In this article, we’re going to look at 304 stainless steel properties and what makes it such a popular choice across a range of applications. Before we get into the properties, have you ever wondered why steel is called ‘stainless’?
As you might expect ‘stainless steel’ is not really stain-free – the reason it is called ‘stainless’ is because it takes a much longer time to stain and eventually rust, compared to other metals. This is because stainless steel contains a significant amount of chromium (at least 10.5%).
Depending on the percentage of chromium present, stainless steel is classified into different grades – 304, 304L, 304H, 316 etc. The addition of chromium, and other elements like molybdenum, copper, nickel, phosphorous, titanium etc., alter the properties of stainless steel, and therefore, the type of steel used for an application depends upon the environment in which it would be used.
What is 304 stainless steel?
304 Stainless Steel is an austenite steel and contains between 16% and 24% chromium and up to 35% nickel. The most common type of 304 stainless steel is the 18/8 or 18-8 steel, which constitutes 18% chromium and 8% nickel. Additionally, it contains about 2% manganese, 0.1% nitrogen, 0.03% sulphur, 0.08% carbon, 0.75% silicon and 0.045% phosphorous. 304 stainless steel is the most popular and widely used grade of steel.
What makes it so popular among all grades of steel?
By looking at 304 stainless steel properties, it’s clear to see why it’s used in so many applications. It’s a versatile steel, and comes with many advantages, making it a popular choice with designers and manufacturers alike. It’s used in a wide range of engineering sectors.
304 Stainless Steel Properties
- 304 stainless steel is non-magnetic and exhibits high resistance to corrosion and oxidation against atmospheric, chemical, petroleum, textile, and food industry sources.
- It has good drawability – the combination of low yield strength and high elongation permits fabrication into complex shapes. (Care should be taken to fully anneal them immediately after forming.)
- This austenitic kind of steel is easily weldable. (During welding, there is a likelihood of chromium carbide formation, which might compromise resistance to corrosion. To overcome this, welding needs to be followed by full annealing, which dissolves chromium carbide. Additionally, the austenitic structure is prone to cracking during welding – this is countered by adding a small amount of ferrite while resolidifying.)
- It has high strength and toughness, even at very low temperatures (cryogenic).
- It has a smooth surface, which is easy to clean.
- Its polished surface gives it a good lustre and appearance.
- It can withstand multiple washings with detergents and house-hold chemical cleaners.
- Vickers hardness = 129
- Melting Point = 1400 – 1455 degree C
- Modulus of Elasticity = 193 – 200 GPa
- Tensile Strength = 505 MPa
- Poisson’s Ratio = 0.29
- Density = 8 g/cc
- Magnetic Permeability = 1.008
- Electrical Resistivity = 7.2 e-005 ohm-cm
Types of 304 stainless steel
304 stainless steel has two sub-categories – grade 304L and grade 304H. The grade 304L has lesser carbon content, and does not require annealing post-welding, and is therefore used in heavy gauge components. The grade 304H has a higher carbon content and is used in applications requiring high temperatures.
Applications and uses
304 Stainless Steel is all around us. It’s used in a variety of products across many different sectors. Here are just a few examples of some common uses:
- Chemical industry – Large storage tanks and containers for liquids and solids
- Food industry – food processing equipment like milking machines, storage tanks, hauling tanks, piping, valves, milk trucks etc. Also used in breweries, wine-making and the fruit juice industry.
- Domestic uses – 304 stainless steel can resist the corrosive action of acids found in fruits, milk, meat and vegetables, and is fairly resistant to abrasion. Therefore, it is widely used in sinks, tabletops, stoves, refrigerators, cutlery, utensils and various other appliances.
- Architectural uses – paneling, molding, railings, décor.
- Industrial applications – tools, bolts, nuts, screws etc.
- Automotive and aerospace industries – fuel tanks, various structural components.
- Hospitals – surgical equipment.
- Commercial – sanitary fittings, pipes.
The disadvantage of 304 Stainless Steel
Despite the versatile applications of 304 stainless steel, a major drawback is that it cannot be used in saline environments like near a coastline (a 316 stainless steel would be more appropriate in such conditions instead). The chlorine in these environments creates “pitting” – small areas of localized corrosion, which spreads beyond the protective chromium. In such environments, the 316 grade is used. This contains 16% chromium and 10% nickel, along with about 2-3% molybdenum, which offers resistance to corrosion, especially against chlorides.
304 stainless steel properties account for it’s popularity. It has a long shelf life and preserves its lustre over many years. It is easy to maintain and is economical. All these factors make it an ideal choice for a wide variety of applications.