Shenzhen Alu Rapid Prototype Precision Co., Ltd.

No, welders are not inherently "cast metal experts" in the sense of specializing in the metal casting process itself—that's a distinct manufacturing technique handled by foundry workers or casters, who pour molten metal into molds to create shapes. Welding, by contrast, is about fusing metals (often already cast or formed) using heat and filler material.That said, many welders do develop expertise in working with cast metals (like cast iron or cast steel) for repairs, fabrication, or modifications. This is a specialized subset of welding because cast metals are brittle, prone to cracking from thermal stress, and can have impurities that cause porosity or defects during welding. 

Techniques like preheating the material, using nickel-based electrodes, and slow cooling are often required to succeed, and not all welders are trained for it.