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Stainless steel Basics | 300 series stainless steel

300 series stainless steel: in-depth analysis of characteristics, applications, and chemical composition

In the field of modern engineering materials, stainless steel has become a key material in many industries due to its excellent corrosion resistance, outstanding mechanical properties, and good processing performance. It is widely used in many fields such as construction, food processing, medical equipment, and automobile manufacturing. As an important branch of the stainless steel family, the 300 series stainless steel stands out among numerous stainless steel materials with its rich and diverse models and wide range of application scenarios. This article will provide an in-depth analysis of the characteristics, chemical composition, and application fields of 300 series stainless steel, and compare it with other series of stainless steel.

A. Common characteristics, uses, and other grades of 300 series stainless steel

1. 301 stainless steel

characteristic:

301 stainless steel has excellent ductility and significant work hardening phenomenon during processing. Its welding performance is good, and it performs better than 304 stainless steel in terms of wear resistance and fatigue strength.

Purpose:

Due to its high strength characteristics, 301 stainless steel is commonly used in applications that require high strength, such as the manufacturing of automotive body structural components. It can reduce the weight of the vehicle while ensuring its strength, and improve the overall performance of the car.

Other brand forms:

In international standards, 301 stainless steel also corresponds to Japanese standard SUS301 and American standard UNS S30100. These grades under different standards, although expressed differently, have similar chemical compositions and main properties, all possessing typical characteristics of 301 stainless steel.

2. 302 stainless steel

characteristic:

The corrosion resistance of 302 stainless steel is similar to that of 304, but its carbon content is relatively higher, which makes it stronger. Through cold rolling process, 302 stainless steel can achieve high strength.

Purpose:

Commonly used for building decorative components, such as stair handrails. Its good strength and corrosion resistance can ensure that the armrest remains beautiful and safe during long-term use.

Other brand forms:

The Japanese standard is SUS302, while the American standard is UNS S30200. In practical applications, different countries and regions choose corresponding grades according to their respective standard systems, but the application characteristics in the field of architectural decoration are consistent.

3. 303 and 303Se stainless steel

characteristic:

303 stainless steel contains sulfur element, while 303Se stainless steel contains selenium element. The addition of these two elements makes them easy to cut stainless steel, with high surface smoothness during processing, which can effectively improve processing efficiency.

Purpose:

Suitable for automatic lathe machining of parts such as bolts, nuts, etc. In large-scale mechanical processing production, 303 and 303Se stainless steel can significantly reduce processing costs and improve production efficiency.

Other brand forms:

The Japanese standard for 303 stainless steel is SUS303, while the American standard is UNS S30300; The Japanese standard for 303Se stainless steel is SUS303Se, while the American standard is UNS S30323. In the mechanical processing industry, these different standard grades are selected based on specific needs and procurement channels.

4. 304 stainless steel

characteristic:

304 stainless steel contains 18% chromium and 8% nickel, which gives it excellent corrosion resistance, heat resistance, weldability, and mechanical properties, as well as high toughness.

Purpose:

Widely applied in various fields, used for curtain walls in the construction industry; Used in the furniture industry for table and chair frames; The kitchenware industry is used for the manufacturing of tableware; Used for food processing equipment in the food processing industry; Used in the medical device industry for surgical instrument casings; Used in the chemical industry for chemical equipment; Used in the field of decoration for decorative lines, etc. Its excellent comprehensive performance makes it one of the most widely used stainless steel models.

Other brand forms:

Common ones include Japanese standard SUS304, American standard UNS S30400, Chinese standard 06Cr19Ni10, etc. The grades under different standards are widely used in global trade and industrial production, and although the markings are different, they all follow the basic quality and performance specifications of 304 stainless steel.

5. 304L stainless steel

characteristic:

304L stainless steel has reduced carbon content on the basis of 304 stainless steel, which improves its welding performance and significantly enhances its resistance to intergranular corrosion.

Purpose:

Mainly used for corrosion-resistant equipment components in the petrochemical industry, such as welded pipe fittings. In petrochemical production, welded pipe fittings need to withstand high temperature, high pressure, and highly corrosive media, and 304L stainless steel can meet these stringent usage requirements.

