Hung Shuh's Professional Testing & Quality Assurance

In steel procurement and processing, it's not unusual for customers to raise concerns such as
"the hardness doesn't match the order specification."
 

Several factors can contribute to such differences:

• Testing equipment & methods : Different hardness testers and techniques may lead to variations.

• Material thickness : Thicker or thinner samples require different testing methods, which can affect consistency.

• Surface condition : Oxide layers, polishing, or coatings may influence results.

• Sampling location : Measuring near the edge vs. the center can produce different readings.

At Hung Shuh, we believe in transparent and scientific testing. 
Below, we outline our standard hardness testing procedure and professional recommendations.

① Following international and national standards

• Testing is based on JIS Z2245.

• For Rockwell or quick verification tests:

  • If the expected hardness is known, testing follows JIS Z2245.

  • If only heat treatment is known (without surface treatment data), thickness is first considered, then the test scale is adjusted accordingly.

② Addressing possible sources of variation
Hardness results can vary due to:

• Operator: individual habits during measurement.

• Machine: different testing equipment.

• Material: different test locations on the sample.

• Method: variation in scale (e.g., HR15N vs. HRC).

• Environment: steel may show different properties in cold climates (harder and more brittle).

To minimize these issues, we:

• Maintain a clear SOP and regularly calibrate testers with standard blocks.

• Ensure stable sample placement and perpendicular contact with the indenter.

• Test multiple points on each sample at proper spacing to avoid mutual interference.

③ Surface preparation & sample positioning

• Clean surfaces of oxide scale, oil, or dirt; polish lightly if needed.

• Test at least 10 mm from edges to avoid distortion.

• Each piece is tested at 3 or more points and averaged for stability.

• Consider manufacturing processes, such as heat treatment, cold work, or surface treatment, which may influence hardness.