Weldability-testingfor quantified results.SOLUTIONS with Effective, Practical AdviceWeldability-testing is generally designed to evaluate the effects of welding on specific properties and characteristics of base materials under definite welding and testing conditions. Such testing is usually performed in research or development laboratories. 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". 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, except for very important situations like nuclear energy or aerospace applications, where 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 define the process conditions suitable to provide acceptable procedures to be approved by 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 were 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, through the study of basic metallurgical principles to predict the results of applying given welding procedures. From studies of the subject it appears that selecting the most appropriate Weldability-testing procedure for obtaining useful results, applicable to a specific case, is critical to 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 Lehigh Restraint Test, the Keyhole Restraint Cracking Test of the Naval Research Laboratory, the Keyhole Slotted Plate Restraint Test of Battelle, the Navy Circular Patch Test, the Controlled Thermal Severity Crack and the Cruciform Cracking Test. 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 and in the Handbooks AWS WHB-1.9 (at page 284) ASM Handbook Volume 06: Welding, Brazing, and Soldering (at page 603) 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. See the Report on and also Welding Research Council - WRC Bulletin No. 400 "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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