Ten kinds of materials commonly used for heat exchange and their applicable conditions

① Type 304 stainless steel

This is the cheapest and most widely used austenitic stainless steel (such as food, chemical, atomic energy and other industrial equipment). Suitable for general organic and inorganic media. For example, nitric acid with concentration < 30% and temperature ≤100℃ or concentration ≥ 30% and temperature < 50℃; Carbonic acid, ammonia water and alcohols with various concentrations at temperature ≤100℃. Poor corrosion resistance in sulfuric acid and hydrochloric acid; It is especially sensitive to crevice corrosion caused by chlorine-containing media (such as cooling water).

② 304L stainless steel

Corrosion resistance and application are basically the same as those of Type 304. Because the carbon content is lower (≤ 0.03%), the corrosion resistance (especially intergranular corrosion resistance, including weld zone) and weldability are better, and it can be used for semi-welded or all-welded PHE.

③ Type 316 stainless steel

Suitable for general organic and inorganic media. For example, natural cooling water, cooling tower water and demineralized water; Carbonic acid; Acetic acid and caustic lye with concentration < 50%; And solvents such as alcohols and acetone; Diluted nitric acid with temperature ≤100℃ (concentration < 20% =, diluted phosphoric acid (concentration < 30% =, etc.). However, it is not suitable for sulfuric acid. Because it contains about 2% Mo, its corrosion resistance in seawater and other chlorine-containing media is better than that of Type 304, and it can completely replace Type 304, as shown in Table 1-34. Is pre25.

④ 316L stainless steel

Corrosion resistance and application are basically the same as those of Type 316. Because the carbon content is lower (≤ 0.03%), the weldability and corrosion resistance after welding are also better, and it can be used for semi-welded or all-welded PHE. Is pre25.

⑤ Type 317 stainless steel

It is suitable for working conditions that require a longer service life than model 316. Because the content of Cr, Mo and Ni elements is slightly higher than that of type 316, it has better resistance to crevice corrosion, pitting corrosion and stress corrosion. PRE is 30.

⑥ AISI 904L or SUS890L stainless steel

This kind of austenitic stainless steel is cost-effective with consideration of both price and corrosion resistance. Its corrosion resistance is better than the above materials, and it is especially suitable for common acids and halides (including Cl-and F-) such as sulfuric acid and phosphoric acid. Because of the high content of Cr, Ni and Mo, it has good resistance to stress corrosion, pitting corrosion and crevice corrosion. PRE is 36.

⑦ Avesta 254 SMO high-grade stainless steel

This kind of ultra-low carbon high-grade stainless steel is improved by increasing Mo content. It has excellent chloride pitting corrosion resistance and crevice corrosion resistance, and is suitable for medium containing salt water, inorganic acid, etc. that can't be used in type 316. Is pre47.

⑧ Avesta 654 SMO high-grade stainless steel

It is an ultra-low carbon high-grade stainless steel with Cr, Ni, Mo and N contents higher than 254 SMO, which is resistant to

The corrosion performance of chloride is better than that of 254 SMO, and it can be used in cold seawater. Is pre64.

Pet-name ruby RS-2 (OCR20ni26mo3cu3si2nb) stainless steel

This is a domestic Cr–Ni–Mo–Cu stainless steel. The pitting corrosion resistance and crevice corrosion resistance are equivalent to Type 316, while the stress corrosion resistance is better. It can be used for concentrated sulfuric acid (concentration 90 ~ 98%) below 80℃ with annual corrosion rate ≤ 0.04 mm/a. Is pre29.

⑩ Incoloy 825

It is a Ni (40%)–Cr (22%)–Mo (3%) high-grade stainless steel. Incoloy is a registered trademark of theInternational Nickel Co, Ltd. Suitable for sulfuric acid with various concentrations at low temperature; In 50% ~ 70% caustic alkali (such as NaOH) solution, it has good corrosion resistance and does not produce stress corrosion cracking. However, it is sensitive to crevice corrosion caused by chloride. In addition, the stamping performance is not very good, so it is not a common material for sheet metal. PRE is 32.