Questions regarding the additional technical requirements for Cr-Mo steel plates in hydrogenation equipment

This post was last edited by zhangjuhua on 2019-2-21 at 13:09. 1. A high hydrogen partial pressure facilitates aggregation, leading to hydrogen embrittlement; CrMo steel, which is commonly used to resist hydrogen effects, is prone to delayed cracking or reheat cracking. Good toughness of the base material helps prevent the occurrence of cracks. The requirement for low-temperature impact testing at -20°C is likely due to the significant impact of low temperatures on toughness and strength, as well as the increased demands on material properties under harsh operating conditions. Passing low-temperature impact tests indicates sufficient toughness reserves, which will be even better at higher temperatures. It’s not clear whether standards and specifications specify any requirements regarding impact resistance for materials used in hydrogen-rich environments. 2. It seems what the original poster said makes sense

Low-temperature shock treatment is primarily aimed at preventing temper brittleness in high-CrMo steels. Cladding is used mainly for 14Cr1MoR, which is typically employed in high-temperature environments; under such conditions, composite sheets are rarely chosen. Although the bonding process in composite sheets can be considered similar to welding, factors such as delamination still need to be taken into account, which is why cladding is given higher priority. If you want to learn more about this, it is recommended to consult API RP934-A, C, E and API TR 934B, D – these are the international requirements for high-temperature, hydrogen-resistant molybdenum steel.

Thank you. I have no experience with high-temperature hydrogenation equipment, so this example seems quite challenging. At 150, only the requirements for high-temperature tensile testing were found.

Thank you. :Handshake has no experience with high-temperature hydrogenation equipment; it’s time to study this properly!

1. Why is it necessary to consider low-temperature toughness requirements? Chromomolybdenum steel has a certain tendency to become brittle upon tempering, and some books state that the brittleness occurs at relatively low temperatures, in the range of around -100 degrees Celsius at room temperature. Therefore, stricter requirements for low-temperature toughness are proposed; if the toughness reserve at low temperatures is sufficient, toughness will still be ensured even within the temperature range where temper embrittlement occurs. 2. In situations with high hydrogen partial pressure, surfacing welding is advisable. Was the strong permeability of hydrogen taken into account? Mainly, the thermal expansion coefficients of carbon steel and stainless steel are different, and the adhesion of the composite plate at high temperatures is not as reliable as that of a surfacing structure.

The original poster should take a look at the standard GB/T30579-2014 \"Identification of Damage Modes in Pressure Equipment\". First question: Why use stainless steel cladding? According to the Nelson curve, carbon steel and low-alloy steel suffer from high-temperature hydrogen corrosion when operating at temperatures above 200°C; hydrogen enters the steel and captures C atoms to form CH4, which in turn leads to defects such as bulging and cracking ； Using stainless steel to separate hydrogen from low-alloy steel is a good method to avoid hydrogen-induced corrosion. Composite panels are not used because their actual production is likely to be limited. Second question: Why consider low-temperature toughness? I think it’s just a passage added by the author casually, as the quality of low-temperature toughness has only a limited impact on preventing temper brittleness in Cr-Mo steels; to avoid temper brittleness, it is still necessary to control the levels of harmful elements such as sulfur, phosphorus, arsenic, and antimony.

:Thank you for the handshake!

This post was last edited by kareale88 on 2019-2-25 at 15:41. Although Cr-Mo steel is used in high-temperature environments, the temperature changes that can occur due to sudden shutdowns must also be taken into account; therefore, the steel needs to have a certain degree of toughness.

May I ask the original poster where you got your picture? I was also looking for this information a few days ago; I remember having seen it in a book, but I can’t find it now. I just don’t know whether it’s from a training manual for pressure vessel engineers or from a design guide for them