ThePipingMart Blog Grades 309H Stainless Steel (UNS S30909) – Composition, Properties, and Uses

309H Stainless Steel (UNS S30909) – Composition, Properties, and Uses

309H Stainless Steel

Looking for a strong, versatile stainless steel material? Then you should consider using 309H stainless steel. This stainless steel is made up of chromium, nickel, and iron but has high levels of carbon. It is known for its excellent resistance to corrosion, oxidation, and heat. In this blog post, we will discuss the composition, chemical properties, physical properties, uses, corrosion resistance, and heat resistance of 309H ss, as well as its machining and welding options.

309H Stainless Steel Composition

The composition of 309H ss is 19% chromium (Cr), 13% nickel (Ni), 2% manganese (Mn), 1% silicon (Si), and 0.45% carbon (C). This combination makes it an ideal material for many applications that require high-level performance in areas such as extreme temperatures or corrosive environments.

Element Content (%)
Iron, Fe 60
Chromium, Cr 23
Nickel, Ni 14
Manganese, Mn 2
Silicon, Si 1
Carbon, C 0.20
Phosphorous, P 0.045
Sulfur, S 0.030

309H Stainless Steel Chemical Properties

Due to its high chromium content, 309H stainless steel has good oxidation and corrosion resistance in comparison to other materials. Additionally, it is also extremely resistant to pitting and crevice corrosion due to its high nickel content, which helps protect the material from attack by acids and other aggressive chemicals. Its carbon content also ensures excellent weldability, which further adds to its versatility as a material.

309H Stainless Steel Mechanical Properties

Stainless steel 309H is a high-temperature-resistant alloy that has excellent mechanical properties. It has good strength and resistance to high temperatures and corrosion. It maintains these properties up to about 1150°C. Furthermore, 309H stainless steel has excellent hot formability, meaning that it can be satisfactorily bent and formed into certain shapes without cracking or breaking. This makes the alloy very suitable for parts that must withstand dynamic loads or be exposed to high heat. Overall, 309H stainless steel has robust mechanical properties, making it an ideal alloy for many applications in construction and other industries.

Yield Strength
0.2% Offset
Ultimate Tensile
in 2 in.
psi (min.) (MPa) psi (min.) (MPa) % (min.) (max.)
45,000 310 85,000 586 50 202 (HBN)

309H Stainless Steel Physical Properties

309H ss has a tensile strength of 515 MPa, while its yield strength is 260 MPa. Its density is 8 g/cm3 with an elongation at a break of 35%. It has a hardness of 217 HBW, which makes it an excellent choice for applications that require wear-resistance properties, such as valves or pumps. Its melting point is 1450°C (2642°F) which allows for easy welding and forming processes when compared with other materials such as titanium or aluminium alloys.

309H Stainless Steel Equivalent

  • UNS S30909
  • ASTM A240
  • ASTM A480
  • ASME SA240
  • AMS 5523

309H Stainless Steel Uses

Some common uses for 309H stainless steel include medical equipment parts due to its excellent corrosion resistance in wet environments; exhaust systems due to its ability to withstand high temperatures; furnace components due to its heat-resistant properties; valve components due to its wear-resistant properties; pressure vessels where welding needs to be done with ease; process piping due to its low thermal expansion coefficient; and even kitchen appliances due to its non-magnetic properties when cold formed or welded properly.

Corrosion Resistance

Since it contains 19% chromium, this alloy offers great protection against oxidizing agents like nitric acid or sulfuric acid, which can cause pitting or crevice corrosion over time if not protected properly against them. Additionally, it also offers good protection against general corrosion caused by exposure to saline solutions or seawater due to its nickel content which helps prevent attack by chlorides or bromides in seawater environments.

Heat Resistance

With a melting temperature of 1450°C (2642°F), this alloy can resist exposure at very high temperatures without losing any mechanical property characteristics, making it suitable for use in furnace components or process piping where extreme temperatures are present on a regular basis. It also provides good creep strength at elevated temperatures ensuring no structural damage occurs when exposed over long durations at high temperatures, making it an ideal choice for applications where durability under extreme conditions is required, such as valves used for cryogenic liquids transfer systems or gas turbine engines blades used in aviation industry engines operating at high altitudes that require reliable performance even under extreme conditions found there.

Heat Treatment

Heat treatment of 309H Stainless steel is an important part of ensuring its strength, toughness and resistance to corrosion. Through this technique, it can be hardened or made softer, allowing engineers and mechanics to tailor the material to suit the needs of various applications. By correctly controlling heat treatment time and temperature, 309H Stainless steel can achieve excellent mechanical characteristics while maintaining its corrosion resistance. With such a high degree of malleability and controllability, this type of stainless steel offers a great deal of flexibility in manufacturing processes that require extremely strong yet malleable metals.


Machining 309H stainless steel is an intricate process that requires experienced professionals and the use of modern high-performance tools. This type of steel is especially resistant to numerous forms of corrosion, making it ideal for a wide range of industrial applications. To achieve its desired strength and resistance, 309H stainless steel is often heat-treated with great precision. When machining this type of steel, it is critical to use the right combination of cutting speeds, feed rates and a variety of specialized tooling depending on the end goals of the project. Experienced machinists make use of today’s highly advanced machines that allow for tight tolerances and higher production yields over traditional methods. By knowing the requirements for working with 309H steel and using modern machinery, machinists are able to produce high-quality parts in record times.


Welding of 309H Stainless steel presents a big challenge to fabricators and engineers alike. It is a high-carbon version of 309 stainless steel and is often used in situations where corrosion resistance is key. However, when welding it, the temperature has to be regulated carefully. If too hot, the part may lose its corrosion resistance; if too cold, cracking may occur. It’s important for welders to have extensive experience with this type of material in order to select the correct welding rod and ensure proper pre-heating temperatures. In addition, welders must pay extra attention to cleaning and post-weld heat treatment to minimize the risk of cracking or distortion of the final product. Ultimately, there is no room for error when it comes to welding 309H Stainless steel, as even small mistakes can lead to costly repairs or replacement parts – ultimately resulting in significant time and labour expenses.


In conclusion, 309H Stainless Steel offers excellent performance characteristics, including good oxidation and corrosion resistance as well as good creep strength at elevated temperatures making it a highly versatile material suitable for many different types of applications ranging from furnace components through medical equipment parts all the way up into aerospace applications where reliability under extreme conditions is an essential requirement. Combined with easy machining and welding options available, this alloy can be considered one of the best choices when looking into materials that offer superior performance characteristics combined with ease of use during manufacturing processes.

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