Select and Prepare Base Materials and Consumables

Selecting and Preparing Base Metals and Consumables

Module Introduction

This chapter covers all the knowledge required by the Welding Apprenticeship Program for the competency block "Selecting and Preparing Base Metals and Consumables." You must master metal identification, consumable selection, joint preparation calculations, and the requirements of Canadian standards. This module represents approximately 15% of the questions on the Red Seal exam. Questions focus on the practical application of standards, weld dimension calculations, and material compatibility.

Identification and Classification of Base Metals

Steel Designation Systems

In Canada, you will primarily encounter two classification systems: the ASTM (American Society for Testing and Materials) standard and the CSA (Canadian Standards Association) standard. For the exam, you must know the equivalencies and fundamental properties.

CSA/ASTM Designation	Steel Type	Tensile Strength (MPa)	Typical Applications
A36 / CSA G40.20	Carbon structural steel	400–550	Structural frames, bridges
A572 Gr. 50 / CSA G40.21 350W	High-strength low-alloy steel	450–620	Heavy structures
A516 Gr. 70	Boiler and pressure vessel steel	485–620	Pressure vessels
A106 Gr. B	Carbon steel for piping	415	High-temperature piping
304L / 316L	Austenitic stainless steel	485–515	Food, chemical industries

Rule of thumb: The "W" suffix in the CSA G40.21 standard indicates a weldable steel. Grade 350W steels are the most common in Canadian construction.

Identification by Spark Test and Colour Code

Visual identification by spark test (grinding test) remains a quick field method:

Mild carbon steel: long, yellow sparks with few branches.

High-carbon steel: shorter, white sparks with multiple branches and bursts.

Stainless steel: short, orange sparks with no branches.

Grey cast iron: very short, red sparks with no branches.

The CSA colour code for structural steels is also tested:

Grade	Identification Colour
260W	Green
300W	Yellow
350W	Red
400W	Blue

Effect of Carbon and Carbon Equivalent (CE)

The weldability of a steel depends primarily on its carbon content and its carbon equivalent (CE) . The IIW (International Institute of Welding) formula is:

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

CE < 0.40%: excellent weldability, no preheat required.

CE = 0.40–0.60%: moderate weldability, preheat recommended.

CE > 0.60%: difficult weldability, preheat mandatory and post-weld heat treatment (PWHT) often required.

Calculation example: Steel with C = 0.20%, Mn = 1.20%, Cr = 0.10%, Ni = 0.05%.

CE = 0.20 + (1.20/6) + (0.10/5) + (0.05/15) = 0.20 + 0.20 + 0.02 + 0.003 = 0.423%

Conclusion: moderate preheat (50–100 °C) recommended.

Classification of Welding Consumables

Covered Electrodes (SMAW) — CSA W48 / AWS A5.1 Standard

The E7018 classification system decodes as follows:

E: electrode.

70: minimum tensile strength of 70,000 psi (≈ 490 MPa).

1: welding position (1 = all positions, 2 = flat and horizontal fillet).

8: coating type and polarity (8 = basic, low hydrogen, direct current).

Classification	Coating	Polarity	Positions	Applications
E6010	Cellulosic	DC+	All	Deep penetration, pipe welding
E6011	Cellulosic	AC or DC	All	Painted, galvanized steel
E6013	Rutile	AC or DC	All	Thin sheet metal, aesthetics
E7018	Basic (low H)	DC+	All	Structures, high-strength steels
E7024	Rutile (iron powder)	AC or DC	Flat, horizontal fillet	High productivity

Key requirement: Low-hydrogen electrodes (E7018, E8018, etc.) must be stored in an oven at a temperature of 120 °C to 150 °C. Once removed from the oven, they must be used within a maximum of 4 hours (or 2 hours in humid environments). If this time limit is exceeded, they must be re-baked at 350–400 °C for 1 to 2 hours.

Flux-Cored Wires (FCAW) — AWS A5.20 / A5.29

Flux-cored wires are divided into two main categories:

Type T-1: gas-shielded (CO₂ or Ar/CO₂ mixture). Classification E71T-1.

Type T-4: self-shielded (no gas). Classification E71T-4.

The E71T-1 decoding:

E: electrode.

7: 70,000 psi strength.

1: all positions.

T: tubular.

1: flux type (gas required).

Solid Wires (GMAW) — AWS A5.18

ER70S-6 solid wires are the most common. The "S" indicates a solid wire, and the "6" indicates the chemical composition (higher manganese and silicon content for better deoxidation). The recommended shielding gas is an Ar/CO₂ (75/25) mixture or pure CO₂.

