304 Stainless Steel Beginners Guide

What Is 304 Stainless Steel?

304 stainless steel, UNS S30400, is the most widely used stainless steel alloy, containing 18-20% Cr and 8-10.5% Ni, also known as 18 8 stainless steel. SS 304 is non-magnetic under annealing, but has weak magnetic properties after cold working.

304 stainless steel has many names in different countries, here are the Equivalent Names:

Standard	Equivalent Names
UNS	S30400
ASTM	A240，A276 and A312
BS	304S15
JIS	Stainless Steel  304
EN	1.4301
DIN	X5CrNi18-10

There are several types of 304 stainless steel, such as 304L, 304N, 304H. The second most widely used 316 stainless steel has enhanced corrosion resistance compared to AISI 304.

304 Stainless Steel Properties

The following are the SS 304 stainless steel material properties and specifications, including chemical composition, physical and mechanical properties, heat treatment, corrosion resistance, machinability and machining, welding, etc.

304 Stainless Steel Composition

ASTM	C, ≤	Si, ≤	Mn，≤	P, ≤	S, ≤	Cr	Ni	N, ≤
ASTM A240/A240M	0.07	0.75	2.00	0.045	0.03	17.5-19.5	8.0-10.5	0.1
ASTM A276/A276M	1.00	2.00	0.045	0.03	18.0-20.0	8.0-11.0	–
ASTM 666; SAE J405	0.75	2.00	0.045	0.03	18.0-20.0	8.0-10.5	0.1
ASTM A313/A313M	1.00	2.00	0.045	0.03	18.0-20.0	8.0-10.5	0.1
ASTM A479/A479M	1.00	2.00	0.045	0.03	18.0-20.0	8.0-10.5	–
ASTM A314; ASTM A580/A580M	1.00	2.00	0.045	0.03	18.0-20.0	8.0-10.5	0.1
ASTM A473	1.00	2.00	0.045	0.03	18.0-20.0	8.0-11.0	0.1
ASTM A959	1.00	2.00	0.045	0.03	17.5-19.5	8.0-11.0	–

304 Stainless Steel Physical Properties

SS 304 stainless steel physical properties include density, melting point, specific heat, resistivity, elastic modulus, thermal conductivity and coefficient of thermal expansion.

Density，g/cm3	7.93
Melting Temperature，°C	1400-1450
Specific Heat，J/kg·K	500 at 20 °C
Resistivity，μΩ·m	0.72 at 20 °C
Conductivity，%，IACS	2.5
Magnetic Permeability	1.02
Modulus of Elasticity, GPa	193
Thermal Diffusivity，mm2/s	3.84
Thermal Conductivity，W/m·K	16.2 at 100 °C  21.5 at 500 °C
Coefficient of Thermal Expansion, 10 -6 /K	17.2 at 0-100 °C  17.8 at 0-315 °C  18.4 at 0-538 °C

304 Stainless Steel Mechanical Properties

AISI 304 stainless steel mechanical properties include tensile strength, yield strength, elongation, area reduction, Brinell hardness and Rockwell hardness, etc.

• Tensile strength ranges from 550 MPa to 700 MPa.

• Yield strength ranges from 200 MPa to 250 MPa.

• Elongation ranges from 30%-40%.

• SS304 has a hardness of 70HRB, providing wear resistance for machinery.

• Stainless steel 304 fatigue strength is 230 MPa.

• AISI 304 has moderate creep strength allowing it to be used below 600ᵒC.

• Shear strength of 310 MPa can be used as fasteners and bolts.

• Impact strength of 70J, with good impact resistance.

• Modulus of elasticity is 193GPa.

• The ratio of poison of SS304 is 0.3, with an appropriate deformation limit.

Stainless Steel 304 Grade Features

Corrosion resistance: Grade 304 stainless steel has excellent corrosion resistance. It has excellent corrosion resistance in oxidizing acids, and has good corrosion resistance in alkaline solutions and most organic acids, as well as in the atmosphere, water, and steam.

High temperature resistance: The material still maintains stable performance under high temperature environment and is suitable for high temperature furnaces, heat treatment equipment, etc.

Excellent processability: SUS304 can be formed by cold processing, hot processing, etc., which is easy to process and manufacture.

Good strength and toughness: The material has good mechanical properties and can withstand a certain load.

SUS 304 Stainless Steel Standard And Product

Product	Material Standard And Grade	Picture
Butt-welding Fittings	ASTM/ASME WP304, WP304L, WP304H, WP304LN, WP304N
Forged Pipe Fittings	ASTM/ASME 304, 304L, 304H
Flanges Forgings	ASTM/ASME F304, 304L, 304H
Fasteners	ASTM 304, 304L
Steel Pipes and Tubes	ASTM A312, ASTM A213, ASTM A269
Steel Bars And Rods	ASTM/ASME SA276/479 ASTM/ASME SA479
Steel Plates Sheets Coils	ASTM A240

Is 304 Stainless Steel Good?

304 stainless steel is very popular because its rust resistance, strength, workability, and best value. But is it the best choice? Let's see how it compares to other common types:

304 vs 316 Stainless Steel: 316 has more molybdenum than 304. This makes alloy 316 much better at resisting rust from salt water and chemicals. Choose 316 for boats or harsh industrial places. 304 costs less and is fine for everyday things like sinks.

18-8 Stainless Steel vs 304: "18-8" usually means the same steel as 304! Both have about 18% chromium and 8% nickel. "18-8" as another name for 304-grade stainless steel.

304 vs 430 Stainless Steel: 430 is magnetic and cheaper than 304. But it has much less nickel, so it rusts easier, especially outdoors or near salt. Use 304 for sinks or appliances; 430 is good for some indoor parts or trim.

18-10 Stainless Steel vs 304: 18-10 has slightly more nickel than 304. It a bit stronger and often gives a nicer finish. It's a premium choice for high-quality cutlery like knives, forks, spoons. Regular 304 is great for most cookware.

304 vs 303 Stainless Steel: 303 has sulfur added to make it easier to cut quickly. But this sulfur makes 303 less resistant to rust than 304. Pick 303 for parts needing lots of machining; choose 304 for better rust resistance.

304 vs 409 Stainless Steel: 409 is cheaper and used mostly for car exhaust parts. It resists heat well but has much less chromium than 304. It rusts much faster in normal conditions. 409 is for exhausts; 304 is for general use.

Stainless Steel 201 vs 304: 201 uses manganese and nitrogen instead of some nickel. It costs less than 304 but doesn't resist rust as well, especially over time or near salt. 304 is the better, more durable choice for most products.

FAQs

Q: Is 304 stainless steel magnetic?
A: Usually no. 304 stainless steel is generally non-magnetic. Sometimes it can show a very slight magnetic response, but it is not strongly magnetic like regular steel.

Q: Is 304 stainless steel food grade?
A: Yes. 304 stainless steel is commonly used for food equipment. It is generally considered food safe. It meets standards like FDA and NSF for food contact because it is non-reactive and corrosion resistant.

Q: Does 304 stainless steel rust?
A: Yes, it can rust, but it is corrosion resistant. Under normal conditions, it resists rust well. However, it can rust if exposed to strong chemicals, salt water, or poor cleaning for long times. Chlorides (like salt) can cause pitting corrosion.