Other brand forms:

The Japanese standard is SUS304L, the American standard is UNS S30403, and the Chinese standard is 022Cr19Ni10. In industries such as petrochemicals that require extremely high material quality and performance, these different standard grades have undergone strict screening and quality control.

6. 316 stainless steel

characteristic:

The chemical composition of 316 stainless steel is 18Cr-12Ni-2.5Mo, which endows it with excellent corrosion resistance, atmospheric corrosion resistance, high temperature strength, and non-magnetic properties.

Purpose:

Widely used in seawater equipment, such as marine ship components; Reactors in the chemical industry; Production equipment for dyes, papermaking, oxalic acid, fertilizers, etc. In these highly corrosive environments, 316 stainless steel can operate stably for a long time, ensuring the normal use of equipment.

Other brand forms:

Japanese standard SUS316, American standard UNS S31600, Chinese standard 06Cr17Ni12Mo2, etc. In industries such as marine engineering and chemical engineering, different countries and regions choose corresponding grades based on their own industrial standards and procurement habits.

7. 316L stainless steel

characteristic:

316L stainless steel is further reduced in carbon content on the basis of 316 stainless steel, making it more corrosion-resistant, especially after welding, which can effectively avoid intergranular corrosion problems.

Purpose:

Mainly used in highly corrosive environments such as chemical pipeline systems. In the chemical production process, pipelines need to transport various corrosive media, and 316L stainless steel can ensure the service life and safety of pipelines.

Other brand forms:

Japanese standard SUS316L, American standard UNS S31603, Chinese standard 022Cr17Ni12Mo2, etc. In the construction of chemical pipeline engineering, these different standard grades need to meet strict quality and performance testing requirements.

8. 321 stainless steel

characteristic:

321 stainless steel has added titanium element, which makes it highly resistant to intergranular corrosion and excellent in high temperature resistance.

Purpose:

Equipment commonly used in high-temperature environments and requiring welding, such as heat exchangers. In high-temperature industrial production, heat exchangers need to withstand high temperatures and pressures, and also require welding installation. 321 stainless steel can meet these complex working conditions.

Other brand forms:

Japanese standard SUS321, American standard UNS S32100, Chinese standard 06Cr18Ni11Ti, etc. In high-temperature industries such as power and metallurgy, these different standard grades are selected based on specific equipment design and process requirements.

B. Chemical composition characteristics

1. Chromium (Cr)

Function: Chromium is a key element for forming a dense oxide film in stainless steel. This oxide film can tightly cover the surface of stainless steel, effectively preventing external corrosive media from corroding the metal substrate, thereby improving the corrosion resistance of stainless steel.

Content: In 300 series stainless steel, the chromium content is usually between 16% and 26%. The chromium content of different models of 300 series stainless steel will be adjusted according to their performance requirements. For example, 304 stainless steel has a chromium content of about 18%, while 316 stainless steel has a chromium content of 18% -20%.

2. Nickel (Ni)

Function: Nickel can significantly improve the corrosion resistance of stainless steel, while also enhancing its strength and plasticity. The addition of nickel element makes the crystal structure of stainless steel more stable and enhances its resistance to various corrosive media.

Content: Generally speaking, the nickel content in 300 series stainless steel is 8% to 10%. 304 stainless steel contains 8% nickel and 316 stainless steel contains 12% nickel. Different nickel contents have a significant impact on the performance of stainless steel. The higher the nickel content, the better the corrosion resistance and processing performance of stainless steel.

3. Molybdenum (Mo)

Function: The main function of molybdenum element is to enhance the stability of stainless steel in high temperature and acidic environments. It can improve the resistance to pitting and crevice corrosion of stainless steel, enabling it to maintain good performance even in harsh corrosive environments.

Content: In 300 series stainless steel, the molybdenum content is usually 0.15% to 0.35%. For example, the molybdenum content in 316 stainless steel is about 2.5%, which makes it superior to 304 stainless steel without molybdenum in terms of chloride corrosion resistance and high temperature strength.

