Most welding professionals are familiar with AWS D1.1 Structural Welding Code – Steel and its allowance for prequalified welding procedures when welding carbon steel. Prequalification under AWS D1.1 is widely used to save time, reduce cost, and establish code-compliant welding procedures without qualification testing. What far fewer people realize is that AWS D1.6 Structural Welding Code – Stainless Steel also allows the prequalification of welding procedure specifications (PWPSs) for several commonly used stainless steel alloys.
As discussed earlier in this series, prequalification is not a shortcut—it is a structured, code-approved framework that provides reasonable assurance of weld quality when its requirements are followed. AWS D1.6 applies the same philosophy to structural stainless steel, with defined limits on welding process, base material, filler metal, joint design, and essential variables. Understanding how prequalified WPSs are used under AWS D1.6—and where engineering judgment and contract requirements extend beyond the code—is essential for applying prequalification correctly in stainless steel fabrication.
This article is part of the Prequalified vs. Qualified Welding Procedures series, which examines how AWS D1.1 and AWS D1.6 requirements are applied in real fabrication environments.
What AWS D1.6 Covers—and What It Does Not
AWS D1.6 primarily addresses:
- Structural integrity of stainless steel weldments
- Mechanical performance of welded joints
- Fabrication and inspection requirements
It does not:
- Guarantee corrosion resistance for specific environments
- Address creep performance in elevated-temperature service
- Address sensitization or other metallurgical issues
In fact, the word corrosion appears only a handful of times across the nine clauses of AWS D1.6. This is intentional. The code assumes that material selection and environmental suitability are addressed elsewhere. The code does, however, provide guidance for selecting filler metals that match both strength and general corrosion resistance, while still leaving final responsibility with the welding engineer.
Prequalified WPSs Are Permitted Under AWS D1.6
Like AWS D1.1, AWS D1.6 allows the use of prequalified welding procedures, providing an exemption from qualification testing under Clause 6. This is advantageous because it allows fabricators to:
- Develop compliant WPSs quickly
- Avoid costly and time-intensive destructive and nondestructive testing
- Begin production without delay
The logic behind prequalification under AWS D1.6 is the same as under AWS D1.1: when defined variables and limits are followed, the procedure provides reasonable assurance of producing sound structural welds.
Prequalified Welding Processes Under AWS D1.6
Not all welding processes are prequalified under AWS D1.6. The following processes are prequalified:
- SMAW
- GTAW
- GMAW
- FCAW
Submerged Arc Welding (SAW) is not prequalified under AWS D1.6. This often surprises people familiar with AWS D1.1. The reason is simple: stainless steel fluxes are not presently classified by AWS, which prevents SAW from being prequalified for structural stainless steel applications.
Approved Base Metals and Filler Metals
To use a prequalified WPS under AWS D1.6, both base metals and filler metals must come from approved tables.
Base Metals
- Must be selected from Table 2 of AWS D1.6
- Covers primarily austenitic stainless steels
Filler Metals
- Must be selected from Table 5.3
- Matching filler metals are provided by the code
While matching strength and composition is often appropriate, the engineer must still evaluate:
The code does not guarantee suitability for all corrosion conditions.
Preheat and Interpass Temperature Requirements
Structural stainless steels generally do not require preheat. Preheat may be used only to:
- Remove moisture
- Prevent condensation
Interpass temperature, however, is limited:
- Maximum interpass temperature: 350°F [175°C]
This limit exists to help control metallurgical behavior and maintain weld quality.
Staying Within Variable Limits
AWS D1.6 defines limits for essential variables that must be followed to maintain prequalified status. These limits are found primarily in:
- Table 5.1
- Table 5.4
They include restrictions on:
- Amperage and voltage
- Travel speed
- Shielding gas composition and flow rate
- Welding position
- Filler metal classification and size
- Root pass thickness
- Fill pass thickness
- Fillet weld size
- Layer width
As discussed earlier in this series, staying within these limits is what preserves prequalification. Exceeding them does not mean the weld will fail—but it does mean the procedure is no longer prequalified.
Use of Prequalified Joints
AWS D1.6 contains a complete set of prequalified joint details, shown in:
- Figures 5.2 through 5.5
Each joint includes:
- Dimensional requirements
- Allowed tolerances
To maintain prequalified status:
- The joint configuration must match one of these details
- Dimensional tolerances must be met (pay attention to “As-Detailed” and “As-Fit” tolerances)
This mirrors the same joint-control discipline required under AWS D1.1 and reinforces the importance of fit-up control discussed earlier in this series.
Three Important Points to Understand
1. You Must Have the Code
If procedures or welders must be qualified to AWS D1.6, you must have access to the code. Even when working with consultants, AWS D1.6 contains fabrication, inspection, and design requirements that the fabricator must understand.
2. You Do Not Need to Be a CWI or Welding Engineer
The code does not require a specific credential to qualify procedures or welders. What is required is a working knowledge of AWS D1.6. CWIs often perform these tasks because of their training, not because the code mandates it.
3. Prequalification Has Limits—Regardless of Material
The considerations discussed earlier in this series apply equally to stainless steel:
- Joint fit-up
- Variable control
- Production changes
These are not “risks of prequalification”—they are requirements for proper use, whether the procedure is prequalified or qualified by testing.
When Qualification by Testing Is Required
There are situations where AWS D1.6 does not permit prequalification of welding procedures. Examples include:
- Base metals not covered by the code (e.g., AL6XN or other super austenitic stainless steels)
- Extremely corrosive environments (subsea, sour service, chemical exposure) requiring specialized testing
- Contract requirements exceeding code scope
In these cases:
- Qualification by testing is required
- Additional requirements must be defined in contract documents
- The engineer in charge must supplement the code
This aligns with the broader theme of this series: prequalification is a foundation, not a limitation.
Practical Takeaways
- AWS D1.6 focuses on structural integrity, not corrosion resistance
- Prequalified WPSs are permitted and highly effective when used correctly
- Only certain processes, materials, joints, and variables are allowed
- Staying within limits preserves prequalification and quality
- Engineering judgment is still required for service-specific concerns
Series Context
This article is part of the Prequalified vs. Qualified Welding Procedures series. You can find the full series here: Prequalified vs. Qualified Welding Procedures – Series Hub
Free Resources for Additional Learning
To further support proper use of prequalified welding procedures, the following free resources are available:
- How to Write AWS D1.1 Prequalified Welding Procedures A practical overview of how prequalified procedures are developed and what the code actually requires.
- Checklists for AWS D1.1 Qualification of Welding Procedures and Welders Structured checklists to help verify compliance with AWS D1.1 qualification requirements and avoid missed steps.
These tools reinforce the discipline required to apply prequalified procedures correctly.
Prequalified Welding Procedures – Ready for Immediate Use
If you need code-compliant welding procedures immediately, the following collections are available:
- 322 AWS D1.1 Prequalified Welding Procedures for Carbon Steel
- 280 AWS D1.6 Prequalified Welding Procedures for Stainless Steel
These procedures were developed by welding engineers and Certified Welding Inspectors and are in full conformance with their applicable AWS structural welding codes. They provide immediate coverage when speed, consistency, and compliance matter.
280 Prequalified Welding Procedures for Stainless Steel
Need AWS D1.6 Prequalified Welding Procedures for welding 304, 304L, 316 and 316L. This collection of 280 Prequalified WPSs for Austentic Stainless Steel covers the 14 most common joints used in production for GMAW, GTAW, FCAW and SMAW. Also, instruction on how to revise these prequalified procedures to accomodate many other weld joints, other stainless steel grades and different filler metals.
