304 Stainless Steel: A Comprehensive Guide

304 Stainless Steel: A Comprehensive Guide to Standards, Properties, and Uses

An in-depth overview of 304 stainless steel—its standards, composition, properties, applications, and precautions—tailored for industry professionals and buyers.

Table of Contents

1. Global Standards for 304 Stainless Steel
2. Chemical Composition & Key Element Functions
3. Mechanical Properties
4. Modified Variants of 304
5. Comparison with Other Stainless Steel Grades
6. Typical Applications
7. Common Forms & Surface Finishes
8. Critical Usage Precautions
9. About Us

1. Global Standards and Designations for 304 Stainless Steel

304 stainless steel has different names depending on the country. For instance, in the US, it is called UNS S30400. However, in China, it goes by 06Cr18Ni9. Therefore, it is important to check the standard before buying.

2. Chemical Composition of 304 Stainless Steel

304 steel follows a strict chemical formula. Specifically, it is an “austenitic” alloy. This means it contains a specific mix of metals to keep it stable.

2.1 Chemical Composition (Mass Fraction, %)

2.2 Key Element Functions in 304 Steel

• Chromium (Cr): This is the most important part. Basically, it fights rust. It reacts with air to create a thin shield. As a result, the steel does not corrode easily.
• Nickel (Ni): Nickel makes the steel structure stable. Furthermore, it helps the steel resist acid. Also, it keeps the steel non-magnetic.
• Manganese (Mn): This element removes oxygen during production. However, too much manganese can make the steel weak against rust.
• Carbon (C): Boosts tensile strength but reduces ductility. High carbon content also increases the risk of corrosion (avoiding >0.08% is critical).
• Phosphorus (P) & Sulfur (S): Harmful impurities. They degrade weldability, plasticity, and cold-forming performance—hence strict upper limits.

3. Mechanical Properties of 304 Stainless Steel

Generally, 304 steel is strong and flexible. Below are the typical numbers for 304 coils:

Please note that these numbers can change. For example, cold rolling or heating the steel will alter its strength.

4. Common 304 Stainless Steel Variants

Sometimes, standard 304 is not the best fit. Consequently, engineers created modified versions.

• 304L: This version has less carbon. Therefore, it is better for welding. Because it has low carbon, it prevents cracks near weld joints.
• 304N: This type has added nitrogen. As a result, it is stronger than standard 304.
• 304J1: This variant adds copper. Thus, it is cheaper but still strong.

5. 304 Stainless Steel vs. Other Grades: A Detailed Comparison

Buyers often confuse 304 with other types. Here is how they compare.

5.1 304 vs. 316 Stainless Steel: Corrosion Resistance

304 works well in dry or fresh water areas. In contrast, 316 contains molybdenum. This added metal helps 316 resist salt. So, if you are near the ocean, use 316. Otherwise, 304 is a cheaper choice.

5.2 304 vs. 430 Stainless Steel: Magnetic Properties

304 has nickel, while 430 does not. Because of this, 430 is magnetic. On the other hand, 304 is usually non-magnetic. Also, 304 resists rust better than 430.

5.3 304 vs. 201 Stainless Steel: Food Safety

304 is food-grade. This means it is safe for cooking. However, 201 contains high manganese. Consequently, it might rust or leach chemicals in acidic food. Therefore, never use 201 for cookware.

6. Industrial and Commercial Applications of 304 Stainless Steel

304’s balanced performance makes it the most versatile stainless steel grade, used across industries:

• Food Industry: Food processing equipment, food-grade kitchenware (pots, pans, utensils), and storage containers.
• Automotive: Windshield wipers, mufflers, fuel tanks, and decorative trim.
• Medical: Non-critical medical devices (e.g., drug storage cabinets, instrument trays).
• Construction: Indoor roofing, wall cladding, handrails, and elevator panels (ideal for dry environments).
• Industrial: Chemical tanks (non-aggressive fluids), water treatment components, and industrial fasteners.

7. 304 Stainless Steel Surface Finishes and Forms

7.1 Common 304 Steel Forms (Coils, Sheets, Pipes)

You can buy 304 steel in many shapes. Most typically, it comes in coils, sheets, or pipes. Additionally, you can choose different surface looks:

Mirror Finish (8K): This looks like a glass mirror.

Satin Finish: This has a lined texture.

Matte: This is dull and not shiny.

• Coils: The primary form (wide-width rolls). Processed into sheets, plates, or strips for downstream manufacturing.
• Bars/Rods: Used for machining parts (e.g., bolts, screws).
• Tubes/Pipes: For fluid transport (e.g., water pipes, industrial pipelines).
• Custom Castings: Tailored to complex shapes (e.g., valve bodies, pump components).

7.2 304 Surface Finishes (Mirrored, Satin, Brushed)

Finishes are chosen for aesthetics, corrosion resistance, or functionality:

8. Critical Precautions When Using 304 Stainless Steel

First, avoid salt. Chloride ions in salt or sweat eat away at 304 steel. Subsequently, it will rust. Second, do not trust a magnet test. Although 304 is technically non-magnetic, bending it can make it slightly magnetic. Therefore, a magnet test is not accurate. Finally, choose the right type for sinks. Specifically, use “304DQ” for deep sinks to prevent cracking.

• Avoid Chloride Exposure: Chloride ions (found in salt, sweat, seawater, or soy sauce) rapidly corrode 304. For long-term contact with chlorides, use 316 instead.
• Kitchenware Selection: For deep-drawn items (e.g., sinks), choose 304DQ (not standard 304) to prevent cracking during forming.
• Magnetism Misconception: 304 is non-magnetic in its original state, but heavy deformation (e.g., stamping) may induce weak magnetism. Do not use “magnet testing” as a reliable way to identify 304.
• Post-Processing Cracking: Austenitic stainless steel (like 304) may crack 5 minutes to 10 days after heavy stretching (due to internal stress). Contact us for stress-relief solutions.

9. Contact Us for 304 Stainless Steel Supply

We are a professional supplier of 304 stainless steel (coils, sheets, tubes, and custom parts) with strict quality control aligned with global standards. For inquiries about 430, 410, 201, or other stainless steel grades, contact our team for personalized quotes and technical support.