AWS Shielded Metal Arc Welding (SMAW) 2 — Questions and Answers

Question 1: The AWS classification E7018 indicates which electrode properties?

70 ksi tensile, all-position, AC/DCEP, low-hydrogen potassium (Correct answer)
70 ksi tensile, flat/horizontal only, DCEP, iron powder
60 ksi tensile, all-position, AC only, cellulosic
70 ksi tensile, vertical down only, DCEN, titania

Correct answer: 70 ksi tensile, all-position, AC/DCEP, low-hydrogen potassium

E7018: E=electrode, 70=70 ksi tensile, 1=all-position, 8=low-hydrogen potassium coating, usable with AC or DCEP.

Per AWS A5.1, E7018 is a low-hydrogen potassium (LHK) electrode: E=electrode; 70=70 ksi minimum tensile strength; 1=suitable for all positions (flat, horizontal, vertical, overhead); 8=coating type: low-hydrogen potassium, iron powder, AC or DCEP. Low-hydrogen electrodes must be stored dry (below 50°F dew point) and reconditioning in ovens per manufacturer requirements to prevent moisture absorption, which causes hydrogen-induced cracking.

Question 2: Why must E7018 electrodes be stored in a rod oven?

To maintain their coating plasticity for easier striking
To prevent moisture absorption by the low-hydrogen coating, which causes hydrogen-induced cracking (Correct answer)
To keep them warm so they arc more easily
To prevent oxidation of the iron powder in the coating

Correct answer: To prevent moisture absorption by the low-hydrogen coating, which causes hydrogen-induced cracking

Low-hydrogen coatings are hygroscopic — they absorb moisture from the air. Moisture releases hydrogen into the weld, causing hydrogen-induced cracking (HIC). Storage in rod ovens (250–350°F) keeps the coating dry.

E7018 and other low-hydrogen electrodes (E7015, E7016, E7018M, E11018) have flux coatings that absorb atmospheric moisture very quickly. When the electrode is used after moisture absorption, water (H2O) in the arc breaks down, releasing atomic hydrogen that diffuses into the weld metal and HAZ. This hydrogen can cause delayed (cold) cracking, particularly in high-strength or hardenable steels. AWS D1.1 and electrode manufacturers specify strict oven storage at 250–350°F and limits on exposure time before reconditioning.

Question 3: When welding in the overhead (4G/4F) position with SMAW, what technique adjustment is most important?

Using a larger diameter electrode for better coverage
Reducing amperage and using a shorter arc length to control the molten pool (Correct answer)
Using AC power instead of DC to reduce arc blow
Pointing the electrode upward at a steep angle

Correct answer: Reducing amperage and using a shorter arc length to control the molten pool

In overhead position, reducing amperage and maintaining a short arc length produces a smaller, more controllable weld pool that resists falling from gravity.

Overhead welding is the most demanding SMAW position because gravity pulls the molten pool downward away from the joint. To control this: reduce amperage 10–15% compared to flat position; maintain the shortest practical arc length to keep the pool small and fast-freezing; use weave or stringer technique as the WPS specifies; avoid excessive dwell time. Electrode angles of 5–10° travel angle (drag) with a 90° work angle to the joint surface are typical. Protective gear is essential to protect against falling spatter.

Question 4: Which SMAW electrode coating type is best suited for pipeline root passes because of its deep penetration and suitability for vertical-down welding?

E6010 (cellulosic, high-cellulose sodium) (Correct answer)
E7018 (low-hydrogen potassium)
E6013 (titania potassium)
E7024 (iron powder, titania)

Correct answer: E6010 (cellulosic, high-cellulose sodium)

E6010 uses a high-cellulose sodium coating that produces a forceful, deeply penetrating arc ideal for open-root joint welding in all positions including vertical down (5G pipeline technique).

E6010 has a high-cellulose sodium coating that generates a gas shield (primarily CO and CO2 from cellulose combustion), producing a stiff, concentrated arc with deep penetration and a thin, fast-freezing slag. This makes it ideal for root pass welding on pipelines (API 1104), structural root passes, and anywhere a keyhole technique on an open root joint is required. It is also one of the few electrodes that weld well in vertical-down position due to its slag behavior. E6010 requires DCEP (DC+ reverse polarity).

Question 5: Arc blow in SMAW DC welding is caused by:

Excessive preheat temperature
Magnetic fields around the base metal deflecting the arc (Correct answer)
High humidity in the welding environment
Incorrect electrode angle

Correct answer: Magnetic fields around the base metal deflecting the arc

Arc blow is the deflection of the welding arc by magnetic forces created by the interaction of the DC welding current with the magnetic fields in the base metal, fixtures, or earth ground connections.

Arc blow results from asymmetric magnetic fields around the arc. The DC welding current magnetizes the base metal and surrounding structures. 'Forward arc blow' deflects the arc in the direction of travel; 'back arc blow' deflects it opposite. Remedies include: switching to AC (AC current doesn't sustain a fixed magnetic field), moving the work lead connection, using backstep technique, reducing current, using a shorter arc, or positioning the electrode to compensate for the deflection. Arc blow is most problematic near ends, corners, and heavy fixtures.

Question 6: Undercut in SMAW is most commonly caused by:

Too low amperage and too slow travel speed
Too high amperage, too fast travel speed, or incorrect electrode angle (Correct answer)
Wet electrodes
Insufficient preheat on low-alloy steel

Correct answer: Too high amperage, too fast travel speed, or incorrect electrode angle

Undercut — a groove melted into the base metal along the weld toe — results from excessive current, excessively fast travel speed, or improper electrode angle directing heat toward the plate edge rather than the joint.

Undercut is a surface discontinuity where the base metal at the weld toe is melted and not filled by weld metal, creating a stress concentration. Primary causes: current too high (excess melting of plate edge), travel speed too fast (insufficient fill), electrode angle directing the arc toward the joint edge instead of into the root, or excessive arc length (low voltage causing irregular arc). AWS D1.1 acceptance criteria limit undercut depth (typically 1/32 inch max for cyclically loaded structures). Correction requires reducing current, adjusting travel speed, and correcting electrode technique.

AWS Shielded Metal Arc Welding (SMAW) 2

The AWS classification E7018 indicates which electrode properties?