REQUESTING THE APPROPRIATE LEVEL OF WELD TESTING FOR SPECIAL ORDER FILLER MATERIALS
When specially tested products are ordered from a manufacturer, it is the customer’s responsibility to specify which of the above schedules of testing is required. In the case of solid wire, it may be the case that the fabricator needs only to know the chemistry of the wire to ensure that the product meets their requirements. For instance, all lots of stainless steel solid wires manufactured by my company are automatically tested to Schedule H requirements for wire chemistry only. In many cases, this is all the verification that the fabricator needs to make certain that this product will perform as intended.
Now compare this Schedule H level of testing of solid wire with the minimum level of testing necessary to ensure that a FCAW-G tubular wire will perform to the fabricator’s expectations. Obviously, more testing is needed to provide reasonable assurance that the combination of the steel sheath and inner core flux mixture will generate the necessary weld metal properties. But just exactly what level of testing is necessary?
In situations such as this, it is commonplace (but not necessarily optimal) for fabricators to request Schedule J level of testing – also known as qualification testing. Although it may be apparent that this level of testing is often not required for solid wires, it is less obvious as to whether or not this level of testing is required for FCAW-G filler materials. This begs the question as to exactly what it means to test to classification.
When testing E71T-1M FCAW-G electrodes to classification, the types of tests required are spelled out in the A5.20 Specification for Carbon Steel Electrodes for Flux Cored Arc Welding. This set of tests is comprised of a tensile test (which provides tensile strength, yield strength and elongation), a Charpy V-notch impact toughness test at 0 deg F (Note: if the electrode is dual classified as a T-1 and T-9 electrode, impact testing is required at minus 20 deg F instead of 0 deg F), a deposit chemistry analysis, a radiographic examination of the weld plate for soundness and a fillet weld test.
The first of these four tests conducted on a representative sample of the electrode from a given lot of product will give reasonable idea of the properties of welds deposit (provided that similar welding procedures are used). What is not clear, however, is the information that a fillet weld test will provide.
Fillet weld testing is important when a filler metal manufacturer undergoes the process of developing a new electrode. It is the responsibility of the manufacturer to ensure that when the electrode is used properly (at a ¾ in to 1 in contact-tip-to-work distance), penetration through the root of the joint is achieved. Therefore classification testing must be conducted by the manufacturer when proving that the electrode design will conform to the classification standard. However, outside of the electrode development process, fillet weld testing becomes unnecessary.
So why should a fabricator pay for an unnecessary test when ordering specially tested product?
Evidently, the forefathers of the AWS filler metal specifications recognized long ago that “conformance” testing of purchased consumables by the electrode manufacturer is not required most of the time. Rather, they determined that a specific subset of tests – Schedule I testing – is sufficient to ensure that the filler material will meet the fabricator’s expectations.
As noted above, Table 2 of the A5.01 Filler Metal Procurement Guidelines lists the Schedule I testing requirements by filler metal specification (A5.1, A5.18, A5.20, etc.). In the case of A5.20 Specification for Carbon Steel Electrodes for Flux Cored Arc Welding, Schedule I testing includes all of the tests of Schedule J, with the exception of fillet weld testing. Substantial savings – upwards of a few hundred dollars – can be realized by specifying Schedule I testing as opposed to Schedule J testing and forgoing the fillet weld testing.
Ultimately, the testing requested for specially ordered welding consumables should reflect the intended application of the weld deposit. Consider the case in which the welds deposited during wind tower fabrication with ER70S-6 solid wire and the GMAW process would be subjected to temperatures as low as minus 60 deg F. According to the A5.18 Specification for Carbon Steel Electrodes and Rods for Gas Shielded Arc Welding, Schedule J testing would call for a tensile test, a radiographic examination, wire chemistry analysis and a Charpy V-notch impact toughness test at minus 20 deg F.
Due to the minus 60 deg F requirement, it would be in the fabricator’s best interest to request that the filler metal manufacturer conduct Schedule K testing. Schedule K is essentially “custom” testing. In this wind tower case, the fabricator may decide that Schedule K testing should entail all of the testing required under Schedule J, with the caveat that the temperature at which impact testing is conducted be changed. In order to better reflect the reality of the service conditions, the impact testing should be performed at minus 60 deg F as opposed to minus 20 deg F.To simplify testing requests, some fabricators and distributors have assembled standardized “checklists” that allow for à la carte selection of the welding tests and parameters to be used for the special order of consumables.
For welding parameters, fields can be provided in order to specify the welding process, polarity, shielding gas, preheat and interpass temperature, and any post-weld heat treatment requirements.
For weld test options, the tensile test criteria, radiographic requirements, Charpy V-notch impact test temperature (and any required reporting of absorbed ft-lb of energy, mils lateral expansion, and percent ductile shear), diffusible hydrogen testing, deposit and/or wire chemistry analysis (which may include ferrite content) and the aforementioned fillet weld tests should be listed. And most importantly, the applicable welding standards (for example, AWS A5.18, ASME Section II SFA 5.18, ASME Section III NB-2400, etc.) and testing schedule should be listed in order to ensure consistency.
A standardized checklist outlining the specific fabricator requirements reduces the chances for confusion and delay in obtaining the properly tested welding consumables. Furthermore, the targeted selection of appropriate weld tests will provide informative results regarding the properties and may ultimately save the customer money.
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About the Author: Regis Geisler III is a registered Professional Engineer, Specials Certification Engineer and AWS Certified Welding Inspector who has worked the last eleven years at The Lincoln Electric Company, 22800 Saint Clair Avenue, Cleveland, OH 44117-8542, 216-481-8100, Fax: 216-486-1751, www.lincolnelectric.com. For questions or comments on this column, contact Regis at firstname.lastname@example.org.