Types of Alloy and the Properties of Alloy Steel

Huyett Marketing Department
04/01/2021
Updated 08/10/2023

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Metal is clearly used in a wide range of industries and applications, each of which have different requirements for the
mechanical properties of the metal in question. Some applications require metals that are machinable and ductile, while others need hard metals with significant corrosion resistance, and still others require any number of property combinations, depending on the application setting.

To accommodate this wide range of needs, different types of metal are made to incorporate specific properties. Obvious options include steel, aluminum, brass, copper, nickel – the list goes on. However, your options are not limited to these broad categories. Metals can also be mixed with other metals or elements to form materials with different or enhanced properties – in other words, metals can be
alloyed
.

As steel is one of the most common metal categories, this guide will focus on what a steel alloy is, what elements can be added to them, and some of the most common types of steel alloys.

What Is Alloy Steel?

To understand what alloy steel is, it’s important to know what the terms
alloy
and
steel
mean on their own.

An
alloy
is a mixture of two or more elements that, when mixed, retain metallic properties. It either mixes multiple more metals or metals with non‑metals, such as carbon or phosphorous. The mixture creates unique mechanical properties that the alloying elements don’t have on their own, such as corrosion resistance, increased tensile strength, or greater hardness.

Steel
is a basic mixture of iron and carbon with only trace amounts of other elements. Technically, carbon steel is an alloy since it mixes two elements, but it’s usually referred to as carbon steel – there is a
difference between carbon steel and steel alloys. Its makeup is mostly iron, but the carbon content is the significant structural component.

As the carbon increases, it increases the steel’s strength, hardness, and wear resistance; however, that increase also lowers the steel’s weldability, machinability, and ductility. Low-carbon steel, medium-carbon steel, and high-carbon steel is only differentiated by around 0.3% carbon content, and the total carbon content doesn’t exceed around 2% (any more than that and the metal would become cast iron).

A
steel alloy
is a metal that adds alloying elements onto the basic steel structure. When they are added onto the carbon steel base, it creates different types of steel with added or changed mechanical properties.

A Note About Alloys

It’s important to note that not all mixtures containing metals are alloys. In a metal alloy, the constituents don’t react chemically. If they did, they would form a compound rather than an alloy. For example, adding a certain proportion of chromium or nickel to iron, usually alongside some quantity of carbon, results in the alloy stainless steel. But mixing the metal sodium and the halogen chlorine does not form an alloy; the elements react to form sodium chloride (table salt).

Characteristics of Common Alloy Elements

The following section lists common alloying elements found in metal alloys and the characteristics they typically offer.

Boron

Boron increases hardenability.

Carbon

Carbon is the basic alloying ingredient in steel. It increases the hardness and strength of iron.

Nitrogen

Nitrogen helps in the formation of austenite and increases its stability and strength.

Aluminum

Aluminum deoxidizes steel and restricts grain growth.

Silicon

Silicon is used as a deoxidizing or killing agent. It increases hardening of the ferritic phase in steels.

Phosphorus

Phosphorus is added to increase machinability; however, it can contribute to cracking during welding.

Sulfur

Sulfur improves machinability but can also damage hot forming characteristics.

Titanium

Titanium is used to keep carbon from combining with chromium so that the piece retains its noncorrosive properties.

Vanadium

Vanadium increases hardenability and corrosion resistance.

Chromium

Chromium is the primary alloy ingredient in stainless steel adding corrosion resistance.

Manganese

Manganese increases strength, toughness, and hardenability and counteracts brittleness from sulfur.

Iron

Iron is the primary ingredient of all steels. It is the foundation element in the chemical composition of steel.

Cobalt

Cobalt can become highly radioactive and is limited in nuclear applications. Used in medical implants and is corrosion resistant.

Nickel

Nickel is used in the most corrosion and heat resistant stainless steels increasing strength and toughness.

Copper

Copper , normally present in stainless steels, can be added to aid in precipitation hardening.

Selenium

Selenium is added to improve machinability.

Niobium

Niobium helps stabilize carbon and adds strength to steel intended for high temperature service.

Molybdenum

Molybdenum enhances corrosion resistance and increases high temperature strengths.

Tantalum

Tantalum is very similar to Niobium and has the same effects when alloying to Iron.

Tungsten

Tungsten increases wear resistance and raises hot strength and hot hardness.

Lead

Lead increases machinability characteristics.

Common Types of Alloy Steel

There are many different steel alloys available, but let’s take an introductory look at a few of the types of steel alloys Huyett uses to manufacture fasteners and machine components such as
keyed shafts.

1018 Steel
is a variety of low‑carbon steel, also known as mild steel. It contains a maximum of 0.2% carbon and smaller quantities of other elements. It offers an excellent compromise between strength, ductility, and machinability and is widely used in many applications. As low‑carbon steel, it can be case-hardened through carburization. It’s used to make fasteners like
rivet nuts and different types of
pins.
1144 Steel
is medium-carbon steel with between 0.4 and 0.8% carbon, plus smaller quantities of manganese. It is relatively easy to machine and it can be heat‑treated to increase its hardness.
304 and 316 Stainless Steel
are austenitic steels that contain chromium and nickel. 316 stainless steel also contains molybdenum, which improves its resistance to some types of corrosion. These stainless steels are widely used in screws and other types of corrosion‑resistant fasteners like
key stock,
pins, some
lifting and rigging hardware, and
hose clamps.
410/416 Stainless Steel
are martensitic steels that contain between 11 and 12% chromium along with other elements including silicon, nickel, sulfur. 410 is a low-cost, heat treatable grade used for cutlery, screens, spring pins, turbine blades, and other non-severe corrosion applications. 416 offers excellent machinability and some magnetism, making it suitable for dowel pins, nuts, bolts, valve trim, and other fasteners.
4140 Alloy Steel
, also called “chrome-moly” steel, is made up of chromium, manganese, and molybdenum. It is tough, ductile, and wear resistant, which makes it ideal for forging and responds well to heat treatments. As arguably the most common alloy steel available, it is used in almost all industries.
8630 Alloy Steel
contains molybdenum, chromium, and nickel. It is tough yet ductile and offers good weldability and machining properties. 8630 is often used to make fasteners like
woodruff keys,
key stock, and
machine keys.

These are just a small fraction of the vast number of steel alloys that are available. You can learn much more about steel alloys, their classification, and their metallurgical properties in our
guide to steel alloy materials and attributes.

Non-Steel Metal Alloys

Alloys of other metals also have valuable properties and are widely used in construction, machine manufacturing, and other scenarios.

Monel
is a nickel alloy. It is predominantly composed of nickel with copper and smaller amounts of iron and manganese. Monel is more expensive than steel, but it is highly resistant to corrosion and high temperatures. It is often used in applications in which components will frequently be in contact with corrosive materials or exposed to very high temperatures. It’s used to make certain types of
machine keys,
rivet nuts, and
grease fittings.
Brass
is an alloy of copper and zinc. It is softer and more ductile than steel while being resistant to corrosion, properties that make it desirable in some applications. It’s used to make certain types of rivet nuts, machine keys, and
pins.

The Bottom Line

Huyett uses steel alloys, non-steel alloys, and many other metals in our fasteners, power transmission components, grease fittings, and more. To learn about our
custom manufacturing capabilities, don’t hesitate to
get in touch with our Sales team for more information.

Types of Alloy and the Properties of Alloy Steel