Hardness of Carbon Materials

The hardness of carbon materials mainly depends on the type of material and the final heat treatment temperature. There are many measurement methods, including Mohs, Brinell, Rockwell and Shore hardness measurement methods.

Artificial graphite: a product made from anthracite, coke, asphalt, etc. through crushing, screening, classification, tempering and other processes.

Carbon-graphite material: an artificial graphite material that has not reached the degree of complete graphitization, containing about 10% carbon.

Carbon products: products made from petroleum coke and asphalt coke (adhesive) or anthracite roasted, with a carbon content of 90%~99%.

Green carbon products: carbon products that have been formed but not roasted.

Graphite products: bonded granular carbon bodies whose matrix has been treated at more than 2400℃, and whose matrix is ​​stable at temperatures below 2400℃.

Hardness Test Standards

American standard: ANSI/ASTM C748-97 "Rockwell hardness test method for fine-grained graphite materials".

Chinese industry standard: JB/T8133.3-1995 "Test Method for Physical and Chemical Properties of Electric Carbon Products Rockwell Hardness" replaces GB/T1994.3-1988.

International Electrotechnical Commission (IEC) Publication No. 413-1972 (First Edition) "Test Procedure for Determining Physical Properties of Brushes for Motors".

Abstract of American Standard ANSI/ASTMC748-97

Applicability HRL. Particle diameter <0.8mm, hardness range (0-120) HRL.

Scale: The diameter of the steel ball indenter is 6.35mm. Test force: The initial test force is 98.07N and the total test force is 588.4N.

The test should be stored in air at room temperature and the test is also carried out under the same conditions. All samples are kept free of contamination.

The Rockwell hardness tester "measures" 5 points on a standard Rockwell hardness (HRL scale) block. Take the hardness average of five points and compare it with the standard value on the standard hardness block. The indication error is within ±2HRL. The test specimen should be straight, with a minimum thickness of 6.35mm, a surface roughness of Ra≤3.175mm, and the parallelism between the working surface and its surface should be within 1%.

Indentation and indentation measurement steps: Before using the hardness tester, it must be verified (calibrated) before it can be used. The time for applying the test force when the hardness tester is idle is (4~7)s, and the test force maintenance time is (5-15)s. The distance between indentations and from the indentation to the edge of the specimen shall not be less than 6.35mm.

For isotropic materials, at least 5-point hardness tests should be performed. Fine-grained graphite is anisotropic, which can cause the hardness of the specimen to change with the direction of the specimen. At least 5-point hardness tests should be performed on the surface perpendicular to the molding or extrusion direction. Rockwell hardness values ​​exceeding 120HRL are not recorded, but reading 120HRL is allowed.

Digital Rockwell Hardness Tester HRS-150 with Touch Screen RS232 Data Interface

Technical Specification: