Stainless Steel 201 vs 304 (food grade): Difference Explained

1. Differences between stainless steel 201 and 304

How to distinguish 201 and 304 stainless steels?

This article will provide a comprehensive analysis of the key differences between stainless steel grades 304 and 201, enabling you to accurately identify and differentiate these alloys in various industrial applications.

Stainless steel grades 304 and 201 are both austenitic stainless steels widely used in manufacturing, but they possess distinct characteristics that affect their performance, cost, and suitability for specific applications. Understanding these differences is crucial for engineers, fabricators, and procurement specialists to make informed decisions in material selection and processing.

Differences and resolution methods between 201 and 304 stainless steels

Reminder:

• It is important to keep in mind that 304 stainless steel should not be purchased at the market price for 201 stainless steel.
• It is recommended to choose reputable companies for procurement. The credibility of a supplier can be evaluated not only through their verbal commitments, but also through their actions.

2. Chemical composition difference between 201 and 304

The following is a comprehensive analysis of the chemical composition differences and identification methods between 201 and 304 stainless steels.

304 stainless steel, manufactured according to ASTM standards, is a widely used austenitic stainless steel. Its national standard designation is 06Cr19Ni10. To maintain its superior corrosion resistance, 304 stainless steel must contain a minimum of 18% chromium (Cr) and 8% nickel (Ni). The typical composition range for 304 is:

• Chromium: 18-20%
• Nickel: 8-10.5%
• Carbon: ≤0.08%
• Manganese: ≤2%
• Silicon: ≤1%
• Phosphorus: ≤0.045%
• Sulfur: ≤0.03%

201 stainless steel, part of the 200 series, was developed as a cost-effective alternative to 300 series stainless steels during World War II. Its brand name is 1Cr17Mn6Ni5N, though production standards may vary among manufacturers. The typical composition range for 201 is:

• Chromium: 16-18%
• Nickel: 3.5-5.5%
• Manganese: 5.5-7.5%
• Carbon: ≤0.15%
• Nitrogen: 0.15-0.25%
• Silicon: ≤1%
• Phosphorus: ≤0.06%
• Sulfur: ≤0.03%

Key differences:

1. Nickel content: 201 has significantly lower nickel content (3.5-5.5%) compared to 304 (8-10.5%), making it less expensive.
2. Manganese content: 201 has higher manganese content (5.5-7.5%) to partially replace nickel and maintain austenitic structure.
3. Nitrogen content: 201 contains nitrogen (0.15-0.25%) to enhance strength and corrosion resistance, while 304 typically does not.
4. Chromium content: 201 has slightly lower chromium content (16-18%) compared to 304 (18-20%).

These compositional differences result in varying mechanical properties and corrosion resistance. 304 generally offers superior corrosion resistance, especially in more aggressive environments, due to its higher nickel and chromium content. However, 201 can provide adequate performance in less demanding applications at a lower cost.

Identification methods:

1. Spark testing: 201 produces a “bushier” spark pattern due to its higher manganese content.
2. Magnetic testing: Both are generally non-magnetic, but 201 may exhibit slight magnetism due to work hardening.
3. Chemical analysis: X-ray fluorescence (XRF) or optical emission spectroscopy (OES) can accurately determine the composition.
4. Density testing: 201 has a slightly lower density (7.8 g/cm³) compared to 304 (8.0 g/cm³).

201 stainless steel is primarily used for decorative tubes, industrial tubes, and some shallow drawn products where cost-effectiveness is prioritized over maximum corrosion resistance. It’s important to note that while 201 can be a suitable alternative in many applications, its lower nickel content may impact its toughness, heat resistance, and overall corrosion resistance compared to 304.

3. How to quickly distinguish 304 and 201 stainless steel?

1. Judgment of dropping liquid medicine

When buying stainless steel, it is essential to determine the type of stainless steel material.

There are several methods for distinguishing between 304 and 201 stainless steels. The most common method is to drop a chemical reagent onto the surface of the stainless steel and observe the color change to determine if it is 304 or 201.

While this method is convenient, it may not always be applicable.

2. Judgment of grinding spark status

Another method is to polish the stainless steel material and identify it as 304 or 201 based on the shape of the sparks produced. This is a commonly used inspection method for scrap recycling personnel.

304 stainless steel produces long sparks, while 201 stainless steel produces relatively dispersed sparks.

3. Tested by the authority

If a definitive quality inspection report is required, it is necessary to seek the services of a third-party organization for chemical composition analysis. This method takes the longest time and incurs the highest cost, but is the only method recognized by the court in the case of a dispute.

4. Spectrometer detection

Another option is the spectrometer detection method, which is a relatively scientific, simple, direct, and widely used method for companies that make large-scale purchases of materials.

The spectrometer instantly reads the elemental content of the stainless steel, allowing for the determination of whether the material is 304 or 201. The reliability and credibility of this method is comparable to that of the chemical analysis method performed by a third-party national testing center.

5. Judge whether there is magnetism

In everyday use, we can also use the magnetic adhesion method to determine the material. 201 stainless steel is magnetic, while 304 stainless steel is typically non-magnetic.

However, some 304 stainless steels may exhibit magnetic properties due to differences in production processes. Therefore, relying solely on the presence or absence of magnetism is not a recommended method for distinguishing between 201 and 304 stainless steels.

