Ⅰ. Introduction
With the continuous development of clean energy technology, LNG carriers, as an efficient and clean energy carrier, are more and more widely used in the field of energy storage and transportation. For LNG carriers, the high cost of LNG equipment has always been a huge bottleneck restricting the development of related products, among which the price of LNG storage tanks accounts for one-third of the entire power system.Marine LNG storage tank materials have strict requirements for low temperature performance, and should have high strength and toughness, good fracture resistance, crack resistance, fatigue resistance and microstructure stability in ultra-low temperature environment, which is one of the core technologies for LNG tank construction. Compared with traditional LNG tank construction materials, the low-temperature toughness, fatigue resistance, corrosion resistance and other properties of high-manganese austenitic low-temperature steel are comparable to those of 9% Ni steel, which is widely used at present, and the plasticity is better than that of 9Ni steel (about 3 times that of 9Ni steel). In terms of cost, the material cost of high-manganese steel is about 1/3 of that of 9Ni steel, and the construction cost is only about 1/10 of that of 9Ni steel, which makes the development of high-manganese steel enter a new stage.
Ⅱ. Advantages of high-manganese austenitic low-temperature steel (hereinafter referred to as high-manganese steel).
With its excellent low-temperature toughness, high strength and good crack resistance, high-manganese steel has significant advantages in welding liquid hydrogen storage tanks and LNG storage tanks in ultra-low temperature environments. Specifically, high manganese steel welding consumables have the following characteristics:
1. Excellent low-temperature toughness: High manganese steel welding consumables can still maintain high toughness in ultra-low temperature environment, which can effectively prevent cracks and fractures during the welding process. That's because the mechanical properties of the deposited metal are stable at ultra-low temperatures, and when the environment is -196 °C, the impact energy that high manganese steel can withstand can reach 95J, so the effect is equal to that of 9Ni steel when used to weld low-temperature pressure vessels such as liquefied gas storage and transportation devices.
2. High strength: High manganese steel has high strength, which can meet the requirements of liquid hydrogen storage tank and LNG storage tank for weld strength.
3. Good crack resistance: through the composition design, it can effectively resist the hot cracks and cold cracks generated during the welding process.
Ⅲ.Solution
After understanding the high nickel price and the high cost of LNG carrier preparation equipment under the international situation, Bocast Welding Technology cooperated with Wuhan University of Science and Technology to provide a complete set of solutions:
1. Choose suitable high-manganese steel welding consumables: According to the material, structure and welding requirements of liquid hydrogen storage tanks and LNG storage tanks, we need to choose high-manganese steel welding consumables with excellent low-temperature toughness, high strength and good crack resistance. For example, Bocast's BC-EHMn series electrodes have excellent welding operation manufacturability and stable mechanical properties.
2. Optimize welding process parameters: By adjusting the welding current, voltage, welding speed and other process parameters, the stable operation of high manganese steel welding consumables in ultra-low temperature environment is realized.
3. Strengthen welding quality control: In the welding process, strictly control the preparation of welding joints, the drying and storage of welding consumables, the cleanliness of the welding environment and other factors to ensure the stability and reliability of welding quality.
4. Carry out performance testing of welded joints: carry out mechanical property testing, metallographic structure analysis and non-destructive testing of welded joints to verify the welding effect of high-manganese steel welding consumables in ultra-low temperature environments.
Ⅳ.Customer benefits
By selecting suitable high-manganese steel welding consumables, optimizing welding process parameters, strengthening welding quality control, and carrying out performance testing of welded joints, we can effectively solve the problem of high nickel prices and high costs of LNG carrier preparation equipment. This will not only improve the welding quality and reliability of liquid hydrogen and LNG tanks, but also promote the further development of clean energy technologies.
