--------------------------- | :-------------------------------------------- | :------------------------------ | | Process (SMAW, GMAW, FCAW, SAW) | As qualified | Yes — changing process | | Base metal thickness | 0.5t to 2t of qualification plate | Yes — outside range | | Electrode classification | As qualified | Yes — different class | | Welding position | 1G/1F qualifies all; position-specific limits | Yes — limited by position | | Preheat temperature | ±50°C from qualified value | Yes — outside range | | Heat input | Maximum 25% above qualified | Yes — above limit | | Post-weld heat treatment | As qualified | Yes — any change | | Shielding gas (GMAW/FCAW) | As qualified | Yes — mixture change |

Preheat and Interpass Temperature

Per CSA W59 Clause 5.3, minimum preheat is determined from Table 5.1 based on carbon equivalent (CEV) and combined thickness:

Minimum Preheat for 350W (CEV ≈ 0.45)

Minimum Preheat for 350WT (CEV ≈ 0.42)

350WT's lower carbon equivalent (0.42 vs 0.45) reduces preheat requirements, making it more forgiving for field welding in cold weather.

Preheat Verification Methods

Per CSA W59 Clause 5.3.3:

Preheat is measured at a point 75 mm from the weld joint on the side opposite the heat source, at mid-thickness.

Heat Input Control

Per CSA W59 Clause 5.4:

Heat Input (kJ/mm) = (V × I × 60) / (S × 1000)

Where:

• V = arc voltage (volts)
• I = welding current (amperes)
• S = travel speed (mm/min)

Typical Heat Input Ranges

For 350W steel, heat input should be controlled between 0.5-3.0 kJ/mm. Below 0.5 kJ/mm risks rapid cooling and HAZ hardening. Above 3.0 kJ/mm risks excessive HAZ softening and grain coarsening.

Electrode Selection

Per CSA W59 Table 5.2:

Matching Electrodes for CSA G40.21 Steels

Procedure Qualification Record (PQR)

Per CSA W59 Clause 6, each WPS must be supported by a PQR demonstrating:

PQR Testing Requirements

PQR Qualification Range

Welder Qualification

Per CSA W59 Clause 7, welders must be qualified:

Qualification Tests

CWB Certification

In Canada, welding is governed by the Canadian Welding Bureau (CWB) under CSA W47.1:

• Division 1: Unlimited welded construction, any thickness, any process
• Division 2: Limited to non-fusion welding or specific processes
• Division 3: Limited to specific products (e.g., trusses, light framing)

Frequently Asked Questions

What preheat is required for welding 350W steel per CSA W59? For 350W with CEV ≈ 0.45, preheat depends on combined thickness: t ≤ 20 mm: none required; 20-40 mm: 10°C; 40-65 mm: 50°C; 65-90 mm: 95°C; > 90 mm: 120°C. The interpass temperature must not exceed 200°C. For 350WT (CEV ≈ 0.42), preheat requirements are less stringent — no preheat needed up to 50 mm combined thickness.

What is the difference between WPS and PQR in CSA W59? WPS (Welding Procedure Specification) is the written document describing how welding will be performed — including process, parameters, electrode, preheat, and heat input. PQR (Procedure Qualification Record) is the documented evidence that the WPS produces acceptable welds — based on mechanical testing of a qualification weld. The PQR supports the WPS. A single PQR may qualify multiple WPS variables within the range of essential variables.

What electrode is used for welding 350W steel in Canadian practice? E48XX (SMAW), E49S-6 (GMAW), or E480T-5 (FCAW) are used for 350W. E48XX has Xu = 480 MPa, matching or slightly exceeding the 450 MPa Fu of 350W. In Canadian fabrication shops, FCAW with E480T-5 is dominant for production welding due to higher deposition rates. GMAW (E49S-6) is common for field erection welding due to its all-position capability.

What is the maximum interpass temperature for 350W steel per CSA W59? 200°C maximum interpass temperature for 350W and all carbon-manganese structural steels. Exceeding 200°C can cause: (a) reduced HAZ toughness due to grain coarsening, (b) increased risk of hot cracking in multi-pass welds, (c) reduced weld metal strength. For quenched and tempered steels (480W, 700Q), the maximum interpass is 150-180°C per the qualified WPS.

Related Pages

• Canadian Weld Inspection — CSA W59 Guide
• Canadian Weld Capacity — Fillet Weld Table
• Canadian Weld Symbols — AWS Standard
• CSA Weld Electrode Selection
• Canadian Steel Chemical Composition
• CSA S16 Connection Design
• Welded Connection Calculator
• All Canadian References

This page is for educational reference. Welding procedure per CSA W59-18. All welding must be performed under a qualified WPS by CWB-certified welders. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.

Design Resources

Calculator tools

• Weld Capacity Calculator
• Weld Symbol Generator

Design guides

• Weld Design Checklist

Disclaimer: This content is for educational purposes only. Results must be verified by a licensed professional engineer. Steel Calculator provides preliminary design tools — NOT a substitute for professional engineering judgment.