How to Select Raw Materials Stainless Steel for Pillow Plates?

1. 304 Stainless Steel 1.1 Chemical Composition and Basic Characteristics - 304 stainless steel mainly contains approximately 18% chromium (Cr) and 8% nickel (Ni), which endows it with good corrosion resistance. It is an austenitic stainless steel and can form a stable passive film in general environments to prevent further oxidation and corrosion. 1.2 Corrosion Resistance - It performs well in mild chemical and atmospheric environments. For example, in the food processing industry for cooling common foods (such as in the heat exchange process during fruit and vegetable processing), it can resist the erosion of organic acids and moisture in the food. However, it may suffer from pitting corrosion in environments with high concentrations of chloride ions, such as seawater or certain salt solutions. 1.3 Mechanical Properties - It has good ductility and toughness, making it easy to be processed into the shape of pillow plates. Its strength can meet the requirements of many general heat exchange applications, such as in ordinary air-conditioning systems or some light industrial heat recovery devices. However, its strength may be somewhat insufficient when subjected to higher pressures or mechanical stresses. 1.4 Cost-Effectiveness - 304 stainless steel is a relatively cost-effective material. Due to its widespread application and large-scale production, the raw material cost is low, and the processing cost is also reasonable. For general heat exchange applications where the requirements for corrosion resistance and mechanical properties are not particularly high, 304 stainless steel pillow plates are a highly cost-effective choice. 2. 316L Stainless Steel 2.1 Chemical Composition and Basic Characteristics - 316L stainless steel adds approximately 2 - 3% molybdenum (Mo) on the basis of 304 stainless steel. The addition of molybdenum significantly improves the corrosion resistance of the stainless steel, especially in environments containing chloride ions. It is also an austenitic stainless steel with good processing properties. 2.2 Corrosion Resistance - It is widely used in industries such as chemical, pharmaceutical, and food. In chemical production, when dealing with solutions containing certain salts or chloride ions (such as in the cooling process during certain fertilizer production), 316L stainless steel pillow plates can effectively prevent corrosion. In the food and pharmaceutical industries, its corrosion resistance can also meet strict hygiene standards for heat exchange processes involving high-purity substances. 2.3Mechanical Properties - Its mechanical properties are similar to those of 304 stainless steel, but it may have a better strength retention rate in high-temperature environments. In some heat exchangers that need to withstand certain pressures at moderate temperatures, 316L can provide reliable structural support. 2.4 Cost-Effectiveness - The cost is slightly higher than that of 304 stainless steel, mainly due to the addition of molybdenum. However, considering the improvement in its corrosion resistance, 316L stainless steel is a worthy investment in applications that require better corrosion resistance. Its life cycle cost is reasonable in some industries that demand high equipment life and stability, such as the pharmaceutical and high-end food processing industries. 3. 2205 Duplex Stainless Steel 3.1 Chemical Composition and Basic Characteristics - 2205 duplex stainless steel contains approximately 22% chromium, 3% molybdenum, and 5% nickel-nitrogen alloy. It combines the advantages of austenite and ferrite, achieving a good balance between strength and toughness. 3.2 Corrosion Resistance - In environments containing chloride ions, such as seawater desalination, marine engineering, and the heat exchange process of handling chlorinated brine in the chemical industry, 2205 duplex stainless steel pillow plates perform excellently. They can resist pitting corrosion, crevice corrosion, and stress corrosion cracking, providing reliable corrosion resistance in complex chemical environments. 3.3 Mechanical Properties

- It has a relatively high yield strength and tensile strength, being more capable of withstanding higher pressures and mechanical stresses than 304 and 316L stainless steels. In some heavy industrial applications (such as high-pressure heat exchange systems in the petrochemical industry or certain cooling processes in the metallurgical industry), 2205 duplex stainless steel pillow plates can provide better structural integrity.

