Advantages of fin aluminized tubes
Advantages of fin aluminized tube
According to zbj.36011-89 "hot dip aluminizing process and quality inspection of iron and steel", aluminizing steel is divided into two varieties
Metallographic structure of hot-dip air-cooled aluminizing at 750 ℃ for 15 minutes 100X
Metallographic structure of diffusion air cooling at 780 ℃ for 2 hours 100X
For the impregnated aluminized steel, the service life is mainly extended, and the physical and chemical properties of the steel pipe before and after the processing of the aluminized steel are mainly considered to meet the requirements of safe operation, including the mechanical properties at room temperature, metallographic structure, while for the diffused aluminized steel, many factors such as its hot working process, surface decarburization, bending deformation, welding process, etc. are also considered.
At present, the product specifications of hot-dip aluminized steel include plates, wires, strips, pipes and various metal structures. According to the requirements of different products and use environment, the thickness of aluminized layer is generally controlled at 0.05-0.37mm, and the hardness of the formed aluminum iron alloy exceeds hv600. The main characteristics of hot-dip aluminized steel for various substrates are as follows:
1. High temperature oxidation resistance
After aluminizing various tomb materials, the oxidation resistance temperature can be increased by - 300 ℃. After aluminizing, the oxidation resistance of ordinary carbon steel or low alloy steel is ten times higher than that of the original base material when it is used at 800-900 ℃, and its performance is better than that of ocrl7mnl3mo2n heat-resistant steel. After aluminizing, the oxidation resistance of lCrl8Ni9Ti heat-resistant steel, which is commonly used in industry, can be increased more than three times at 1100 ℃.
2. High temperature sulfide corrosion resistance
A large number of test results show that aluminized steel is the most effective material to resist sulfide corrosion, especially high-temperature sulfide. Aluminized steel is the only economic corrosion-resistant metal. In the working environment of 480 ℃ and 6% H2S content, the corrosion resistance of hot-dip aluminized carbon steel is increased by 29 times, and that of aluminized molybdenum steel is increased by 53 times. In the working environment of 650 ℃ and 100% H2S content, aluminized steel is the most effective material to resist sulfide corrosion The corrosion resistance of aluminum carbon steel is 290 times higher than that of aluminized molybdenum steel, chromium steel and 18-8 steel.
3. Resistant to atmospheric corrosion
The results of 19 years outdoor exposure test abroad show that the galvanized layer of hot-dip galvanized material is damaged after 7 years, but the aluminized steel has not changed after 19 years. When the thickness of hot-dip aluminum layer is 0.15-0.20 mm and 0.25-0.37 mm, its service life is 10-20 years and 20-40 years respectively.
4. Resistant to wet H2S corrosion
The dry H2S does not corrode the steel, but when there is water, the H2S corrosion is very serious, and causes hydrogen embrittlement, stress corrosion cracking and corrosion fatigue. The corrosion rate of aluminized carbon steel is 0.006 mm / year, the corrosion rate of carbon steel is 0.15 mm / year, and the corrosion resistance is increased by more than 20 times when the H2S concentration is 2000 ppm and the test is carried out under normal temperature and pressure for 100 hours. The hydrogen embrittlement of 50Mn tubing steel was tested in saturated H2S medium. The coefficient of hydrogen embrittlement was 55% without Aluminizing and zero after aluminizing. It shows that aluminized steel has excellent hydrogen embrittlement resistance.
5. Seawater corrosion resistance
The corrosion resistance of aluminized steel is 4-10 times higher than that of hot-dip galvanizing. The corrosion resistance of the aluminized carbon steel is 6-8 times higher than that of the base material
6. Prevent stress corrosion
Austenitic, martensitic stainless steel and other materials are prone to stress corrosion cracking under the condition of high temperature and high pressure and in the sulfide medium. After aluminizing, this kind of harm can be effectively prevented. After aluminizing, the stress corrosion resistance of lCrl8Ni9Ti stainless steel increased 5-10 times in 42% mgc12 + 50% FeC13 boiling solution. High strength Cr Mo steel is very sensitive to H2S corrosion cracking, but after aluminizing, it can completely prevent the tendency of stress corrosion cracking
7 other characteristics
In 60% nas04 + 40% NaCl (600 ℃), 16,5% ammonia water, 40 ℃ cn-39-500 mg / L, h2s16-96 mg / L, ph8-9 and 34% NH4N03 solution (40 ℃, pH5), the corrosion resistance of aluminized carbon steel is significantly higher than that of substrate. The erosion wear resistance of solid particles is twice as high as that of hard chromium plating.
