WPS
TABLE of CONTENTS
1 -Introduction
2 - Article:Welding Procedure Specifications
3 - How to do itwell: Welding thin Stainless Sheets
4 - Filler MetalFCAW ElectrodesCommercial Suppliers Resources
5 - Online Press: recentWeldingrelated Articles
6 - Terms and DefinitionsReminder
7 - Article:Corrosion of Weldments
8 - SiteUpdating: FCA Welding Tips
9 -Short Items
10 - Explorations:beyondthe Welder
11 - Contribution:FSW
12 -Testimonials
13 - Correspondence: a fewComments
14 -Bulletin Board
- GİRİŞ
Our first article deals withWPS(Welding Procedure Specifications). We detected some interest in the subject from our readers, in the Correspondence we receive, and we are glad to supply the information requested.
Next, also per a reader's request, we present some tips forwelding thinstainless steel sheets. We hope this will be useful to a larger audience.
In the Filler Metal Department we present the websiteResourcesof a few commercial suppliers of electrodes for Flux Cored Arc Welding. This is done to let our readers obtain specific information if needed in their daily practice.
An article onCorrosion in Weldmentsfollows, with information on causes and effects. It appears that, in spite of widely available information of the effects of welding onstainless steels, users are time and again surprised by the poor performance of the expensive materials they contributed to spoil by careless decisions.
For the Site Updating we present our Page of the Month, dealing this time withFlux Cored Arc WeldingTips. It is generally agreed that this successful process could contribute to increased productivity with expanded use where appropriate.
In the Contribution we present a summary of successful applications of a process described as the most significant welding innovation in the last fifty years. We refer toFriction Stir Welding, now reaching out new and different industries. Other departments are included as usual, to fill curiosity and needs of whoever is interested. We ask our readers to let us know how can we provide needed information to help them in achieving practical results.
Write us by e-mail. Click to send usYour Questions and Feedback.
2 - Article: Welding Procedure Specifications
The subject of this article was previously exposed briefly in our page onWelding Procedures(Opens a new page) that gives anoverviewof the matter.
We would like to add here useful details and links to provide interested readers with further know how and information.
A Welding Procedure Specification is adetailed documentthat specifies the required welding conditions, including variables and parameters involved, for a given application, for the purpose of assuringconsistencyof operation in welding.
It is required tomake surethat the process and technique employed will:
- provide consistently the mechanical properties specified
- meet structural and dimensional requirements
- produce the required quality without resorting to repair
- obtain acceptable metallurgical microstructures
- meet code requirements.
All accepted welding processes are covered bycodes or specifications. The Welding Procedure Specifications represent the detailedinstructionsthat workers must observe when realizing the specific welding operation for the given structure.
The adequacy of such a procedure to meet certain minimum requirements of safety and stability is demonstrated by itsqualification, consisting in verifying that the welded joints produced according to the procedure, meet in fact the prescribed requirements.
The formal document recording the welding conditions (per WPS) and the results of the qualification tests is called aProcedure Qualification Record(PQR). Both documents must be signed by authorized employees, dated and made available when required to those in need to know.
Although it is recommended that any shop prepare WPS forevery job, to control internally the quality of weldments and the performance of different welders, in most cases the establishment of such a document is a requirement of the regulating authority for approval and endorsement of many types of welded construction.
In general the applicable Code is spelled out in thePurchase Order. Different Codes, covering welded constructions in one of a number of application types (likeboilers, bridges, buildings, cranes, piping and pressure vessels), are issued by various originators (voluntary professional associations, technical societies, trade associations and governmental agencies) but are then made binding bylawand enforced by appointed authorities in charge of the well being of people and enterprises.
The Codes represent a distillation ofcommon knowledgeand engineering expertise accumulated over the years and believed to be a proper guarantee against human errors and fabrication deficiencies. As such the Codes are frequentlyupdatedaccording to recently acquired insight and technological progress.
