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Weld testing quality

1. Dr. Babasaheb Ambedkar technological University, lonere WELD TESTING QUALITY BY Vivek Deepak Marne 2130331612030

2. Contents Introduction Types of weld quality testing Destructive testings Non destructive testings Importance of weld quality testing conclusion

3. Introduction Weld quality assurance is the use of technological methods and actions to test or assure the quality of welds, and secondarily to confirm the presence, location and coverage of welds.[original research?] In manufacturing, welds are used to join two or more metal surfaces. Because these connections may encounter loads and fatigue during product lifetime, there is a chance they may fail if not created to proper specification. Methods of weld testing and analysis are used to assure the quality and correctness of the weld after it is completed. This term generally refers to testing and analysis focused on the quality and strength of the weld, but may refer to technological actions to check for the presence, position and extent of welds

4. Types of weld quality tests Destructive Methods Destructive tests are applied to samples representative of the welded joint under review, often made especially for test purposes. In a destructive test, the test piece or specimen is destroyed, in most cases by fracturing. After destructive testing the specimen remains no longer applicable to further use. The following presents the most frequently used destructive methods of evaluating welds.

5. Tensile test Longitudinal and transverse tension tests are performed on specimens removed from actual welded joints and from the Weld-metal area. Stress-strain curves are then ploted . These curvesindicate the yield strength, Y, ultimate tensile strength, UTS, and ductility of the Welded joint(elongation and reduction of area) in different locations and directions.

6. Bend test Several bend tests have been developed to determine the ductility and strength of welded joints. In one common test, the welded specimen is bent around a fixture (wraparound bend test). In another test, the specimens are tested in three-point transverse bending. These tests help to determine the relative ductility and strength of welded joints.

7. Impact test Fracture toughness tests commonly utilize the impact testing techniques. Charpy V-notch specimens are first prepared and then tested for toughness. Another toughness test is the drop weight test, in which the energy is supplied by a falling weight.

8. Nick break test The nick break test is useful for determining the internal quality of the weld metal. This test reveals various internal defects, such as slag inclusions, gas pockets, lack of fusion, and oxidized or burned metal. The test specimen is cut transversely to the welded joint and has the full thickness of the plate at the joint. Slots are sawed at each edge through the center of the weld of the specimen to be tested

9. Brinell hardness test The test comprises forcing a hardened steel ball indentor into the surface of the sample using a standard load as shown in Fig.The diameter/load ratio is selected to provide an impression of an acceptable diameter. The ball may be 10, 5 or 1 mm in diameter, the load may be 3000, 750 or 30 kgf . The load, P, is related to the diameter, D, by the relationship P/D 2

10. Vickers hardness test The Vickers hardness test operates on similar principles to the Brinell test; however, the major difference is the use of a square-based pyramidal diamond indentor rather than a hardened steel ball. Also, unlike the Brinell test, the depth of the impression does not affect the accuracy of the reading. The diamond does not deform at high loads, so the results on very hard materials are more reliable. The load may range from 1 to 120 kgf and is applied for 10 to 15 seconds.

11. Non destructive methods These tests neither break nor alter the structure or appearance of the welded component. Non-destructive tests have the ability to detect invisible subsurface defects. Although non-destructive tests do not provide direct measurement of mechanical properties, they are extremely useful in revealing defects in components that could impair their performance when put in service.

12. Visual inspection Visual inspection is the simplest, fastest, economical and most commonly used testing method for detecting defects on the surfaces of welded objects. The weld surface and joint are examined visually; however, sometimes a magnifying lens is employed. Visual weld inspection has the benefit of being able to be done in-house, it causes minimal production delays and provides immediate feedback to welders and designers. Fig. 1 shows a robotic crawler which is used for the internal inspection of pipe welds.

13. Ultrasonic testing Ultrasonic flaw detection has long been the preferred method for nondestructive testing in welding applications. This safe, accurate and simple technique has pushed ultrasonic to the forefront of inspection technology. It can reveal a majority of the commonly occurring defects in welded joints, such as porosity, slag inclusions, a lack of side-wall and inter-run fusion and root penetration, undercutting, and longitudinal or transverse cracks. Most of the applications are for low-alloy construction quality steels, however, welds in aluminum can also be tested.

14. X ray and gamma ray radiography test This radiographic test method is used to reveal the presence and nature of internal defects in a weld, such as cracks, slag and blowholes, and zones where proper fusion is lacking. In practice, an X-ray tube is placed on one side of the welded plate and an X-ray film, with a special sensitive emulsion, on the other side. Radiography using X-ray and gamma γ-ray on welds radiography is one of the most useful of the nondestructive tests which can be applied for assessing the quality of the welded joints. Radiography has been used for the inspection of welds of all types and thicknesses ranging from minute welds in electronic components to welds up to 50 cm thick employed in heavy fabrications.

15. Magnetic particle inspection This method of nondestructive testing tends to supplement rather than displace radiography. For example, radiography ordinarily cannot detect small cracks, especially when they are too small to be seen by the naked eye. Magnetic particle inspection is a relatively simple and easy technique. It is almost free from any restriction as to size, shape, composition and heat-treatment of a ferromagnetic specimen. This method is used on magnetic ferrous weldments for detecting invisible surface or slightly subsurface defects.

16. Liquid penetrant test Liquid penetrant methods are used to inspect metals for surface defects that are similar to those revealed by magnetic particle inspection. Unlike magnetic particle inspection, which can reveal subsurface defects, liquid penetrant inspection reveals only those defects that are open to the surface. Three groups of liquid penetrants are presently in use: i ) non water-washable, ii) water-washable, and iii) fluorescent dye penetrants. Before using a liquid penetrant to inspect a weld, all slag, rust, paint and moisture must be removed from the surface

17. Eddy current test As eddy current is best used for detecting surface-breaking cracks, its most practical applications relate to the in-service inspection of welded structures that are subject to a cyclical loading that can lead to fatigue crack propagation in critical welded areas. In eddy current testing, a sinusoidal AC voltage is applied across the eddy current probe or inspection coil.

18. Importance of weld testing quality The main reason that weld quality assurance is so important is because a poor-quality weld is more likely to break or leak. The consequences of weld failure can range from a small inconvenience, such as a kitchen pipe bursting, to something that’s far more dangerous like the structural failure of a bridge or gas pipe.

High-quality welds help improve the safety of structures, like pipelines

19. Conclusion Considering destructive tests, there are several quite similar methods which are aimed to reveal different types of welding defects. Ultrasonic testing is considered as one of the most common, cheap, fast and convenient methods to use. Considering destructive tests, there are several quite similar methods which are aimed to reveal different types of welding defects. Also, to perform successful production it is not only important to evaluate welds afterwards, but also to carefully check all the starting conditions and equipment. Moreover, nowadays some welding evaluation techniques tend to be used as real-time welding evaluation. Non-destructive methods are highly valuable techniques that can save both time and money in evaluating welds and conducting research in metals welding.

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