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443 vs 304 Stainless Steel: Key Differences Explained

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Key takeaways:

1. SUS443 stainless steel (21CT) emerges as a cost-effective and environmentally sustainable alternative to the widely used SUS304, offering comparable corrosion resistance and superior thermal properties without relying on nickel, thus reducing susceptibility to volatile raw material prices and providing a more stable pricing structure for manufacturers and end-users.

2. The addition of titanium and copper to 21CT not only enhances its corrosion resistance and formability but also improves its suitability for a variety of applications, including kitchenware and appliances, by allowing it to maintain structural integrity after deep processing without the need for annealing, thereby cutting production costs.

3. Despite the lower tensile strength compared to SUS304, 21CT's advantageous physical properties, such as higher thermal conductivity and lower density, combined with its strong performance in corrosion and stress corrosion cracking tests, position it as a viable and potentially preferable material for industries prioritizing cost-efficiency, durability, and environmental compliance.

I. Price Comparison Between Stainless Steel 304 and 443

Material/ThicknessSUS443/2BSUS304/2B
0.31900025100
0.41850023600
0.51750022800
0.61680022500
0.71680022400
0.81660022200
0.91650022100
11650022100
1.21630021900
1.51610021700
1.81610021700
21600021700
2.21600021700
2.5160001700
31600021700
>3.01700023200

Unit: CNY/Ton.

II. Introduction to 304 Stainless Steel and 443 Stainless Steel

304 is a common and widely used type of steel, commonly known as Stainless Steel 304. To maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 12% chromium and above 8% nickel.

Stainless Steel 304 is widely used in daily life, for instance, in high-end stainless steel tableware, outdoor railings, etc., and also in the manufacturing of equipment and parts that require good combined performance (corrosion resistance and formability).

However, the constant fluctuation in the international price of nickel has also affected the price of 304, as nickel is a limited resource. Consequently, the overall price trend of Stainless Steel 304 is rising, which is one of the significant factors limiting its development.

Given the current instability in the international market for stainless steel raw materials and the increasingly fierce competition, the demand for reducing material costs is becoming more urgent among users. End users are becoming more detailed in their requirements for stainless steel materials.

Therefore, there is an urgent need for a product that can replace Stainless Steel 304. Our company, in collaboration with Japan’s JFE and TISCO, has developed 21CT (brand name: SUS443) to address this issue. 21CT was successfully developed in September 2005, with official sample pieces provided for customer testing from January 2006. By November 2006, it had been widely accepted and used by consumers.

III. Main Features of 443 Stainless Steel (21CT)

1. The chromium content has been increased to 21%, showing excellent corrosion resistance similar to stainless steel 304, and its pitting resistance is better than 304.

2. The impurities such as carbon and nitrogen have been reduced, and elements like titanium and copper have been added, significantly enhancing its corrosion resistance.

3. 21CT belongs to the ferritic 400 system, with the brand number SUS443, it has the characteristics of ferritic stainless steel, and its mechanical properties are superior to SUS430.

4. Since nickel is not added, its price is about 30% cheaper than 304, providing better cost control.

5. The thermal conductivity of 21CT is about 30% higher than stainless steel 304, plus good magnetic conductivity, making it more advantageous in cooking product applications.

6. Owing to the inherent characteristics of ferrite, components that have undergone deep processing will not experience delayed fracture due to the release of internal stress, hence, annealing treatment is generally not required, effectively reducing processing costs.

IV. Application Fields of Stainless Steel 443 (21CT)

Kitchenware: Dish sinks, barbecue stoves, kitchen equipment, kettles, cooktops, tableware, range hoods, stove panels, cooking pots…

Appliances: Dishwashers, rice cookers, microwaves, washing machines, freezers, mixers, coffee machines…

Transportation: Refrigerated containers, automotive exhaust system parts, heat exchangers…

Construction: Elevators, escalators, roofs, door and window accessories, miscellaneous hardware, decorative pipes, construction hardware…

Others: ERW pipes, water tanks, water pipes, combustion nets, barbecue nets, mufflers…

Currently, the main application fields of 443 materials in our company (mainly stainless steel plates) include the elevator industry, small appliance industry, food equipment, tableware industry, kitchen engineering, etc.

