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Welding-testingthe all important proofSOLUTIONS with Effective, Powerful AdviceWelding-testing, destructive testing in welds, tension Welding Testing, bend tests, weld sections, metallographic tests, optical microscope examinations, etching and heat tinting, hardness testing, fatigue testing, vibration testing, acoustic emission testing, spot welding tests, routine testing, useful links, test tips, how to interpret results, joining questions needing answers: these are some of the items developed in this Site page for the benefit of interested readers. What is in here for me? Welding-testing is usually understood as a destructive testing. Use it to certify your welders. Know and prove to others adequacy of procedures and of performance, show to customers that the operation is successful as expected and needed. How do you know if there is a test requirement in the weld job? Welding-testing has to be spelled out on the drawings, or on a technical document, or on a called for Specification or on the purchase order. The purchaser may be able to help you out with the test, as he knows what will satisfy engineering.
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Details on standard Welding-testing methods can be found in AWS B4.0-98 AWS B4.0M-00 Mechanical testing... Mechanical Welding-testing is regarded as the most reliable and least expensive to determine strength and other properties. Welding-testing specimens to destruction is one of the most important means to assess the quality of welds. The other complementary element, you can find in another page, is nondestructive WELDING INSPECTION of actual welded structures. Among mechanical Welding-testing, classic tensile tests are performed using instruments called Universal Mechanical Testing systems, on prepared test specimens precisely machined through weld material to the dimensions and shape required by Standards. Sometimes Specifications require to get strength results in the weld equal at least to those of the base metal. Other times they permit that a weld exhibit a given percentage (80%, 90%) of the base metal strength. An Article on Extensometers was published in the July 2006 Issue of Practical Welding Letter No. 36. To read the article click on PWL#036. In house Welding-testing or outside? If it is performed with simple testing instruments, (like tensile testing of spot weld coupons) and if it is routine and repetitive you may gain time from testing with some simple instrument and getting the answer on the spot, so that you may easily reweld and retest. Simple testing... What are non instrumented Welding-testing? These are tests that anybody can perform in the shop, and give a measure of understanding and of confidence in the results. It is recommended to perform some sort of these tests just to know for yourself. You should first establish the form and dimensions of the test piece, to reproduce features as similar as possible to those of the real weld, and weld it. Then destroy the test piece in a vice, under a press, by giving blows with a chisel or a hammer, by peeling etc. Obviously, if the test piece pulls off too easily then the weld is not adequate. You may also initiate saw cuts in the weld to be sure of the location of rupture upon bending: the fracture may then reveal internal defects (porosity, slag inclusions etc.). Nick-Break?... One such test is performed on Nick-Break specimens, which are transversally welded strips where slots are machined at both weld ends, and then stressed in bending so that a crack will initiate at one of the cuts and propagate through the weld. The structure of the fractured surface is then examined for DEFECTS. By providing you as much information as you may need, we hope to help you to establish your Welding-testing routines and assist you in raising your welding quality. That will also avoid discussions with your customer, improve productivity, save rework and repair, save your time, (think of it...). Bend tests... Bend tests are popular and informative tests. Usually they can be performed with simple equipment, like a jack or a press, readily available in many shops. But Specification requirements must be followed accurately for the test to be valid. The result of the test should be as demanded. Sometimes a certain angle of bend should be reached without fracture. Either warping of the test piece without fracture or a break outside the weld or whatever other feature should be according to Specification requirements. In any case the Welding-testing result must be documented in a test report, possibly with a photo, and the test piece itself must be identified (welder's name, equipment, procedure, date) and kept for later inspection by the customer's agent. Guided bend tests are a special type, being performed on specially prepared test pieces, using a jig manufactured to constrain the specimen to follow a given contour.
An Article on Bend Tests was published in the September 2004, Issue No. 13 of Practical Welding Letter. To read the article, click on PWL#013. An interesting Article is available by clicking on Two examples of weldability tests are given in past issues of PWL. In Section 9, covering Short Items, the Sigmajig Test (9.4) can be found by clicking on PWL#039, and the Varestraint Test (9.6) by clicking on PWL#014. To receive the newsletter as it is released, please subscribe at no cost. Weld sections... Metallographic tests require a minimum of metallurgical experience, and some specific equipment, like a disk sectioning machine, a specimen mounting press, grinding, polishing turntables, some acid etching capabilities and an optical metallurgical microscope with magnification capacity of up to x500 at least. Welding-testing to find the weld position or to view the weld bead shape or obvious discontinuities in a prepared section is not difficult to interpret, but if a need arises to discern between metallographic phases in different areas of the weld, for determining the adequacy of a certain welding procedure, or for investigating the reasons of unacceptable results, one must use the resources of a professional metallurgist whose preparation is tuned to these more demanding tasks. In a new page on Weld Macro, we present a simplified procedure that could be easily set up in any welding shop, even the simplest one. It is meant to provide a way to examine the Macro structure of cross sections of weld test pieces. The observations help to assess the welding quality level and to improve on it. We consider this essential to the positioning of the welding shop as one that cares for the customers and for the quality of the work they get. And essential to the economic success.
Hardness testing on metallographic sections as above gives indications on the microstructure developed in and around the weld: too hard a material may be prone to cracking, and special procedures may be required to avoid such dangerous conditions. See further down the page our offer of a free book on the subject. These are... These are the main destructive Welding-testing methods used for monitoring welding procedures before starting and during production, for maintaining a constant high level of performance including equipment, procedures and workmanship. More specialized test have been developed for special needs. Among them we may mention fatigue testing, vibration testing, acoustic emission testing, but we cannot cover them here in any detail, unless... You can find independent Agencies authorized to certify for a fee your Welding Procedures by testing the required specimens, if you need a complete professional Test Report as a record for your Contract. An Article on Testing Filler Metals was published (4) in Issue No. 47 of Practical Welding Letter for July 2007. Click on PWL#047 to read it. An Article on Metallurgical Aspects of Abusive Grinding was published in Issue 52 of Practical Welding Letter for December 2007.
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We believe that you can find in the book some useful insights on the meaning of hardness testing results, readily applicable to your welding jobs. To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics.
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