DIN EN 10325 specifies a method for determining the increase in yield strength through heat treatment (bake hardening index). Bake hardening is a controlled ageing process that can be attributed to the carbon and nitrogen present in the steel in solid solution. The test determines an index that indicates the increase in yield strength of a sample that has been plastically pre-stretched by 2% and then heat treated in a defined manner.
The Bake-Hardening Index (BHI) is a metallurgical and materials science metric used to evaluate the extent to which a high-strength steel becomes harder after a specific baking or heat treatment process. This process, called bake-hardening, is typically applied to certain types of automotive steels.
Bake-hardening steels are designed to have increased strength and hardness after a specific heat treatment, which usually involves baking the steel at a set temperature for a defined period of time. This post-forming heat treatment is used in the automotive industry to improve the dent resistance of body panels.
The Bake Hardening Index is calculated by measuring the difference in the yield strength (the stress level at which a material exhibits plastic deformation) of the steel before and after the bake hardening process. The index is expressed as a percentage and represents the increase in yield strength due to the heat treatment. A higher Bake Hardening Index indicates a greater increase in strength, which can lead to improved dent resistance in automotive components made from these steels.
The Bake-Hardening Index in Car Body Construction
The (BHI) is a metric used in the automotive industry to evaluate the change in strength and hardness of special high-strength steels after heat treatment. This process, known as bake-hardening, is used to improve the dent resistance of body steels.
Bake-hardening steels are designed to have increased strength and hardness after a special heat treatment in which the steel is baked at a certain temperature for a defined time. This process is used in the automotive industry to increase the resistance of body panels to dents, which is particularly important in the manufacture of car bodies.
The Bake Hardening Index is calculated by measuring the difference in the yield strength (that is the stress value at which a material exhibits permanent deformation) of the steel before and after the Bake Hardening treatment. This index is expressed as a percentage and indicates how much the yield strength has increased due to the heat treatment. A higher Bake Hardening Index indicates a greater increase in strength, which means that the body steels are more resistant to dents after heat treatment.
In the automotive industry, the Bake Hardening Index is therefore an important tool for evaluating and selecting steels used in body components to ensure the safety and durability of vehicles.