Different or International Codes for the same broadly described application, may stress variously their test requirements. Generally however a procedure approved for a Code will be easily qualified for another one bysupplementing the testingas required by the new one.
A first type of WPS will include broad andgeneral indicationsthat apply to all welding of a given kind on certain metals. Such a document provides the manufacturer with flexibility to change selected parameters within established limits and still meet code requirements.
The other type is muchmore descriptiveand provides details of specific base metal, thickness and joint design. It is used to control repetitive welding operations.
The amount of detail required from WPS is essentially established byCode requirementsbut also high quality work may suggest the good practice of writing detailed procedures for documentation and control.
At a minimum the document should include in sufficient detail the description of the welding process with itsparameters rangesand a sketch illustrating the joint design and the welding technique to be used.
The variables to be specified in the document are requested by the applicable code. Some codes distinguish betweenessentialor qualification variables, strictly constrained within given limits, and other parameters whose values can be varied as convenient.
Among the first are:
- base materials specification to be employed
- filler metals and other consumables
- welding process
- welding sequence, positions and technique
- joint type and dimensions
- electrical parameters
- eventual preheat and post weld heat treatments
Nonessential variables can be leftundefined, unless changes of any of them might require adjustment of essential ones outside their approved range. In that case nonessential variables must be specified and maintained.
In case electrode size (sometimes described as nonessential variable) is changed, electrical parameters are going to change: if the authorized range is exceeded then the substitution cannot take place.
Certain Codes, like AWS D1.1 - Structural Welding Code - Steel, accept the use ofprequalifiedjoint welding procedures. This is based on reliability record established with certain proven procedures. The application of these does not relieve the manufacturer from writing the proper documents and from using sound judgement in their application.
AWSStructural Welding Code - Steel
Document Number: AWS D1.1/D1.1M-2004
American Welding Society, 01-Jan-2004
541 pages
Click to Order.
A complete presentation of this subject is available in Chapter 15 on"Qualification and Certification"of the AWS Welding Handbook, ninth edition, Volume 1 from page 638 to 681. Sample Forms of the proposed documents are presented.
AWSWelding Handbook
9th Edition Vol. 1
Welding Science and Technology
Document Number: AWS WHB-1.9
American Welding Society
Click to Order.
Whenever the properties demanded from a welded construction cannot be met with an existing and available WPS, anew and improvedone has to be developed and its qualification must be secured before proceeding with the welding job.
All welders engaged in work with WPS must have passed requiredWelder Teststo demonstrate performance qualification, and obtained Certification for the processes involved, by an Independent Agency or Accredited Test Facility.
If you look for specific WPS asexamplesto copy or adapt, you could browse the LANL Welding Procedure Specifications archive at
A number of Standard Welding Procedure Specifications, covering different materials, thickness ranges and processes were developed by the American Welding Society (AWS) and the Welding Research Council (WCR).
They are available to interested manufacturers and can be used as anoutlineto prepare different documents in case they do not cover exactly the procedures sought.
The list of AWS Standard Welding Procedures Specifications can be seen online at page 22 and 23 of the AWS2006 Catalog, downloadable from
3 - How to do it well: Welding thin Stainless Sheets
Q:Gas Tungsten Arc Welding thin sheets of austenitic stainless steel type 304L results in unacceptable distortion. What can be done to improve results?
A:Compared to carbon steels, austenitic stainless steels have higherthermal expansion and lower thermal conductivity: these are the main reasons contributing to unacceptable distortion.
GTAWis a proper process to weld such jobs but, due to the low current employed, manual operation may be difficult to control. Better results could be obtained by mechanized welding.
Other precautions include properfixturing, pulsed currentif possible andstep welding. Good cleaning and preparation are always important.
Constant current, non pulsed power supplies of drooping-voltage characteristic are used with direct current straight polarity, electrode negative. Pulsed current may provide betterweld controlto avoid burn through.
