What is corten steel pipe?
What is corten steel pipe? #NDsteelpipe #09CrCuSb #ASTM A588 STANDARD GR.A/B
Corten steel pipe, as a pipe made of special steel, plays an important role in the industrial field, especially in the air preheater system. Its unique weather resistance and corrosion resistance make it perform well in high temperature, high humidity and corrosive environments. ND steel pipe (acid-resistant steel pipe) is widely used in the transportation of corrosive media in chemical, power and other industries due to its excellent acid corrosion resistance. As a key component in the boiler system, the material selection of the air preheater tube directly affects the thermal efficiency and service life of the equipment.
The core advantage of Corten steel pipe lies in its alloy composition design. By adding elements such as copper, chromium, and nickel, a dense oxide layer will be formed on the surface of the steel when exposed to the atmospheric environment, thereby preventing corrosion from spreading further inside. This self-protection mechanism allows it to be used for more than 20 years without painting in an open-air environment, greatly reducing maintenance costs. For example, in the flue gas treatment system of thermal power plants, Corten steel pipes are widely used in the inlet section of desulfurization towers to withstand the erosion of sulfur-containing flue gas and the corrosion of condensed acid. The company has achieved a breakthrough in the localization of this product, and its Corten steel pipes can maintain stable performance under working conditions of -40″C to 450’C. It is worth noting that the welding process of Corten steel needs to be strictly controlled. Due to the high alloy content, hot cracks are prone to occur during welding, and low-hydrogen welding rods and preheating measures are usually required. A case of a power plant shows that the weld cracks of the pipeline that was not welded according to the specifications appeared after 3 months of operation. After repair, ER70S-6 welding wire was used and preheated to 150℃, and the problem was solved. This reminds users to pay attention to the supplier’s process qualifications and engineering cases when purchasing.
- Acid resistance mechanism and selection points of ND steel pipe
ND steel pipe (such as 09CrCuSb material) significantly improves its resistance to dew point corrosion by adding antimony (Sb) elements. Its corrosion rate is only 1/8~1/10 of that of ordinary carbon steel, and it is particularly suitable for the cold end module of coal-fired boiler air preheater. Experimental data show that after 720 hours of soaking in simulated flue gas condensate (pH=2, 60°), the weight loss of ND steel sample is only 0.12g/m2, while Q235 steel reaches 1.83g/m2. The ND steel pipe provided adopts controlled rolling and controlled cooling process, and the grain size can reach more than 8 levels, so that the product has both strength and toughness. In actual selection, attention should be paid to the matching of medium characteristics and materials. Although ND steel has excellent tolerance to dilute nitrate, it performs generally in hydrochloric acid environment. A chemical plant mistakenly used ND steel pipe in the HCl tail gas treatment system, resulting in pitting perforation after 6 months. The problem was solved by replacing it with duplex stainless steel 2205. Therefore, it is recommended that users entrust a third-party organization to conduct medium corrosion tests before purchasing.
As a key component of waste heat recovery, the design of air preheater tubes needs to comprehensively consider heat transfer efficiency and durability. At present, the mainstream structures are divided into tubular and rotary types. Among them, tubular preheaters mostly use 040×1.5mm ND steel tube matrix arrangement, and the flue gas flow rate is controlled at 9~12m/s to avoid wear. The actual measurement can reduce the exhaust gas temperature from 160℃ to 120℃℃. Common failure modes include low-temperature corrosion, ash accumulation and vibration fatigue. The maintenance report of the base power plant shows that the corrosion and perforation rate of the preheater tube that did not use ND steel reached 37% after 18 months of operation. After replacing it with 09CrCuSb material, the damage rate dropped to less than 5% during the same period. For high-ash fuels, it is recommended to configure an acoustic soot blowing system and combine it with high-pressure water flushing maintenance during shutdown.
Seamless corten steel tube #63.5*3 ASTM A588 STANDARD GR.B
