ASME SA387 Gr.11 Class 2 Chrome Moly Steel Plate
ASME SA387 Grade 11 Class 2 is a high-quality 1.25Cr‑0.5Mo chromium‑molybdenum alloy steel plate conforming to ASME and ASTM standards. It is engineered for welded boilers, high-temperature pressure vessels and process equipment operating under severe thermal and pressure service conditions. This grade (UNS K11789) possesses a balanced alloying composition of 1.25% chromium and 0.5% molybdenum, which distinguishes it from conventional carbon steels and ordinary low-alloy steels. Unlike softer, annealed Class 1 plates, Class 2 plates adopt Normalized + Tempered heat treatment, offering higher tensile and yield strength, stable high-temperature creep resistance and excellent compatibility with sour service environments.
Company Profile
GNEE Steel is a global manufacturer and exporter specializing in ASME-compliant alloy steel plates for pressure vessels, with more than 18 years of profound experience in the production, processing and export of chromium‑molybdenum steels. We focus on high-specification SA387 Gr.11 Class 2 products and operate independent production lines, complete heat treatment facilities and a stringent full-process quality control system. If you need verified batch test reports, authentic product performance data or custom project-specific technical solutions, feel free to contact our engineering team for complimentary consultation.
ASME SA387 Gr.11 Class 2 Low Alloy Steel Plate Specification
| Specifications | ASTM A387 / ASME SA387 |
| Standard | ASTM, ASME |
| Grade |
ASTM A387 GR.11 CL.2 |
| Thickness | 6mm-250mm |
| Width | 1500mm-4200mm |
| Length |
4m–12m or as required |
| Heat Treatment | Normalized+Tempered |
| Technique | Hot Rolled |
| Classification | Alloy quality steel |
ASME SA387 Gr.11 Class 2 Hot Rolled Steel Plate Mechanical Property
| Designation | Requirement | Grade 11 |
|---|---|---|
| A387 Grade 11 | Tensile strength, ksi [MPa] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 43 [310] | |
| Elongation in 8 in. [200mm], min % | 18 | |
| Elongation in 2 in. [50mm], min, % | 22 |
ASME SA387 Gr.11 Class 2 Hot Rolled Steel Plate Chemical Composition
| Carbon (C) | % |
| Heat Analysis: Product Analysis: |
0.05 – 0.17 0.04 – 0.17 |
| Manganese (Mn) | % |
| Heat Analysis: Product Analysis: |
0.40 – 0.65 0.35 – 0.73 |
| Phosphorus (P) | % |
| Heat Analysis: Product Analysis: |
0.020 0.020 |
| Sulfur (S) (Max) | % |
| Heat Analysis: Product Analysis: |
0.025 0.025 |
| Silicon (Si) | % |
| Heat Analysis: Product Analysis: |
0.50 – 0.80 0.44 – 0.86 |
| Chromium (Cr) | % |
| Heat Analysis: Product Analysis: |
1.00 – 1.50 0.94 – 1.56 |
| Molybdenum (Mo) | % |
| Heat Analysis: Product Analysis: |
0.45 – 0.65 0.45 – 0.70 |
ASME SA387 Gr.11 Class 2 Chrome-Moly Low Alloy Plate Main Properties
1. High-Temperature Performance & Corrosion Resistance
Service Temperature Range
Optimum service temperature for ASME SA387 Gr.11 Class 2: 350–480°C (hydrogen service environment), with a typical design maximum limit ≤566°C. Long-term operation above 500°C accelerates strength degradation.
High-Temperature Strength Retention
Yield strength remains at minimum 220 MPa at 454°C. Creep resistance stays stable at 500°C, preventing plastic deformation.
Hydrogen and Oxidation Resistance Mechanism
Chromium generates a dense Cr₂O₃ oxide scale for high-temperature oxidation resistance. Molybdenum increases the recrystallization temperature and suppresses grain coarsening. The combined effect offers resistance to hydrogen attack, hydrogen blistering and sulfide corrosion.
Microstructural Stability Risks
Extended service within the 480–566°C range promotes pearlite spheroidization, which leads to strength reduction. Impurities (P, S, As, Sn) must be controlled to reduce susceptibility to temper embrittlement.
2. Machinability and Welding Characteristics
General Fabrication Performance
This steel plate supports hot forming, cold forming, cutting and precision machining with excellent process adaptability:
Hot forming
Recommended forming temperature range: 870–1050°C. Secondary normalizing plus tempering shall be performed after hot bending and forming to restore standard mechanical properties and compliant microstructure.
Cold forming
Conventional rolling, bending and ambient-temperature forming can be implemented. For processes involving severe cold deformation, targeted stress-relief heat treatment is advised to eliminate residual stress and ensure safety of pressure-containing components.
Thermal cutting
Oxy-fuel cutting and plasma cutting are suitable. A thin hardened layer will form along cut edges. GNEE can provide pre-cut and beveled finished plates with dimensional tolerance strictly limited to ±1.5 mm, reducing customers' on-site fabrication workload and material loss.
