Perform Shielded Metal Arc Welding (SMAW)

Performing Shielded Metal Arc Welding (SMAW)

Introduction to the SMAW Process

Shielded Metal Arc Welding (SMAW), also known as stick welding, is an arc welding process that uses a consumable electrode consisting of a metal core surrounded by a flux coating. This process is one of the most versatile and widely used in Canadian industry, particularly for structural steel work, pipelines, heavy equipment repair, and shipbuilding.

The fundamental principle relies on creating an electric arc between the electrode and the workpiece. The heat generated (arc temperature: 3,500 °C to 6,000 °C) simultaneously melts the electrode, the coating, and the base metal, forming the weld pool. The coating decomposes into shielding gases (CO₂, H₂, etc.) that form a gaseous shield around the arc, protecting the weld pool from atmospheric contamination (oxygen, nitrogen, hydrogen).

Advantages and Limitations of SMAW

Advantages	Limitations
Simple and portable equipment	Relatively low deposition rate
Works in all positions	Slag must be removed between passes
Suitable for thick materials	Limited operating factor (≈ 60-70 %)
Resists drafts	Requires a qualified operator
No external shielding gas required	Electrodes sensitive to moisture
Low initial equipment cost	Arc length varies with operator technique

Equipment and Components of the Welding Station

Power Source

The SMAW welding station can be powered by:

Transformer: alternating current (AC) only, economical, no electronic components.

Rectifier: direct current (DC) with polarity adjustment, better arc stability.

Generator: portable, often driven by diesel or gasoline engine, ideal for remote job sites.

Essential characteristics of a power source for SMAW:

Open-circuit voltage (OCV): 50 V to 80 V (AC), 50 V to 70 V (DC). This voltage must be sufficient to strike the arc but must comply with safety standards.

Welding current: adjustable from 20 A to 600 A depending on the application.

Drooping characteristic (constant voltage): voltage decreases as current increases, allowing self-regulation of arc length.

Polarity and Its Importance

Polarity determines the direction of electron flow and influences penetration, deposition rate, and heat distribution.

Polarity	Designation	Penetration	Typical Applications
Electrode negative	DCEN	Deep	Thin sheets, high iron powder filler metals
Electrode positive	DCEP	Medium to deep	Most electrodes (E7018, E6010)
Alternating current	AC	Medium	E6011, E7014 electrodes, reduces arc blow

Rule of thumb: most rutile and basic electrodes operate on DCEP. Cellulosic electrodes (E6010) require DCEP for deep penetration. AC is used to minimize arc blow (arc deflection caused by magnetic fields) on magnetized parts.

Cables and Connections

Electrode cable (electrode holder): minimum recommended cross-section based on amperage (e.g., 35 mm² for 200 A, 50 mm² for 300 A).

Work cable (ground clamp): must be the same cross-section as the electrode cable. A defective work connection causes voltage drop and an unstable arc.

Total cable length: do not exceed 30 m without increasing the cross-section to avoid line losses (ΔV = R × I).

Electrode Classification According to CSA W48 Standard

CSA W48 (Filler metals and allied materials for metal arc welding) is the Canadian reference for classifying covered electrodes. The four- or five-digit classification system follows the American Welding Society (AWS) A5.1 format.

Decoding the EXXXX Designation

Using the E7018 electrode as an example:

Position	Meaning	Value for E7018
E	Electrode	Electrode
70	Minimum tensile strength (ksi)	70,000 psi (490 MPa)
1	Welding position	All positions
8	Coating type and polarity	Basic, low hydrogen, DCEP or AC

Welding positions (3rd digit):

1: all positions (flat, horizontal, vertical up, overhead)

2: flat and horizontal positions only

3: flat position only

Coating types (4th digit):

Digit	Coating Type	Polarity	Characteristics
0	Sodium cellulosic	DCEP	Deep penetration, powerful arc
1	Potassium cellulosic	DCEN, DCEP, AC	Deep penetration, smooth arc
2	Sodium rutile	DCEN, AC	Medium penetration, fluid slag
3	Potassium rutile	DCEN, DCEP, AC	Smooth arc, good bead appearance
4	Iron powder rutile	DCEN, DCEP, AC	High deposition rate
5	Sodium basic	DCEP	Low hydrogen, high strength
6	Potassium basic	DCEP, AC	Low hydrogen, stable AC arc
7	Iron powder iron oxide	DCEN, DCEP, AC	Very high deposition rate
8	Iron powder basic	DCEP, AC	Low hydrogen, high deposition rate

