grade B under ASTM A302 is a welded boiler and pressure-vessel plate. Mn-Mo steel is welded with low-hydrogen procedures. For Code work, procedures are qualified to ASME Section IX.

Consumables are selected to match molybdenum and the required joint strength and toughness. Preheat depends on thickness, hydrogen control and restraint. When ASME Section VIII requires PWHT, the shop cycle is commonly in the 595–650°C range for this alloy family. If properties after that cycle are needed, simulated PWHT of mill coupons should be ordered before shipment.

SHH STEEL recommends a qualified WPS/PQR for each thickness break and can support procedure review through steel welding services. Do not assume an A516 procedure is automatically valid for A302 Gr.B.

Heat treatment of A302 Grade B follows ASTM A302/A302M:

• Plates 50 mm (2 in.) and under are normally supplied in the as-rolled condition. They may be ordered normalized, stress relieved, or both.
• Plates over 50 mm (2 in.) shall be normalized.

Normalizing is heating into the austenite range followed by air cooling. Stress relieving, when ordered, is a separate lower-temperature hold to reduce residual stress. Quench-and-temper practice used for A533 / A537 Class 2 must not be applied to Grade B unless the order is changed to a QT specification.

If the specification fixes a normalizing temperature band or holding time per thickness under ASTM A20, SHH STEEL writes those parameters into the mill instruction and reports them on the certificate.

SHH STEEL delivers ASTM A302 Grade B / A302 Gr.B as follows:

• ≤ 50 mm: as-rolled as standard, or normalized / stress relieved when ordered

• 50 mm: normalized as required by ASTM A302

The certificate lists A302 Gr.B and, when dual certified, SA302 Gr.B; heat number; heat analysis; product analysis when ordered; tensile results; heat-treatment condition; agreed Charpy values; and supplementary tests. Plates are industrial vessel plate: heat-treated as required, then pickled or shot-blasted as agreed.

Decorative finishes such as 2B, BA or No.4 are not used. Surface condition is vessel-plate quality for welding, NDE and coating. Heat number and grade marking support mill and Code traceability.

Certificates may be EN 10204 3.1 or EN 10204 3.2. Third-party stamps (BV, LR, DNV, TUV, SGS or the purchaser’s agency) are arranged when written on the order.

Typical supply range from SHH STEEL for A302 Gr.B Mn-Mo vessel plate:

• Thickness: 6 mm – 150 mm (heavier by mill enquiry)
• Width: up to about 4600 mm
• Length: up to about 12000 mm

Because heat treatment changes at 50 mm in ASTM A302, the purchase order should state the ordered thickness and the required condition. Cut-to-length shells, heads and nest sizes are available.

Dimensional tolerances follow ASTM A20 / ASME SA-20 for pressure-vessel plates.

Thickness, width, length, flatness and camber are vessel-plate tolerances, not strip tolerances. Restricted thickness or extra-flatness can be accepted when the vessel drawing requires it. Ultrasonic testing to A435 or A578 is added when specified. Cutting to finished sizes is available through steel cutting services.

Vessel specifications often add tests beyond the base A302 Grade B table. SHH STEEL treats the following as supplementary requirements.

Simulated PWHT. Coupons from the same heat and thickness receive the vessel PWHT cycle. Tensile and Charpy tests are run on those coupons.

Nondestructive examination. UT to A435, A577 or A578 with purchaser acceptance levels. Edge MT/PT after cutting if required.

Impact testing. Test temperature, specimen size, orientation and minimum average/single values as written on the RFQ.

Special hardness. HBW or HV window after the agreed heat treatment or after simulated PWHT.

Restricted chemistry. Tighter C, P, S, residuals or carbon equivalent on heat and product analysis per ASTM A302 / A20.

HIC testing. NACE TM0284 with purchaser solution and CLR/CTR/CSR limits. Not automatic on A302 Gr.B.

NACE / sour-service notes. Review against NACE MR0175 / ISO 15156 or MR0103 only when the datasheet cites the clause.

Z-direction testing. ASTM A770 or purchaser Z15/Z25/Z35 for thick nozzles and restrained joints.

Third-party witnessing. Witness of heat treatment, mechanical tests, UT and documents. Output can be EN 10204 3.2.

Supplementary tests go through steel testing service and appear line by line on the certificate. Items not on the purchase order are not assumed.

For ASME stamping, the purchase order should say dual A302 / SA302 Grade B. Nearby carbon vessel grades include ASTM A516, ASME SA516, ASME SA515 and ASTM A285.

ASTM A302 Grade B / A302 Gr.B is selected for boilers and vessels that need Mn-Mo strength at 345 MPa yield. Typical applications of ASTM A302 Grade B Steel Plate include:

SHH STEEL supplies A302 Gr.B with full heat traceability. Related industry pages include petrochemical industry and energy industry. Supporting services include steel cutting services, steel welding services, steel testing service and worldwide shipping service.

SHH STEEL is a China mill-Direct Supply for plates to ASTM A302/A302M. For A302 Grade B we offer:

• China mill-Direct Supply pricing on A302 Gr.B / SA302 Gr.B
• Dual ASTM A302 / ASME SA302 marking
• Heat analysis and product analysis per ASTM A20 / A302
• EN 10204 3.1 standard; EN 10204 3.2 or nominated third-party inspection on request
• As-rolled or normalized delivery per thickness rule
• Supplementary PWHT simulation, UT, HIC, NACE review and Z-direction testing
• Cutting to shell and head nest sizes
• Technical support to separate Grade B from A/C/D and from A516 / SA387 / A537
• Export packing through worldwide shipping service

For company scope and other vessel grades, visit China steel Mill Agent-SHH STEEL.

ASTM A302 Grade B Steel Plate is the manganese-molybdenum, 345 MPa yield vessel grade in ASTM A302/A302M. Whether the inquiry says A302 Gr.B, A302GRB, A-302 Grade B or Mn-Mo vessel plate, SHH STEEL supplies plate with heat and product analysis, thickness-correct heat treatment, optional supplementary tests, and EN 10204 3.1 or 3.2 certification.

As a professional China mill-Direct Supply, SHH STEEL provides ASTM A302 Grade B / A302 Gr.B Mn-Mo Vessel Plate with full traceability for boiler and ASME Section VIII fabrication.

Contact SHH STEEL today for stock, normalizing, dual A302/SA302 marking, 3.2 inspection or a quotation.

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