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Preliminary communication

Fracture of drilling head pipe connection due to quenching of heat affected zone (HAZ)

B. Zorc ; Welding Institute Ltd,, Slovenia and University of Ljubljana, Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia
M. Bizjak ; University of Ljubljana, Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia
B. Kosec ; University of Ljubljana, Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia
A. Nagode ; University of Ljubljana, Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia


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Abstract

The drilling head pipe connection is made of quenched and tempered steel 34CrNiMo6. The steel characteristic is high hardenability. Due to unsuitable and untested welding technology the heat affected zone (HAZ) cooling rate after welding surpassed the upper critical cooling rate. During horizontal drilling of the rock, the resulting brittle martensite could not bear the dynamic loads which led to a brittle fracture of the pipe connection.

Keywords

welding; heat affected zone (HAZ); martensite; fracture

Hrčak ID:

141839

URI

https://hrcak.srce.hr/141839

Publication date:

1.1.2016.

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