3.4 Cost-Effectiveness

- The cost is relatively high, falling between that of 316L and 2507 stainless steels. However, due to its excellent corrosion resistance and mechanical properties, in applications that require both of these requirements to be met, 2205 duplex stainless steel can reduce long-term maintenance costs and equipment replacement frequencies. From the perspective of the full life cycle cost, it is an economically efficient choice. 4. 2507 Super Duplex Stainless Steel 4.1 Chemical Composition and Basic Characteristics - 2507 super duplex stainless steel contains approximately 25% chromium, 4% molybdenum, and 7% nickel. Its alloy composition endows it with higher strength and corrosion resistance. 4.2 Corrosion Resistance - It is one of the most corrosion-resistant materials among all stainless steels. In extremely corrosive environments, such as in strongly acidic, high-concentration chloride ion or other extremely corrosive media (such as certain highly corrosive chemical synthesis processes or heat exchange applications in offshore oil extraction), 2507 super duplex stainless steel pillow plates can effectively resist corrosion, ensuring the long-term stable operation of the equipment. 4.3 Mechanical Properties - It has extremely high strength, with its yield strength and tensile strength being higher than those of 2205 duplex stainless steel. It performs excellently in heavy industrial applications that bear huge pressures and mechanical stresses, such as in the key heat exchange processes of large chemical plants or heat exchange equipment in deep-sea engineering, providing reliable structural support. 4.4 Cost-Effectiveness - The cost is high because it contains more precious alloy elements. However, in special application scenarios where extremely high requirements for corrosion resistance and mechanical properties are imposed, although the initial investment is large, from the long-term perspective, due to its extremely long service life and low maintenance rate (it can remain in good condition even in harsh environments), it can reduce the total cost within the entire heat exchanger life cycle, especially in avoiding high repair and replacement costs caused by corrosion or mechanical damage. 5. 310S Austenitic Stainless Steel 5.1 Chemical Composition and Basic Characteristics - 310S stainless steel contains approximately 25% chromium and 20% nickel. Its high chromium and nickel composition endows it with excellent high-temperature oxidation resistance. 5.2 Corrosion Resistance - It can form a stable oxide film in high-temperature environments, thereby effectively resisting oxidation. In some high-temperature industrial processes, such as the furnace heat recovery system in the glass manufacturing industry (with a temperature that can reach around 1000°C), and the waste heat recovery heat exchanger in the metallurgical industry's high-temperature furnaces, 310S stainless steel pillow plates can withstand the corrosion and oxidation in high-temperature environments, ensuring the normal operation of the heat exchanger. Meanwhile, it also has a good performance in general chemical corrosion environments, showing a certain tolerance to some weak acidic and alkaline environments. 5.3 Mechanical Properties - It has good ductility and toughness, making it easy to be processed into the shape of pillow plates. In high-temperature environments, it can still maintain a certain strength, although its normal temperature strength is relatively lower compared to some high-strength duplex stainless steels. However, in some high-temperature application scenarios where extremely high pressures do not need to be borne, it can meet the requirements of the heat exchanger's structure. In the case of temperature fluctuations, it also has a good stability, not easily developing cracks or deformations due to thermal expansion and contraction. 5.4 Cost-Effectiveness - The cost is at a medium level. Due to its unique advantages in high-temperature applications, it has a high cost-effectiveness in heat exchanger projects that require high-temperature resistance. From the perspective of the full life cycle cost, its low maintenance cost (due to high-temperature corrosion resistance) and relatively stable performance make it an economical and practical choice, especially for those industrial heat exchange equipment that operates stably in high-temperature conditions for a long time. 6. 904L Stainless Steel 6.1 Chemical Composition and Basic Characteristics - 904L stainless steel is a high-alloy austenitic stainless steel, containing approximately 19% - 23% chromium, 23% - 28% nickel, 4% - 5% molybdenum, and a small amount of other elements such as copper. This complex alloy composition endows it with excellent comprehensive properties. 6.2 Corrosion Resistance - It performs excellently in a variety of corrosive media, including strong acids such as sulfuric acid and phosphoric acid, as well as media containing chloride ions. In the chemical industry, for the heat exchange process during the production of some high-precision, high-purity chemical products (such as in the production of certain electronic-grade chemicals), 904L stainless steel pillow plates can resist the erosion of chemical substances, ensuring product quality. It also has good corrosion resistance in marine environments or industrial environments containing salts. 6.3 Mechanical Properties - It has good strength and toughness, being able to withstand certain pressures and mechanical stresses. Although its strength may not be as high as that of some duplex stainless steels, it can meet the requirements in applications where extremely high corrosion resistance is required along with certain mechanical property requirements. 6.4 Cost-Effectiveness - The cost is high due to its high alloy content. However, in industries where extremely high requirements for material purity and corrosion resistance are imposed, such as high-end chemical, pharmaceutical, and food processing industries, the high quality and long life of 904L stainless steel can justify its high cost. From the perspective of the full life cycle cost, it can reduce equipment failures and maintenance costs caused by corrosion, improving the reliability and efficiency of production. 7. How to Select 7.1 Consider the Corrosion Environment - If the application environment is a general atmospheric environment or a mild chemical environment (such as in ordinary food processing, heat exchange in light industrial applications), 304 stainless steel may be a suitable choice. - For environments containing chloride ions (such as applications related to seawater, handling of some chemical salt solutions), 316L, 2205, or 2507 duplex stainless steels may be more appropriate, with 2507 performing best in extremely chloride-ion-rich environments. - In high-temperature oxidation environments (such as waste heat recovery from high-temperature furnaces), 310S stainless steel is a good choice, while for environments where both high temperature and strong corrosion exist (such as in certain high-temperature chemical syntheses), 2507 or 904L may be more capable of meeting the requirements. 7.2 Consider the Mechanical Property Requirements - If the heat exchange equipment needs to bear higher pressures or mechanical stresses (such as in high-pressure chemical systems, heavy industrial cooling), the high-strength properties of 2205 or 2507 duplex stainless steels are advantageous. - For applications where the strength requirements are not particularly high, but good processing properties and a certain degree of toughness are needed (such as in ordinary air-conditioning heat exchangers), 304 or 316L stainless steels may be more appropriate. 7.3 Consider the Cost-Effectiveness - For general applications with limited budgets and not extremely high performance requirements, 304 stainless steel provides an economical solution.

- In applications that require long-term stability and high performance, although duplex stainless steels (2205, 2507) and high-alloy stainless steels (904L) have higher costs, from the perspective of the full life cycle cost, they can reduce the total cost by reducing the frequency of repairs and replacements.