D1.1 Fabrication for CWI Part C: Clause 7 Guide

What fabrication questions ask

AWS's Part C information guide sets fabrication at a minimum of 25% of the scored questions. In D1.1:2020, fabrication is Clause 7 (Clause 5 in the 2015 edition). The skill being tested is finding the right subclause quickly and reading it exactly, not remembering numbers.

Fabrication questions usually describe a shop or field situation and ask what the code requires or allows. Before you look anything up, underline the details that change the answer. These include electrode classification, thickness, loading type, whether backing is used, and whether a joint is back gouged.

How Clause 7 is organized

Read Clause 7 once from start to finish so you know its order. Its main topics, roughly in sequence:

• Base metal and its preparation, including cut edges and laminations.
• Welding consumables, including storage of low-hydrogen electrodes.
• Preheat and interpass temperature, and heat input for quenched and tempered steels.
• Stress-relief heat treatment.
• Backing, and the welding environment (wind and temperature).
• Assembly tolerances for fillet and groove joints, and dimensional tolerances of members.
• Weld profiles.
• Repairs, peening, caulking, arc strikes and cleaning.

The tables sit next to the subclause they support. Tab each one as you read.

Electrodes and consumables

Low-hydrogen SMAW electrodes get a lot of attention because hydrogen causes delayed cracking. The storage subclause covers three situations, and questions often mix them up:

• Holding. Once out of sealed containers, electrodes go into a holding oven at a stated minimum temperature.
• Exposure. The table of permissible atmospheric exposure gives how long an electrode may be out of the oven. Read the row for the electrode classification. Electrodes with a moisture-resistant designator, or shown by test to resist moisture, can be allowed longer.
• Re-drying and wet electrodes. Electrodes out too long may be re-dried, but only once. Electrodes that have been wet are a separate case, and re-drying does not cover them.

Worked example: E7018 electrodes with no moisture-resistant designator have been out of the oven for 5 hours. The exposure table allows 4 hours for E70XX, so they must be re-dried or discarded. Higher-strength classifications have shorter limits, so always check the classification before you read the time.

Welding environment and preheat

The welding environment subclause sets a wind limit for gas-shielded processes and a minimum ambient temperature for welding. It also says when shelters or enclosures make welding acceptable.

The prequalified minimum preheat and interpass temperature table is in Clause 5. Clause 7 tells you how to apply preheat. It says how far from the joint the temperature must be reached, and when it must be measured. The notes under the preheat table matter as much as its cells, so read them.

Worked example: the thicker part of a joint is 2 in. thick. Clause 7 ties the preheated distance to that thickness, with a 3 in. minimum in every direction from the point of welding. Here the 3 in. minimum governs.

Fit-up and joint tolerances

This is one of the most calculation-heavy parts of the clause. Three rules come up often:

• Fillet weld root openings. There is a normal maximum gap. Above a smaller threshold, the fillet leg must be increased by the gap. The exception is when the contractor shows the required effective throat was achieved.
• Butt joint alignment. Offset is limited to a percentage of the thinner part, with an absolute cap.
• Groove dimensions. The workmanship tolerance figure gives plus and minus limits for root face, root opening and groove angle.

Worked example: a 5/16 in. fillet is specified on a T-joint with a 1/8 in. root opening. That gap is over the threshold, so the leg grows by the full 1/8 in., to 7/16 in.

Read the tolerance figure's headings carefully. Limits differ for joints that are back gouged and joints that are not, and for joints with or without steel backing.

Minimum fillet weld size

The minimum fillet weld size table is read by base metal thickness, T. The notes decide which part T is:

• For low-hydrogen processes, or non-low-hydrogen processes with preheat set to prevent cracking, T is the thinner part joined.
• For non-low-hydrogen processes without that preheat, T is the thicker part, and single-pass welds are required.
• Another note caps the minimum at the thickness of the thinner part.

Worked example: a 1/2 in. plate is joined to a 3/4 in. plate with a low-hydrogen process. T is the thinner part, 1/2 in., and that row gives 3/16 in.

Weld profiles

Weld profiles have two parts. One is a figure of acceptable and unacceptable profiles. The other is a table and schedule that set limits on convexity and reinforcement. The fillet convexity limit depends on the face width, W, so measure or calculate W first.

Worked example: a fillet weld with a 1/2 in. face width falls in the middle band of the schedule. That band allows 1/8 in. of convexity.

Repairs and workmanship

The repairs subclause gives a method for each kind of defect. Match the defect to its method rather than guessing:

• Some defects are fixed by removing excess weld metal.
• Some are fixed by preparing the surface and adding weld metal.
• Some need the unacceptable portion removed and rewelded.
• Cracks have their own steps. Find the full extent, remove the crack plus a stated length of sound metal past each end, then reweld.

Worked example: a weld shows overlap. Overlap is excess metal, so the repair is to remove it, not to add more.

Other workmanship rules have their own short subclauses. Tab them, because questions on them usually turn on one word:

• Arc strikes outside the weld.
• Peening (which layers) and caulking.
• Steel backing left in place, and how it is spliced.
• Reentrant corners, and weld access holes.
• Laminations on cut edges, judged with a table by length and depth.

Stress relief

When stress relief is required, a table gives the minimum holding time by thickness band. The subclause also sets heating and cooling limits.

Worked example: a 1-1/2 in. weldment falls in the band held for 1 hour per inch. It needs at least 1-1/2 hours at temperature.

Study plan

1. Read Clause 7 once so you know its order.
2. Tab the electrode exposure table, the preheat subclause and the tolerance figures. Then tab the minimum fillet size table and the weld profile figure and schedule. Last, tab the laminations table, the stress-relief table and the repairs subclause.
3. Practice word problems that combine two rules, such as a root gap plus a minimum fillet size.

Mark J. Curry tip: when a question gives two thicknesses, circle which one the rule uses before you look anything up.

Common traps

• Re-drying electrodes that were wet, rather than only those out too long.
• Reading the E70XX exposure time for a higher-strength electrode.
• Using the thicker part for the fillet size table when a low-hydrogen process is used.
• Adding only the excess over the threshold to a fillet leg, instead of the full root opening.
• Mixing up the back-gouged and not back-gouged columns of the tolerance figure.

Related: how to pass CWI Part C with the D1.1 code book.

Practice this domain

Sources

The D1.1 Fabrication questions cite these documents, by document and, where we can confirm it, chapter or section. We never reproduce them.

1. AWS D1.1 (43 questions)

Found a mistake? Use "Report a problem" under any question, and Mark J. Curry checks it.

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