Dear teachers, I would like to learn more about the information related to these two materials: TP347 and TP347H

I earnestly implore those who know how to teach me! ! !

It’s probably under hydrogen-rich conditions; it definitely differs from normal situations, as carbon deposition occurs. If the carbon content is too low, the strength of the pipes will be insufficient

Thank you for your reply. Which book does the standard you mentioned refer to? Could you please explain this? I work as a purchaser for a supplier that does business with factories, and sometimes I need to learn about certain things on the spot. I checked the stainless steel application manual; these two grades are part of the American standards. The carbon content in 347C is 0.08 or less, while in 347H it ranges from 0.04 to 0.1. Some other sources state that the carbon content in 347 is exactly 0.08, whereas the carbon content in 347H is within a range. According to this manual, 347H is more resistant to high temperatures, but the carbon content range for 347H already includes the carbon content range for 347. What’s the reason for this? Do you know about it? Do you have any information on the prices of these two grades of material as well as the production situation in China?

Thank you for responding and providing some ideas. The plant operates in the petrochemical industry, and based on the suggestions you gave, it seems that the application does not involve hydrogen-rich environments. The plant requires pipes made of material 347; however, during the procurement process, it was found that this material is quite rare, while 347H is more available. Both pipe manufacturers and suppliers claim that these two materials are essentially the same, but regarding prices, some say that 347 is cheaper than 347H, while others say the prices are identical. I would like to ask you for your opinion on this matter

This post was last edited by yjaigtt on 2019-3-28 at 17:40. The original poster is absolutely correct; these two grades are part of the American standards. The carbon content in 347C is less than or equal to 0.08, while the carbon content in 347H ranges from 0.04 to 0.1. However, there is no specified minimum limit for the carbon content in 347. When it is used in high-temperature conditions (such as 538°C and above), if no minimum requirement is set for the carbon content in 347, its high-temperature resistance cannot be guaranteed; in such cases, 347H is a more suitable choice.

Please refer to the standard ASTM A312, which contains relevant information; I hope it will be helpful to you~

TP347 has the UNS designation S34700, while TP347H has the UNS designation S34709. ASTM 312 specifies that TP347H is a variant of TP347, and it is more suitable for temperatures where creep and fatigue resistance are particularly important. The specific differences are as follows: in terms of chemical composition, TP347 has a carbon content of 0.08 or less, whereas TP347H has a carbon content ranging from 0.04 to 0.10. Additionally, for both grades, the niobium content must be at least ten times the carbon content, but not exceed 1%. Based on the heat treatment requirements, TP347H requires a heat treatment temperature of not less than 1100°C for cold working, and not less than 1050°C for hot working; (for 347, this value is not specified, so it should be not less than 1040°C). Based on the grain size requirements, TP347H requires a grain size of 7 or coarser. For other distinctions, experts are welcome to add more

Thank you for your reply; it has helped me understand the details. Thank you