Slag inclusions

Fig. 5 dives an image of a steel plate weld 18 mm thick. The sensitivity is of the first accuracy class. Both gas pores, slag inclusions and a cut have been detected in this weld... 

Sampling of checkpoints during the review exercise confirmed some predictable features, notably that radiography would miss planar defects such as lack of side wall fusion, and that ultrasonic operators tended not to report undercut, porosity or the smaller slag inclusions. 

The integrity of welded stmctures depends on the integrity of the welds, and much attention is given to testing methods, such as destmctive tests, nondestmctive tests, and general weld inspection. An objective of many tests is to determine whether welds contain specific defects, such as porosity, slag inclusions, cracks, or lack of fusion (14,15). 

General description. Slag inclusions are various nonmetallic substances that become entrapped in the weld during the welding process. Typically, the inclusions are located near the surface and along the sides of the weld (Fig. 15.15). The inclusions may form from reactions occurring in the weld metal or may be metal oxides present on the metal prior to welding. They may be isolated particles or may form relatively continuous bands. 

Locations. Slag inclusions are principally a result of improper welding techniques and therefore may he found wherever welds are present. 

Figure 15,15 Common slag inclusion sites in a weld.

Identification. Slag inclusions will not be visually identifiable unless slag particles emerge at the weldment surfaces. Radiography, eddy-current testing, and ultrasonics are nondestructive testing techniques that can disclose slag inclusions. 

Often contain defects (hydrogen cracks, slag inclusions, stop-start marks). Help initiate fatigue cracks. Critical welds must be tested non-destructively and defects must be gouged out. 

The silicon map shows the distribution of slag inclusions, while the position of the weld lines can be seen to be marked by boundaries between areas of high and low phosphorus content and by enrichments of nickel and/or arsenic at the weld lines. Higher resolution maps can be made of welds to reveal their fine structure. 

Hedges, R. E. M. and C. J. Salter (1979), Source determination of iron currency bars through analysis of the slag inclusions, Archaeometry 21,161-175. 

F Slag inclusion, tungsten inclusion, or elongated indication Individual length Individual width Cumulative length <7 /3 <. 5 mm (%2 in) and < T /3 < in any 12T weld length ... 

Slag inclusions or elongated defects 100% radiography D D NA DandH... 

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