ASTM E18 Test for Rockwell Hardness of Metallic Materials

ASTM E18 test method determines Rockwell hardness of metallic material by Rockwell hardness test. In this test, an indentor applies a load on the metal, causing dents, which are measured to determine the Rockwell hardness of metals.

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ASTM E18 Test for Rockwell Hardness of Metallic Materials

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM E18 is a widely used standard test method for determining the Rockwell hardness of metallic materials. The test measures the depth of permanent indentation produced by a specified indenter under a minor and major load. Rockwell hardness testing is valued for its speed, simplicity, and direct readout, making it suitable for production control, material comparison, and quality assurance of metals and alloys.

Scope, Applications, and Benefits

Scope

The ASTM E18 Rockwell hardness test is an empirical indentation-based hardness test that provides useful information about metallic materials. Rockwell hardness (HRC) is commonly used for high-hardness materials and to determine hardness after heat treatment. The standard is used to determine the relevant physical characteristics of metallic materials under test, to meet acceptance testing requirements for commercial shipments, and to support quality control and material selection.

Applications

Quality control and inspection of metallic components
Material selection and comparison of metals and alloys
Heat treatment verification and process control
Evaluation of mechanical properties in manufacturing
Testing of finished parts and semi-finished products

Benefits

Rapid and simple hardness measurement
Minimal specimen preparation required
Non-destructive to finished components
High repeatability and reproducibility
Applicable to a wide range of metallic materials

Testing Process

Specimen Preparation

Prepare a clean, smooth, flat test surface, then select the appropriate Rockwell scale.

Minor Load Application

Apply the specified minor load to seat the indenter and establish a reference position.

Major Load Application

Apply the major load for the required dwell time, then remove it while retaining the minor load.

Hardness Reading

Read and record the Rockwell hardness value directly from the machine or display.

Technical Specifications

Parameter	Details
Materials	Metallic materials
Preliminary Force	10 kgf
Rockwell Scales	HRA, HRB, HRC
Test Temperature	10°C–35°C
Result Format	Hardness number + scale

Instrumentation Used

Rockwell hardness testing machine
Diamond cone (Brale) or steel ball indenter
Load the application and control system
Specimen anvil or support
Hardness value display or data recording system

Results and Deliverables

The Rockwell hardness value is obtained for the selected scale (e.g., HRA, HRB, HRC)
Results indicate the material’s resistance to permanent indentation.
Consistent readings confirm uniform material hardness.
Variations in values may indicate differences in material composition or heat treatment.

Results support quality control, material comparison, and process verification.

Frequently Asked Questions

Material resistance to indentation is measured by Rockwell Hardness through the use of different loads and indenters to determine a material's deformation nature under compressive forces.

There are different scales for materials of different hardness. Hard materials, such as hardened steel are subjected to the C scale (using a diamond indenter) while softer materials such as brass use the B scale (with a steel ball indenter).

The Rockwell C scale, HRC, is generally used for hardened steel, while softer metals like aluminum and copper are usually tested in the Rockwell B scale, HRB.

Yes, approximate conversions do exist between the Rockwell, Brinell, and Vickers hardness scales, but they must be used with caution because they are empirical.

Not suitable for testing fragile materials, curved surfaces, or highly elastic materials due to possible inaccuracies.