Most widely used nonconsumable tungsten electrode type is that with 2% Thoria (EWTh-2).High frequencyshould be used to start welding and to avoid contamination due to electrode contact with the weld pool. Argon is used as the shielding gas.
The conical electrode tip can be ground with different apex angles. Anarrow angleof about 15 to 30 degrees tends to produce a relatively wide bead with shallow penetration. A larger angle of 60 to 75 degrees would give a narrow bead with increased penetration.
Thin gage stainless steel sheet should be properlyclampedand aligned to avoid buckling. Fixturing of the abutting edges, with no gap for thickness up to about 1 mm (0.040"), is done with copperchill bars, usually nickel plated.
The backside chill bar includes a groove, placed under the joint, where argon can be provided to preventbackside oxidation. The two front side chill bars should be beveled to make room for the torch.
Good contact between stainless and copper bars helps in removing excessive heat. If the clamp down bars are very close to the line of welding and held with considerable pressure, acompressive forcewill act on the seam while welding, as lateral expansion is prevented. The upsetting force will reduce shrinkage stresses and distortion.
Tack welding should be provided atclose intervalsbut with a proper sequence that will maintain alignment.
Pulsed current if available may be advantageous in reducing heat input. Current ispulsedat regular intervals between a background level and a peak level. A stable arc is more easily maintained.
In case of long seams,shortwelding stretches should be performed, at relatively far locations, taking care to let the joint cool down between welds. The start and stop of each weld and the tack welds should begroundto eliminate possible flaws in those places.
Implementing most of the aboveprecautionsshould result in weldments of reduced and acceptable deformation.
4 - Filler Metal: FCAW Commercial Supplier Resources
A short article onSelectionof Electrodes for GMAW and FCAW was presented in Practical Welding Letter issue No. 6 for February 2004. Click onPWL#06(Opens a new page).
A short note onFCAW Electrodeswas presented in Practical Welding Letter issue No. 18 for February 2005. Click onPWL#018(Opens a new page) for seeing it.
As remarked elsewhere, in our page onFlux Cored Arc Welding Tips(Opens a new page), the complexity of the FCAW AWS Electrode Classification makes the selection difficult, except maybe for the simplest cases.
Furthermoredifferencesin performance among manufacturers and slow progress providing better results from newer products, suggest to contact manufacturers before starting an important job.
The purpose of this note is to provideaddressesfor getting, from electrode manufacturers, detailed recommendations on the best selections, suggested parameters and techniques, and the opportunity to test practical applications.
Testingis the best way to evaluate the suitability of the proposal and to judge such items as weldability, fume level, welders comfort, arc stability, final weld appearance, ease of slag removal, weld quality and weld deposition rate.
We are only presenting here those manufacturers that we couldeasily locatethrough a short search on the Internet. We apologize, knowing that many more, including important ones, are missing from this list. We are ready to update the list if qualified manufacturers will provide us with relevant links.
But we urge our interested readers todeepentheir own search with other suppliers they know and trust, and to compare the service level they can get.
The documents viewed can generally beexplored in depthby use of the proposed links, from one page to the next, depending on the specific interests of the reader.
The longer addresses should be copied and pasted in the browser in a single line without spaces (and ENTER).
- ESAB- Lesson 7 (Note: the document includes 43 pages)
Flux Cored Arc ElectrodesCarbon Low Alloy Steels - Lincoln Electric: Mild SteelGas ShieldedElectrodes
- Lincoln Electric: Mild SteelSelf ShieldedElectrodes
- PraxairFlux cored Electrodes
- Harris- Stainless FCAW Electrodes
- HobartElectrodes (Dig deeper through the List)
- AvestaStainless Electrodes (Single products to explore one by one)
- MetrodeElectrodes (List to research, requires registration)
5 - Online Press: recent Welding related Articles
From the Fabricator:
Our article onTack Weldingwill appear online on April 11, 2006
Guidelines fortungsten electrodes
Identifying, selecting, and preparing tungsten electrodes
From The Welding Institute:
Fatigue TestingPart 3
(with Links to Part 1 and Part 2)
From the Welding Technology Institute of Australia:
DownloadableTechnical GuidanceNotes from
From Plastic Technologies:
Plastics Welding, Laser and Infrared Systems
6 - Terms and Definitions Reminder
Age Hardeningrepresents a microstructural modification due to precipitation of constituents (phases) occurring naturally at room temperature with time or artificially under controlled heating for shorter times at temperature. It generally results in hardness increase and ductility decrease. Hardening by aging occurs usually after rapid cooling (quenching) from solutioning temperature or cold working.
