SA 387 Gr.22 Cl.1 refers to a Chrome-Moly alloy steel plate (ASTM A/ASME SA 387) for high-temperature pressure vessels, containing about 2.25% Chromium and 1% Molybdenum, with Class 1 indicating lower tensile strength (60-85 ksi) compared to Class 2 (75-100 ksi), providing good strength and corrosion resistance in elevated temperature applications like oil, gas, and power industries.
Equivalents for ASME SA387 Grade 22 Alloy Steel Plates
| BS | EN | ASTM/ASME | DIN |
| 622-515B | 10 CRMO910 | SA387-22-1 | 10 CRMO910 |
Specifications for ASME SA387 Grade 22 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| SA387 Grade 22 | 2.25% | 1.00% |
Tensile Requirements for ASME SA387 Grade 22 Alloy Steel Plates Class 1 Plates
| Designation: | Requirement: | Grade 22 |
| SA387 Grade 22 | Tensile strength, ksi [MPA] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 45 [310] | |
| Elongation in 8 in. [200mm], min % | ... | |
| Elongation in 2 in. [50mm], min, % | 18 | |
| Reduction of area, min % | 45 (measured on round specimen) 40 (measured on flat specimen) |
Chemical Requirements for ASME SA387 Grade 22 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| SA387 Grade 22 | ||
| Carbon: | Heat Analysis: | 0.05 - 0.15 |
| Product Analysis: | 0.04 - 0.15 | |
| Manganese: | Heat Analysis: | 0.30 - 0.60 |
| Product Analysis: | 0.25 - 0.66 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Silicon: | Heat Analysis: | 0.50 max |
| Product Analysis: | 0.50 max | |
| Chromium: | Heat Analysis: | 2.00 - 2.50 |
| Product Analysis: | 1.88 - 2.62 | |
| Molybdenum: | Heat Analysis: | 0.90 - 1.10 |
| Product Analysis: | 0.85 - 1.15 |
key steps
SA 387 Grade 22 Class 1 is a Cr-Mo alloy steel plate specified in ASME, designed for elevated-temperature and high-pressure service. Its production flow focuses on improving steel cleanliness and ensuring stable mechanical properties. The key steps are as follows:
Charging and Electric Arc Furnace (EAF) Melting
Raw materials are proportioned according to the required chemical composition, with strict limits on sulfur, phosphorus, and tramp elements (Sb, Sn, etc.) to avoid temper embrittlement and reduce corrosion resistance. The charged materials are melted in an EAF to remove initial impurities. For demanding applications, secondary processes such as electroslag remelting (ESR) may be used to further improve purity.
LF (Ladle Furnace) Refining
The molten steel is transferred to an LF for temperature maintenance and chemical composition adjustment. Refining reduces inclusions and ensures uniform distribution of key alloying elements such as chromium and molybdenum, meeting the tight specifications of SA 387 Gr.22 Cl 1.
VD (Vacuum Degassing) Treatment
The refined steel is subjected to vacuum degassing to remove hydrogen, oxygen, and other gases. This step minimizes the risk of porosity, internal cracks, and hydrogen-induced defects, which is critical for ensuring reliability under high-temperature and high-pressure conditions.
Casting and Controlled Rolling
The degassed steel is cast into slabs. Controlled rolling is then applied, with precise control of temperature and rolling speed to refine the grain structure and improve mechanical property uniformity. The slab is rolled to the target thickness, typically limited to ≤150 mm for this grade.
Ultrasonic Testing (UT)
As a Class 1 material, the plates undergo stringent ultrasonic inspection to detect internal flaws such as laminations, cracks, and inclusion clusters. Any unacceptable areas are removed or the plate is rejected to ensure internal soundness.
Normalizing and Tempering
This is a critical stage for achieving the required microstructure and properties.
Normalization:
The plate is heated to the appropriate temperature, held, and then cooled (air cooling or accelerated cooling may be used) to refine grains and homogenize the structure.
Tempering:
A minimum tempering temperature of 675°C is typically applied to relieve residual stresses, balance strength and toughness, and stabilize the microstructure.
