ASTM A387 Gr11 vs Gr22: Which Steel Is Better Suited for Your Project?

20 10 月, 2025

Introduction

ASTM A387 Gr11 and Gr22 are common choices when selecting alloy steels suitable for high temperature and high pressure applications. These chromium-molybdenum steels are designed for pressure vessels, boilers, and piping systems used in a wide range of applications in the petrochemical, oil and gas, and power generation industries. So which steel is better for your project? This article will compare the chemical composition, mechanical properties, application scenarios and key selection factors of ASTM A387 Gr11 and Gr22 to help you optimise performance, ensure safety and reduce costs.

Comparison of Chemical Composition and Mechanical Properties

chemical composition

ASTM A387 The main difference between Gr11 and Gr22 is their alloying elements, which directly affects corrosion and high temperature resistance.

Gr11(Class 2):Containing about 0.94-1.56 per cent chromium (Cr) and 0.40-0.70 per cent molybdenum (Mo), carbon (C) is 0.04-0.17 per cent, manganese (Mn) is 0.35-0.73 per cent, silicon (Si) is 0.44-0.86 per cent, and the content of phosphorus (P) and sulphur (S) are not more than 0.035 per cent. This composition provides good weldability and moderate oxidation resistance.
Gr22(Class 2):The chromium content is higher at 1.88-2.62 per cent, molybdenum 0.85-1.15 per cent, carbon 0.04-0.15 per cent, manganese 0.25-0.66 per cent, silicon not exceeding 0.50 per cent, and phosphorus and sulphur contents are similar. Higher Cr and Mo enhance creep resistance and high temperature stability.

Although the alloy bases of the two are 99 per cent similar, the higher alloy content of Gr22 makes it a better performer in harsh environments.

Mechanical Properties

Both steels are available in Class 1 and Class 2, with Class 2 having a higher tensile strength due to normalising and tempering.

Gr11(Class 2):It has a tensile strength of 75-100 ksi (515-690 MPa), a yield strength of 45 ksi (310 MPa), and an elongation of at least 18% (2 inches). It has a minimum tempering temperature of 1150°F (621°C) and is suitable for environments up to about 1000°F.
Gr22(Class 2):Tensile strength (75-100 ksi) and yield strength (45 ksi) are similar to those of Grade 11, but fracture strength at elevated temperatures is superior, e.g., 38 MPa for long term use at 600°C. With a minimum tempering temperature of 1250°F (677°C), it can withstand even higher temperatures.

In terms of workability, both require post-weld heat treatment, but Gr22 requires a higher tempering temperature, which may increase manufacturing costs. For more on mechanical testing, see The American Society of Mechanical Engineers.

Comparison of Application Scenarios for ASTM A387 Gr11 and Gr22

ASTM A387 Grade 11 is suitable for moderately high-temperature environments such as pressure vessels, heat exchangers, and piping handling sour gases or hydrogen sulfide at temperatures up to 1000°F (538°C) in refineries and chemical plants.

Gr22 excels in more demanding scenarios such as power plant boilers, steam turbines and petrochemical reactors operating at temperatures in excess of 1,000° F. Its superior resistance to creep and oxidation makes it the preferred choice for the fossil fuel and nuclear industries.

Key factors in selection

The temperature range of the project is key: if the temperature is below 1100°F, Grade 11 is more cost-effective, saving material costs while maintaining safety. At higher temperatures or in hydrogen-rich environments, Gr22’s resistance to hydrogen embrittlement is more worth the investment.
Also, consider weldability – Gr11 is easier to work with – and compliance with ASTM specifications.

Conclusion

In ASTM A387 Gr11 vs Gr22, there is no absolute “better” choice – it’s all about the project’s needs: Gr11 is suitable for standard high-temperature applications, combining economy and versatility, while Gr22 offers superior durability in extreme conditions. By evaluating temperature, pressure and environmental factors, you can select the most suitable steel to ensure long-term performance and efficiency.

For expert advice, contact Henan Hennes.Our dedicated team offer free quotes and bespoke advice. Choosing the right steel plate not only improves efficiency but also ensures safety. Act now to optimise your industrial applications!