🔍 Key Concepts

• Arc welding heat-affected zone (HAZ) and how different metals respond to rapid heating and cooling • Differences between welding on castings vs. rolled/structural steel • Purpose of preheating and post heating (stress relief, crack prevention) in weld repairs

💭 Think About

• Think about which type of material is most likely to crack or develop internal stresses if it is heated and cooled too quickly during welding. • Ask yourself: where would the weld repair be most sensitive to thermal shock and require slow, controlled cooling? • Consider which choice refers to a type of metal piece rather than just the welding polarity or the general location on the vessel.

✅ Before You Answer

• Identify which option names a specific type of metal product that is known to be brittle or prone to cracking if not heated/ cooled properly. • Distinguish between welding process settings (like polarity) and material properties (like casting vs. structural plate). • Recall that post heating is mainly used for stress relief and crack prevention in susceptible metals, not just because the weld is on a ship’s main structure.