Australian Welding Procedure Specification (WPS) — AS/NZS 1554.1

Comprehensive reference for welding procedure specifications (WPS), procedure qualification records (PQR), welder qualification testing, preheat and interpass temperature requirements, and electrode selection per AS/NZS 1554.1:2014 for structural steel welding in Australia.

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The WPS/PQR System

AS/NZS 1554.1 requires all structural welding to be performed in accordance with a documented and qualified Welding Procedure Specification (WPS). The WPS is a written document that provides direction to the welder on how to produce a weld that meets the specified requirements.

A WPS is supported by a Procedure Qualification Record (PQR), which is the record of a test weld made to demonstrate that the procedure produces a sound weld with the required mechanical properties. The PQR documents the actual welding parameters used, the test results from mechanical testing (tensile, bend, Charpy impact), and the essential variables.

WPS Contents

A WPS must include, as a minimum (AS/NZS 1554.1 Clause 5.2):

Preheat Requirements — AS/NZS 1554.1 Table 4.2

Preheat is required to control the cooling rate after welding, which prevents the formation of brittle microstructures (martensite) in the heat-affected zone (HAZ). The required preheat temperature depends on the steel grade, the carbon equivalent value (CEV), and the combined plate thickness.

Carbon Equivalent Value (CEV)

CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15 (all elements in weight percent)

For Australian structural steels:

• Grade 300: CEV <= 0.44 (typical)
• Grade 300PLUS: CEV <= 0.42 (lower carbon for improved weldability)
• Grade 350: CEV <= 0.48 (section), <= 0.46 (plate)
• Grade 400: CEV <= 0.52

Preheat Temperature Table (Minimum Preheat, degrees C)

Measured at a distance of 75 mm from the weld centreline, in all directions, immediately before welding commences.

Preheat temperature must be maintained until welding is complete. For multi-pass welds, the interpass temperature (temperature between successive weld passes) must be maintained at or above the minimum preheat temperature and must not exceed 250 degrees C for Grade 300/350 or 200 degrees C for Grade 400.

Electrode and Filler Metal Selection — AS/NZS 1554.1 Table 5.1

The filler metal must match or exceed the tensile strength of the base metal. For structural steels, electrode selection follows the principle of "matching" strength:

Manual Metal Arc Welding (MMAW / Stick)

Gas Metal Arc Welding (GMAW / MIG)

Flux-Cored Arc Welding (FCAW)

Welder Qualification — Clause 5.2

A welder must be qualified by testing to demonstrate the ability to produce sound welds using a qualified WPS. The qualification test includes:

Qualification Test Requirements

Position Qualification

Qualification Validity

A welder qualification is valid for 2 years from the date of the test, provided that the welder has been actively engaged in welding using the qualified process during that period. If the welder has not welded using the qualified process for 6 months or more, re-qualification is required.

Worked Example: WPS Development

Problem: Develop a Welding Procedure Specification for welding a 25 mm thick Grade 350 plate splice using gas metal arc welding (GMAW) in the flat position. The joint is a single V butt with a 60-degree included angle and a 12 mm root face/opening. SP category.

Solution:

Step 1: Determine preheat

Grade 350 plate, t = 25 mm: from the preheat table, the minimum preheat is 75 degrees C for 20-30 mm plate. CEV <= 0.46 for plate.

Step 2: Select filler metal

Grade 350 base metal: matching filler metal is ES4 solid wire (AS/NZS 2717.1), AWS ER70S-6 equivalent. Nominal tensile strength = 490 MPa.

Step 3: Select shielding gas

For GMAW of structural steel in the flat position: Argon + 20% CO2 provides good arc stability, low spatter, and adequate penetration. Flow rate: 18 L/min.

