Should heat treatment be carried out at a hydrogen partial pressure of 0.0113 MPa(A)?
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Does equipment designed for a temperature of 400 degrees with a hydrogen partial pressure of 0.0113 MPa(A) require heat treatment? The medium is quench oil/cracking gas, with a diameter of DN7800. Thank you!
The limitations regarding the use of materials in hydrogen-corrosion environments are specified in HG/T 20581-2011 \"Requirements for the Selection of Materials for Steel Chemical Vessels\": (1) When the design temperature of a chemical pressure vessel is 200°C or higher, and it is in contact with a hydrogen atmosphere, it is considered to be in a hydrogen-corrosion environment. (2) The usage limitations of carbon steel and pearlitic heat-resistant steel in a hydrogen atmosphere are shown in the figure below. (3) In a hydrogen corrosion environment, if other factors such as high-temperature sulfur corrosion, high-temperature creep, the synergistic effect of creep and hydrogen corrosion, and temper embrittlement are also present, the impact of these factors on the high-temperature mechanical properties of the steel should also be considered. (4) The condition of steel in a hydrogen corrosion environment shall comply with the standard requirements, and stress-relief heat treatment shall be carried out after welding. (5) Austenitic stainless steel will not suffer from hydrogen corrosion when used at the temperatures and hydrogen partial pressures shown in the figure below, and therefore no post-weld heat treatment is required.
Does the hydrogen partial pressure also contribute to hydrogen corrosion off-line? The material is Q345R.
The hydrogen partial pressure depends on the pressure of the reaction system and the purity of hydrogen. An increase in the hydrogen partial pressure is beneficial for catalytic reactions, as it can suppress coking reactions and reduce the rate of catalyst deactivation； On the other hand, it can improve the removal rates of HDS, HDN, and HDM, while also promoting the hydrogenation and saturation of polycyclic aromatic hydrocarbons. Therefore, the hydrogen partial pressure in the reaction system should be increased as much as possible within the limits permitted by the equipment and operations. Ways to increase the hydrogen partial pressure in the reaction system are: 1) Increase the pressure of the entire system ； 2) Improve the purity of new hydrogen ； 3) Increase the flow rate of recycled hydrogen ； 4) Improve the purity of recycled hydrogen ； 5) Increase the emission of waste hydrogen. 6) Reduce the amount of low-pressure gas sent to the inlet of the new hydrogen machine.
Still no hit. . . . . . . .
Heat treatment is required; refer to the Nelson curve.
The last edit to this post was made by nj1952 on 2017-8-7 at 21:24. Reply to post #4: (1) The curve showing the limitations for the use of carbon steel and pearlitic heat-resistant steel in hydrogen atmospheres, as referenced in HG/T 20581-2011 \"Specifications for the Selection of Materials for Steel Chemical Containers\", is the Nelson curve. In 1949, Nelson from the United States, based on his experience in production practices and experimental research, established the operating limits for carbon steel and certain low-alloy steels in hydrogen-containing environments; this curve is what is commonly known as the Nelson curve. These curves specify the safety limits for using various steels at different temperatures and hydrogen partial pressures; that is, steel can be used safely for any length of time at temperatures and hydrogen partial pressures below its Nelson curve. This set of curves was subsequently supplemented and revised several times based on new practical experience. The Nelson curve provides an important basis for material selection and safety assessment of hydrogen-related equipment under actual production conditions. (2) Note: In accordance with GB 150-2011 \"Pressure Vessels\", when the thickness of Q345R material plates exceeds 32 mm, post-weld heat treatment is required.