3.08 WELDING PROCEDURES MANUAL Page 1 of 2

OPERATING PROCEDURES

MACRO ETCH AND HARDNESS TESTING OF WELDS

12/31/06

HIS SECTION PROVIDES STANDARD PROCEDURES FOR MACRO ETCH AND

HARDNESS TESTING of welds performed in conjunction with testing of in-service

welding procedures. T

GENERAL

MACRO ETCH TESTING

Macro etch testing (normally used with other destructive testing methods during

qualification of in-service pipeline welding procedures) evaluates the macro-structure of

a weld’s heat-affected zone for anomalies. An etchant is used to clarify the weld

structure; and magnification is used to clarify the view. For permanent test records,

photomacrographs are commonly developed.

To examine the penetration

profile and fusion of a weld,

macro etching involves:

Figure 3.08.1: Macro etch cross section of an acceptable weld

1. Cutting the sample

through the weld with a

non-thermal process

2. Polishing the surface to

at least a 600-grit finish

3. Applying an etchant,

ammonium persulfate or

diluted hydrochloric acid

4. Visually examining the

cross section of the weld

An acceptable weld (see Figure 3.08.1) will show complete fusion, free of any cracks.

HARDNESS TESTING

The hardness of a weld is affected by:

Composition of the pipe and weld metal

Metallurgical effects of the welding process

Heat treatment

3.08 WELDING PROCEDURES MANUAL Page 2 of 2

OPERATING PROCEDURES

MACRO ETCH AND HARDNESS TESTING OF WELDS

12/31/06

Experience has proven that limitations should be placed on the hardness of the pipe metal, heat-affected zones and weld metal. If too hard, they will not have sufficient ductility for the service conditions, their corrosion resistance may be impaired, or some other factor may dictate this limitation.

This is particularly important for weldments exposed to hydrogen-bearing environments such as sour-crude or sour gas service in pipelines. Increased hardness coupled with hydrogen may cause cracking.

Depending on the application, there are several types of hardness testing machines.

The three most widely used are:

Brinell Hardness

Rockwell Hardness

Vickers Hardness

The hardness testing will be preformed in accordance with ASTM Standard E92. A minimum of five indentations should be made using a Vickers indenter and a 10-kg load in the coarse-grained heat affected zone (HAZ) at the weld toe of each specimen. If the result of this test produces, HAZ hardness values in excess of 350 HV they should be further evaluated for risks of hydrogen cracking.

ACCEPTANCE STANDARDS

The API 1104 acceptance standards applicable to macro etch and hardness testing are contained in Appendix B.