SA387 Gr.11 Class 2 Cr-Mo steel plate is a weldable low-alloy pressure vessel steel. However, improper welding thermal cycles may lead to cold cracking, heat-affected zone (HAZ) hardening and degraded toughness. Standardized welding procedures shall be implemented during engineering manufacturing.
Selection of welding consumables
Low-hydrogen welding materials are mandatory. E7018-B2L low-hydrogen covered electrodes shall be used for SMAW, while B2-series solid wire is specified for SAW and GMAW, to minimize diffusible hydrogen and prevent hydrogen-induced cracking.
Preheat and interpass temperature control
Minimum preheat temperature is 149°C. For plates above 25 mm in thickness and highly restrained components, the preheat temperature shall be increased to 175–205°C, and interpass temperature shall be strictly maintained below 315°C. Strict temperature control brings the risk of welding cold cracking close to zero.
Mandatory Post-Weld Heat Treatment (PWHT)
All welded joints for pressure equipment require PWHT, with soaking temperatures ranging from 650°C to 750°C. Proper PWHT fully relieves welding residual stress, reduces HAZ hardness and stabilizes HAZ hardness below 22 HRC, substantially enhancing resistance to temper embrittlement and hydrogen embrittlement.
Typical applications of ASME SA387 Gr.11 Class 2 Chrome Moly Plates
- Medium-temperature hydrogenation equipment: Shells for hydrodesulfurization (HDS) reactors and medium-to-low pressure hydrogenation reactors.
- Coke drums: Coke drums in delayed coking units; this is one of the most classic and high-volume applications.
- High-temperature, high-pressure heat exchangers: Tubesheets and shells.
- Coal chemical equipment: Shells for shift converters and methanol synthesis towers (under relatively mild operating conditions).
- Power plant boilers: Steam drums, headers, steam piping, etc.
- Catalytic cracking units: Regenerator and reactor shells.
Why Choose us?
Stable Material Supply & Flexible Inventory Support
We maintain regular stock of SA387 Gr.11 Class 2 plates in multiple thickness specifications. Apart from standard dimensions, we support bulk order production for special thickness, width and length requirements. Short lead time can be arranged for urgent project orders to help buyers tackle tight construction schedules.
One-stop Steel Processing Service
Oxy-fuel cutting, plasma cutting and CNC precision cutting according to customer drawings
Plate edge beveling for welding preparation
Surface grinding, flattening and trimming Controlled dimensional tolerance ensures less secondary machining work at your workshop and reduces material waste.
Customized Inspection & Third-party Test Arrangement
Beyond standard UT, tensile test and chemical analysis required by ASME SA387, we organize extra special testing as specified in project technical specifications:
Charpy V-notch impact test at designated temperatures
HIC & SSCC testing for wet H₂S sour service
PMI, MT, PT surface defect examination
Elevated-temperature tensile testing
All test reports can be issued by internationally recognized third-party laboratories. Complete, traceable MTC documents with full heat treatment records will be provided for every shipment.
Standardized Export Packaging & Global Logistics Arrangement
Waterproof plastic wrapping, anti-rust protection, steel strip bundling and fumigated wooden pallets for ocean transportation
Flexible logistics solutions: sea freight, railway transport to match destination port requirements
Complete set of export documents: commercial invoice, packing list, certificate of origin, MTC, inspection certificates to smooth customs clearance.
After-sales Quality Tracking Service
We track cargo status after delivery. In case of any questions regarding material performance, documents or surface conditions upon arrival, our team responds promptly to coordinate verification and solutions.
If you have specific size demands, special testing requirements or need to submit material documents for tender evaluation, send over your project specifications and drawings. GNEE will prepare a compliant technical proposal and competitive quotation for you within 24 hours.
Send your drawings to get a quote
FAQ
Q: Is SA387 Gr.11 steel plate easy to weld?
A: SA387 Gr.11 steel plate is weldable using standard industrial methods, but it is not considered easy because it requires strict heat control and specialized handling to prevent cracking.
Q: How is the hydrogen corrosion resistance of SA387 Gr.11 steel plate?
A: SA387 Gr.11 steel plate has good hydrogen corrosion resistance, significantly better than standard carbon steel, due to its chromium (1.00%-1.50%) and molybdenum (0.45%-0.65%) content. It resists high-temperature hydrogen attack and hydrogen embrittlement up to Nelson curve limits around 450°C to 550°C.
Q: What is the price of SA387 Gr.11 and Gr.22 plates?
A: The price of SA387 Grade 11 and Grade 22 alloy steel plates generally ranges from $500 to $1,200 per ton (or roughly $115+ per kg depending on thickness and processing).
Q: What are the differences between SA387 Gr.11 and Gr.12 plate?
A: The main differences between SA387 Grade 11 and Grade 12 involve chromium content, silicon content, and high-temperature performance capabilities. Grade 11 has more chromium and silicon than Grade 12, making it better for harsher, hotter environments.
