What hardness can reveal

Unexpectedly high or low hardness can indicate incorrect heat treatment, local cold work, decarburization, unsuitable PWHT or another condition requiring investigation. It is a screening and acceptance tool, not a substitute for all mechanical or metallurgical testing.

Interpret the result in context of grade, condición, section thickness, location and instrument method.

Test method and surface preparation

Bench Brinell or Rockwell testing can provide controlled results on suitable surfaces. Portable rebound, ultrasonic contact impedance or other field methods may support inspection when qualified by the project.

The surface should be clean, stable and sufficiently smooth. Curvature, thin edges, scale, decarburized layers and inadequate support can distort readings.

Location and sampling strategy

A single reading on a flange rim may not represent the hub, bore or weld interface. The procedure should define the number and position of readings and whether each flange, each heat-treatment batch or a sample is tested.

For welded F91 joints, a traverse across base metal, both heat-affected zones and weld metal can identify local variation after PWHT.

How buyers should specify the report

• Material grade and required condition
• Applicable limit and source document
• Test method, scale and equipment identification
• Calibration/verification record
• Surface preparation and exact test locations
• Individual readings, conversions if any and acceptance
• Flange heat number and inspector authorization