Hot-rolled plate, formally known as hot-rolled steel plate, refers to a single-sheet flat steel product manufactured from steel billets. This is achieved through continuous rolling in a rolling mill at elevated temperatures, ultimately forming a sheet of specified thickness, width, and length. Both fall under the category of ‘hot-rolled steel products’, sharing identical core production processes. They differ solely in their final form – coils versus plates – and constitute one of the most widely used foundational steels in industrial applications.

I. Core Production Logic: ‘Same Origin, Different Form’ as Hot-Rolled Coils

The production process for hot-rolled plates is fundamentally identical to that of hot-rolled coils, essentially representing the ‘subsequent processing form of hot-rolled coils’. The core distinction lies solely in the ‘finished product stage’, with the specific logic as follows:

Common Pre-Processing Stages: From billet heating, rough rolling, finish rolling to laminar cooling, the production sequences for hot-rolled sheets and coils are identical — high-temperature billets undergo multiple rolling passes to form continuous hot-rolled strip.

Differentiated Finishing Stages:

Hot-rolled coils: The continuous strip is directly wound into coils via a coiler for storage and transport in ‘coil form’.

Hot-rolled sheets: After cooling, the continuous strip is cut into individual flat sheets at predetermined lengths (e.g., 2m, 6m, 12m) via a cross-cutting (or slitting) line according to customer specifications, ultimately delivered as ‘individual sheets’.

In essence: Hot-rolled coils can be processed into hot-rolled plates via ‘uncoiling’ (unwinding and cutting); conversely, hot-rolled plates cannot be directly reconverted into hot-rolled coils. This represents a difference in form between ‘coil stock’ and ‘plate stock’, while the core material and properties remain identical.

II. Core Classification: By Thickness and Steel Grade

The classification logic for hot-rolled plates mirrors that of hot-rolled coils, primarily based on ‘thickness specifications’ and ‘steel grade applications,’ with different categories catering to distinct usage scenarios:

1. Classification by Thickness Specifications (Most Common Method)

Thickness is the most critical specification indicator for hot-rolled plates, directly determining their load-bearing capacity and processing adaptability:

Heavy plates: Thickness ≥4.5mm, common specifications 4.5-200mm (or even thicker), widths typically 1500mm, 1800mm, 2000mm, etc., with lengths customised to requirements (e.g., 6m, 9m, 12m).

Characteristics: High strength and rigidity, suitable for heavy loads and impact resistance. Primarily used in heavy-duty structures, machinery bases, etc.

Medium Plate: Thickness 1.5–4.5mm, width 1000–2000mm, length 2000–6000mm.

Characteristics: Balances strength and ductility with moderate workability. The most versatile hot-rolled plate with the widest applications.

Thin plate: Thickness <1.5mm (some standards classify <3mm as thin plate). Features lighter, thinner specifications requiring higher rolling precision.

Characteristics: Excellent ductility and bendability. Primarily serves as substrate for downstream deep processing (e.g., subsequent cold rolling, coating/plating) or for lightweight structural components.

2. Classification by steel grade and application

Consistent with hot-rolled coils, the chemical composition determines the mechanical properties and special functions of hot-rolled plates, primarily categorised as:

Carbon Structural Steel Hot-Rolled Plates: Carbon content 0.06%-0.22%, low-alloy, medium strength, good plasticity, weldable, e.g. GB standard Q235B.

Applications: Building steel structures (beams, columns), general machinery components, container bodies, etc.

High-strength hot-rolled plates: Alloyed with Mn, Si, Nb, V, etc., featuring tensile strength ≥420MPa, impact resistance, and fatigue resistance. Examples include GB Q355 series.

Applications: Construction machinery (excavator booms, crane undercarriages), bridge steel structures, heavy-duty vehicle chassis, etc.

Specialised hot-rolled plates: Composition tailored for specific applications, offering specialised properties such as weather resistance, wear resistance, and heat resistance.

Examples: Weathering steel hot-rolled plates (e.g., Q295NH) for outdoor bridges and lighthouses; wear-resistant steel hot-rolled plates (e.g., NM450) for mining machinery and dump truck bodies; heat-resistant steel hot-rolled plates for boilers and heat exchangers.