Search results
Results from the WOW.Com Content Network
Engineering Critical Assessment (ECA) is a procedure by which the safety of a welded structure with defects or flaws can be determined. ECAs utilize the material properties and expected stress history to determine a flaw acceptance criteria which will ensure that welds will not fail during the construction or service life of the welded structure. [1]
Cold cracking—also known as delayed cracking, hydrogen-assisted cracking (HAC), or hydrogen-induced cracking (HIC)—is a type of defect that often develops after solidification of the weld when the temperature starts to drop from about 190 °C (375 °F); the phenomenon often arises at room temperature, and it can take up to 24 hours to appear even after complete cooling. [8]
Arc blow tends to occur if the material being welded has residual magnetism at a certain level, particularly when the weld root is being made, and the welding current is direct current (DC positive or negative). Magnetic arc blow is popularly attributed to a change in the direction of current as it flows into and through the workpiece.
A common case of embrittlement during manufacture is poor arc welding practice, in which hydrogen is released from moisture, such as in the coating of welding electrodes or from damp welding rods. [ 22 ] [ 31 ] To avoid atomic hydrogen formation in the high temperature plasma of the arc , welding rods have to be perfectly dried in an oven at ...
Hydrogen picked up during melting and casting segregates at internal voids and discontinuities and produces these defects during forging. Fish-eyes are bright patches named for their appearance seen on fracture surfaces, generally of weldments. Hydrogen enters the metal during fusion-welding and produces this defect during subsequent stressing.
In welding, undercutting is when the weld reduces the cross-sectional thickness of the base metal. This type of defect reduces the strength of the weld and workpieces. One reason for this defect is excessive current, causing the edges of the joint to melt and drain into the weld; this leaves a drain-like impression along the length of the weld.
Welding - Studs and ceramic ferrules for arc stud welding: ISO 13919-1: Welding - Electron and laser-beam welded joints - Guidance on quality level for imperfections - Part 1: Steel ISO 13919-2: Welding - Electron and laser-beam welded joints - Guidance on quality level for imperfections - Part 2: Aluminium and its weldable alloys ISO 13920
The defect or discontinuity creates a characteristic parabolic indication, due to the apparent change in depth as the probes travel. Manually-guided TOFD probes. Time-of-flight diffraction (TOFD) method of ultrasonic testing is a sensitive and accurate method for the nondestructive testing of welds for defects.