1.The chemical composition of N5 is similar to that of N02201, while that of N6 and N7 is similar to that of N02200. Since N02200 has a carbon content of ≤0.15%, graphitization at 315°C makes the material brittle, resulting in a maximum operating temperature of 315°C.
2. 800, 800H, and 800HT share the same chemical composition according to the ASME standard. 800 has the lowest carbon content, an annealing temperature of 982-1038°C, and an operating temperature below 600°C. 800H has a limited Al+Ti content, but after a special solution treatment (1121-1177°C), it produces coarse grains, with a grain size of ASTM-5.0, and significantly improves creep rupture strength above 600°C. 800HT has a higher Al+Ti content and, after a special solution treatment (1121-1177°C), it produces coarse grains, with a grain size of ASTM-5.0, and achieves the highest creep rupture strength above 700°C, with a significant improvement. Excessive heat treatment temperatures can cause grain expansion, resulting in higher creep limit and ultimate strength, and reduced toughness. Higher heat treatment temperatures accelerate nucleation, increase the number of crystals, and result in relatively fine grains. Longer holding times increase grain size, and slower cooling also increases grain size. Generally speaking, higher temperatures (smaller gradients) produce larger grains. Smaller grains increase strength, hardness, and plasticity and toughness. However, under high-temperature operating conditions, grains coarsen and the total length of grain boundaries decreases, improving creep resistance against deformation or failure caused by sliding along grain boundaries.
3. The main chemical composition of N06600 is 72Ni-15Cr-8Fe, and the main chemical composition of N08800 is 33Ni-42Fe-21Cr. This is equivalent to splitting the 72Ni content in N06600 into 33Ni+45Fe, reducing costs by partially replacing nickel.
4. The main chemical composition of N10675 is 65Ni-29.5Mo-2Fe-2Cr, and the chemical composition of N10276 is 54Ni-16Mo-15Cr. This can be roughly considered as splitting the 29.5Mo content in N10675 into 16Mo+15Cr. The increased Cr content improves the material's corrosion resistance in oxidizing media.