4. Other elements

Carbon (C):

Carbon has a significant impact on the hardness and tensile strength of stainless steel. Generally speaking, the higher the carbon content, the higher the hardness and tensile strength of stainless steel. However, excessive carbon content can reduce the intergranular corrosion resistance of stainless steel. Therefore, in some stainless steel models with high requirements for welding performance and intergranular corrosion resistance, such as 304L and 316L, the carbon content will be strictly controlled.

Manganese (Mn): Manganese can improve the strength and ductility of stainless steel. In the production process of stainless steel, an appropriate amount of manganese can improve the processing performance of steel, making it easier for stainless steel to undergo cold and hot working forming.

Silicon (Si): The main function of silicon in stainless steel is to facilitate deoxidation of molten metal. In the steelmaking process, silicon as a deoxidizer can remove oxygen from the molten steel, improve the purity and quality of the steel, and also have a certain impact on the strength and hardness of stainless steel.

Nitrogen (N): Nitrogen can enhance the strength of stainless steel. In some special stainless steel models, the strength is enhanced by adding nitrogen element, which can also improve the corrosion resistance and processing performance of stainless steel.

C. Common characteristics of materials

1. Corrosion resistance performance

The 300 series stainless steel generally has good corrosion resistance, mainly due to the dense oxide film formed by chromium on the surface of stainless steel. This oxide film can isolate the contact between corrosive media such as oxygen, moisture, acid and alkali from the outside and the metal substrate, thereby protecting stainless steel from corrosion. Although there are differences in the specific performance of corrosion resistance among different models of 300 series stainless steel, they can generally meet the corrosion resistance requirements of most industrial and civilian fields.

2. Processing performance

The 300 series stainless steel belongs to austenitic stainless steel, and the austenite crystal structure endows them with good workability. These stainless steels can be formed through various methods such as cold working, hot working, and welding. During cold processing, 300 series stainless steel can be produced into various shapes of products such as plates, pipes, wires, etc. through processes such as cold rolling and cold drawing; During the hot processing, they can be processed through processes such as hot rolling and forging; In terms of welding, the 300 series stainless steel has good weldability and can be connected using various welding methods to meet different engineering requirements.

3. Physical properties

The density of most 300 series stainless steels is similar, generally between 7.93-8.03g/cm ³. They have good toughness and are not prone to fracture when subjected to external impact. In addition, at room temperature, 300 series stainless steel is usually non-magnetic, which makes them widely used in fields with special requirements for magnetism, such as electronic devices, medical equipment, etc.

D. Material relationship context

1. Based on component derivation

304L and 316L are models derived from 304 and 316 with reduced carbon content. The purpose of reducing carbon content is to improve the corrosion resistance after welding and reduce the risk of intergranular corrosion. 316Ti and 316N are based on 316L with the addition of Ti and N elements respectively. Adding titanium element (Ti) can enhance the resistance to intergranular corrosion, while adding nitrogen element (N) can improve strength. 317L increases the Ni and Mo content on the basis of 316L, further enhancing its corrosion resistance, especially its resistance to pitting corrosion. These stainless steel models derived from composition meet the diverse demands for material properties in different engineering fields.

2. Performance similarity classification

301, 302, 304, 304L, 304N, etc. have similarities in corrosion resistance and basic processing performance, and belong to universal stainless steels. They are widely used in various fields such as construction, furniture, and food processing, and can meet general requirements for corrosion resistance and mechanical performance. Stainless steels such as 309, 310, 314, and 330 exhibit outstanding high-temperature performance due to their high nickel and chromium content, and are therefore classified as one type. These stainless steels are mainly used in high-temperature industrial fields such as metallurgy, power, heat treatment, etc., and can withstand various working conditions in high-temperature environments.

3. Usage association

In the construction industry, stainless steel models such as 301, 302, and 304 are used for different building structures and decorative components. 301 stainless steel can be used as load-bearing structural components in buildings due to its high strength; 302 stainless steel is commonly used in building decoration components, such as stair handrails, railings, etc; 304 stainless steel is widely used in building curtain walls, roof materials, etc. In the food processing industry, stainless steels such as 304 and 316 are widely used due to their hygienic properties. These stainless steels have good corrosion resistance, are not easy to contaminate food, meet the hygiene standards of the food processing industry, and are commonly used in the manufacturing of food processing equipment, storage tanks, pipelines, etc.

