AWS Classification of Consumables :
American Welding Society has evolved a system of identifying classes of consumables in an alfa-numeric code, which is commonly referred to as AWS class. An explanation of what this classification signifies is given below for typical four common examples:
1. Classification of covered Electrodes for SMAW (Shielded Metal Arc - also known as Manual Metal Arc):
AWS - E - XX - YY - G e.g. AWS E-7018
or, AWS E 8018 B2 E …..Coated electrode
XX….. Minimum tensile strength in ksi YY……Coating Type & chemistry G…… Alloy addition, if any
2. Classification of GTAW / GMAW / PAW Bare Wire Rod
AWS - ER - XX -S - YY e.g. AWS ER-70-S-G2
ER….. Bare Rod / electrode
XX….. Minimum tensile strength in ksi S…….Solid
YY……Specific chemical composition
3. Classification of SAW Wire and Flux for Carbon Steel AWS - F - XXX - E - YYY
F...Flux
1st X...Tensile strength in 10,000 psig 2nd X...Condition of Heattreatment ..
carbon steel wire, e.g. EL8, EM12K, or EH14.
4. Classification of SAW Wire & Flux for Alloy Steel AWS - F - XXX - E C- YYY N- ZM
F...Flux
1st X...Tensile strength in 10,000 psig 2nd X...Condition of Heattreatment ..
Classification of Parent Materials and Welding
Consumables as per ASME Code Section IX
In developing ASME Section IX, each welding process that was included in the Section, was reviewed with regard to those parameters, called VARIABLES, which have significant effect upon welding operations and fabricator's ability to qualify Welding Procedures and Welders' performance. Variables are categorized as Essential,
Non-essential and Supplementary (for assurance of notch toughness) variables in the case of low temperature operation.
Essential Variables are given in comprehensive details in the chapter called "Welding Data". Change in an Essential Variable of an established Welding Procedure requires re-qualification of a Procedure with a new set of Essential Variables. Broadly speaking, and for ease of remembering, following main Essential Variables should be considered in proposing any Welding Procedure Specification :
i. Welding Process, e.g. SMAW, GTAW, SAW etc.
ii. Parent Material , material specifications categorized into P Nos.
iii. Material Thickness
iv. Welding Consumable, categorized into F No. & A No.
v. Maintenance of Preheat, Interpass & Post heat
vi. Post Weld Heat Treatment and finally, the supplementary essential requirement of, vii. Impact Testing to assure notch toughness properties. Assignment of P Numbers To rationally reduce the number of Welding Procedure required to be qualified, base materials have assigned P Numbers, essentially based on comparable material characteristics, such as chemical composition, mechanical properties and weldability.
(Refer QW-442)
Assignment of F Numbers : Electrodes and welding rods have been grouped into F Numbers ( Refer QW-432), essentially on the basis of their usability characteristics, which fundamentally determine the ability of the Welders to make satisfactory welds, with a given filler metal. This grouping also reduces the number of welding procedures and performances which required to be qualified, where it can be logically done.
Assignment of A Numbers :Weld Metal compositions have been classified and grouped into A Numbers, essentially on the basis of their weldability characteristics, as reflected by the nominal chemical composition obtained from their actual weld metal analyses.
Cautionary Note
These assignments do not imply that base materials and filler materials be indiscriminately substituted for a base metal or a filler metal which was used in the qualification test, without consideration of compatibility , from the standpoint of metallurgical properties, postweld heat treatment, design, mechanical properties and service requirements.
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6. GUIDELINES FOR REVIEW OF WPS/PQR .
An inspector has to review the WPS, PQR and WPQ documents to ensure that they meet the ASME sect IX requirements. A checklist shall be used to verify that the WPS is properly completed and is addressing all the requirements of ASME Sect IX and
construction code. It is also necessary to verify that PQR has been completed to meet all the ASME sect IX requirements (including test results as per acceptance criteria)
The important part here is also to verify that values of essential variables recorded on the PQR properly support the specified range of WPS
Checklist for Review of WPS (SMAW Process)
Refer QW 250 for variables.
(Supplementary variables not needed)
1) See identification block showing WPS no.___________, Rev__________ and PQR no.___________. Also at the end the reviewer shall give his comments.
There is signature of the viewer at the end.
2) QW 402 gives joint details. QW 403 is indicating Base metals for example if a PQR is having base metal thk. 25.4mm the WPS supported by it can be from 4.8mm to 5.8mm. So if these variables are written in QW 403.8 properly in WPS and PQR column then the column at qualification shall indicate OK which
confirms that the variable is within the requirements and addressed properly.
3) QW 404 is for filler metals 4) QW 405 is for positions.
5) QW 406 is for preheat.
6) QW 407 is for PWST
7) QW 409 is for electrical characteristics.
8) QW 410 is for technique.
9) Additionally QW 401 says “A change in process is an essential variable.” This has to be verified here and documented.
10) QW 202.2, 3,4 are mentioned for reminder to the verifier.
11) This is reminder for QW 200.4 combination of processes.
12) This is reminder for reviewer for bend and tension test as per QW 451.1 13) This is reminder for QW 404.5. The basis for assigning A numbers.
14) This is reminder for QW 170- Notch toughness – if required by construction code.
15) This is to remind if there are any contracts /company/other 16) requirements to be addressed (QW201)