Reading a Plate Test: Visual Limits and a Bend Failure
A welder completes a 3/8 in. A36 plate test in the 3G position using SMAW with E7018, a 1/8 in. root gap, and a 60 degree included angle. The test is for AWS D1.1 welder qualification. Visual inspection finds cap undercut up to 1/32 in. deep along one toe, a single 1/16 in. surface pore on the cap, root reinforcement of 3/32 in., and several arc strikes on the plate surface about 1 in. outside the weld zone. Two side-bend specimens are cut. One opens with a visible defect at the weld root edge measuring about 1/8 in.; the other bends cleanly.
1. Evaluate each visual discontinuity against typical D1.1 test-weldment acceptance criteria and state whether the weldment passes visually.
Read the worked answer
- Undercut at 1/32 in.: This is at the typical maximum allowed for statically loaded work. It is acceptable only if it does not exceed 1/32 in. anywhere; a feeler gauge or pit gauge should confirm depth, not eyeball.
- 1/16 in. surface pore: Surface porosity is generally treated strictly on a qualification test. A single small pore may be evaluated under the code's visual limits, but it is a warning sign of arc instability, moisture, or travel technique and should be investigated.
- 3/32 in. root reinforcement: This is modest and generally acceptable; excessive root reinforcement is the usual concern because it concentrates stress.
- Arc strikes outside the weld zone: These are not acceptable as a matter of good practice. Arc strikes create hard, brittle spots and can initiate cracks. The test plate should be evaluated under the code's provisions for arc strikes, and they are commonly grounds for rejection or require removal and inspection.
Conclusion: the visual result is marginal at best and does not clearly pass because of the arc strikes and the surface pore.
2. What does the bend result mean, and what disposition is required?
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- Side bends test ductility and root fusion. A defect that opens at the root edge indicates incomplete fusion, slag, or a similar root discontinuity.
- The defect is described as about 1/8 in. That is at the threshold where bend specimens commonly fail; a defect exceeding the code's limit in any direction is a failure. Even at exactly the limit, the specimen should be measured carefully and judged against the applicable edition of the code.
- Because one specimen failed, the standard disposition is a retest, usually by cutting additional specimens from the same test weld and testing them. If the retest specimens pass, the welder may be accepted; if any retest specimen fails, the welder fails the qualification.
- The failed area should be examined to identify the cause, since a root defect on a 3G test often points to root gap, land, or travel-angle problems rather than bad luck.
3. What are the likely causes of the arc strikes and the cap undercut, and how should each be prevented?
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Arc strikes:
- Caused by striking the electrode outside the joint, often from an awkward restart or a habit of tapping the plate.
- Prevent by starting the arc in the joint or on a runoff tab, using a hot-start setting correctly, and training the welder to restart within the groove.
- Arc strikes outside the weld zone should be removed and the area inspected; they are not simply cosmetic.
Cap undercut:
- Caused by excessive current, a long arc, too fast a travel speed, or an incorrect work angle that lets the arc gouge the toe.
- Prevent by reducing current, shortening the arc, pausing briefly at each toe to fill, and maintaining a consistent drag angle.
- On a qualification test, undercut at the limit is a warning; the same technique in production will frequently exceed it.