E. Comparison with other series of stainless steel

1. Comparison with 316 stainless steel

304 stainless steel contains 18-20% chromium and 8-10.5% nickel, and has good corrosion resistance, but it is not as strong as 316 stainless steel in terms of chloride corrosion resistance and high temperature strength. 316 stainless steel has added molybdenum element, which makes it perform better in terms of chloride corrosion resistance and high temperature strength. In marine environments or chemical production, 316 stainless steel can better resist the erosion of chloride ions and is suitable for manufacturing seawater equipment, chemical reaction vessels, etc; And 304 stainless steel is more commonly used in general construction and food processing fields.

2. Comparison with 430 stainless steel

The comprehensive performance of 304 stainless steel, including corrosion resistance, strength, toughness, etc., is superior to 430 stainless steel. 430 stainless steel belongs to ferritic stainless steel and is mainly used in decoration and other fields. Its temperature resistance and corrosion resistance are relatively weak. In the field of architectural decoration, 430 stainless steel can be used in some occasions where corrosion resistance is not high, such as indoor decorative panels; And 304 stainless steel can be used in more harsh environments, such as outdoor decorative components, and has more advantages in fields such as food processing and medical equipment that require high material performance.

F. Application Fields

1. Construction industry

300 series stainless steel is widely used in the construction industry, including beams, columns, roof materials, decorative components, etc. Its corrosion resistance can ensure that the building structure is not corroded by the external environment during long-term use, extending the service life of the building; High strength characteristics enable it to withstand the weight and external forces of the building; Durability and aesthetics meet the decorative needs of buildings, such as stainless steel curtain walls, decorative lines, etc., adding modernity and aesthetics to the building.

2. Food processing industry

In the food processing industry, 300 series stainless steel is used to manufacture equipment such as storage tanks, pipelines, and conveying systems. Due to its hygiene, corrosion resistance, and resistance to food contamination, it meets the strict hygiene standards of the food processing industry. In the food production process, these stainless steel equipment can effectively prevent food contamination, ensuring the quality and safety of food.

3. Medical device industry

The 300 series stainless steel is used for the production of surgical instruments, implants, dental tools, hospital equipment, etc. based on its biocompatibility and easy sterilization properties. Biocompatibility ensures that the human body does not produce any rejection reactions to these medical devices, while the easy sterilization property ensures that medical devices can be effectively disinfected before use to prevent cross infection and ensure the health and safety of patients.

4. Automotive industry

In the automotive industry, 300 series stainless steel is used for components such as exhaust systems, fuel tanks, and bumpers. Its strength to weight ratio is excellent, which can reduce weight while ensuring the strength of automotive components and improve the fuel economy of the car; At the same time, it can withstand harsh environments such as high temperature, humidity, acid and alkali during the operation of the car, ensuring the reliability and service life of car components.

5. Energy sector

In the energy field, 300 series stainless steel is used for pipelines in refineries and power plants. These pipelines need to withstand high pressure and corrosive environments. The high strength and corrosion resistance of 300 series stainless steel can meet the stringent requirements in energy production processes, ensuring the safety and stability of energy transmission.

6. Household appliance industry

In the household appliance industry, 300 series stainless steel is used for sinks, cookware, faucets, shower heads, and more. Its beautiful and easy to maintain features meet consumers' needs for the appearance and convenience of using household appliances. Stainless steel made household appliance components not only enhance the overall texture of the appliance, but also have good corrosion resistance, are not easy to rust or damage, and extend the service life of the appliance.

summarize

The 300 series stainless steel plays an irreplaceable role in modern industry and daily life due to its diverse models and excellent performance. From construction to food processing, from medical equipment to automotive manufacturing, the 300 series stainless steel meets the needs of different industries with its unique advantages. By gaining a deep understanding of its characteristics, chemical composition, application areas, and comparison with other series of stainless steels, powerful technical support can be provided for material selection and application in various industries, promoting their sustainable development.