Does AWS D1.1 allow plasma-cut surfaces to be welded without grinding?

AWS D1.1:2025 permits thermally cut surfaces (plasma and oxyfuel) for welding provided they meet the surface condition requirements in Clause 7.14. The surface must be free of cracks, notches, and discontinuities exceeding the specified limits. Light grinding to remove slag or hardened edge material may be required depending on the base metal and cutting parameters. Smooth machine cuts that meet the roughness criteria generally do not require grinding.

What surface roughness is acceptable for thermally cut joint edges per AWS D1.1?

AWS D1.1:2025 Clause 7.14.4 specifies that thermally cut surfaces must not exceed 1,000 µin [25 µm] Ra surface roughness for members subject to cyclic loading. For statically loaded structures, the requirement is less strict, but the surface must still be free of cracks, gouges, and notches deeper than 3/16 in [5 mm]. Check your project specification — the engineer of record may specify tighter limits than the code minimum.

How does the heat-affected zone from plasma cutting affect weld quality?

Plasma and oxyfuel cutting create a narrow heat-affected zone along the cut edge. For most low- and medium-carbon structural steels (A36, A572 Gr. 50), this HAZ is thin and acceptable without remediation. For higher-strength or higher-carbon-equivalent steels (A514, A709 HPS 70W), the hardened HAZ can be a source of hydrogen cracking. The WPS should address whether edge preparation grinding is required and what preheat is specified for the joint.

Who is responsible for approving thermally cut joint preparation before welding?

Under AWS D1.1, the inspector (CWI or inspector designated by the fabricator or contractor) is responsible for verifying that joint preparation meets the WPS and code requirements before welding begins. The fabricator's QC plan should include a pre-weld inspection hold point for joint fit-up and surface condition. The inspector must document the approval — 'fit-up accepted' with date, WPS reference, and joint identification.

Plasma and Flame-Cut Edges for Structural Welding: AWS D1.1

AWS D1.1:2025 permits plasma-cut and flame-cut joint surfaces — but with conditions. Here's what your WPS and CWI inspection plan must address before weld prep is approved.

Thermal cutting — plasma arc and oxyfuel — is the standard method for preparing structural steel plates, flanges, and gussets for welding in most fabrication shops. It is faster than sawing, more flexible than shearing, and capable of producing nearly any joint geometry. But cut quality varies, and AWS D1.1:2025 sets specific conditions that thermally cut surfaces must meet before welding begins.

A CWI who approves joint fit-up without verifying cut surface condition is accepting a defect risk that may not show up until UT or RT on completed welds — or worse, in service. Understanding what the code requires, what your WPS must address, and what visual indicators to look for at pre-weld inspection saves costly repairs downstream.

What AWS D1.1:2025 Says About Thermally Cut Surfaces

Clause 7.14 is the governing provision. It covers both oxyfuel (flame) cutting and plasma arc cutting, and it distinguishes between surfaces that simply need to meet dimensional and surface quality requirements versus surfaces that require additional preparation.

The key requirements are:

Surface condition. Thermally cut surfaces must be free of cracks, notches, and slag inclusions before welding. Visible roughness, gouges, and notches deeper than 3/16 in [5 mm] in statically loaded members — or any depth for dynamically or cyclically loaded members — must be repaired by grinding or welding before the joint is assembled.

Surface roughness for cyclic loading. For members subject to cyclic or fatigue loading (crane girders, cyclically loaded connections, bridges), Clause 7.14.4 limits cut surface roughness to 1,000 µin [25 µm] Ra. This is a meaningful limit — hand-held plasma cuts routinely exceed it. Machine-guided plasma or oxyfuel cutting with proper parameters typically meets it; freehand cuts often require grinding.

Hardened layers. On higher-strength steels, thermal cutting creates a hardened surface layer in the cut edge HAZ. For prequalified procedures on the base metals listed in AWS D1.1:2025 Table 6.4 (Prequalified Base Metals), this hardened layer is typically thin enough to be acceptable without removal. For base metals not in Table 6.4 or for project specifications requiring tested procedures, the WPS may need to address edge grinding to remove the hardened layer before welding.

Gouges and notches. Individual gouges or notches between 3/16 in and 1/4 in [5–6 mm] deep may be repaired by welding, provided the repair is performed per a qualified repair WPS and the area is blended smooth. Defects exceeding 1/4 in require engineering review before repair.

