To weld on sheet steel, which Code Book must a welder be certified for?

The correct choice is the AWS D1.3, which specifically addresses welding requirements for sheets and plates of steel. This code focuses on the welding of thin materials typically found in structural applications. When a welder is certified under AWS D1.3, they demonstrate their understanding of the particular challenges and techniques necessary to ensure sound welds in sheet steel, such as controlling heat input, mitigating warpage, and addressing potential burn-through.

In contrast, the other codes, while related to welding steel, are pertinent to different applications. AWS D1.1 focuses on structural welding for buildings and bridges, AWS D1.5 pertains to bridge welding specifically, and AWS D1.6 relates to the welding of stainless steel. Each of these codes has unique requirements and considerations specific to their application, thus making them unsuitable for the particular needs associated with welding sheet steel.