09-03-27 Topic — Discussion on several materials (prize for participation)
Thread Content
What do the stainless steels 304, 316, 304L, and 316L refer to, and what are their specific compositions? For plate heat exchangers dealing with dilute nitric acid solutions at around 45°C, what material is suitable? Note: This topic was provided by member darkdream159. The provider is requested to pay close attention and provide a summary or the correct answer within 24 hours. If you have any good topics, you can also share them with us; please refer to the “Special Thread for Submitting Daily and Monthly Topics” in the pinned post at the top of the forum. Link: http://bbs.hcbbs.com/thread-335484-1-1.html. There are prizes for participation, and you can also enter the end-of-month competition with generous rewards.
SS304: The number 304 denotes the grade of stainless steel; 304L (L=lower) indicates that its carbon content is lower than that of SS304. SS316 is also a grade of stainless steel, and 316L follows the same principle. Nitric acid is highly corrosive and oxidizing; you can refer to the discussions in this post for more information. http://bbs.hcbbs.com/thread-179092-1-1.html However, personally, I suggest that dilute nitric acid is a relatively dangerous substance, so it’s best to use a shell-and-tube heat exchanger with a high safety factor.
304 and 316 are the most widely used stainless steels at present. 304: C ≤ 0.08, Ni 8.00–10.00, Cr 18.00–20.00, Mn
Stainless steels 304, 316, 304L, and 316L all conform to the American ASTM standards; their corresponding GB/T5216 grades are 0Cr18Ni9, 00Cr19Ni10, 0Cr17Ni12Mo2, and 00Cr17Ni14Mo2 respectively. 0Cr18Ni12Mo2Ti exhibits good corrosion resistance in nitric acid solutions at concentrations below 65% and temperatures below 85°C； Corrosion depth
304, 316, 304L, and 316L are grades of stainless steel produced in accordance with the American ASTM standards. According to China’s standards, they correspond to 304–0Cr18Ni9, 304L–00Cr19Ni10, 316–0Cr17Ni12Mo2, and 316L–00Cr17Ni14Mo2. In terms of corrosion resistance, the order is 0Cr18Ni9 (304) → 00Cr19Ni10 (304L); 0Cr17Ni12Mo2 (316) → 00Cr17Ni14Mo2 (316L). For 45° dilute nitric acid, 316L should be used due to its better corrosion resistance. If detachable plate-type heat exchangers are used, full ethylene propylene diene monomer fluororubber or fluororubber should be used for the gaskets
Material reproduced from another source; I’ve forgotten the exact address, but it seems to be from within the site. It’s 304 standard 0Cr18Ni9 – a steel with wide-ranging applications, offering good corrosion resistance, heat resistance, low-temperature strength, and mechanical properties； It has good hot workability for stamping, bending, etc., and shows no hardening due to heat treatment (non-magnetic, operating temperature range: -196°C to 800°C). 304L, corresponding to the national standard 00Cr19Ni10, is a low-C version of 304 steel. Under normal conditions, its corrosion resistance is similar to that of 304 steel; however, after welding or stress relief, it exhibits excellent resistance to intergranular corrosion. It can also maintain good corrosion resistance even without heat treatment, and its operating temperature range is from -196°C to 800°C. It is used in outdoor machinery in the chemical, coal, and petroleum industries where high resistance to intergranular corrosion is required, as well as in heat-resistant building materials and components for which heat treatment is difficult. 316 is a stainless steel grade containing molybdenum. Due to the molybdenum in the steel, this grade exhibits overall superior properties compared to 310 and 304 stainless steels. Under high-temperature conditions, 316 stainless steel has a wide range of applications when the concentration of sulfuric acid is below 15% or above 85%. 316 stainless steel also has good resistance to chloride corrosion, which is why it is commonly used in marine environments. Corrosion resistance: It has better corrosion resistance than 304 stainless steel, and exhibits excellent corrosion resistance during the pulp and paper production process. Moreover, 316 stainless steel is also resistant to corrosion by marine and aggressive industrial atmospheres. Heat resistance: 316 stainless steel exhibits good oxidation resistance when used intermittently at temperatures below 1600 degrees and continuously at temperatures below 1700 degrees. It is not advisable to expose 316 stainless steel to continuous stress in the temperature range of 800–1575 degrees; however, it maintains good heat resistance when used continuously outside this temperature range. 316L stainless steel has better resistance to carbide precipitation than 316 stainless steel, and can be used within the aforementioned temperature range. 316L: Corresponding to the national standard 00Cr17Ni14Mo2, it is part of the low-C series of 316 steel; in addition to sharing the same properties as 316 steel, it offers better resistance to intergranular corrosion than 316. Applied to: products with special requirements to resist grain corrosion in special applications involving 316 steel.
Stainless steels 304, 316, 304L, and 316L all conform to the American ASTM standards; their corresponding GB/T5216 grades are 0Cr18Ni9, 00Cr19Ni10, 0Cr17Ni12Mo2, and 00Cr17Ni14Mo2 respectively. In terms of corrosion resistance, the order is 0Cr18Ni9 (304) → 00Cr19Ni10 (304L); 0Cr17Ni12Mo2 (316) → 00Cr17Ni14Mo2 (316L). For 45° dilute nitric acid, 316L should be used due to its better corrosion resistance. If a detachable plate-type heat exchanger is used, perfluoroelastomer or fluororubber should be used for the gaskets
The types and contents of these material elements vary; what was mentioned above covers them fairly comprehensively