What is SA 387 GR 22-1 material?

SA 387 Grade 22 Class 1 is a chromium‑molybdenum (Cr‑Mo) alloy steel plate specified in the ASME Boiler and Pressure Vessel Code, primarily used for pressure vessels, boilers, and other high‑temperature, high‑pressure equipment in the oil and gas, petrochemical, and power generation industries. It contains approximately 2.25% chromium and 1% molybdenum, which provide excellent high‑temperature strength, creep resistance, and oxidation resistance, as well as good toughness and weldability when properly heat treated. The steel is typically processed through electric arc furnace melting, ladle refining, vacuum degassing, controlled rolling, and a heat treatment cycle of normalization followed by tempering to achieve a fine‑grained microstructure and stable mechanical properties. The "Class 1" designation indicates that the plate must meet stricter ultrasonic inspection requirements to ensure high internal soundness, making it suitable for critical pressure‑retaining applications where reliability and structural integrity are essential.

process flow

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.

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 Which standards apply to this material?

SA 387 Gr.22 Cl 1 is covered by the ASME Boiler and Pressure Vessel Code. It is listed in ASME Section II, Part A (SA-387) and is referenced in other sections such as Section VIII (Pressure Vessels) and Section I (Power Boilers). The material must also comply with additional requirements for chemistry, mechanical properties, and NDT as specified in these codes.

What are its common applications?

SA 387 Gr.22 Cl 1 is widely used in the oil and gas, petrochemical, and power generation industries. Typical applications include pressure vessels, boilers, heat exchangers, reformer tubes, and other equipment that operates under high temperature and pressure. It is especially suitable for parts exposed to hydrogen-rich environments and high-temperature steam.

How is it welded?

SA 387 Gr.22 Cl 1 can be welded using common processes such as SMAW (stick), GMAW (MIG), FCAW, and SAW. The choice of filler metal is important and usually involves matching Cr-Mo compositions, such as E8018-B2 or ER80S-B2. Proper preheating and post-weld heat treatment (PWHT) are essential to prevent cold cracking and ensure good mechanical properties in the heat-affected zone (HAZ).

Why is preheating needed for welding?

Preheating is necessary to reduce the cooling rate of the weld and HAZ, which helps prevent the formation of hard, brittle microstructures that can lead to cracking. It also helps remove moisture from the joint area, reducing hydrogen pickup. Typical preheat temperatures range from 150–250°C, depending on plate thickness and welding process. Thicker plates generally require higher preheat temperatures.

What NDT is performed on these plates?

SA 387 Gr.22 Cl 1 plates undergo rigorous non-destructive testing. The primary requirement is ultrasonic testing (UT) to ensure internal soundness, as specified for Class 1. Additional inspections may include visual inspection (VI) for surface quality, magnetic particle testing (MT) for surface cracks in ferromagnetic materials, and liquid penetrant testing (PT) for detecting surface discontinuities. Some applications may also require radiographic testing (RT) depending on design and customer specifications.

How does SA 387 Gr.22 Cl 1 differ from SA 387 Gr.11?

SA 387 Gr.22 Cl 1 has a higher chromium content (around 2.25% Cr) compared to SA 387 Gr.11 (around 1.25% Cr). This gives Gr.22 better high

temperature strength, creep resistance, and oxidation resistance, making it suitable for more demanding pressure vessel applications. Gr.11 is often used at lower temperatures and in less severe services where cost is a consideration.

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 is the difference between SA 387 Gr.22 Cl 1 and SA 537 Cl 1? 

SA 537 Cl 1 is a carbon manganese silicon steel used for moderate temperature pressure vessel applications, while SA 387 Gr.22 Cl 1 is a Cr Mo alloy steel designed for higher temperatures. SA 387 Gr.22 Cl 1 offers superior creep resistance and oxidation resistance compared to SA 537 Cl 1. SA 537 is often used in boilers and pressure vessels at lower temperatures, while Gr.22 is preferred for refinery and petrochemical equipment operating at higher temperatures.