What is the difference between SA 387 Grade 11 CL 1 and SA 387 Grade 11 Class 2?

2026-08-07 | More News

SA387 Grade 11 is a chromium-molybdenum low-alloy steel specially manufactured for high-temperature service in boilers and pressure vessel systems. It is categorized into two standard classes: Class 1 (CL1) and Class 2 (CL2). While both grades share identical chemical compositions per ASME SA-387/SA-387M specifications, they differ significantly in heat treatment processes, mechanical performance, low-temperature toughness and industrial application scenarios.

1. Chemical Composition: Do SA387 Gr11 CL1 and CL2 have different chemical elements?

SA 387 Grade 11 CL1 and CL2 feature exactly the same chemical component specifications with no dimensional or compositional differences. The standardized composition range and the functional purpose of each element are listed below:

Element	Composition Range (%)	Core Purpose
Carbon (C)	0.15–0.25	Balances structural strength and welding performance of the steel plate
Manganese (Mn)	0.40–0.65	Improves material hardenability and overall structural uniformity
Phosphorus (P)	≤0.030	Strictly limited to prevent material brittleness and fracture risks
Sulfur (S)	≤0.030	Controlled within a narrow range to ensure stable machinability and pressure vessel safety
Silicon (Si)	0.15–0.35	Acts as a deoxidizer during steelmaking and strengthens ferrite structure
Chromium (Cr)	1.00–1.50	Enhances high-temperature oxidation resistance and thermal stability
Molybdenum (Mo)	0.45–0.65	Provides critical high-temperature creep resistance, the core alloy element for high-temperature service
Nickel (Ni)	≤0.30	Optional auxiliary alloying element with limited content control

2. Mechanical Properties: What are the strength and toughness differences between CL1 and CL2?

The core distinctions between SA387 Grade 11 CL1 and CL2 lie in mechanical property indicators. Class 2 delivers higher strength and better low-temperature toughness, while Class 1 offers qualified ductility for conventional working conditions. Detailed standardized parameters are as follows:

Mechanical Property	Class 1 (CL1)	Class 2 (CL2)
Tensile Strength (MPa)	415 – 585	450 – 600
Minimum Yield Strength (MPa)	240	275
Elongation (50 mm gauge length)	≥ 22%	≥ 22%
Elongation (200 mm gauge length)	≥ 18%	≥ 19%
Charpy Impact Test	Tested per customized project requirements	Mandatory low-temperature impact testing (e.g., -20°C, -40°C) for guaranteed low-temperature toughness

3. Heat Treatment Specifications: Why do CL1 and CL2 have different performance?

Different heat treatment processes are the fundamental reason for the performance gap between the two classes of SA387 Grade 11 steel:

SA387 Grade 11 Class 1

Class 1 steel plates are typically supplied in as-rolled condition without additional heat treatment. The natural mechanical properties formed during hot rolling can meet the basic strength requirements of conventional equipment. This untreated state is suitable for scenarios that do not require ultra-high toughness or stress relief treatment.

SA387 Grade 11 Class 2

Class 2 steel plates are supplied after standardized normalized and tempered (N+T) or quenched and tempered (Q+T) heat treatment. The precise thermal processing refines the internal grain structure of the steel, effectively improving material strength, low-temperature toughness, thermal fatigue resistance and structural stability. It eliminates internal residual stress and is tailored for severe high-temperature and high-pressure working conditions.

4. Typical Industrial Applications: Where to use SA387 Gr11 CL1 and CL2 respectively?

SA387 Grade 11 Class 1 Applications

CL1 steel is widely used for general-purpose pressure vessels, low-to-medium temperature boiler bodies and auxiliary supporting equipment. It is the preferred choice for conventional projects due to its cost-effectiveness and easy fabrication performance, fully meeting the mechanical strength demands of medium and low-load working environments.

SA387 Grade 11 Class 2 Applications

With higher strength, toughness and operational reliability, CL2 steel is applied in critical high-temperature and high-pressure equipment, including high-pressure boilers, industrial heat exchangers, chemical reactors and core pressure vessel components. It is extensively used in petrochemical, oil & gas and power generation industries where strict safety margins and long-term operational stability are required.

GNEE Steel provides a full range of standardized boiler and pressure vessel steel plates, including A204 Grade B, A515 Grade 70, A537 Class 1, SA387 Grade 11 Class 1, P265GH, S537 Class 2, P355Q, P275N, P355N, P690Q, Q345R and other mainstream grades. For product parameters, factory prices and customized service solutions, please contact our consultation hotline: +8615824687445, or send an inquiry email to [email protected]. We provide professional technical support and one-stop steel supply services.

FAQ

Q1: What is the core difference between SA 387 Grade 11 CL1 and CL2?

The two grades share identical chemical composition standards. The key differences lie in heat treatment processes and mechanical properties: CL2 has higher tensile strength, yield strength and low-temperature toughness, as well as better ductility at 200mm gauge length, while CL1 adopts as-rolled delivery for cost-effective conventional applications.

