Composite Steel Plate is a composite metal material obtained by metallurgically bonding a special-performance, high-value steel layer (the Cladding Material) to a low-cost, high-strength steel substrate (the Backing Material). By combining the advantages of both layers, composite steel plates offer significant benefits in economy and process adaptability, leading to their widespread use in various industrial fields .

Production Processes of Composite Steel Plates

Hot Roll Cladding

Hot roll cladding is the most widely used production process for composite steel plates, accounting for over 90% of the global output. Its production flow is similar to that of conventional steel plates .

First, cladding and backing metal slabs are obtained through conventional melting and casting processes. The joint surfaces of these slabs are ground and chemically cleaned to remove defects and impurities .

Slab assembly is a key step. The mainstream assembly method uses a "sandwich layered structure": two cladding slabs are placed in the center, with two backing slabs on the bottom and top. This avoids contamination of the cladding material by direct contact with the rolls, allows production of thinner plates, and compensates for warping tendencies due to different hot roll elongation between the layers. A separating agent (e.g., Cr₂O₃ or ZrO₂ powder) is applied between the central cladding slabs to prevent adhesion for post-rolling separation .

After assembly, the periphery of the slab stack is seal-welded, and the interior is often vacuumed to prevent oxidation at the interface during rolling. During hot rolling, the cladding and backing metals contact directly at high temperatures, achieving a solid-state metallurgical bond. The backing material can be delivered in as-rolled (AR), normalized rolled (NR), or TMCP states. Post-rolling, the cladding material is typically heat-treated first (e.g., solution heat treatment for austenitic or duplex stainless steel cladding) to achieve expected functional properties, followed by adjusting the backing material to the target state (normalizing, quenching and tempering, etc.). High cladding heat treatment temperatures (e.g., over 1050°C) may coarsen the backing material's grains, affecting its toughness .

The sandwich plate is then split down the center, yielding two composite plates simultaneously. The cladding surface usually requires cleaning and chemical treatment. Ultrasonic testing assesses the bond integrity and layer thicknesses, with ASTM A578 being a common standard. Hot-rolled composite plates typically range from 6-200mm in total thickness, with cladding layers usually 2-4mm thick .