Can cast iron be used as pressure-bearing components in hydrogen-rich environments?
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1. Can cast iron be used as a pressure-bearing component in hydrogen-containing environments? Especially in environments with temperatures above 200°C. Is cast iron prone to hydrogen embrittlement or hydrogen attack?
Cast iron has a high carbon content, poor plasticity, uneven microstructure, and poor weldability； Cast iron also has lower tensile strength, plasticity, and toughness compared to carbon steel, and it is considered a brittle material. Therefore, HG/T20531 \"Cast Steel and Cast Iron Vessels\" stipulates that they shall not be used for pressure vessel components that are intended to hold media with an extremely high, high, or moderate degree of toxicity as well as flammable media, nor for components of non-pressure vessels with a pressure of 0.05 MPa or higher; they also shall not be used for pressure components in shell-and-tube waste heat boilers. For carbon steel and alloy steel equipment and pipelines operating at temperatures of 200°C or higher, with hydrogen present in the medium, appropriate hydrogen-resistant steel materials should be selected by adding a margin of 20–40°C to the highest operating temperature, taking into account the partial pressure of hydrogen in the medium; refer to SH/T 3059-2012 \"Code for Selection of Materials for Designing Petrochemical Pipelines\" and Appendix C of SH/T 3075-2009 \"Code for Selection of Materials for Steel Pressure Vessels in Petrochemical Industries\" for the Nelson curve.
This post was last edited by dodoren on 2017-6-14 at 15:33. Thank you very much; I’ll download the materials to see why cast iron can’t be used for applications involving toxicity
Cast iron has a high carbon content, poor plasticity, uneven microstructure, and poor weldability； Its tensile strength, plasticity, and toughness are also lower than those of carbon steel. Since cast iron is a brittle material, once it fractures, it breaks into fragments, resulting in tremendous destructive force ； If containing toxic substances, the risk of use will be even greater. Pressure vessels are hazardous devices; materials with high plasticity and high toughness are chosen to ensure safety during use. Therefore, HG/T 20531 \"Cast Steel and Cast Iron Vessels\" stipulates that they shall not be used as pressure-bearing components in pressure vessels intended to hold media with an extremely high, high, or moderate degree of toxicity or flammable media, nor as components in non-pressure vessels with a pressure of 0.05 MPa or higher; they shall also not be used as pressure-bearing components in shell-and-tube waste heat boilers. Regarding this, ** and industry standards both stipulate this.