Tungsten Electrodes (GTAW) — AWS A5.12

Designation	Colour	Use
EWP (pure tungsten)	Green	Aluminum (AC)
EWCe-2 (ceriated)	Grey	Steel, stainless steel (DC-)
EWLa-1 (lanthanated)	Black	Versatile
EWTh-2 (thoriated)	Red	Steel, stainless steel (DC-) — limited use (radioactive)

Weld Joint Preparation

Joint Types and Angles

According to CSA W59 (Welding of steel structures), the main joint types are:

Joint Type	Symbol	Application
Lap	—	Thin sheet metal
Tee	—	Reinforcements, stiffeners
Butt	—	Piping, plates
Corner	—	Frames, boxes
Edge	—	Thick plates

Calculating Preparation Dimensions

For a single V-groove joint, the critical parameters are:

Bevel angle (α): generally 60° (30° on each side).

Root gap (g): 2 to 3 mm for SMAW, 3 to 4 mm for GMAW.

Root face (f): 1.5 to 2.5 mm.

Bevel angle: half of the total angle.

Formula for calculating deposited metal volume for a single V-groove joint:

V = (b × t) + (t² × tan(α/2))

Where:

V = volume of deposited metal (mm³)

b = root gap (mm)

t = plate thickness (mm)

α = total bevel angle (degrees)

Example: 12 mm plate, 3 mm root gap, 60° total angle.

V = (3 × 12) + (12² × tan(30°)) = 36 + (144 × 0.577) = 36 + 83.1 = 119.1 mm³ per mm of length

For a 1-meter weld (1000 mm), the total volume is 119,100 mm³ = 119.1 cm³.

Calculating the Number of Passes

The number of passes depends on the maximum cross-sectional area per pass. For SMAW with a 3.2 mm E7018 electrode, the recommended maximum cross-section is approximately 25 mm². For a 4 mm electrode, it is approximately 40 mm².

Number of passes = Total cross-section / Cross-section per pass

Using the previous example: total cross-section = 119.1 mm².

With a 3.2 mm electrode: 119.1 / 25 = 4.8 → 5 passes.

With a 4 mm electrode: 119.1 / 40 = 2.98 → 3 passes.

Surface Preparation

CSA W59 requires that surfaces to be welded must be:

81.Free of rust, oil, grease, paint, and moisture (clause 5.4).

82.Dry — moisture is a source of hydrogen.

83.Cleaned over a minimum width of 25 mm on each side of the joint.

Accepted cleaning methods are:

Wire brushing (stainless steel brush for stainless steel).

Grinding (abrasive disc).

Chemical cleaning (solvents, degreasers).

Shot blasting (for large surfaces).

Caution: Never use carbon steel brushes on stainless steel — risk of cross-contamination (corrosion).

Pipe Preparation

Applicable Standards

For pressure piping, CSA B51 (Boilers and pressure vessels) and the Canadian Electrical Code, Chapter V do not apply directly to welding. The reference standard is ASME B31.3 (Process Piping) or ASME Section IX (welder qualification). In Canada, CSA Z662 (Oil and gas pipeline systems) is the primary standard for pipelines.

Pipe Joint Preparation

For pipes, the V-groove joint is the most common. Typical dimensions for a 6 mm thick pipe:

Bevel angle: 37.5° on each side (75° total).

Root gap: 2.4 mm.

Root face: 1.6 mm.

Rule of thumb: For pipes with a nominal diameter ≤ 2 inches (50 mm), an open root joint is often used with a cellulosic E6010 electrode for the root pass.

Alignment and Tack Welding

Pipe alignment must respect a maximum misalignment of 1.5 mm (or 10% of the wall thickness, whichever is smaller). Tack welding must be performed with the same process and consumables as the final weld. Tacks must be:

3 to 4 in number for a small-diameter pipe.

10 to 15 mm in length.

Ground or filed at the ends to ensure complete fusion.

Preheat and Heat Treatment

Calculating Preheat Temperature

CSA W59 (clause 5.6) provides minimum preheat requirements based on thickness and CE. A simplified method:

T°C = 350 × (CE − 0.25)

Where CE is the carbon equivalent calculated previously.

Example: CE = 0.423%.

T = 350 × (0.423 − 0.25) = 350 × 0.173 = 60.5 °C → round up to 65 °C

Verifying Temperature

The preheat temperature must be verified using:

Temperature stick — colour change.

Infrared pyrometer — non-contact measurement.

Thermocouple — contact measurement.

The temperature must be measured at a distance of 75 mm from the joint (on the side opposite the heat source) before welding begins.