Common Electrodes and Their Applications

Electrode	Coating	Positions	Current	Typical Applications
E6010	Sodium cellulosic	All	DCEP	Pipelines, single-pass root, unpainted steel
E6011	Potassium cellulosic	All	AC, DCEP	Work on galvanized or painted steel, AC only
E6013	Potassium rutile	All	AC, DCEN, DCEP	Thin sheets, decorative welding, low penetration
E7014	Iron powder rutile	All	AC, DCEN, DCEP	Fast assembly, fillet welds, medium sheets
E7018	Iron powder basic	All	DCEP, AC	Structural steel, boilermaking, medium-strength steels
E7024	Iron powder rutile	Flat, horizontal	AC, DCEP, DCEN	Flat fillet welds, high productivity

Electrode Storage and Drying Requirements

Basic electrodes (E7018, E8018, etc.) are particularly sensitive to moisture. Hydrogen absorbed by the coating causes cold cracking (delayed cracking) in the deposited metal.

Electrode Type	Storage Conditions	Recommended Drying
Cellulosic (E6010, E6011)	Dry, room temperature	Do not dry (destroys the coating)
Rutile (E6013, E7014)	Dry, room temperature	1 h at 100-150 °C if damp
Basic (E7018)	Oven at 40-50 °C, relative humidity < 60 %	1-2 h at 350-400 °C after exposure
Basic (E8018, E9018)	Oven at 40-50 °C	2 h at 400 °C

Canadian Electrical Code, Part I (CE Code), Chapter V rule: basic electrodes must not be exposed to open air for more than 4 hours before use. After this period, they must be re-dried according to the manufacturer's specifications.

Welding Parameters and Settings

Current Intensity (Amperage)

Current intensity is the most critical parameter. It determines penetration, deposition rate, and arc stability. The approximate formula for common electrodes:

I = D × k

Where:

I = current in amperes

D = electrode diameter in mm

k = constant depending on electrode type (30 to 50 A/mm)

Reference values by electrode diameter:

Diameter (mm)	E6010/E6011 (A)	E6013 (A)	E7018 (A)
2.4 (3/32")	40-80	40-90	60-110
3.2 (1/8")	75-120	80-130	90-150
4.0 (5/32")	110-160	120-180	140-200
5.0 (3/16")	150-210	170-240	200-275
6.3 (1/4")	200-280	230-320	260-350

Arc Voltage and Arc Length

Arc voltage is directly proportional to arc length. A correct arc length corresponds approximately to the diameter of the electrode core.

Arc too long: high voltage, excessive spatter, porosity, poor gas shielding.

Arc too short: frequent short circuits, electrode sticking, narrow and crowned bead.

Rule of thumb: maintain an arc length equal to the diameter of the metal core. For a 3.2 mm electrode, the arc should measure approximately 3 mm.

Travel Speed

Travel speed influences bead geometry:

Too fast: narrow bead, insufficient penetration, risk of lack of fusion.

Too slow: wide bead, excessive metal buildup, risk of overheating and distortion.

The optimal speed produces a bead whose width is approximately 2 to 3 times the electrode diameter, with penetration of 1.5 to 2 mm beyond the surface.

Electrode Angle

Position	Travel Angle	Work Angle
Flat	10-15° (drag)	90°
Horizontal (fillet)	10-15°	45° (bisector)
Vertical up	0-10° (slightly upward)	90°
Overhead	5-10° (drag)	90°

Operating Techniques

Striking the Arc

Two main methods:

69.Scratch start: scrape the electrode on the workpiece like striking a match. Recommended for basic electrodes.

70.Tap start: touch the workpiece then quickly lift the electrode. Risk of sticking if separation is too slow.

Caution: striking the arc outside the weld zone (on the workpiece) can create arc strikes that act as stress concentration points. On high-strength steels, these marks can cause cracking.

Flat Welding Technique

Position the electrode perpendicular to the workpiece with a 10-15° drag angle.

Maintain a constant arc length.

Move the electrode at a uniform speed.

Observe the weld pool and slag formation.

Vertical Up Welding

Use small-diameter electrodes (2.4 to 3.2 mm).

Use a triangular or half-moon motion to control the pool.

Reduce current by 15-20 % compared to flat welding.

Keep a short arc to prevent the metal from running.

Overhead Welding

Use currents reduced by 20-25 %.

Very short arc, rapid travel.

Drag angle of 5-10° to direct the pool backward.

Avoid excessive weaving motions.

Horizontal (Fillet) Welding

Work angle at 45° (bisector of the angle).

