Bend tests on corner, but, lap and tee welds are shown in Fig. 10.8(a).

Final bend for free-bend

У//////Л I/////K

Initial bend for free-bend specimens

Fig. 10.8 (b) Typical fixtures for free bend testing (top) and guided bend (bottom). (for SI equivalents U. S. customary values)

10.2.1 Procedures of Preparing Test Sample

Procedure for butt welds specimen preparation is given step-wise as follows:

1. Cut the coupon from the center of the plate approximately 5.08 cm wide along the length of the weld (Fig. 10.9). Use a shear or cutting torch depending on the thick­ness of the material. Steel plates of 4.76 mm should be cut with a cutting touch.

2. Save the material from each side for use on the next joint.

3. Cut the weld into sections 7.62 cm (3 in.) long (Fig. 10.10). Use a cutting torch if the material is thicker than the capacity of the shear available. For most SMAW, a cut­ting torch will be required.

4. Grind the cut sections and finish with a fine file.

5. Check the sectioned surfaces for defects.

(а) Undercut

(б) Lack of fusion

(b) Slag inclusions

(c) Prosity

6. Show test pieces to the instructor for evaluation and recording.

Remember that the final test will be by bending. Bend test requires much more material and will be done under the guidance of the instructor.

Fig. 10.10 Sample cut into equal pieces

10.2.2 Guided Bend Tests

The guided bend test for plate and pipe requires a special test jig to hold the specimen in place while the bending takes place. Specifications for the test jig design and the bending procedure for specific materials must be followed. Various organizations have designed bending jigs and prescribed procedures for testing different materials. Some of these organizations are:

AWS American Welding Society Standard for Qualification of Welding

Procedures and Welders for Piping and Tubing. D10.9 - 69.

ASME American Society of Mechanical Engineers Code for Boilers and

Pressure Vessels.

API American Petroleum Institute Standard for Welding Pipe Lines and

Related Facilities.

A typical guided bend jig and test samples are shown in Fig. 10.11. This device can be used with a hydraulic jack or manual jack that has a force of about 703 kg/cm2 (10,00 psi).

Fig. 10.11 Typical bend test jig. (All dimensions are in inches)

10.2.3 Preparing the Sample for Bend Testing

Once the weld has been completed, it must be allowed to cool slowly. Test specimens will vary with the type of joint and with the position in which the test is made, that is flat plate (Fig. 10.12) or all position box pipe (Fig. 10.13). For all test coupons, the reinforcement of the weld must be removed completely and the edges rounded slightly (Fig. 10.14).

The grind or file marks from the reinforcement removal should travel lengthwise on the bend test specimen. The sides of the specimen should be smooth and the corners rounded to a maximum of 3.17 mm radius (Fig. 10.15). This smoothness and roundness will allow the speci­men to slide freely in the bending jig. Any deep scratches or grooves running lengthwise in the specimen in the weld area are potential breaking points (stress riser).

Fig. 10.12 Flat plate test. (All dimensions in inches)

Tack weld Fig. 10.13 Fixed box pipe all position test. 1G-1 Flat position root bend 1G-2 Flat position face bend 2G-3 Horizontal position root bend 2G-4 Horizontal position face bend 3G-5 Vertical position root bend 3G-6 Vertical position face bend 4G-7 Over­head position root bend 4G-8 Overhead position face bend.

Fig. 10.14 Reinforcement removal

Fig. 10.15 Prepared specimen for bending 10.2.4 Root and Face Bend Specimens For most welding qualification tests, root and face bend specimens are required (Figs. 10.16 and 10.17). However, the AWS allows 100 percent X-ray in place of bend tests. These speci­mens may be located on the joint surface before the welding is begun. The root bend will test the quality of the first pass in the joint. The face bend will test the last pass or passes in the joint. Satisfactory welds must be free of slag inclusions and have complete fusion. In most tests, a total distance of 3.2 mm discontinuity (crack, inclusion, or lack of fusion) is acceptable. If the defect is longer than 3.2 mm in any direction, the test piece is considered to be a failure. For example, the 6G position pipe test requires the removal of four test pieces. If the number of defects in one test sample adds up to more than 3.2 mm in length, the test is a failure.

Top of pipe for 5G

Weld joint

Root Bend Rooy

Fig. 10.16 (b) Relative orientations of face, root, and side-bend tests from a welded plate