Step 4: Welding parameters

For 1.2 mm diameter ES4 wire in the flat position:

• Voltage: 28-30 V
• Current: 280-320 A (DC electrode positive)
• Wire feed speed: 9-11 m/min
• Travel speed: 300-400 mm/min
• Heat input: (28 x 300 x 60) / (1000 x 350) = 1.44 kJ/mm (mid-range)

Step 5: Weld pass sequence

Root pass: 1.2 mm wire, 28 V, 280 A, ensure full penetration to the backing bar Fill passes: multiple passes, 1.2 mm wire, 30 V, 320 A, approximately 8-10 passes to fill the 25 mm groove Cap pass: final pass, 28 V, 280 A, slight weave to achieve 2-3 mm reinforcement

Step 6: Interpass temperature control

Measure interpass temperature with a contact thermocouple or Tempilstik at 75 mm from the weld centreline. Maintain interpass >= 75 degrees C (min preheat) and <= 250 degrees C (max interpass).

Step 7: Post-weld

Allow the weld to cool slowly in still air. No post-weld heat treatment is required for Grade 350 at 25 mm thickness. Cover with an insulating blanket if cooling in high wind conditions (to avoid excessive cooling rate and potential martensite formation).

Step 8: PQR documentation

Weld a test coupon using the above procedure. Conduct:

• 2 root bends + 2 face bends (all must show no single defect > 3 mm)
• 2 transverse tensile tests (must fail in base metal, tensile strength >= 480 MPa)
• Visual inspection (no cracks, undercut <= 0.5 mm, convexity <= 2 mm)
• If all tests pass: the PQR is valid, and the WPS is qualified.

Result: WPS developed for 25 mm Grade 350 butt weld using GMAW. Preheat 75 degrees C, ES4 wire, Ar+20%CO2 shield, 1.44 kJ/mm heat input. PQR testing to follow.

Frequently Asked Questions

What is a WPS and why is it required for structural welding in Australia?

A Welding Procedure Specification (WPS) is a documented set of welding parameters that directs the welder on how to produce a weld that meets the specified requirements. It is mandatory for all structural welding per AS/NZS 1554.1 Clause 5.2. The WPS ensures consistency, repeatability, and traceability in structural welding. Without a qualified WPS, the weld cannot be certified as complying with AS/NZS 1554.1, and the structural certificate of compliance cannot be issued.

What electrode is used for welding Grade 350 steel in Australia?

For Grade 350 structural steel, matching electrodes are required: E48XX (typically E4818 low-hydrogen) for manual metal arc welding, ES4 solid wire for gas metal arc welding, or E71T-1 flux-cored wire. The electrode tensile strength must match or exceed the base metal tensile strength (480 MPa for Grade 350). Using an undermatched electrode (e.g., E41XX with 410 MPa tensile) on Grade 350 is not permitted for structural welds per AS/NZS 1554.1.

How is the preheat temperature measured and applied per AS/NZS 1554.1?

Preheat temperature is measured at a distance of 75 mm from the weld centreline in all directions using a contact thermocouple, infrared thermometer (emissivity set for steel), or temperature-indicating crayons (Tempilstiks). The measurement must be taken immediately before welding commences and at intervals during welding to confirm the temperature is maintained. Preheat can be applied by gas flame (oxy-acetylene rosebud), electric resistance heating pads, or induction heating. The preheated zone must extend at least 75 mm from the weld centreline in all directions.

How long is a welder qualification valid in Australia?

A welder qualification is valid for 2 years per AS/NZS 1554.1 Clause 5.2, provided the welder has been actively engaged in welding using the qualified process. If the welder has not used the qualified process for a period of 6 months or more, the qualification lapses and re-qualification is required. The employer must maintain a record of the welder's production welding activity to support the ongoing validity of the qualification.

What is the difference between CEV (carbon equivalent) and why does it matter for preheat?

The Carbon Equivalent Value (CEV) is a single number that predicts the hardenability of the steel -- its tendency to form hard, brittle martensite in the heat-affected zone during rapid cooling after welding. Higher CEV = higher hardenability = more preheat required to slow the cooling rate. Grade 300PLUS is specifically designed with a lower CEV (<= 0.42) to minimise or eliminate preheat for thicknesses up to 20 mm, reducing fabrication costs. Grade 400 has a higher CEV (<= 0.52) and typically requires preheat even for thin sections.

Educational reference only. All welding procedures must be verified against the current edition of AS/NZS 1554.1 and the project specification. This information does not constitute professional engineering advice.