Rockwell Hardness Tester Product

Overview

A Rockwell hardness tester measures material hardness by indenting a specimen with a calibrated diamond cone or hardened-steel ball under controlled load and then measuring the depth of the residual indentation. The Rockwell scale (ISO 6508) maps indentation depth to a hardness number: higher hardness materials produce shallower indentations. The tester consists of a motorized spindle holding the indenter, a load system applying minor (588 N) and major (980–1471 N) loads in programmed stages, a depth-measurement transducer (LVDT), and a microcontroller that executes the test sequence and calculates the hardness number from the depth.

Rockwell hardness testing is faster and more portable than Vickers or Brinell tests, making it the industry standard for quality control in manufacturing (ISO 6508 Class A for precision testing). Common scales include HRC (diamond cone, used for steels), HRB (steel ball, used for non-ferrous metals and lower-hardness alloys), and HRA (diamond cone, rarely used).

How it works

The specimen is placed on the Specimen Anvil, which is then raised to contact the Diamond Cone Indenter (120° diamond, 0.5 mm tip) or Steel Ball Indenter (1.5875 mm hardened-steel ball). The Load System first applies a 588 N minor load (preload) to ensure stable contact and zero the Depth Measurement Transducer baseline.

Next, the system applies the major load (e.g., 1471 N for Rockwell C) via a Load Cylinder actuated by the Load Control Solenoid. The indenter penetrates the specimen, compressing it plastically. After 10–15 seconds of dwell at constant major load, the Load Timer Solenoid triggers the solenoid to release the major load, leaving the minor load in place.

The LVDT transducer continuously monitors the specimen platform height. The residual indentation depth is calculated as:

Depth (mm) = Initial Contact Height − Final Height (at minor load)

The Controller Unit microcontroller converts this depth into a hardness number using the ISO 6508 formula:

Rockwell Hardness = 100 − (Depth ÷ 0.002 mm) (for HRC scale)

The result is displayed on the Display and Data Logger and optionally logged to SD card for batch testing and statistical process control (SPC).

Indenter selection and scales

Different Rockwell scales use different indenters and major loads to suit various material hardness ranges:

• HRC: 120° diamond cone, 1471 N major load. Steels, cast iron, and hardened materials (20–70 HRC range).
• HRB: 1.5875 mm steel ball, 980 N major load. Non-ferrous metals, annealed steels, aluminum, and brass (30–100 HRB range).
• HRA: 120° diamond cone, 588 N major load. Hardened tool steels and carbide (60–88 HRA range).

The tester''s Spindle Motor rotates the Quick-Change Collet to exchange indenters in <30 seconds, enabling multi-scale testing without tool change-outs.

Specimen preparation and testing procedure

Test specimens must be smooth (Ra < 0.8 µm), flat, and free of deformation. Thickness should be at least 20 mm for reliable results. The indentation must be at least 10 mm from the specimen edge and 40 mm from any other indentation to avoid elastic strain interference.

The operator cleans the anvil and indenter, places the specimen, and initiates the test via button or LIMS integration. The machine automatically executes the load cycle, measures depth, and computes hardness. Modern machines can run a 5-point indentation pattern and report mean, standard deviation, and trend for batch acceptance.

Calibration and traceability

ISO 6508 Class A machines (laboratory-grade) must be calibrated annually using standardized hardness reference blocks (e.g., 45 HRC ±1 HRC). The ADC Module monitors LVDT signal stability and flags out-of-tolerance conditions. Calibration records are often archived electronically for ISO 9001 compliance and supply-chain traceability.

Advantages and limitations

Rockwell testing is non-destructive (indentations are typically <0.5 mm diameter), fast (30–45 seconds per test), and requires minimal specimen prep compared to Vickers or tensile testing. However, results are sensitive to specimen surface finish and proper support—poor anvil contact yields invalid shallow indentations. Most labs combine Rockwell QC with periodic Vickers or tensile verification on witness specimens to ensure accuracy.