What is quenched and tempered steel?

Editor’s note: This blog article was originally published in June 2015 and has been updated for accuracy and comprehensiveness in May 2019. 

Modern steel manufacturing processes have advanced so considerably in the past few decades that we now have cleaner, leaner, stronger and more workable steel than ever before.

In the past, ductility and weldability came at a cost to strength and toughness. Now, there’s quenched and tempered steel, a high strength and abrasion-resistant steel that comes with enhanced fabrication qualities.

Before we launch into a list of benefits and applications, let’s first outline how quenched and tempered steel plate is produced.

What is quenching and tempering?

Quenching and tempering are processes that strengthen and harden materials like steel and other iron-based alloys. The process of quenching or quench hardening involves heating the material and then rapidly cooling it to set the components into place as quickly as possible. The process is tightly controlled, with the heating temperature, cooling method, cooling substance and cooling speed all dependent upon the type of material being quenched and the desired hardness. A typical heating range is between 815 and 900 degrees celcius, with extra care being taken to keeping the temperature as stable as possible. Variances in the degree of heat being applied during the process can result in distortion in the resultant metal.

Likewise, the temperature of the cooling element needs to remain constant or the edges of the metal can wind up brittle. Different cooling elements have come into prominence over the years, naturally starting with water and moving onto mineral oils and even inert gases like nitrogen or helium.

After the material has been quenched to its hardest state, the process of tempering is used to achieve greater toughness and ductility by decreasing hardness. Tempering is achieved by heating the quenched material to below the critical point for a set period of time, then allowing it to cool in still air. Both the temperature and heating time depend on the composition of the material and will determine the amount of hardness removed.

Benefits of quenched & tempered plate

By tempering quenched steel, it becomes less brittle and more ductile without sacrificing too much hardness. It is the combination of these two processes that produces a harder, tougher steel that’s more weldable and ductile than ordinary carbon steel. While it takes longer to manufacturer, the increased strength makes up for the delay. If the steel becomes too hard after quenching, it can be tempered. This involves heating the element again, but to a point far below the temperature reached in the quenching stage – usually around 540 degrees Celsius. The amount of time the quenched metal is tempered is the determining factor to how much hardness is removed.

The toughness-factor means greater resistance to wear and abrasion. That is why quenched and tempered steel is particularly useful in machinery and structures where greater abrasion resistance and higher yield strength are necessary, such as mining, quarrying, earth moving and construction.

Common applications

Quenched and tempered plate steel comes in several grades and thicknesses for different applications. Some of the common grades include: 80 Grade – a high strength, low alloy structural steel; 400 400 Grade  – a high hardness, abrasion-resistant steel; and 500 Grade – a medium carbon, high hardness and abrasion-resistant steel.

Here are several examples of applications where quench and tempered plate steel is ideal:

  • Storage tanks (80 Grade)
  • Bridges and high-rise buildings (80 Grade)
  • Excavator and loader buckets (80 Grade)
  • Deflector plates (400 Grade)
  • Gear wheels (400 Grade)
  • Cutting edges (500 Grade)
  • Earthmoving buckets (400 & 500 Grade)
  • Dump truck wear liners (500 Grade)
  • Chutes (80 Grade, 400 and 500)
  • Low Loader Trailers (80 Grade)

Having a thorough understanding of how quenched and tempered steel is produced and its material properties helps define how best to cut, bend and work the steel. At ShapeCUT, we have 5,000+ tonnes of steel in stock, including quench and tempered plate, and the technical know-how and experience to craft it into any form imaginable.

Contact us today on 1800 ShapeCUT (1800 742 732) and have us deliver your steel profile cutting needs with precision, reliability and speed – no matter the job size.