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Weldability-testingfor quantified results.SOLUTIONS with Effective, Practical Advice
Weldability-testing is designed to evaluate the effects of welding. Such testing is usually performed in research or development laboratories. Checks are performed on specific properties and characteristics of base materials. But only under definite welding and testing conditions. Weldability is the ease or the ability of a material to be welded successfully under given conditions. The official AWS definition makes reference to a specific, suitably designed structure and requires it to perform satisfactorily in the intended service. This definition means that weldability is not a material property but an application and procedure dependent characteristic. The susceptibility to cracking, of both weld and base metal, is a favorite subject of investigation, as are weld penetration, pool shape and fluid flow.
As a matter of fact it is quite unusual that Weldability-testing be performed on a production structure. The exceptions include very important situations like nuclear energy or aerospace applications. There, instrumented models are tested to destruction to document the acceptability of definite welding procedures. More often, test pieces of special design, refined by long experience, are used to approve the process conditions. To demonstrate acceptable procedures, such specimens must pass the mechanical tests required by Codes and Standards. Only a few of the Weldability-testing practical arrangements gained so wide acceptance to be standardized. Most of the remaining ones are used only for research programs.
As it happens there is no universal answer for Weldability-testing. The common tests can be compared for effectiveness, but all have advantages and limitations that suggest their preferred use in certain cases only. Instead of performing physical Weldability-testing, one can obtain answers indirectly. The study of basic metallurgical principles may help predict the results of applying given welding procedures. Selecting the most appropriate Weldability-testing procedure for obtaining useful results, is critical in any specific case. From the choice depends the success of that test in anticipating correctly the welded material behavior in real constructions. For examining the susceptibility to cracking of base and weld metals, test pieces of different design were proposed. Self restraint test pieces are those that submit the weld, upon cooling, to internal shrinkage stresses. Among these are:
The geometric dimensions of the test pieces and other information can be found in the following: ANSI/AWS B4.0:2007 ANSI/AWS B4.0M:2000 (R2010)
and in the Handbooks AWS WHB-1.9 (at page 284)
ASM Handbook Volume 06:
Other tests, instead of relying on the internal, residual stresses, use externally applied loads during Weldability-testing. Among these are the Implant Testing, the Varestraint Test, the Sigmajig Test and the thermomechanical testing device called Gleeble. A note on the Varestraint Test was published (9.6) in Issue 14 of Practical Welding Letter for October 2004. Click on PWL#014 to see it. A note on the Gleeble Testing was published (9.4) in Issue 15 of Practical Welding Letter for November 2004. Click on PWL#015 to see it. An Article on Weldability-testing for Weld Repair was published (2) on Issue 27 of Practical Welding Letter for November 2005. Click on PWL#027 to read it. The Definition of Weldability was published (6) in Issue 35 of Practical Welding Letter for July 2006. Click on PWL#035 to see it. A note on the Sigmajig Test was published (9.4) on Issue 39 of Practical Welding Letter for November 2006. Click on PWL#039 to see it. An Article on Gleeble Simulations was published (2) in Issue 79 of Practical Welding Letter for March 2010. Click on PWL#079 to see it. An Article on Benefits of Low Hydrogen Filler Metal Electrodes was published (4) in Issue 141 of Practical Welding Letter for May 2015. See the Report on and also Welding Research Council - WRC Bulletin No. 400 A supplier for the above is found by performing a Search. "It provides insight into the practical aspects of Weldability-testing including capabilities, reproducibility, experience, flexibility, influence of variables, and other issues bearing on the utility of the test including suitability for standardization."
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