What does dual-grade austenitic stainless steel mean?

Literally, there are countless types of materials with multiple grades; almost all of them can be considered as such, and it’s also possible to speak of three grades, four grades, and so on. I think what is meant here is that there is a comparison table between old and new grades, as well as between Chinese and American grades, for materials that have slight differences in their properties.

Dual-grade austenitic stainless steel is a type of austenitic stainless steel that features two different standard grades; these grades generally refer to the corresponding grades under various standards in different **regions, and it is designed to meet certification requirements in multiple regions. For example, 304 and 1.4301, 316 and 1.4401, etc. .

It is also known as double-standard steel. That’s 304/304L. Also, may I ask in which reference was the photo taken? Thank you

It’s such a pointless effort; since it’s being formulated anew, it’s naturally supposed to have better performance than the two previous versions – otherwise why go through the trouble of formulating it?

The last edit to this post was made by AMAN04 on 2025-4-8 at 09:09. The document states that with the rapid development of the chemical and petrochemical industries, there is an increasing demand for stainless steel materials, and the requirements for these materials are becoming more stringent; it is necessary to ensure both their corrosion resistance and compliance with the specified strength requirements. With the advancement of stainless steel smelting technology, the mechanical properties of stainless steel have improved significantly. For example, the 304L stainless steel produced by a certain company (with a carbon content well below 0.03%) has strength values that exceed the lower limit for 304 stainless steel; such stainless steel can therefore be classified as 304/304L dual-grade stainless steel. In other words, its chemical composition meets the requirements of 304L, while its mechanical properties satisfy those of 304 stainless steel. Similarly, there are also dual-grade stainless steels such as 316/316L. Studies indicate that dual-grade stainless steel possesses the high strength of conventional stainless steels as well as the corrosion resistance of ultra-low carbon stainless steels. The use of two different grades of stainless steel can address the issue of weakened weld joint properties in most austenitic stainless steels currently in use. At present, dual-grade stainless steel is widely used abroad, and it is beginning to be adopted in the equipment of low-temperature LNG receiving stations as well as in large-diameter pipelines in China. The prices of dual-grade stainless steels and ultra-low carbon stainless steels are roughly the same, and domestic steel mills can supply them in part at present. References: Wu Ruiping, Wang Tianxian, Wang Wenli, et al. Comparative analysis of the properties of SA-240 304/304L dual-grade stainless steels and 304/304L stainless steels. Welding, 2017, (10). Zhang Guoxin, Su Yue. Outlook on the future development trends of metal materials used in petrochemical equipment. Petrochemical Corrosion and Protection, 2018, 35(3). ——————From “WeChat official account” – “Rousseau Talks about Pressure Vessels””

S30408/304, S30403/304L – these are stainless steels with two different grades

The standards make it clear that there is a type of steel that meets the requirements for ultra-low carbon corrosion resistance as well as low carbon high-temperature resistance; examples include 304/304L and 316/316L. These steels possess the ultra-low carbon corrosion resistance of 304L and 316L, along with the high-temperature performance of 304 and 316. In simple terms, it involves using a technique to endow steel with ultra-low carbon properties while also giving it the high-temperature performance of low-carbon steel.

It should be a duplex austenitic stainless steel. It refers to a material in which ferrite and austenite each account for about 50%, combining the properties of both austenitic and ferritic stainless steels. Its main feature is that its yield strength can reach 400–550 MPa, which is twice that of ordinary stainless steels; as a result, it allows for reduced material usage and lower costs in equipment manufacturing. In terms of corrosion resistance, especially in harsh medium environments such as seawater with high chloride content, duplex stainless steel exhibits significantly better performance against pitting corrosion, crevice corrosion, stress corrosion, and corrosion fatigue compared to ordinary austenitic stainless steels, and can rival highly alloyed austenitic stainless steels. Such as 00Cr22Ni5Mo3.

Dual grade refers to meeting (being in compliance with) two standards simultaneously. Dual-grade austenitic stainless steel refers to stainless steel that meets the requirements of two different grade standards at the same time, such as 304/304L, 316/316L. It should be noted that 304 or 304L is not considered dual-grade stainless steel; rather, it is the stainless steel that satisfies both the 304 and 304L standards.

The photo is from GB/T20801.2-2020, PAGE 8