The hot-rolled stainless steel plate processing is a systematic industrial process designed to convert steel slabs into steel plates of desired dimensions through high-temperature rolling, achieving the desired mechanical properties and microstructure.

Step 1: Steelmaking and Continuous Casting
This is the foundation of all processes and determines the “genesis” of stainless steel plate.

Purpose: To produce stainless steel with a chemical composition that precisely meets standards (such as 304, 316, etc.).

Process:

Electric Steelmaking: Scrap steel, molten iron, and alloying elements (such as chromium, nickel, and molybdenum) are melted in an electric arc furnace.

Refining: In refining furnaces such as AOD or VOD, an argon-oxygen mixture is injected to significantly reduce the carbon content while retaining the precious chromium and precisely adjusting other alloying components.

Continuous Casting: Qualified refined molten steel is injected into a continuous casting machine, where it cools and solidifies into slabs of a specific thickness (e.g., 200mm) and width.

Step 2: Slab Heating
Purpose: To uniformly heat the slab to a high temperature, achieving good ductility for rolling.

Process: The slab is fed into a walking beam furnace and heated to 1200-1300°C. At this temperature, the steel’s microstructure transforms into a single austenite phase, making it easily deformable.

Step 3: Hot Rolling
This is the core step in forming and consists of two stages:

Roughing Rolling:

Purpose: To reduce thick slabs to intermediate thicknesses.

Process: The hot slab passes through a roughing mill (usually a reversing mill) in multiple passes, reducing thickness from over 200mm to tens of millimeters. Irregularities at the ends and sides are trimmed off at this stage.

Finishing Rolling:

Purpose: To achieve a precise final thickness and excellent surface quality.

Process: The intermediate slab after roughing is continuously rolled through a finishing mill (a series of rolling mills in series) to produce hot-rolled coils or flat sheets of the desired thickness. The finishing temperature of finish rolling is typically controlled between 800-900°C.

Step 4: Heat Treatment (Solution Treatment)
Purpose: This is a critical step in restoring the corrosion resistance and mechanical properties of stainless steel!

Removes work hardening: After hot rolling, the steel plate becomes hard and brittle.

Dissolves carbides: The chromium carbides precipitated during rolling are dissolved back into the austenite matrix, restoring its resistance to intergranular corrosion.

Process: The steel plate is heated to approximately 1050-1150°C, held for a period of time, and then rapidly cooled (usually quenched in water).

Step 5: Pickling and Passivation
Purpose: Removes the oxide scale (black ferroferric oxide and ferrous oxide) formed on the steel plate surface during hot rolling and heat treatment, and rebuilds the passive film.

Process:

Shot Peening/Scaling: First, mechanically break up the majority of the oxide scale.

Pickling: The steel plate is immersed in a mixed acid bath (usually a mixture of nitric acid and hydrofluoric acid) to chemically dissolve any remaining scale and oxidized metal layers.

Rinsing and Drying: Rinse thoroughly with clean water and dry.

Passivation: After pickling, the clean chromium, in contact with oxygen in the air, spontaneously forms an extremely thin and dense chromium-rich oxide film (passivation film), which is the key to stainless steel’s “rust-proof” properties.

Step 6: Straightening and Finishing
Purpose: Ensure the straightness and dimensional accuracy of the steel plate.

Process: The steel plate is straightened using a straightening machine. Edge trimming and cut-to-length processing are then performed according to customer specifications.

Step 7: Inspection and Packaging
Purpose: Ensure product quality and protect it from damage during transportation.

Process:

Inspection: The steel plate is inspected for dimensions, surface quality, mechanical properties (sample testing), and chemical composition.

Packaging: A protective film is typically applied to the surface. Depending on the product form (coil or flat plate), different packaging methods (such as steel strapping, wooden pallets, etc.) are used, clearly labeling information such as specifications and batch numbers.

Final Product Form
After the above process, two main hot-rolled products are obtained:

Hot-rolled coil: Coiled after finish rolling.

Hot-rolled flat plate/plate: Directly rolled from slabs or sheared from hot-rolled coils.

Summary
The processing of hot-rolled stainless steel plate involves a complex process chain integrating metallurgy, press working, heat treatment, and surface treatment. Each step plays a decisive role in the final product’s strength, toughness, corrosion resistance, and surface appearance. The off-white, matte surface of hot-rolled stainless steel plate we commonly see is a typical characteristic of the passivation film after pickling.

Cherry
Website: www.jinyoumetal.com
Email: Cherry@jinyoumetal.com
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