Regarding ND steel for industrial boilers

It’s 09CrCuSb – that’s the grade I remember; this material is often used for heat exchange tubes. As something used for cylinders, I haven’t come into contact with it

ND steel (niobium steel): Niobium can refine the grain structure, reduce the steel’s sensitivity to overheating and temper brittleness, and increase strength; however, it reduces plasticity and toughness. Adding niobium to ordinary low-alloy steel can improve its resistance to atmospheric corrosion as well as to hydrogen, nitrogen, and ammonia corrosion at high temperatures. Niobium can improve welding properties. Adding niobium to austenitic stainless steel can prevent intergranular corrosion.

ND steel 09CrCuSb is an acid- and corrosion-resistant steel, which is used for chimneys.

ND steel (09CrCuSb) is currently the most ideal steel material for resisting corrosion caused by low-temperature dew points in sulfuric acid, both domestically and internationally. It is widely used in the manufacture of devices such as economizers, air preheaters, heat exchangers, and evaporators that operate in environments with high sulfur content, to prevent corrosion resulting from the dew point of such sulfur-containing flue gases. ND steel also possesses resistance to chloride ion corrosion. The main performance indicators of ND steel pipes (after being immersed in a 50% H2SO4 solution at 70 degrees Celsius for 24 hours) show that their corrosion resistance is superior to that of carbon steel, similar steel imported from Japan, and stainless steel.

ND steel (with grades such as 09Cu and 09CuWSn) is an excellent material resistant to corrosion by sulfuric acid at low temperatures. The organization that first developed this material was likely the Shanghai Low-Temperature Steel Research Institute (this name is based only on memory and may not be accurate). The corresponding foreign grade is CR1A (1.25Cr-0.3Cu-0.02S).

ND steel (09CrCuSb) is generally used as a material resistant to sulfuric acid dew point corrosion. However, considering the current usage of desulfurization equipment in China, there are almost always problems with this material; the main reason is that it has to cope with both low-temperature corrosion and high-temperature operation conditions, and it is unable to meet both of these requirements simultaneously. Based on domestic and international experience, there are mainly three types of anti-corrosion coatings for the inner lining of chimney steel cylinders (in addition to raising the dew point temperature): The first type uses acid-resistant coatings, with glass flake coatings being representative examples. The second type of lining sheet uses acid-resistant metal alloy sheets as the lining material; such materials include titanium sheets (TiCr2) and nickel-based alloy sheets (AL-6XN stainless steel or C-276). The third type employs corrosion-resistant, lightweight insulating materials that are used to isolate the flue gases from the inner steel cylinder.

May I ask what the main chemical composition of this steel is and what its welding properties are?

　ND steel, also known as 09CrCuSb steel, is currently the most ideal material for resisting corrosion caused by low-temperature dew points in sulfuric acid environments, both domestically and internationally. It is widely used in the manufacture of economizers, air preheaters, heat exchangers, and evaporators that operate in environments with high sulfur content, to prevent corrosion resulting from the dew point of such sulfur-containing gases. ND steel also possesses resistance to chloride ion corrosion. The main performance indicators of ND steel pipes (after being immersed in a 50% H2SO4 solution at 70 degrees Celsius for 24 hours) show that their corrosion resistance is superior to that of carbon steel, similar steel imported from Japan, and stainless steel. After being used by major domestic refineries and manufacturing units, the product has received widespread praise and achieved excellent performance. The specific data are shown in the table below: Corrosion rate of ND steel, mg/c㎡·h (70°C, 50% H2SO4). Steel types: ND, CRIR (Japan), 1Cr18Ni9, Corten, 20G. Corrosion rates: 7.30, 13.40, 21.70, 63.00, 103.50

ND steel (niobium steel) (Sb is antimony, not niobium)

ND steel, also known as 09CrCuSb steel, is currently the most ideal material for resisting corrosion caused by low-temperature dew points in sulfuric acid environments, both domestically and internationally. It is widely used in the manufacture of economizers, air preheaters, heat exchangers, and evaporators that operate in environments with high sulfur content, to prevent corrosion resulting from the dew point of such sulfur-containing gases. ND steel also possesses resistance to chloride ion corrosion. The main performance indicators of ND steel pipes (after being immersed in a 50% H2SO4 solution at 70 degrees Celsius for 24 hours) show that their corrosion resistance is superior to that of carbon steel, similar steel imported from Japan, and stainless steel. After being used by major domestic refineries and manufacturing units, the product has received widespread praise and achieved excellent performance. The specific data are shown in the table below: Corrosion rate of ND steel, mg/c㎡·h (70°C, 50% H2SO4). Steel types: ND, CRIR (Japan), 1Cr18Ni9, Corten, 20G. Corrosion rates: 7.30, 13.40, 21.70, 63.00, 103.50