Q390B coiled plate and medium plate are two different steel products, with certain differences in their smelting processes and performance.

First, in terms of smelting process, the smelting processes for Q390B coiled plate and medium plate are basically the same, both adopting the oxygen top-blown converter smelting, continuous casting, and continuous rolling process. However, in the specific smelting process, the medium plate's smelting process is more refined, requiring higher purity of molten steel and stricter control of chemical composition. Therefore, the smelting of medium plate is more challenging, and the production cost is relatively higher.

Second, in terms of product performance, both Q390B coiled plate and medium plate have good comprehensive mechanical properties and machinability, making them suitable for various machining and manufacturing fields. However, due to differences in smelting processes and production costs, there are certain performance differences between Q390B coiled plate and medium plate.

Specifically, Q390B coiled plate has higher strength and hardness, making it suitable for manufacturing mechanical parts and structural components that need to bear larger loads. At the same time, due to the smaller thickness of Q390B coiled plate, its yield strength is relatively lower, giving it good impact toughness, making it suitable for manufacturing parts and structural components that need to withstand impact loads.

On the other hand, medium plate has higher tensile strength and yield strength, making it suitable for manufacturing mechanical parts and structural components that need to bear higher loads. Additionally, medium plate has good weldability and machinability, making it suitable for manufacturing parts and structural components that require welding or complex processing.

Furthermore, there are certain differences in the applications of Q390B coiled plate and medium plate. Q390B coiled plate is mainly used in construction, bridges, ships, vehicles, and other fields, while medium plate is primarily used in manufacturing various mechanical parts, boilers, pressure vessels, and other large mechanical products.

In summary, the smelting processes for Q390B coiled plate and medium plate are basically the same, but the medium plate's smelting process is more refined, and its production cost is relatively higher. In terms of performance, Q390B coiled plate has higher impact toughness and good machinability, making it suitable for mechanical parts and structural components that bear larger loads; while medium plate has higher strength and weldability, making it suitable for mechanical parts and structural components that bear higher loads. Additionally, there are certain differences in the applications of Q390B coiled plate and medium plate. When selecting, it is necessary to choose based on specific usage requirements and design needs.