A welding procedure is used to make a record of all of the elements, variables, and factors that are involved in producing a specific weld or weldment.  Welding procedures should be written whenever it is necessary to:

• Comply with specifications and codes

• Maintain dimensions by controlling distortion

• Reduce residual or locked-up stresses

• Minimize detrimental metallurgical changes

• Consistently build a weldment the same way each time

The American Welding Society in the Standard Welding Terms and Definitions (AWS A3.0-2001) defines a welding procedure as, “The detailed elements of a process or method used to produce a specific result.”  Welding procedures must be tested or qualified and they must be communicated to those who need to know.  This includes the designer, the welding inspector, the welding supervisor, and most important, the welder.

When welding codes or high-quality work are involved, this document becomes a welding procedure specification, known as WPS, which is defined (A3.0) as “a document providing the required welding variables for a specific application to assure repeatability by properly trained welders and welding operators.”  Different codes and specifications may have different requirements for a welding procedure, but in general, a welding procedure consists of three parts:

1. A detailed written explanation of how the weld is to be made

2. A drawing or sketch showing the weld joint design and the conditions for making each pass or bead

3. A record of the test results of the resulting weld

The variables involved in most specifications are considered to be essential variables (those factors which must be recorded and if they are changed in any way, the procedure just be retested and requalified.)  In some codes, the “nonessential variables” may also be used.  These are usually of less importance and may be changed within prescribed limits and the procedure need not be requalified. 

Essential variables usually include the following:

1. Welding process and its variation

2. Method of applying the process

3. Base metal type, specification, or composition

4. Base metal geometry, normally thickness

5. Base metal preheat or postheat

6. Welding position

7. Filler metal and other materials consumed in making the weld

8. Weld joint design

9. Electrical or operational parameters involved

10. Welding technique

Nonessential variables may include:

1. Weld Preparation

2. Cleaning

3. Peening

4. Appearance of individual layers on a multi-layered weld

Some specifications also include other variables, such as travel speed, travel progression (uphill or downhill), size of the electrode of filler wire, or use and type of weld backing.

The procedure write-up must include each of these variables and describe in detail how it is to be done.  The second portion of the welding procedure is the joint detail sketch and table of schedule of welding conditions.

Tests are performed to determine if the weld made to the WPS meets the standards described by the code or specification.  If these tests meet the minimum requirements, the document becomes the welding procedure qualification record (WPQR).  This is “a record of welding variables used to produce an acceptable test weldment and the results of tests conducted on the weldment to qualify a welding procedure specification.” (A3.0)  The writing, testing, and qualifying procedures becomes quite involved and may be different for different specifications.

In certain codes, welding procedures are prequalified.  By using data provided in the code, individual qualified procedure specifications are not required for the standard joints on common base materials using specific arc welding processes. 

The factors included in a procedure should be considered in approaching any new welding job.  Using knowledge and experience, establish the optimum factors or variables in order to make the best and most economical weld on the material to be welded and in the position that must be welded.

Welding procedures take on added significance based on the quality requirements.  When exact reproducibility and perfect quality are required, the procedures will become mush more technical with added requirements, particularly in testing.  Tests will become more complex to determine that the weld joint has the necessary properties to withstand the service for which the weld is designed.

Procedures are written to produce the highest quality weld required for the service involved, but at the least possible cost and to provide weld consistency.  It may be necessary to try different processes, different joint details, etc. to arrive at the lowest cost weld that will satisfy the service requirements of the weldment.  Welding procedures are important in defining the factors involved in making a successful weld.

References

Modern Welding Technology by Howard B. Cary.  5^th edition.  2002.  Prentice-Hall, Inc. 

Standard Welding Terms and Definitions.  AWS A3.0:2001.  American Welding Society.

Both books are available from Hobart Institute of Welding Technology.  E-mail: hiwt@welding.org or call 1-800-332-9448, ext. 5433.