ASTM E140 Standard Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, and Superficial Hardness

ASTM E140 Introduction

ASTM E140 can be used to convert values of hardness as determined with a particular method to your equivalent hardness value on another of the various hardness scales in common use. With all the hardness testing techniques having relative differences concerning the type of indenters, desired loads, and test specimens, the conversion tables serve as a convenient outcome, facilitating the understanding of readings from various systems. The standard contains information about various metals, including carbon and alloy steels, stainless steel, cast irons, copper alloys, aluminum, titanium, and nickel-based alloys. The conversion values are empirical and based on a large body of test data, and are comparative rather than certifiable.

ASTM E140 Test Method

ASTM E140 Equipment and Sample Preparation

ASTM E140 Results and Interpretation

These method conversion tables are the most used when comparing the hard values obtained by different test methods with one another. For example, a Brinell hardness of 200 HBW on carbon steel can be related to approximately 93 HRB or 210 HV. Such correlations can be used when test equipment is inadequate or when test equipment specifications or history necessitate alternative hardness values. Due, however, to the non-exactness of conversions because of metallurgical considerations, the results may be regarded as approximate and need not be employed in acceptance testing unless it is stated as such in the governing specification.

ASTM E140 Related Test Methods

ASTM E384 provides guidelines on conducting microindentation hardness tests, covering both the Vickers method and the Vickers and Knoop methods. The mechanical testing prerequisites for steel products, as outlined in ASTM A370, encompass product specifications that include hardness testing as a quality requirement for many steel products.

ASTM E140 Applications in Industry 

This standard has even found wide application in metallurgical laboratories, quality control, and specification compliance. It is applied in industries such as automotive, aerospace, construction, and manufacturing, in an attempt to achieve results when numerous rigorous testing methods are employed. It is also useful to validate historical data or compare the hard values set by customers when selecting, inspecting, or certifying materials.

ASTM E140 Materials Commonly Tested

These method conversion tables have extensive uses for metallic materials; hence, the standard is expected to have broad applicability to many industries. We typically test materials such as carbon steels, low-alloy steels, stainless steels, cast iron, ductile iron, and aluminum alloys. The tables are made of copper-based alloys, such as brass and bronze, as well as titanium and nickel-based alloys, in high-performance applications.

ASTM E140 Common Challenges and Troubleshooting

The most widespread cause of conversion errors is the improper classification of materials. The tables do work on just one type of material; they were created. Users are also not allowed to use conversion values to accept anything unless it is explicitly permitted. Anomalies in the surface structure or scale, or surface treatment, can also distort results; therefore, clean and flat test surfaces are necessary.

ASTM E140 Safety and Best Practices

Hard testing in and of itself is comparatively safe; best practices include using calibrated instruments, ensuring specimens are well supported, and avoiding placement of hands near the moving parts of indentation machines. When conducting strenuous tests, protective eyewear of the rebound type is recommended.

Importance of ASTM E140 Test Method

This method is a crucial component of material testing and quality control, as it enables safe cross-reference between hardness scales. Because different industries and labs may employ varying methods due to equipment availability, technique usage, or historical data, the conversion of results makes them compatible and consistent across testing procedures. This is particularly of concern in manufacturing, inspection, and certification operations where hard values have a bearing in the selection of materials, verification of heat treatment, and acceptance of products.