• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.257-266
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• 2008

AHydrogen induced cracking (HIC) was phenomenologically studied in terms of the effect of nonmetallic inclusions and hot rolling process parameters. By comparing the level of non-metallic inclusions in two different kinds of commercial grade steels having different HIC resistance, the role of non-metallic inclusions in HIC occurrence was investigated. Change in inclusion morphology and distribution during hot rolling was also studied throughout slab, rolling at austenite recrystallization region (roughing mill; RM) and rolling at austenite non-recrystallization region (finish mill; FM). In addition, the contribution of RM and FM parameters to HIC was investigated from the standpoint of change in inclusion morphology during hot rolling processes. As a result, HIC was closely related to the separation of large complex inclusion during hot rolling process. Large complex inclusions originated from the improper Ca treatment, after which equilibrium composition of slag should have resulted in eutectoid composition. By controlling the equilibrium slag composition equivalent to eutectoid one, HIC resistance could be improved due to the reduced size of inclusions. In addition, change in reduction/pass in RM had an effect on HIC resistance of steels while that in FM did not. Increase in the reduction/pass in the latter stage of RM improved HIC resistance of steels by enhancing the void enclosure around inclusions.

• Korean Journal of Construction Engineering and Management
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• v.25 no.1
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• pp.62-72
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• 2024

Due to the distribution structure of domestic temporary equipment, quality control of temporary equipment is essential because more than 80% of temporary equipment is repeated and reused. Due to this importance, the Ministry of Land, Infrastructure and Transport has proposed quality management standards for temporary equipment for 10types of temporary equipments, including steel pipe support, but the overall quality of temporary eqipment cannot be confirmed because the quality is managed through sampling quality tests. In addition, although quality control standards exist for temporary material rental company, practical utilization was investigated and analyzed to be very low as they are mainly presented based on qualitative inspection standards by visual inspection. Therefore, the purpose of this study is to develop individual temporary material/quality/delivery management standards (Guides) for temporary equipment rental company to preemptively secure the quality of temporary equipment before bringing them into the construction site. If the standards developed through this study are applied to domestic temporary equipment rental companies, it is expected that high-quality temporary equipment with secured quality will be brought into the construction site as the quality of temporary equipment quality of domestic medium and small temporary equipment rental companies is improved safety accidents related to temporary structures.