Procedure and performance qualification and testing standards for welding procedures, thermal spraying, brazing, testing and inspection are published by the American Welding Society.
AWS C2.16, Guide for Thermal Spray Operator and Equipment Qualification provides for qualification of operators and equipment for applying thermal sprayed coatings. It recommends procedural guidelines for qualification testing. The criteria used to judge acceptability are determined by the certifying agent alone or together with the purchaser.
AWS D10.9, Specification for Qualification of Welding Procedures and Welders for Piping and Tubing, covers circumferential groove and fillet welds but excludes welded longitudinal seams involved in pipe and tube manufacture. An organization may make this specification the governing document for qualifying welding procedures and welders by referencing it in the contract and by specifying one of the two levels of acceptance requirements. One level applies to systems that require a high degree of weld quality. Examples are lines in nuclear, chemical, cryogenic, gas, or steam systems. The other level applies to systems requiring an average degree of weld quality, such as low-pressure heating, air conditioning, sanitary, water, and some gas or chemical systems.
MIL-STD-248, Welding and Brazing Procedure and Performance Qualification, and MIL-STD- 1595, Qualification of Aircrafi, Missile, and Aerospace Fusion Welders may be used when federal government or military requirements are involved.
AWS B2.1, Standard for Welding Procedure and Performance Qualification, provides requirements for qualification of welding procedures, welders and welding operators. It may be referenced in a product code, specification, or contract documents. Applicable base metals are carbon and alloy steels, cast irons, aluminum, copper, nickel, and titanium alloys.
AWS B2.2, Standard for Brazing Procedure and Performance Qualification, covers requirements for qualification of brazing procedures, brazers, and brazing operators for furnace, machine, and automatic brazing. It is to be used when required by other documents, such as codes, specifications, or contracts. Those documents must specify certain requirements applicable to the production brazement. Applicable base metals are carbon and alloy steels, cast iron, aluminum, copper, nickel, titanium, zirconium, magnesium, and cobalt alloys.
ANSYAWS C3.2, Standard Method for Evaluating the Strength of Brazed Joints in Sheal; describes a test method used to determine shear strengths of brazed joints. For comparison purposes, specimen preparation, brazing practices and testing, procedure must be consistent. Production brazed joint strength may not be the same as test joint strength if the brazing practices are different. With furnace brazing, for example, the actual part temperature or time at temperature, or both, during production may vary from those used to determine joint strength.
ANSIIAWS B4.0, Standard Methods for Mechanical Testing of Welds, describes the basic mechanical tests used for evaluation of welded joints, weldability, and hot cracking. The tests applicable to welded butt joints are tension, Charpy impact, drop-weight, dynamic-tear, and bend types. Tests of fillet welds are limited to break and shear tests.
For welding materials and procedure qualifications, the most commonly used tests are round-tension; reduced-section tension; face-, root-, and side-bend; and Charpy V-notch impact. Fillet weld tests are employed to determine proper welding techniques and conditions, and the shear strength of welded joints for design purposes.
AWS B 1.10, Guide for the Nondestructive Inspection of Welds, describes the common nondestructive methods for examining welds. The methods included are visual, penetrant, magnetic particle, radiography, ultrasonic and eddy current inspection.
Qualification tests help determine the proficiency of welders to ensure that failures will not be caused by lack of skill. Also, the application of the welding processes in some fields is subject to regulation and inspection which, in some cases, is very rigid. Most welding codes require that individual operators pass a qualification test.
The nature and the comprehensiveness of qualification tests varies with the work to be done. In general, the qualifying welds made by an operator will be made under conditions which duplicate, as nearly as practicable, the working conditions of the prospective job. For example, there would be a great deal of difference between the test required of a welder working on an aerospace application and those required for a welder who works wholly with structural steel.
There is some difference of opinion as to the necessity of examining a welder on the theoretical knowledge of a process. Whether or not it is worthwhile to insist that an operator know something about the scientific background of the process would seem to depend on individual circumstances. There are many supervisors who think that if the foreman or head welder is well informed, satisfactory results can be obtained from welders who have demonstrated only their ability to manipulate the torch or the arc. It is certain, however, that knowledge of the process is no handicap.
Before requiring welders to take qualification tests for any kind of work, it is advisable to prepare forms on which a record can be made of all the operating conditions, the observations made by the inspector, and a complete record of test results. These individual records should be carefully preserved for reference.
A good deal of unnecessary expense can be circumvented if the qualification test is divided into two parts: first, observation of a preliminary break test, and second, a quantitative test.
Preliminary Break Test
A preliminary break test should be a made with a simple weld that can easily be broken through the weld itself. There are several methods of doing this:
(1) using a plain butt weld and breaking it in a vise,
(2)welding one plate to another in the form of a T on one Welding Encyclopedia
side only and breaking by a sharp blow on the side of the plate opposite the weld and
(3) making a lap fillet weld on one side only, then breaking through the weld by supporting the outside edges of the plates and hammering or pressing on the center of the weld;
(4) making a butt weld and cutting nicks in both ends of the weld so that a sharp blow with a sledge hammer will result in a break directly through the weld metal.
Other methods of designing an observation test can, of course, be used. It is always desirable to use a design which approximates the working conditions. The important thing is to complete a fracture through the weld so that the entire cross section of the inside of the weld can be examined for fusion, penetration, porosity, slag inclusions and grain structure.
This test can be made with ordinary shop tools and involves a minimum of expense. It is obviously unnecessary to proceed to a more expensive laboratory test in the case of operators who do not show satisfactory proficiency at this point.
Quantitative Test
The quantitative test is for the purpose of determining how strong a weld the operator can make. If the welder is to be tested on butt welds only, the specimen plates are welded together and coupons are cut from these. The coupons are then tested for tensile strength and ductility in a laboratory. If the welder is to be tested on fillet welds, a double-strap lap joint is recommended. As a rule, it is difficult to make these test specimens with the welds in longitudinal shear.
The Hartford Test refers to qualifying an employer’s organization for an insurance company. The qualifying tests of the procedures and the welding which operators have completed are part of the requirements for qualifying the employer’s organization. The welding operators can weld on code work only for the employer with whom the tests were performed.
An insurance company engaged in shop inspection does not issue certificates of qualification to welding operators, since the certificates would be of no value to another shop.
See TESTING for further reference to various qualification tests and testing methods. See also QUALIFICATION FOR CODE WORK, ASME BOLER CONSTRUCTION CODE; BOILER WELDING; BUILDING CONSTRUCTION
CODES; HARTFORD TEST; and TRAINING.