Alloy steel is steel that has been combined with other elements to create a new kind of material with different mechanical properties. Some of the most common elements that are combined with steel via alloying are aluminum, copper, boron, nickel, silicon, sulfur, and titanium.
Bismuth and lead improve the machinability of steel, boron makes it even harder, and copper helps with corrosion resistance.
Nickel is one of the rare elements that has a double effect. It can improve the toughness of steel if its concentration in the alloy is between 2 and 5 percent. If its concentration is between 12 and 20 percent, it can improve the corrosion resistance greatly. Thanks to its diversity and strength, nickel alloy is used in several areas: consumer, business, army, transport, aerospace, marine, and architectural applications. Many companies provide various nickel alloy products in different shapes and even custom made upon request.
Of course, steel is itself an alloy of iron and carbon. It is one of the strongest materials that we have as well as one of the cheapest to create. Alloy steel and high speed steel are the most important type of tool steel.
Alloy Steel Types
Alloy steel is divided into two types: low alloy steel and high alloy steel. There is no agreed upon definition of what constitutes low alloy steel and high alloy steel but in general, when speaking about alloy steel we refer to low alloy steel. Some of the most common types of alloy steel are 300M and 256A.
When we talk about alloy steel applications we can divide alloy steel into four distinct groups:
1. Magnetic Alloys
These alloys contain at least one of three elements with magnetic properties, most likely iron, nickel, and cobalt. The strongest alloys in this class include iron as part of their composition. This gives them magnetic properties.
2. Tool and Die Steel
These alloys are characterized by a combination of abrasion resistance and air-hardening characteristics. 4140 steel belongs in this category.
3. Stainless and Heat Resistant Steel
Stainless steel includes elements that hinder corrosion in its composition, while heat resistant steel is steel that has been treated so it can resist very high temperatures.
4. Structural Steel
This is probably the most known and widespread application of alloy steel. It is usually used in large buildings for structural stability. People have realized the potential of this type of alloy and many structures that are deemed very safe, even when hit by a powerful earthquake, come with some sort of structural steel.
Popular Steel Alloys and Their Applications
4140 Alloy Steel
One of the most versatile types of steel is 4140 alloy steel. There are a wide variety of industries that use this alloy steel. 4140 steel is steel alloyed with chromium and molybdenum. Chromium gives the steel much greater hardness penetration, while molybdenum increases its strength and hardness. These properties make this alloy a great material for manufacturing shafts, nuts, bolts, all kinds of machinery parts, gears, slides, steel collets, drill collars, and other parts.
4130 Alloy Steel
Another popular and widely available type of alloy steel is 4130 steel. Like 4140 steel, it is also an alloy of steel, chromium and molybdenum, albeit with different concentrations of these elements. The carbon content in this alloy is around 0.30 percent. Its small concentration of carbon makes this material a very good choice for fusion weldability. One of the most common applications for this type of steel is for structural purposes, including aircraft engine mounts and tubing applications. It can be easily machined, but is most easily treated when in a normalized and tempered condition. If you are looking for an alloy steel that is easy to weld and easy to cold work, 4130 steel is one of the best options.
Now you have a better idea of what kind of steel to choose for your specific purpose.