How to Choose the Right Hardness Tester for Ferrous Castings & Non-Ferrous Materials

Different tools are used for measuring hardness on ferrous (e.g. cast iron, steel castings) and non-ferrous (e.g. aluminum, copper, magnesium alloys) materials depending on their density, brittleness, and surface characteristics. These materials also require different methods for indentation. Measuring hardness on cast aluminum may be soft, and cast iron that is brittle may be damaged, if the wrong hardness tester is used. This wrong usage can also compromise quality control. The following guide is designed to help select a suitable tester for both types of materials, yielding dependable results whether for manufacturing, maintenance, or laboratory analysis.

1. Start With the Properties of Ferrous and Non-Ferrous Materials

When it comes to selecting a hardness tester for ferrous castings: It is usually hard (Brinell hardness 150-300HB) and often has a coarse casting surface. It may be brittle (for instance, gray cast iron) so the hardness tester is required to not fracture the specimen while ensuring sufficient penetration to obtain an accurate measurement.

When it comes to selecting a hardness tester for non-ferrous materials: They are softer (Brinell hardness 20-100HB for aluminum, 50-150HB for copper) and more ductile. They also require careful indentation because excess indentation or indentation deformation can cause soft non-ferrous materials to squashed, yielding erroneous measurements.

2. Effective Hardness Testers for Analyzing Hardness of Fe Castings

Select hardness testers that measure hardness and surface roughness.

Brinell hardness testers are best suited for Fe castings. The large indentors (10 mm steel balls) and heavy loads (3000 kgf) average out castings surface irregularities. The testers are versatile across soft (malleable cast iron) and hard (ductile cast iron) ferrous varieties. This mitigates the ‘spot errors’ associated with smaller indentors, ensuring soft and hard ferrous varieties are accurately measured.

Rockwell Hardness Testers (Scales B and C) are scalable. For hard ferrous castings (e.g., hardened steel castings), use Scale C (diamond indentor, 150 kgf) and for the softer ones, Scale B which consists of a 1/16” steel ball and applies 100 kg of force. This tester is significantly faster than the Brinell testers (test results take 5-10 seconds) and is ideal in scenarios requiring high volume testing (e.g., casting production lines). If you require on-site testing (e.g., large cast iron machinery), choose portable Rockwell testers.

3. Best Hardness Testers for Non-Ferrous Materials

Select testers with low loads and accurate indentations for lightweight, non-ferrous metals.

The Vickers Hardness Testers are particularly effective for non-ferrous metals. Th measured indentation loads are light (100-500 gf for Al, 500-1000 gf for Cu) and diamond indentors are used so over indentation is avoided. The tester is suitable for thin non-ferrous constituents (e.g., Al foils, Cu wires) in contrast to Brinell where crushing loads are used.

Brinell Hardness Testers (Low Loads): In the case of larger non-ferrous workpieces (e.g., aluminum castings), employ Brinell with lower loads (500–1000 kgf) and smaller ball indenters (5 mm). This achieves a balance between covering the surface and protecting the sample. This is important for ductile non-ferrous materials that are easily dented.

Shore Hardness Testers (Scale D): For hard non-ferrous plastics or composites (e.g., fiberglass-reinforced non-ferrous parts), the Shore D provides rapid, non-destructive readings, which is an advantage. However, do not use it for pure metals, as it lacks accuracy regarding the hardness of metals.

4. Key Extra Considerations  

Surface Finish: For ferrous castings with rough surfaces, if one has to chose between Brinell (large indentor) and Vickers (small indentor), use Brinell to avoid false high readings. For polished non-ferrous parts (e.g., machined aluminum), Vickers or Rockwell B works best.  

Portability vs. Benchtop: In the case of portable Rockwell or handheld Brinell testers, they are used for on-site testing (e.g., inspecting cast iron pipes or aluminum machinery). For lab testing (e.g., small non-ferrous samples), benchtop Vickers testers offer better precision as the expectation is higher.

Standards Compliance: For results to be used for industrial or regulatory purposes, the tester must comply with ASTM standards—ASTM E10 (Brinell for ferrous), ASTM E18 (Rockwell for metals), and ASTM E92 (Vickers for non-ferrous).