🔩 Hardness of arc welded joints — rows of indentations and individual Vickers indentations on the transverse cross-section

Materials and NDT PN-EN ISO 9015-1

Overview

The standard specifies hardness testing on transverse cross-sections of arc welded joints in metallic materials. It covers Vickers hardness measurements according to ISO 6507-1, usually with test forces of 49.03 N or 98.07 N (HV 5 or HV 10). The principles may be applied correspondingly to Brinell hardness measurement (with forces HB 2.5/15.625 or HB 1/2.5) according to ISO 6506-1 and to microhardness according to ISO 6507-1 and ISO 9015-2.

The type and extent of the test are specified by the relevant product standard or by agreement between the parties; unless otherwise agreed, the test is carried out at an ambient temperature of (23 ± 5) °C. Measurements are made as rows of indentations (designation R) or as individual indentations (designation E) — rows make it possible to assess the hardness distribution across the joint. The aim of the test is to capture the highest and lowest hardness levels of both the parent metal and the other zones of the joint.

Hardness testing belongs to the standard set of destructive tests on test joints carried out in welding procedure qualification: in the presentation of the Lublin University of Technology, for a butt joint, among others 2 transverse tensile test pieces, 4 transverse bend test pieces, 2 impact test sets, a macroscopic examination and the required hardness test are specified.

Method principle

A cross-section, usually transverse to the weld axis, is cut mechanically from the joint under test. Cutting and further surface preparation are carried out carefully so as not to change the hardness of the tested surface metallurgically. The surface is prepared and preferably etched so that accurate measurement of the indentations in the individual zones of the joint is possible: the parent metal, the heat-affected zone and the weld metal. Hardness is measured according to ISO 6507-1 (Vickers) or ISO 6506-1 (Brinell), and the indentations are arranged in rows (R) at a specified distance from the surface or from the fusion line, or as individual indentations (E). Symbols describing the position: L — distance between the centres of indentations in the heat-affected zone, H — distance of the rows of indentations from the reference surface or the fusion line, t — thickness of the test specimen.

Applications

• Welding procedure qualification (WPQR) — testing of test joints
• Checking the hardness of the heat-affected zone in high-strength steels and quenched and tempered steels
• Assessment of the effects of post-weld heat treatment
• Acceptance tests of welded structures and pipelines
• Analysis of the causes of cracks and failures of welded joints

Key parameters

Standard

Standard number

PN-EN ISO 9015-1:2011

Title (PL)

Badania niszczące złączy spawanych metali — Badanie twardości — Część 1: Badanie twardości złączy spawanych łukowo

Title (EN)

Destructive tests on welds in metallic materials — Hardness testing — Part 1: Hardness test on arc welded joints

Step-by-step procedure

1. Determining the extent of the test

   Adopt the type and extent of the test according to the product standard or the agreement between the parties; plan whether the test will be carried out as rows of indentations (R) or individual indentations (E).

2. Cutting the cross-section

   Cut the cross-section of the specimen mechanically, usually transverse to the welded joint, avoiding heating and cold working.

3. Surface preparation

   Prepare the surface in accordance with ISO 6507-1 or ISO 6506-1 — carry out grinding and polishing so as not to change the hardness of the tested surface metallurgically.

4. Etching

   Preferably etch the surface to obtain accurate measurement of the indentations in the different zones of the joint (parent metal, HAZ, weld metal).

5. Arrangement of the indentations

   Make the indentations in rows according to the examples in Figures 1–7 of the standard, at the specified distance from the surface, so that the rows or their parts allow the joint to be assessed. At the request of the parties additional rows or other positions may be used — state the position in the report.

6. Measurement

   Carry out the hardness measurements according to ISO 6507-1 (or ISO 6506-1) at a temperature of (23 ± 5) °C, unless otherwise agreed.

   🌡 Temperature: (23 ± 5) °C

7. Special cases

   In metals such as aluminium, copper and their alloys, rows on the root side of butt joints may be unnecessary; for T-joints in these materials the typical rows shown in Figure 2 of the standard are used.

8. Report

   Give the hardness results with the location of the indentations; examples of reports for testing with rows (R) and individual indentations (E) are given in Annexes A and B of the standard.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Cutting and grinding of sections — safety glasses, wheel guards, liquid cooling
• Etchants (acids, alcohols) — fume hood, gloves, goggles; prepare solutions in accordance with the safety data sheet
• Hardness tester under load — do not interfere in the indenter area during measurement
• Sharp edges of cut cross-sections — deburr or handle with gloves

Frequently asked questions