Quenched And Tempered Steel

Quenched and tempered steel is a steel alloy that undergoes specific heating and subsequent cooling (quenching and tempering) to alter its mechanical properties. This process improves the strength and toughness of the steel and is widely used in various applications.

Table of contents:

• Difference between case-hardened steel and heat-treatable steel
• Unalloyed heat-treatable steel
• Is heat-treatable steel stainless steel?
• When is steel considered heat-treatable steel?
• Tempering in heat treatment
• Applications of heat-treatable steel
• Summary and conclusion

Difference between case-hardening steel and heat-treatable steel

The main difference between case-hardening steel and heat-treatable steel lies in their manufacture and properties. Case-hardening steel is an unalloyed or low-alloy steel with too low a carbon content for hardening. Heat-treatable steel, on the other hand, usually contains 0.2-0.65% carbon and is optimised to the desired strength and toughness properties through heat treatment.

Unalloyed tempering steel

Unalloyed tempering steel can also be referred to as carbon steel and usually contains little to no alloying elements such as chromium or nickel. An example of an unalloyed tempering steel is C45E, which is characterised by its excellent toughness and wear resistance.

Is quenched and tempered steel stainless steel?

Quenched and tempered steel is generally not stainless steel, but it is usually not corrosion-resistant high-alloy stainless steel either. This stainless steel is characterised by high corrosion resistance due to its high chromium content. While tempered steel is modified for improved mechanical properties in terms of strength and toughness, the focus with high-alloy stainless steel is on corrosion resistance.

When is steel considered tempered steel?

Steel is referred to as tempered steel when it undergoes a special heat treatment process known as tempering. This process involves heating the steel to a critical temperature, followed by controlled cooling or quenching with subsequent tempering to achieve the desired mechanical properties. Quenched and tempered steel is often used for applications requiring high strength and toughness, such as in the automotive, mechanical engineering and aerospace industries.

Tempering in heat treatment

An important step in the heat treatment process is tempering, in which the steel is heated to a lower temperature after hardening in order to reduce excess hardness and increase toughness again. This step is crucial to ensure that the steel does not become brittle and achieves its desired mechanical properties.

Applications of quenched and tempered steel

Quenched and tempered steel, also known as hardened steel, is a versatile material that is used in a wide range of applications due to its specific properties. Examples of applications for quenched and tempered steel include:

1. Tool manufacturing: Heat-treatable steel is often used to manufacture tools and cutting tools that require high hardness, wear resistance and toughness. This includes drills, milling cutters, cutting blades, punching tools and many other precision tools.
2. Automotive industry: In the automotive industry, heat-treatable steel is used for parts that have to withstand high loads, such as transmission shafts, axles, crankshafts, camshafts and valve springs. High strength and wear resistance are crucial in these applications.
3. Mechanical engineering: Tempered steel is used in machines and equipment that carry or move heavy loads, such as construction machinery, agricultural equipment and industrial machinery. It provides the necessary strength and durability for such applications.
4. Aerospace: In the aerospace industry, tempered steel is used in components such as bearings, gears, connecting elements and fasteners. These parts must withstand extreme loads at high speeds and in demanding environments.
5. Construction industry: In the construction industry, heat-treatable steel is used in components for heavy machinery, cranes, bridges and other structural elements. Its strength and durability help to ensure the structural integrity and safety of buildings.
6. Energy sector: In energy production, particularly in power stations and in oil and gas extraction, parts made from heat-treatable steel are used to withstand high pressures, temperatures and wear conditions.
7. Medical technology: In medical technology, heat-treatable steel is used for surgical instruments, implants and medical devices, where hygiene, durability and precision are crucial.

Summary and conclusion

Quenched and tempered steel is an important steel alloy that obtains improved mechanical properties through targeted heat treatment. Unlike case-hardened steel, which can only be hardened in the diffused edge zone, heat-treatable steel is optimised for strength and toughness through targeted thermal processes due to its high carbon content. This steel is widely used in various key industries and is an essential component of machines and components that are exposed to high loads.