The selection of structural materials is a critical aspect in the design of ships operating in polar low-temperature environments. Currently, the requirements of relevant rules from different classification societies exhibit both similarities and differences. The lack of a unified definition for the design temperature poses significant challenges in the selection of hull steels for polar service. Through a systematic review of the rules pertaining to material selection for hull structures in polar low-temperature environments, and based on differences in their foundational principles and definitions of design temperature, these rules can be categorized into three main types: IACS Unified Requirement S6 (UR S6) along with the winterization rules of classification societies, the POLAR CLASS (PC) rules and the rules of the Russian Maritime Register of Shipping (RMRS). This paper conducts a comparative analysis of the differences among these three categories of rules, covering aspects such as the scope of application, design temperature, and steel grade selection. Valuable conclusions and suggestions are summarized, which are expected to provide a reference for the selection of hull steels in polar low-temperature environments.

Polar heavy icebreaker is the key supporting equipment for polar merchant shipping, rescue support, scientific investigation and resource exploitation. The polar heavy breaker deserves special consideration in the application of high-strength steel and other special materials, the structural safety assessment under ice load and the hull structural layout, due to the high ice load compared with the medium and low ice class polar ships/icebreakers. The previous structural design experience for medium and low ice class polar ships cannot be arbitrarily applied to the polar heavy icebreaker. The structural design and evaluating experience of a PC2 polar heavy icebreaker that was developed by Marine Design & Research Institute of China (MARIC) are summarized. It focuses on the application of high strength steel for the ice belt structure, the application requirements and characteristics of composite steel plate for the ice belt outer plate, the impact of the non-linear evaluation technology on the ice belt scantlings, and the distribution of the ice-induced shear/bending moment and its influence on the structure in non-ice-belt regions, such as the inner platform of the main ship and the side hull of the bridge. It presents the structural design characteristics of the polar heavy icebreaker and the main differences between the polar heavy icebreaker and the medium and low ice class polar ships/icebreakers in terms of the overall structural layout and the design and evaluation of the ice belt structure. With the increase of the ice class, it is believed that the ice load not only affects the outer plate and its attached components in the ice belt region, but also has significant impact on the material selection of the ice belt structure and the overall structural layout and design of the whole ship.