Testing Procedure

Initial Setup: Place the prepared sample on the anvil of the testing machine. Apply the minor load (pre - load) to the sample using the indenter. This minor load is used to seat the indenter on the sample surface and to zero the depth - measuring device.

Major Load Application: After the minor load is applied and the system is zeroed, the major load is then applied for a specific period of time (usually around 10 - 15 seconds). The major load causes the indenter to penetrate the sample surface, creating an indentation.

Hardness Calculation: After the major load is removed, the depth of the indentation is measured. The Rockwell hardness number is calculated based on the difference between the depth of the indentation under the major load and the depth under the minor load. The formula for calculating the Rockwell hardness number (HRC for the Rockwell C scale) is , where is the difference in indentation depth (in mm) between the major and minor loads.

Multiple Measurements and Averaging

To obtain a more accurate result, multiple measurements should be taken at different locations on the sample. At least three to five measurements are recommended. These measurements should be evenly distributed across the sample surface to account for any possible inhomogeneities in the material. The average of these measurements is then taken as the Rockwell hardness value of the AH36 steel plate.

 

 

 

Quenching and TemperingQuenching Effect on Hardness

Quenching is a rapid cooling process after heating the steel to a high temperature. When AH36 steel is quenched, it can form a martensitic microstructure, which significantly increases the hardness of the steel. The rapid cooling rate traps the carbon atoms in a supersaturated state within the iron lattice, creating a hard and brittle structure. For example, quenching from a temperature above the austenitizing temperature (usually around 850 - 900°C) in water or oil can lead to a substantial increase in hardness.

Tempering and Hardness Modification

Tempering is carried out after quenching to reduce the brittleness caused by the formation of martensite. During tempering, the steel is reheated to a lower temperature (usually between 550 - 650°C). This process allows the carbon atoms to diffuse and form more stable carbide particles. As a result, the hardness decreases slightly compared to the as - quenched state, but the toughness and ductility of the steel are improved. The specific tempering temperature and time can be adjusted to achieve the desired balance between hardness and other mechanical properties.

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We take pride in our ability to provide custom solutions for our customers' unique needs.
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Our customers trust us to deliver high-quality Cold-rolled Steel products on time and on budget.
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