ASTM A387/A387M covers chromium-molybdenum alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service. The standard applies to plates in various thickness ranges. Two specification systems are provided: A387 (Inch-Pound) and A387M (SI/Metric).

2. Grades Covered by ASTM A387

ASTM A387 covers 8 chromium-molybdenum alloy steel plate grades, ranging from basic 1/2Cr-1/2Mo to advanced 9Cr-1Mo-V-Nb-W alloys. Grades 22 and 91 are the most widely used in power generation and refinery applications.

3. Chemical Composition Requirements

Product analysis tolerances per ASTM A387 Table 1. Values shown are maximum unless otherwise indicated.

4. Mechanical Property Requirements

Tension test requirements per grade. Values are minimum unless otherwise indicated. Testing per ASTM A20/A20M.

5. Heat Treatment Requirements

ASTM A387 plates must be heat treated by one of the following methods before delivery. The heat treatment condition must be selected based on grade and service requirements.

6. Testing & Inspection Requirements

7. Related Standards & Companion Specifications

8. ASTM A387 vs ASME SA-387 vs A542 Compared

9. How to Order — Required Information

10. Frequently Asked Questions

Q: What is the difference between ASTM A387 and ASME SA-387?

ASTM A387 is the material specification published by ASTM International. ASME SA-387 is the identical specification adopted into the ASME Boiler and Pressure Vessel Code (Section II Part A). For Code-certified pressure vessels, you must use SA-387. The technical requirements (chemistry, mechanics, heat treatment) are identical; only the designation differs to indicate Code compliance. Always specify SA-387 when the material will be used in ASME Code construction.

Q: Why is Grade 91 (9Cr-1Mo-V) preferred over Grade 22 in modern power plants?

Grade 91 (9Cr-1Mo-V) offers superior creep strength, oxidation resistance, and thermal fatigue resistance compared to Grade 22 (2-1/4Cr-1Mo). Grade 91 operates effectively at temperatures up to 1200°F (649°C) in ultra-supercritical and supercritical boilers, while Grade 22 is limited to approximately 1100°F (595°C). The vanadium (0.18-0.25%) and niobium (0.06-0.10%) additions in Grade 91 create stable MX carbonitrides that resist coarsening at elevated temperatures. Although Grade 91 requires stricter process control and PWHT, its superior performance justifies the additional cost in modern high-efficiency power plants.

Q: What is the PWHT requirement for ASTM A387 welds?

Post-weld heat treatment (PWHT) for A387 plates is governed by ASME Section VIII Division 1 UCS-56 or the applicable design code. For Cr-Mo steels, PWHT is typically required when thickness exceeds 1-1/4 inches (32mm). PWHT temperature must be at least 25°F (14°C) below the original tempering temperature. For Grade 22, PWHT is usually 1225-1275°F (665-690°C). For Grade 91, PWHT must be 1350°F (730°C) minimum but not exceed the original tempering temperature. Always verify against the governing code for specific thickness and temperature requirements.

Q: What impact testing is required for A387 plates?

Charpy V-notch impact testing is not universally required by ASTM A387 but may be specified in the purchase order or required by the design code. Per ASME Section VIII Division 1, impact testing is typically required when: (1) minimum design temperature is below -50°F (-45°C), (2) plate thickness exceeds 3/4 inch (19mm) for certain grades, or (3) service conditions require notch toughness. When impact testing is specified, use ASTM A673 H的组织 (P) methodology with minimum absorbed energy of 20 ft-lbf (27 J) unless otherwise specified.

Q: Can ASTM A387 Grade 22 be welded without PWHT?

In most applications, A387 Grade 22 welds require post-weld heat treatment (PWHT) to relieve residual stresses and achieve the required microstructure. However, ASME Section VIII Division 1 UCS-56 permits exceptions for certain conditions: thin sections under 1-1/4 inches may not require PWHT if impact testing is performed, and some welding processes with low heat input may qualify for exemptions. Always consult the governing Code and the specific design conditions. For safety-critical applications, PWHT is strongly recommended even when not strictly required.

Q: What are the storage and handling precautions for A387 chrome moly plates?

Store A387 plates on wooden dunnage to prevent moisture accumulation and avoid direct contact with concrete (which can cause staining). Keep plates dry and covered in controlled indoor storage. For long-term storage, apply rust preventive oil or mill varnish. When handling, use appropriate slings and lifting points to prevent bending. Grade 91 plates require extra care due to their higher strength — avoid impacts and gouges that could affect surface integrity. Inspect for surface defects before fabrication and report any mill defects to the supplier within the agreed inspection period.
 

Request a Quote — ASTM A387 Chrome Moly Steel Plate

Zhengzhou Huitong (HT Pipe) supplies ASTM A387 / SA-387 compliant chrome moly steel plates in all standard grades (Grade 22, Grade 91, Grade 11, Grade 12) with full EN 10204 3.1 Mill Test Certificates. Normalized+tempered condition standard. Available with Charpy impact testing and ultrasonic examination.