Q2: What is the equivalent material of SA 387 GR 11 CL2?

In the US market, it complies with the standard ASME SA387 Grade 11 Class 2 specification. The corresponding European equivalent grade is 13CrMoSi5-5, which matches its high-temperature and pressure resistance performance.

Q3: What is SA 387 GR 11 steel?

SA 387 Grade 11 is a 1.25Cr-0.5Mo silicon-containing chromium-molybdenum alloy pressure vessel steel. It features excellent high-temperature tolerance, creep resistance and oxidation resistance, and is specially developed for long-term high-temperature industrial service.

Q4: What is the difference between SA 516 GR 70 and SA 387 GR 11?

SA 516 GR 70 is a common carbon steel for pressure vessels, while SA 387 GR 11 is a chromium-molybdenum low-alloy steel. Compared with SA 516 GR 70, SA 387 GR 11 possesses far better high-temperature oxidation resistance, corrosion resistance and thermal stability, making it the optimal material for high-temperature working environments that carbon steel cannot adapt to.

Q5: What is the P number of SA 387 GR 11?

SA-387 Grade 11 steel has a UNS number of K11789 and a standard ASME P number of 4, which is the unified identification for welding procedure qualification in pressure vessel manufacturing.

Q6: What is SA 387M GR 22 CL2 material?

ASTM A387 GR 22 CL2 is another high-grade chromium-molybdenum alloy steel under the same standard series. Composed of carbon, manganese, chromium, molybdenum, silicon and other elements, it features high tensile strength, stable yield performance and excellent section shrinkage, suitable for more extreme high-temperature and high-pressure industrial scenarios.

What steel plate products does GNEE Steel supply?

Product Category	Material Grade	Specification (mm)	Stock/Tonnage	Product & Test Remark
Clad Steel Plate	P265GH+410, S355JR+410, A516Gr70+316, A537CL1+304L, Q235B+304L, Q345B+304, A516Gr70(NACE)+410, A537CL1+904L, A537CL1+316L, A516Gr70+304L, A516Gr70+410, A516Gr70+904L	Base plate: 2–300mm; Composite layer: 1–50mm	Customizable	UT inspection, AR/TMCP process, normalized/quenched & tempered treatment, Z-direction test, Charpy V-notch impact test, third-party inspection, shot blasting and painting service available
Low Alloy Steel Plate	Q345A, Q345B, Q345C, Q345D, Q345E, Q390, Q420, Q460C, ST52-3, S355J2+N, SS400, SA302GrC, S275NL, 35CrMo	6–350mm	5788.56 tons	Normalizing, tempering, controlled rolling and hot rolling; multi-level factory inspection
Pressure Vessel Plate	A204 Grade B, A515 Grade 70, A537 Class 1, SA387 Grade 11 Class 1, P265GH, S537 Class 2, P355Q, P275N, P355N, P690Q, Q345R	3–300mm	8650 tons	Normalizing, tempering, hot rolling and controlled rolling; full standard factory inspection
High-Strength Steel Plate	A514 Grade F, A572 Grade 50, A588 Grade A, S355JR, S690Q, SS400, S690QL, Q345B, Q345E	8–120mm	3086.352 tons	Quenched and tempered heat treatment for high structural strength
Wear-Resistant Steel Plate	NM360, NM400, NM450, NM500	6–150mm	3866.297 tons	Professional quenched and tempered process for excellent wear resistance
Shipbuilding Steel Plate	ABS AH32, ABS DH32, ABS EH32, ABS FH36, ASTM A131 A, ASTM A131 EH32, ASTM A131 AH36, CCS A, CCS AH32, LR AH32, DNV A36, BV AH32	8–200mm	2853.621 tons	Hot rolling, normalized controlled rolling, quenched and tempered treatment; guaranteed toughness and brittle fracture resistance

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What is the difference between SA 387 Grade 11 CL 1 and SA 387 Grade 11 Class 2?

1. Chemical Composition: Do SA387 Gr11 CL1 and CL2 have different chemical elements?

2. Mechanical Properties: What are the strength and toughness differences between CL1 and CL2?

3. Heat Treatment Specifications: Why do CL1 and CL2 have different performance?

SA387 Grade 11 Class 1

SA387 Grade 11 Class 2

4. Typical Industrial Applications: Where to use SA387 Gr11 CL1 and CL2 respectively?

SA387 Grade 11 Class 1 Applications

SA387 Grade 11 Class 2 Applications

FAQ

Q1: What is the core difference between SA 387 Grade 11 CL1 and CL2?

Q2: What is the equivalent material of SA 387 GR 11 CL2?

Q3: What is SA 387 GR 11 steel?

Q4: What is the difference between SA 516 GR 70 and SA 387 GR 11?

Q5: What is the P number of SA 387 GR 11?

Q6: What is SA 387M GR 22 CL2 material?

What steel plate products does GNEE Steel supply?

Product Processing

Raw Materials

Pressure Vessel and Boiler Steel Plate

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