Prakt. Met. Sonderband 47 (2015) 39 
ale Aufla. . . . 
deny Bei Warmrissen in Anhebepollern besser den Kopf einziehen — eine 
V® Ver. Fallstudie aus dem Großmaschinenbau 
1 dies 
ge Beware of Hot Tearing in Lifting Lugs — a Case Study in Mechanical 
Engineering 
A. Neidel, B. Fischer" 
Siemens AG, Power and Gas, Gas Turbines, Gasturbinenwerk Berlin 
Magnus Oden, 
ly, Johar Q 
Se I Introduction 
One out of eight lifting lugs intended for a large gas turbine engine exhibited indications upon 
magnetic particle surface crack inspection (MT), that were later verified by ultrasonic testing (UT). 
The subject parts are made of a low-alloy steel casting (Figs. 1, 2). They had already been used in 
service and were supposed to be re-used, together with the other lifting lugs of the set. In order to 
determine the cause of the indications, non-destructive metallographic examinations by means of 
the replica technique were performed. In that investigation, the indications were determined to have 
8.0.32 been caused by crack-like decohesions of material. In one of the examined areas, these 
imperfections were associated with small casting defects, namely micro shrinkage. This might have 
contributed to crack initiation. The described small surface cracks at the cylindrical part of the 
lifting lug itself were probably caused by bending stresses in service. Indications were found only 
on one out of the entire set of eight bollards. There, only the upper side of the short spigot, were 
axial tension on the surface is to be expected in service when the bollards are in lifting action, was 
affected. Casting defects like micro shrinkage might well have contributed to the cracking, was the 
main conclusion at the time. The crack path in that first non-destructive investigation was at least 
14.0. 157 partly transgranular, which is consistent with tensile overload failure. From that first laboratory 
o Wiley 2000 effort, it was recommended to blend out the affected areas until no more indications were detectable 
ing Materials by MT. Because of the rather high Hertzian stresses in that same area, it was further recommended 
to weld repair the blended sections so that the original shape could be reproduced by machining. 
This material is readily weldable. However, engineering declared the subject lifting lug to be 
27 scrapped and ordered a comprehensive destructive metallurgical root cause investigation of the 
. indications. That second investigation is the subject of this paper. 
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il of Alloys 
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