Finishing and Performance Testing
The plates are cut, straightened, and surface-conditioned to meet dimensional and surface quality requirements. Mechanical tests (tensile, yield, impact) and corrosion-related evaluations are performed, along with chemical composition verification. Only plates that pass all inspections are released for delivery.
Advantages:
High Temperature Strength: Enhanced by molybdenum, it maintains superior tensile strength and resists creep at elevated temperatures (up to around 600°C).
Corrosion & Oxidation Resistance: The chromium content provides excellent resistance to oxidation and corrosion, crucial for aggressive environments.
Sour Service Capability: Well-suited for applications involving sour gas (hydrogen sulfide), common in oil & gas.
Good Weldability: Can be welded effectively, even at higher temperatures, though Class 2 (normalized & tempered) offers better toughness.
Cost-Effective for High-Temp Needs: Provides a balance of performance and cost for demanding conditions where stainless steel might be overkill.
As-Rolled Condition (Class 1): Often supplied without extra heat treatment, offering adequate mechanical properties (strength) for many applications at a lower cost than Class 2.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
What is SA 387 Gr.22 Cl 1?
SA 387 Gr.22 Cl 1 is a pressure vessel steel plate made of chromium-molybdenum (Cr-Mo) alloy. It is specified in the ASME Boiler and Pressure Vessel Code and is widely used in high-temperature and high-pressure applications. The material offers good creep strength, oxidation resistance, and toughness, making it suitable for boilers, heat exchangers, and refinery equipment. The "Class 1" designation means it must meet stricter ultrasonic inspection requirements for internal soundness.
What are the main alloying elements?
The key alloying elements are chromium and molybdenum. Chromium improves oxidation resistance and high-temperature strength, while molybdenum enhances creep resistance and provides stability under long-term thermal loading. These elements work together to ensure the steel can withstand elevated temperatures without significant degradation. Other elements such as carbon, manganese, and silicon are also carefully controlled to maintain weldability and mechanical properties.
What heat treatment is used?
SA 387 Gr.22 Cl 1 is typically heat treated by normalization followed by tempering. Normalization involves heating the steel to a temperature around 890–940°C, holding it to ensure uniformity, and then cooling in air. This process refines the grain structure and improves toughness. Tempering is done at a minimum of 675°C to reduce residual stresses, enhance ductility, and stabilize the microstructure. The exact temperatures may vary based on plate thickness and manufacturer practice.
What does "Class 1" mean?
"Class 1" indicates that the steel plate must undergo a higher level of ultrasonic testing (UT) compared to Class 2. This stricter inspection ensures that the material has fewer internal defects such as laminations, inclusions, or voids. The goal is to provide a more reliable material for critical pressure vessel applications where structural integrity is essential. Plates that do not meet Class 1 standards may be reclassified as Class 2 if they meet the lower inspection requirements.
What is the difference between SA 387 Gr.22 Class 1 and Class 2?
The main difference is the level of ultrasonic inspection. Class 1 requires stricter UT to ensure fewer internal defects such as laminations or inclusions. Class 2 has more lenient inspection criteria. Class 1 is typically chosen for critical pressure vessel components where high reliability is essential, while Class 2 may be used in less critical areas.
How does SA 387 Gr.22 Cl 1 compare to carbon steel plates?
Unlike standard carbon steels, SA 387 Gr.22 Cl 1 contains chromium and molybdenum, which significantly improve its high temperature strength, creep resistance, and resistance to temper embrittlement. Carbon steels soften and lose strength at elevated temperatures, making them unsuitable for many pressure vessel and boiler applications where Gr.22 excels.
What is the difference between SA 387 Gr.22 Cl 1 and SA 516 Gr.70?
SA 516 Gr.70 is a carbon steel designed for low to moderate temperature pressure vessel service, while SA 387 Gr.22 Cl 1 is a Cr Mo alloy steel for high temperature applications. SA 516 Gr.70 offers good toughness at lower temperatures but lacks the creep strength and oxidation resistance of Gr.22. Gr.22 is used in refineries and power plants, while SA 516 Gr.70 is common in storage tanks and low temperature vessels.