Plasma vs. Oxyfuel: Practical Differences for Weld Prep

From the standpoint of AWS D1.1:2025 compliance, plasma and oxyfuel cuts are treated alike under Clause 7.14. In practice, however, they produce different surfaces with different strengths and failure modes:

Oxyfuel (flame) cutting uses an oxidizing flame to heat the steel to ignition temperature, then a high-velocity oxygen jet burns through the metal. It is slower than plasma but produces excellent edge quality on thicker sections (over 1 in). The cut face can have a hardened surface layer — typically 0.005–0.020 in deep depending on cutting speed and base metal chemistry. For A36 and A572 Gr. 50, this layer is typically benign. For A514 or higher-alloy steels, the hardened layer warrants attention.

Plasma arc cutting uses an electrical arc through a constricted high-velocity plasma gas to melt and eject metal. Modern CNC plasma cutting produces excellent surface quality on plates up to about 1-1/2 in thick. The HAZ is narrower than oxyfuel for the same plate thickness. However, plasma cut edges on very thick sections can have more dross adherence and rougher surfaces than oxyfuel cuts at the same thickness.

Both methods produce acceptable surfaces for welding when the cutting parameters are properly set and the cut is visually sound. Both require the same pre-weld inspection.

What the WPS Should Specify

The WPS does not typically need to specify the cutting method in detail — thermal cutting is a fabrication operation, not a welding parameter. But the WPS must address the joint preparation condition that is assumed at the start of welding, and that description is what the CWI uses to accept or reject the joint.

For CJP groove welds, the WPS joint detail (often referencing AWS D1.1:2025 Annex A or B prequalified joint geometries) specifies root face, groove angle, and root opening dimensions. The WPS should also state:

Whether back-gouging is required for the root pass (and if so, to what minimum depth/width)
The joint surface condition required before assembly (e.g., "free of slag, scale, and moisture — grinding of thermally cut surfaces required for A514 base metal")
Whether preheat is required for the joint prep thermal cut itself (unusual, but specified for some high-restraint or high-carbon-equivalent materials)

For a deeper look at how CJP groove weld joint design is documented, see CJP groove weld backing removal requirements and groove weld fit-up tolerances under AWS D1.1.

Pre-Weld Inspection: The CWI's Checklist

The pre-weld inspection hold point for thermally cut joints should cover:

Surface condition — cut face. Look for drag lines, dross adherence, and irregular edges. Dross (solidified slag on the bottom edge of a plasma or oxyfuel cut) must be removed before welding — it contains oxides that will create inclusions in the root pass if left in place. This is often the single most common finding at pre-weld inspection on plasma-cut joints.

Surface condition — joint groove. Check the groove angle and root face against the WPS joint detail. Plasma and flame cutting can produce inconsistent angles if the cutting head is off-square or the travel speed varies. A groove that is too narrow will trap slag in multi-pass welding; one that is too wide wastes filler metal and adds heat input.

Notches and gouges. Run a straightedge along the cut edge and look for notches or depressions. Any notch deeper than 3/16 in must be documented and dispositioned before proceeding.

Hardened edge. On A514, A517, A709 HPS 70W, or other high-strength steels, a visual check is not sufficient to identify a hardened HAZ layer. The WPS should specify the required grinding depth for these materials. If the shop relies on visual inspection alone for high-strength steel joint prep, they are accepting a risk that the code does not authorize.

Scale and contamination. Thermal cutting leaves heat-discolored scale on the surrounding base metal. For most structural applications, this oxide scale is acceptable beyond the immediate joint area. The 1-in zone adjacent to the joint should be clean — free of heavy mill scale, moisture, grease, or paint — per Clause 7.14.1. See steel surface preparation before welding per AWS D1.1 for the full surface cleanliness requirements.

Documenting Pre-Weld Acceptance

The inspector's pre-weld acceptance record should identify the joint (by weld number or weld map reference), the WPS number, the cut method, the inspection findings, and the disposition. For projects under AISC certification or IBC Chapter 17 special inspection, this record is part of the required QC documentation.

A frequent gap in shop QC plans is treating thermal cut surface inspection as informal — a welder or fitter eyeballs the joint and calls it good. When the AISC auditor asks for pre-weld inspection records, "we looked at it" is not an audit-compliant response. The record must exist and must be traceable to the weld. See CWI inspection report documentation under AWS D1.1 for what the record must contain.

Shops managing multiple concurrent structural projects benefit from digital inspection logs that tie directly to the WPS library — so the inspector can call up the correct acceptance criteria for A572 Gr. 50 vs. A913 vs. A514 without hunting through a binder. If your shop is evaluating whether digital WPS and inspection management makes sense, see pricing and features.

Rule library based on AWS D1.1:2025; verify against your governing edition.