The main difference between AISI 8620 and AISI 8620H is the guarantee of hardenability.

The suffix "H" stands for Hardenability. Unlike standard 8620, 8620H is produced with controlled chemistry to meet a specified hardenability range (typically verified by a Jominy hardenability test). This ensures that, after carburizing and quenching, the steel develops a more predictable case depth, hardness profile, and core properties. As a result, heat treatment results are more consistent from one production batch to another.

Standard 8620 has the same nominal chemical composition but does not include a hardenability requirement. Although it can also be carburized and quenched successfully, variations in hardenability between different heats may lead to differences in core hardness and mechanical properties after heat treatment.

Typical Applications

8620H

• Automotive transmission gears

• Differential gears and shafts

• Tractor drivetrain components

• Oilfield and mining equipment

• Heavy-duty carburized parts where consistent heat treatment performance is essential

8620

• Steam turbine gears

• Connecting rods

• General machinery components

• Other carburized parts where slight variations in heat treatment performance are acceptable

Which Grade Should You Choose?

If your application requires high consistency in heat treatment results, especially for high-volume manufacturing or critical power transmission components, 8620H is generally the preferred choice. The guaranteed hardenability helps reduce variation in case hardness and core strength, resulting in more reliable product performance.

For general engineering applications where strict control of hardenability is not critical, standard 8620 is often sufficient and may offer a cost advantage.

In short, 8620H is essentially the hardenability-controlled version of 8620, providing more predictable heat treatment performance and improved consistency for demanding applications.

VIM STEEL sells exclusively AISI 8620H round bars from Dongbei Special Steel.

https://www.dgvimsteel.com/

https://www.dgvimsteel.com/engineering-steel-8620

Contact us: info@dgvimsteel.com Whatsapp: +86 13423121371