Indices<\/strong><\/td>| Test standards<\/strong><\/td> | Typical value range<\/strong><\/td> | Influence mechanism of galvanizing<\/strong><\/td><\/tr> | Yield strength<\/td> | GB\/T 228.1<\/td> | Q235: 235-265MPa<\/td> | May lift 5-10% after galvanizing(work hardening) <\/td><\/tr> | Tensile strength<\/td> | GB\/T 228.1<\/td> | Q235: 375-500MPa<\/td> | No significant change<\/td><\/tr> | Elongation after fracture<\/td> | GB\/T 228.1<\/td> | Q235: \u226526%<\/td> | 2-5% reduction (zinc layer brittleness effect)<\/td><\/tr> | Reduction of area<\/td> | GB\/T 228.1<\/td> | Q235: \u226550%<\/td> | Down about 10%<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n | 2. Hardness and toughness<\/p>\n\n\n\n Surface hardness: zinc coating HV (Vickers hardness) is about 50-70, significantly lower than the steel itself (Q235 HBW\u2248120).<\/p>\n\n\n\n Impact toughness: -20\u2103 Charpy V-notch impact energy \u226527J (GB\/T 18984-2016), low-temperature toughness may decrease by 10-15% after galvanizing.<\/p>\n\n\n\n 3. Fatigue performance<\/p>\n\n\n\n Fatigue limit: The fatigue limit of smooth specimens is about 35-45% of the tensile strength. Defects in the galvanized layer (such as microcracks) may reduce the fatigue life by 15-20%.<\/p>\n\n\n\n III. Effect of process on performance<\/p>\n\n\n\n 1. Hot-dip galvanizing<\/p>\n\n\n\n Advantages: The zinc layer and the substrate form a Fe-Zn alloy layer (thickness 5-15\u03bcm), and the bonding force is \u226535N\/cm (GB\/T 2694-2018).<\/p>\n\n\n\n Disadvantages: High temperature (450\u2103) treatment may cause grain coarsening and a decrease in elongation of 5-8%.<\/p>\n\n\n\n 2. Electrogalvanizing<\/p>\n\n\n\n Advantages: No high temperature effect, maintaining the original mechanical properties of the substrate.<\/p>\n\n\n\n Disadvantages: The zinc layer has weak adhesion (cross-cut test \u22654B level), and the corrosion resistance is only 1\/3-1\/2 of hot-dip galvanizing.<\/p>\n\n\n\n 4. Performance requirements for typical application scenarios<\/p>\n\n\n\n 5. Standards and test methods<\/p>\n\n\n\n 1. International standards<\/p>\n\n\n\n ASTM A53: The yield strength of galvanized steel pipes is \u2265250MPa (Grade B) and the minimum elongation is 18%.<\/p>\n\n\n\n EN 10217-1: The thickness of the hot-dip galvanized layer is required to be \u226585\u03bcm, and the impact test temperature is -20\u2103.<\/p>\n\n\n\n 2. Chinese standards<\/p>\n\n\n\n GB\/T 3091-2015: The uniformity test of the galvanized layer is \u22655 times of copper sulfate immersion without red rust.<\/p>\n\n\n\n GB\/T 13793-2016: The flattening test of the straight seam electric welded steel pipe is pressed to 1\/3 of the outer diameter without cracks.<\/p>\n\n\n\n 6. Performance optimization direction<\/p>\n\n\n\n 1. Alloying treatment<\/p>\n\n\n\n Adding 0.1-0.3% Al can refine the grains of the galvanized layer and improve the toughness by 10-15%.<\/p>\n\n\n\n The use of Zn-Al-Mg coating (such as Zn-55% Al-1.6% Si) can improve corrosion resistance by 3-5 times without reducing mechanical properties.<\/p>\n\n\n\n 2. Surface treatment<\/p>\n\n\n\n Phosphating pretreatment can enhance the adhesion of the zinc layer, and the cross-cut test can reach 5B level.<\/p>\n\n\n\n Coating epoxy resin (300-500\u03bcm) can simultaneously improve corrosion resistance and wear resistance.<\/p>\n\n\n\n VII. Summary and suggestions<\/p>\n\n\n\n 1. Performance characteristics<\/p>\n\n\n\n The comprehensive mechanical properties of hot-dip galvanized pipes are slightly lower than those of the substrate, but the corrosion resistance is improved by 5-10 years.<\/p>\n\n\n\n Electro-galvanized pipes maintain the performance of the substrate, but require regular maintenance.<\/p>\n\n\n\n 2. Selection suggestions<\/p>\n\n\n\n Select hot-dip galvanized Q345B for high corrosion environments, and select calm steel (such as Q235D) for low-temperature toughness requirements.<\/p>\n\n\n\n Precision mechanical parts should preferably select electro-galvanized seamless steel pipes.<\/p>\n\n\n\n 3. Data limitations<\/p>\n\n\n\n The softening of the weld heat affected zone (HAZ) needs to be considered in actual engineering (hardness decreases by 15-20%).<\/p>\n\n\n\n The mechanical properties of girth welds of large diameter steel pipes (DN \u2265 300) need to be verified.<\/p>\n\n\n\n <\/p>","protected":false},"excerpt":{"rendered":" The mechanical properties analysis of galvanized pipes requires a comprehensive evaluation based on material properties, galvanizing process and application scenarios. The following is a detailed analysis based on the latest industry standards and research data: I. Basic materials of galvanized pipes 1. Substrate type 1. Carbon steel: commonly used Q195, Q215, Q235 (corresponding to American […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"yoast_head":"\n |
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