V. Comparative Analysis of Chemical Composition of Stainless Steel 304 vs 21CT

Steel Type21CTSUS304
Chromium2118.2
Nickel8.1
Molybdenum
Titanium0.3
Carbon0.0080.06
Nitrogen0.010.04
Copper0.43

*21CT increases the chromium content to 21%, thus providing better corrosion resistance, and additionally includes titanium and copper elements.

*Titanium can enhance the resistance to intergranular corrosion and improve weldability.

*Copper can improve resistance to acidic substances.

VI. Comparison of the physical properties of SUS304 and SUS443 (21CT)

Steel Type21CTSUS304
Density(g/cm37.747.93
Density(10-6Ω·cm)5870
MagnetismYesNo
Specific Heat 25℃(J/kg·℃)440500
Thermal Conductivity 100℃(W/m·℃)22.516.2
Thermal Expansion Rate 20-100℃(10-6/℃)10.517.3
Young’s Modulus (Gpa)204193

Compared to 304, 21CT has: Lower density, allowing for an approximately 2.5% increase in material area for the same weight, better thermal conductivity, less thermal expansion, magnetism, and excellent properties suitable for use with induction cookers.

VII. Comparison of Mechanical Properties between SUS304 and 443 (21CT)

Steel TypeSUS443SUS304
Yield Strength (MPa)305260
Tensile Strength (MPa)483645
Extension Rate (%)3160
Average R Value1.31
Hardness (Hv)161185
Cone Cup Protrusion (mm)38.637.7
Bendability (Bend Angle 180°)Good(R=0T)Good(R=0T)

The R value is an indicator of the deep drawing performance of the material. The higher the R value, the better the deep drawing performance!

VIII. Comparison of thermal conductivity between SUS304 and 21CT

Test result graph for boiling 2 liters of water.

Conclusion: When heating with gas or an induction stove, the thermal conductivity of 443 is superior to that of stainless steel 304!

IX. Comparison of the welding performance between 304 and 443 (21CT):

CombinationTIG Welding  MIG Welding  Arc Welding
Welding of the same type: 21CT and 21CT
Welding of different types: 21CT and SUS304
  • □: Corrosiveness will not decrease or decrease very slightly
  • ■: Corrosiveness will decrease

Note: For more detailed welding technical data and welding skills, you can contact our company to obtain them.

X. Comparison of Corrosion Performance Results between 304 and 443 Stainless Steel Plate

Steel Type    Cyclic Corrosion TestingSalt Spray Test (NSS)Exposure Test Corrosion of Welded Parts
SUS443     
SUS304     

Methods to test corrosion resistance:

1. Surface #600 polished stainless steel plate, saltwater spray (5% NaCl, 35℃, 2hr) → dry (60℃, 4hr) → moisten (40℃, 2hr), repeat 30 times.

2. Surface #600 polished stainless steel plate, neutral saltwater spray (5% NaCl, 35℃), 1000 hours.

3. Surface #600 polished stainless steel plate, exposed for 9 months in Chiba Prefecture, Japan, 10 meters from the shore, with sea salt adsorption quantity of 0.25mg.dm-2.day-1.

4. TIG welding, plate thickness is 0.8mm, contact start arc welding, using argon gas for protection, and polished with surface #600 after welding.

XI. Comparison of Stress Corrosion Cracking Tests Between SUS304, SUS304, and SUS443

Comparison of Stress Corrosion Cracking Tests:

Steel Type 304 Stainless Steel443 Stainless Steel
Presence or Absence of a BreakBreakage occurs within ≤15 hours.No breakage after 100h test
Appearance After Testing  

Condition: 42% MgCl2U, JIS G 0576 shape bending

Conclusion: 304 stainless steel may undergo stress corrosion cracking, but 443 stainless steel is not at risk of this occurrence.

XII. 443 Certified

EU ROHS CertificationCompliant with the European Union’s environmental protection standards (SGS certified)
International Health CertificationConforms to the requirements of GB-9684-1988 “Hygienic Standard for Stainless Steel Food Utensils and Containers”
Germany LFGB CertificationComplies with German food and commodity laws, and meets the requirements for metal release from stainless steel tableware
US FDA CertificationMeets the food safety regulatory standards of the United States, and the requirements for metal release from stainless steel tableware

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