Drag angle of 10-15°.

For fillet welds, the bead should be slightly convex to avoid lack of fusion on the horizontal member.

Joint Preparation and Geometry

Joint and Groove Types

Joint Type	Typical Thickness	Preparation	Included Angle
Lap	All	None	—
T (fillet)	All	None or bevel	—
Butt (I)	≤ 3 mm	None	—
Butt (V)	6-20 mm	Single bevel	60°
Butt (X)	> 20 mm	Double bevel	60° (total)
Butt (U)	> 20 mm	U-groove	45°

Groove Dimensions According to the Code

The Canadian Electrical Code, Part I (CE Code), Chapter V and CSA W59 standards (welding of steel structures) specify minimum groove dimensions:

Root gap: 1.5 to 3 mm depending on thickness and process.

Bevel angle: 30° per side (60° included) for SMAW.

Root face (land): 1.5 to 2.5 mm.

Surface Cleaning and Preparation

Remove all traces of rust, mill scale, oil, grease, or paint for a minimum of 25 mm on each side of the joint.

Use a grinder, wire brush, or degreaser.

Surfaces must be dry before welding (moisture causes porosity).

Weld Defects and Remedies

Porosity

Cause	Remedy
Moisture in the coating	Dry electrodes according to specifications
Drafts	Install wind screens
Contaminated surface	Clean thoroughly
Arc too long	Reduce arc length
Arc blow	Change ground clamp position

Cold Cracking (Delayed Cracking)

This crack appears several hours after welding. It is caused by the combination of:

Diffusible hydrogen in the deposited metal

High residual stresses

Hard microstructure (martensite) in the heat-affected zone (HAZ)

Prevention:

Use properly dried low-hydrogen basic electrodes.

Preheat the workpiece according to specifications (generally 100-200 °C for carbon steels).

Control interpass temperature.

Perform post-weld heat treatment if required.

Lack of Fusion and Lack of Penetration

Lack of fusion: poor bond between the deposited metal and the base metal or between successive passes. Causes: current too low, incorrect angle, travel speed too fast, slag not removed.

Lack of penetration: the root of the joint is not fused. Causes: insufficient root gap, bevel angle too small, current too low.

Slag Inclusions

Slag trapped in the deposited metal between passes.

Causes: poor cleaning between passes, incorrect electrode angle, excessive weaving motion.

Prevention: brush and grind each pass carefully before the next one.

Arc Blow

Arc deflection caused by magnetic fields created by the welding current. More pronounced with direct current.

Remedies:

Use alternating current.

Move the ground clamp closer to the welding zone.

Wrap the work cable around the workpiece to create an opposing field.

Tilt the electrode in the direction opposite to the deflection.

Essential Calculations and Parameters

Preheat Temperature Calculation

The minimum preheat temperature can be estimated using the carbon equivalent (CE) method:

CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

For steel with CE > 0.40 %, preheating is generally required.

Approximate preheat temperature:

CE < 0.35 %: no preheat required (except if thickness > 25 mm)

CE = 0.35-0.45 %: preheat at 50-100 °C

CE > 0.45 %: preheat at 100-200 °C

Heat Input Calculation

H = (V × I × 60) / (S × 1000)

Where:

H = heat input in kJ/mm

V = arc voltage in volts

I = current in amperes

S = travel speed in mm/min

Example: V = 24 V, I = 150 A, S = 200 mm/min

H = (24 × 150 × 60) / (200 × 1000) = 216,000 / 200,000 = 1.08 kJ/mm

Deposition Rate Calculation

Deposition rate (kg/h) = (I × E) / 1000

Where E is the electrode deposition efficiency (typically 60-75 % for SMAW).

Example: E7018, I = 150 A, efficiency = 70 %

Rate = (150 × 0.70) / 1000 = 0.105 kg/h (approximate, depends on manufacturer)

Estimated Number of Passes

N = (A_total) / (A_pass)

Where A_total is the cross-sectional area of the joint (mm²) and A_pass is the area deposited per pass (approximately 10-15 mm² for a 3.2 mm electrode).