6. Judge by unit price and supplier reputation

Distinguishing 304 and 201 stainless steel by visual inspection alone can be challenging.

When buying stainless steel, one suggestion is to first consider the price (per unit) as a factor in determining if it is 201 or 304. Typically, 304 stainless steel is about twice as expensive as 201 stainless steel.

Additionally, it is advisable to choose reputable merchants.

By following these steps, it is possible to avoid purchasing substandard stainless steel products.

4. Which is better, 304 or 201 stainless steel?

The choice between 304 and 201 stainless steel depends on specific application requirements, cost considerations, and performance needs. 201 stainless steel offers a lower unit price, making it a more economical option for applications with less demanding toughness and corrosion resistance requirements.

304 stainless steel, while typically more expensive, provides superior overall performance and versatility. It exhibits higher strength, toughness, and corrosion resistance, making it the preferred choice for applications requiring these properties. Additionally, 304 stainless steel is approved for food-grade applications, whereas 201 is not recommended for food contact.

Key differences and applications:

1. Corrosion Resistance: 304 contains higher nickel content (8-10.5%) compared to 201 (3.5-5.5%), resulting in superior corrosion resistance, especially in chloride-containing environments.
2. Mechanical Properties: 304 generally offers better ductility and work hardening characteristics, while 201 can achieve higher strength through work hardening.
3. Weldability: Both grades are weldable, but 304 typically exhibits better weld quality and less susceptibility to intergranular corrosion in the heat-affected zone.
4. Magnetic Properties: 201 is slightly magnetic, while 304 is non-magnetic in the annealed condition.
5. Cost: 201 is more cost-effective due to lower nickel content, making it suitable for applications where budget constraints are a primary concern.

Applications for 201 stainless steel include:

• Structural components in less corrosive environments
• Decorative elements
• Non-food contact container linings
• Low-cost consumer products (with caution)

Applications for 304 stainless steel include:

• Food processing equipment
• Chemical processing vessels
• Heat exchangers
• Architectural applications
• Medical devices
• High-quality consumer products

When selecting stainless steel products, particularly for food-related or safety-critical applications, it is crucial to verify the material grade, manufacturer reputation, and compliance with relevant standards. While 201 stainless steel products may be prevalent in the market due to their lower cost, they may not meet the necessary performance or safety requirements for certain applications.

In summary, 304 stainless steel offers superior overall performance and is the safer choice for a wider range of applications, especially where corrosion resistance and food safety are concerns. However, 201 stainless steel can be a cost-effective alternative for less demanding applications where its properties are sufficient.

5. Procurement risk of 201 and 304 stainless steel

A comprehensive understanding of the metallurgical and performance differences between 201 and 304 stainless steel is crucial for mitigating procurement risks in industrial applications.

Currently, some unscrupulous suppliers may misrepresent 201 stainless steel as the higher-grade 304 in transactions. This practice is not only unethical and illegal but also poses significant risks to the structural integrity, corrosion resistance, and overall safety of engineering projects and equipment.

Each grade of stainless steel possesses distinct chemical compositions, mechanical properties, and corrosion resistance characteristics, leading to specific usage scenarios and environmental limitations. For instance, while 304 offers superior corrosion resistance in chloride-containing environments, 201 may be more suitable for applications requiring high strength-to-weight ratios.

By now, you should be equipped with the knowledge to differentiate between 304 and 201 stainless steel through various methods, including chemical analysis, magnetic testing, and density measurements. However, it’s important to note that visual inspection alone is insufficient for accurate identification.

Once more, it is crucial to exercise due diligence in material selection and procurement. Consider all factors, including mechanical properties, corrosion resistance, weldability, and long-term performance, rather than being swayed by superficial price differences. Implementing rigorous quality control measures, such as material certifications and third-party testing, can further safeguard against potential material substitution risks.

6. Is 201 stainless steel food grade?

While 201 stainless steel is frequently utilized in kitchenware manufacturing due to its cost-effectiveness, it is not classified as food grade according to industry standards. This austenitic stainless steel contains higher levels of manganese (5.5-7.5%) and nitrogen (0.25% max) compared to food-grade alternatives, which can potentially lead to metal ion migration into food under certain conditions, particularly when exposed to acidic ingredients or high temperatures.

For food-contact applications, the industry standard typically recommends using 304 (18/8) or 316 (18/10) stainless steel. These grades are considered food-grade due to their superior corrosion resistance and chemical stability:

1. 304 stainless steel: Contains approximately 18% chromium and 8% nickel, offering excellent resistance to most oxidizing acids and forming a stable, self-healing chromium oxide layer.
2. 316 stainless steel: Contains 16-18% chromium, 10-14% nickel, and 2-3% molybdenum, providing enhanced corrosion resistance, particularly against chlorides and industrial solvents.

Both 304 and 316 grades exhibit lower reactivity with food substances, minimal leaching potential, and better resistance to pitting and crevice corrosion compared to 201 stainless steel. These properties make them more suitable for food processing equipment, commercial kitchen appliances, and high-end culinary tools where food safety is paramount.

It’s worth noting that while 201 stainless steel is not ideal for direct food contact, it may still be used in non-food-contact parts of kitchen equipment or in less critical applications where its mechanical properties and cost-effectiveness are advantageous. However, for any components in direct, prolonged contact with food, especially in commercial or industrial settings, food-grade stainless steel should be prioritized to ensure compliance with food safety regulations and standards.