17.5 – 19.5
8.0 – 10.5
The chromium content of 304 stainless steel varies between 17.5% and 19.5%. The most common grades of stainless steel 304 are referred to as 18/8 and 18/10.
In each case, the first number indicates the percentage composition of chromium. The second number indicates the percentage composition of nickel. So, 18/8 contains 18% chromium and 8% nickel. Steel can have a nickel composition of up to 35%, but the most common grades have a nickel composition between 0 and 10%.
Nickel helps increase the corrosion resistance of the steel and also makes it austenitic. Properties of austenitic steels include being non-magnetic and non-heat treatable. 304 stainless steel is also far less electrically and thermally conductive than carbon steel.
By adding enough nickel, the crystalline structure of the steel alloy changes from a ferritic structure to an austenitic one. Most of the 300 series grades are austenitic, giving them great strength and corrosion resistance. Because 304 stainless steel withholds attacks from most oxidizing agents, it can be sanitized. This makes it ideal for manufacturing medical and surgical equipment.
The 304 stainless steel grade is also easy to work with. It has higher elongation and better drawdown properties, combined with low yield strength. 304 stainless steel can be fashioned into more complex shapes. This makes it ideal for products as diverse as kitchen utensils and architectural paneling.
This working flexibility is why Type 304 austenitic grade stainless steel is the most versatile stainless steel in the world. It’s also why it’s the first choice for making food-grade container-shaped objects such as sinks and saucepans.
One of the characteristics of austenitic steel is having a low carbon content, and 304 stainless steel contains a mere 0.07% carbon. In fact, 304 stainless steel has a quite diverse chemical composition. All ferrous steels contain varying amounts of iron and carbon, according to their grade. Manganese forms 2% of the makeup of 304 stainless steel. Aside from carbon, this grade also contains trace amounts of phosphorus, sulfur, silicon, and nitrogen. The remaining balance is made up of iron, around 70%.
The Standard, L & H Grades
There are two variants of 304 stainless steel: 304L and 304H. 304L is the low carbon version of 304 stainless steel, the carbon is reduced to improve weldability. The lower carbon content of 304L, less than 0.030% C, improves weldability by lowering the cracking in the heat affected zone of the weld.
304H stainless steel is used for high-temperature applications. These 304 stainless steels are able to be exposed continuously to temperatures around 1500°F before they begin to suffer scaling. Grade 304H is used for applications requiring elevated temperatures as it retains its strength well in the 900 – 1500°F range. As a downside, 304H has reduced corrosion resistance in wet conditions at lower temperatures.
With its strength, durability and corrosion resistance, the 304 grade is a prime choice among stainless steels. It can be supplied in sheet, strip, tube, and bar.