Post-Weld Heat Treatment (PWHT)

PWHT is required for:

Steels with CE > 0.50% and thickness > 20 mm.

Pressure vessels according to ASME Section VIII.

Piping according to ASME B31.3 (under certain conditions).

Typical PWHT temperatures for carbon steels: 600–650 °C for 1 hour per 25 mm of thickness (minimum 1 hour).

Shielding Gases and Flow Rates

Gas Selection by Process

Process	Gas	Flow Rate (L/min)	Applications
GMAW (steel)	Ar/CO₂ 75/25	15–20	All-position welding
GMAW (steel)	Pure CO₂	18–25	Flat, horizontal fillet, economical
GMAW (aluminum)	Pure argon	18–25	All positions
FCAW (gas-shielded)	CO₂ or Ar/CO₂	18–25	High productivity
GTAW (steel)	Pure argon	10–15	Precision welding
GTAW (aluminum)	Pure argon	12–18	AC

Effects of Incorrect Flow Rate

Flow rate too low: porosity, lack of penetration, weld pool contamination.

Flow rate too high: turbulence, air entrainment, porosity, excessive cooling.

Rule of thumb: The flow rate should be adjusted based on the welding current. For GMAW, an approximate formula: Flow rate (L/min) = Current (A) / 10 — for a 150 A current, flow rate = 15 L/min.

Storage and Handling of Consumables

Storage Requirements per CSA W48

Consumable	Storage Temperature	Relative Humidity	Maximum Time Out of Oven
Low-H electrodes (E7018)	120–150 °C (oven)	< 60%	4 hours
Cellulosic electrodes (E6010)	10–40 °C (dry)	< 60%	8 hours
Flux-cored wires (FCAW)	10–40 °C (dry)	< 60%	N/A (packaging)
Solid wires (GMAW)	10–40 °C (dry)	< 60%	N/A (packaging)

Handling Rules

138.Never use damp or damaged electrodes.

139.Always reseal wire containers after use.

140.Check the expiry date of consumables.

141.Use clean gloves when handling low-hydrogen electrodes (avoid contamination from skin oils).

Common Pitfalls to Avoid

144.Confusing E6010 and E7018: E6010 is cellulosic (deep penetration, root pass), E7018 is basic low-hydrogen (structural). They are not interchangeable.

145.Forgetting re-baking: An E7018 electrode left in the air for more than 4 hours must be re-baked. Don't throw it away, but don't use it as-is.

146.Calculating CE with the wrong units: Percentages are in % (not decimal fractions). C = 0.20% means 0.20, not 0.002.

147.Confusing total angle and bevel angle: a 60° bevel means 30° on each side. The total angle is 60°.

148.Neglecting surface cleaning: CSA W59 requires a minimum of 25 mm of cleaning. A dirty joint is a major cause of porosity.

149.Using a carbon steel brush on stainless steel: cross-contamination, future corrosion.

150.Ignoring preheat for high-CE steels: risk of cold cracking (hydrogen).

151.Incorrect gas flow rate: too low = porosity, too high = turbulence. Always check with a flow meter.

152.Confusing tungsten colours: green = pure (AC aluminum), red = thoriated (DC steel). A red electrode used on AC will be destroyed quickly.

153.Forgetting tack welds: tack welds must be ground at the ends to avoid root fusion defects.

Summary

Metal identification: know CSA G40.21 designations (260W, 300W, 350W, 400W) and ASTM (A36, A572, A516). The spark test is a quick identification method.

Carbon equivalent (CE) : formula CE = C + (Mn/6) + (Cr + Mo + V)/5 + (Ni + Cu)/15. CE < 0.40% = weldable without preheat.

Consumables: complete decoding of AWS/CSA classifications (E7018, E71T-1, ER70S-6). Store low-H electrodes at 120–150 °C, use within 4 hours.

Joint preparation: angles, gaps, root faces. Calculation of deposited metal volume: V = (b × t) + (t² × tan(α/2)).

Preheat: T°C = 350 × (CE − 0.25). Verify at 75 mm from the joint.

Shielding gases: Ar/CO₂ 75/25 for GMAW steel (15–20 L/min), pure argon for GTAW (10–15 L/min).

Canadian standards: CSA W59 (structures), CSA W48 (consumables), CSA Z662 (pipelines), ASME B31.3 (piping).

Final exam tip: Questions in this module are often case studies — you are given an application (e.g., 8 mm pipe, 350W steel, vertical position welding) and asked to choose the consumable, preparation, and parameters. Practice decoding classifications and calculating CE quickly. Master the storage tables and preheat temperatures — these are frequent short-answer questions.