As manufacturing processes have evolved and become more complex, steel buyers’ options have expanded to suit many unique needs across a variety of industries.
But not all types of steel are equal. Piping industry professionals can become better buyers by examining the types of steel available today and understanding why some steels make great pipe and others do not.
This rundown should help.
Steel is created when carbon is added to iron, which is relatively weak on its own. In modern industry, carbon is the most prominent additive to a ferrous material, but alloying elements of all sorts are common.
In fact, alloying elements are common even in piping products still considered to be carbon steel.
According to the American Iron and Steel Institute (AISI), ferrous material is designated as carbon steel when its core makeup is specified to include no more than 1.65 percent manganese, 0.60 percent silicon and 0.60 percent copper and when no minimum content is specified for other alloying elements.
Carbon steel pipe enjoys wide use across many industries due to its strength and ease of workability. Because it contains relatively few alloying elements and in low concentrations, carbon steel pipe is relatively inexpensive.
However, it isn’t suited for extreme temperature or high-pressure service because the lack of alloying elements makes it less resistant to the accompanying stresses.
Alloy steels are what they sound like: Steels that include specified amounts of alloying elements. Generally, alloying elements make steels stronger and more resistant to impact or stress. While the most common alloying elements include nickel, chromium, molybdenum, manganese, silicon and copper, many others are used in the production of steel.
There are countless combinations of alloys and concentrations in use in industry, with each combination designed to achieve specific qualities.
High-alloy types of steel are favored in the piping industry for service in extreme conditions, whether it be in hot or cold conditions or subject to rough use. That’s because the combination of chemistry and proper heat treating can yield strong yet ductile pipe that can take a beating. The oil & gas and power generation industries often favor alloy pipe due to its toughness.
Alloying elements also impart increased corrosion resistance to steel pipe. That makes it a leading choice for chemical companies as well.
The term is a bit of a misnomer. There’s no one combination of iron and alloying elements that makes stainless steel what it is. Instead, stainless steel refers to the fact that products made from it do not rust.
Alloys in stainless steels can include chromium, manganese, silicon, nickel and molybdenum. These alloys work together to interact with oxygen in water and air to quickly form a thin but strong film over the steel that prevents further corrosion.
Naturally, stainless steel pipe is used in any industry where corrosion protection is necessary. While stainless steel pipe is essentially alloy pipe by another name, it is not well suited for extreme service unless it’s been appropriately heat treated to increase strength and impact resistance.
Due to its aesthetic appeal, stainless steel is often chosen if pipe must be visible in public or professional settings.
Tool steels are what turn other types of steel into products or equipment used in industry. They must be incredibly strong, tough, ductile and resistant to corrosion. They also must be able to retain cutting edges and maintain their shape in high temperatures. To achieve those qualities, these steels contain very high concentrations of alloying elements and are precisely heat treated.
Sometimes called super-alloys, tool steels are not well-suited for piping products. For one thing, incorporation of higher quantities of alloys makes tool steels more expensive to produce. For another, the amount of alloying elements present in tool steels make them harder to form into piping products. Finally, pipes don’t need cutting edges.
It’s cheaper and easier to use comparatively softer, lower-alloy steels to form pipe and then heat treat up to a specified hardness.
The complex chemistry and metallurgy present in steel production can be hard to grasp, but it’s helped industries refine and improve their critical processes.
Become a better buyer by learning more about the types of steel well-suited for specific piping applications. Then, choose a supplier that offers stellar inventory, value-added services and experience on the world market.