Anionis a negatively-charged ion, which has more electrons in its electron shells than it has protons in its nuclei. It is attracted to anodes and migrates through the electrolyte toward the anode (positive terminal) under the influence of a potential gradient.
Base Metalis commonly referred to the metal to be brazed, cut, soldered, or welded. It is the material of the element to be joined or dismantled by the selected process. After welding, that part of the metal that was not melted.
Buildupis a weld or thermal spray surfacing variation in which surfacing metal is deposited to restore the worn out or mismachined dimensions to the original or required value.
Cold Crackingis a type of weld cracking that usually occurs after solidification is complete. Cracking may occur during or after cooling to room temperature, sometimes with a considerable time delay.
Exhaust Boothis a partially enclosed volume with mechanical aspiration designed to remove fumes, gases and particles from the space where welding is performed.
Melt-throughrepresents the complete joint penetration for a joint welded from one side. It is also an unacceptable defect if a hole is left in the weld root because of inadequate welding technique.
Slagis a nonmetallic product resulting from the mutual dissolution of flux and nonmetallic impurities in certain welding operations. It protects the weld bead from air contamination and is designed generally to be easily removed after cooling down.
7 - Article: Corrosion of Weldments
It is known that corrosion phenomena can originate fromdifferencesor heterogeneity of composition that occur within various scale ranges. While wrought materials display a high degree of uniformity, fusion welding introduces regions with modified or different microstructures.
The fusion zone represents a region where the chemical composition is acomplex resultof different proportions of base metal and filler materials mixed together. Compositional difference causes a galvanic couple that can influence corrosion processes near the weld.
At a more subtle level one may findmicrostructural segregationoccurring during solidification. At the boundary of the fusion zone two regions have been described. One is called the partially melted zone, next to the chilled, unmixed zone of material fused and promptly solidified without compositional modification.
The heat affected zone (HAZ) represents a space where each location underwent aunique cyclecharacterized by maximum temperature and a definite cooling rate. The results of microstructural transformations depend on base metal composition and characteristics of thermal cycle.
All the rates of change can be referred to asgradientseven at microscopic level, and may influence corrosion susceptibility depending on their importance and on the local environmental conditions.
The specificforms of corrosionthat can occur in weldments include galvanic corrosion, pitting, stress corrosion, intergranular attack (IGA) and hydrogen assisted cracking. Good welding design should consider ways and means to control and limit development of corrosion in weldments.
In most aluminum alloys, weld metal and HAZ becomemore noblein relation to the base metal, and are therefore immune from corrosion in the weld in salt water environment. Other alloys, typically 7005 and 7039, form narrowanodicregions in the HAZ, and are consequently prone to localized attack.
The common practice of field repairing heavy machinery elements made of high strength low alloy steels withaustenitic stainless steels, mainly because of their ductility and resistance to cracking, leaves a cathodic stainless steel in contact with the steel. If the environment is corrosive, hydrogen can develop at the cathodic boundary and cause stress corrosion cracking in the high strength steel, especially in presence of a high residual stress field due to the welding.
Stainless steels are often perceived as beingimmune from corrosionin any and every environment and condition. Unfortunately it is not so, especially if welding or other thermal processes are undertaken without proper precautions.