Applicable Standards and Codes

CSA W59 — Welded Steel Construction

This standard specifies:

Welder qualifications (clause 4.2)

Required welding procedure specifications (WPS)

Qualification tests (clause 5)

Weld acceptance criteria (clause 6)

Preheat and interpass temperature requirements

CSA W47.1 — Certification of Welding Companies

This standard requires that companies performing welding on steel structures be certified to its requirements. It covers:

Qualification of welding processes

Qualification of welders

Responsibilities of the welding engineer

Verification testing

CSA B149.1 — Canadian Electrical Code, Part I

Although primarily focused on electrical work, this code contains requirements related to electric welding installations:

Rule 8-200: protection of conductors against overcurrent

Rule 8-202: calculation of welding circuit loads

Rule 8-204: demand factor for welding stations

Other Relevant Standards

CSA W48: electrode classification

CSA W186: welding of reinforcing steel bars for concrete

CSA Z662: oil and gas pipelines (specific requirements for SMAW in pipeline work)

Quality Control and Inspection

Non-Destructive Testing (NDT)

Method	Detects	Application
Visual (VT)	Surface defects, dimensions	100 % of welds
Magnetic particle (MT)	Surface and near-surface cracks	Ferromagnetic steels
Liquid penetrant (PT)	Surface cracks	All materials
Ultrasonic (UT)	Internal defects	Thicknesses > 8 mm
Radiographic (RT)	Internal defects	Critical welds

Acceptance Criteria According to CSA W59

Porosity: visible surface porosity must not exceed 1.5 mm in diameter.

Blowholes: no more than 6 blowholes per 25 mm of weld length.

Lack of penetration: not acceptable for loaded butt welds.

Cracks: no cracks are acceptable, regardless of size.

Reinforcement (profile): reinforcement must not exceed 1.5 mm above the surface.

SMAW Welding Safety

Electrical Hazards

Open-circuit voltage: 50-80 V — dangerous in damp conditions.

Wear dry, insulating gloves.

Check cable insulation before each use.

Never change electrodes with bare hands.

Use insulated electrode holders conforming to CSA standards.

Fume Hazards

SMAW welding fumes contain metal oxides, fluorides (basic electrodes), and organic compounds. Ventilation must comply with the Canada Occupational Health and Safety Regulations (Part II of the Canada Labour Code).

Radiation Hazards

The arc emits intense ultraviolet and infrared radiation.

Wear a helmet with the appropriate shade lens (shade 10 to 13 depending on current).

Protect exposed skin with flame-resistant cotton clothing.

Common Pitfalls to Avoid

202.Confusing polarities: E6010 requires DCEP, never DCEN. Reversed polarity produces an unstable arc and poor penetration.

203.Neglecting to dry basic electrodes: a damp E7018 electrode produces porosity and cold cracks. Always check storage history.

204.Using excessive arc length: this creates spatter and insufficient gas shielding. The arc should be short and controlled.

205.Forgetting interpass cleaning: residual slag causes inclusions. Brush and inspect each pass.

206.Confusing welding positions: digit 1 means all positions, digit 2 means flat and horizontal only. An E7024 electrode cannot be used vertically.

207.Ignoring preheat: on thick or high-strength steels, lack of preheat causes immediate or delayed cracking.

208.Calculating heat input incorrectly: check the units (kJ/mm, not kJ/cm) and travel speed in mm/min.

209.Using excessive current: this causes coating burn-off, excessive spatter, and loss of pool control.

210.Not meeting qualification requirements: every welder must be qualified according to CSA W47.1 for the process, position, and joint type.

211.Forgetting arc blow protection: on magnetized parts, use AC or reposition the ground clamp.

Summary

SMAW is a consumable covered electrode process, using the electric arc as the heat source and the coating as gas shielding and slag generator.

Electrode classification follows the EXXXX format: E = electrode, first 2 digits = tensile strength (ksi), 3rd digit = position, 4th digit = coating type.

Basic electrodes (E7018) require dry storage and drying at 350-400 °C if exposed to moisture.

Polarity influences penetration: DCEP for most electrodes, DCEN for specific applications, AC to reduce arc blow.

Critical parameters are current (based on diameter and electrode type), arc length (equal to core diameter), travel speed, and electrode angle.

Common defects (porosity, inclusions, lack of fusion, cracking) are preventable through rigorous parameter control and proper preparation.

Applicable Canadian standards are CSA W59 (structural steel), CSA W47.1 (company certification), CSA W48 (electrodes), and the Canadian Electrical Code, Part I (CE Code), Chapter V.

Essential calculations include carbon equivalent (CE), heat input (H = V × I × 60 / S × 1000), and deposition rate.

Safety requires insulating gloves, a helmet with appropriate filter lens, and adequate fume ventilation.

This chapter covers the essential knowledge for the Interprovincial (Red Seal) exam for the welder trade. Master the concepts, calculations, and standards cited to pass your certification.