Modern steels made using complicated alloying strategies and thermomechanical rolling processes have exhibited unprecedented weldability since World War II. Using this advantage, steel structure designers and fabricators have achieved many modern marvels from machinery to deep-water oil and gas platforms. Through extensive research on the integrity of steel structures, rigid qualification welding tests have evolved for various fabrication codes. Weldability testing, for example, is no longer focused only on producing crack-free welds as was the case in the early part of the last century. Testing now emphasizes the robustness of the weld. As a result qualifying steels and welding procedures to build important structures, such as oil and gas pipelines, well heads, and offshore platforms, is significantly more challenging. To streamline this process, fabricators need a method of effectively evaluating the robustness of steel base-materials and welding consumables before the start of a fabrication project. Carbon equivalent (CE) equations are capable of predicting the cold-cracking tendency of steels and have recently been receiving significant attention, leading to this retrospective work on their evolution….