Q215 hot-rolled steel plate is a common low-carbon structural steel grade widely used in manufacturing and construction due to its excellent formability, weldability, and cost-effectiveness. It is specified under the Chinese National Standard GB/T 700-2006, which outlines the technical delivery conditions for carbon structural steels.

Key Characteristics & Properties

1. Mechanical Properties

The mechanical properties are defined for steel plates with a thickness typically ≤ 16mm. Properties can vary slightly with increasing thickness.

Yield Strength (ReH): ≥ 215 MPa (Minimum)

Tensile Strength (Rm): 335 - 450 MPa

Elongation at Break (A): ≥ 31% (Based on a gauge length of 5.65√S₀, indicating good ductility)

Hardness: Low, making it easy to cut, form, and machine.

2. Chemical Composition (Grade A)

The composition is a primary factor in its properties. Q215 is subdivided into quality grades A, B, C, which mainly differ in impact toughness and chemical control. Grade A is the most common.

Manufacturing Process: Hot-Rolling

The "hot-rolled" process involves heating steel slabs above their recrystallization temperature (typically over 1000°C / 1700°F) and then passing them through a series of rollers to achieve the desired thickness.

Advantages: Cost-efficient, high production rate, improves ductility and toughness.

Surface Finish: Characterized by a slightly scaled, non-shiny, dark gray finish. This mill scale must often be removed (via pickling, shot blasting, or grinding) before painting or further processing.

Advantages

Excellent Formability: Its high ductility allows it to be easily bent, stamped, and drawn into various shapes without cracking.

Superior Weldability: The low carbon equivalent enables all common welding methods (ARC, MIG, TIG) with minimal risk of cracking, requiring minimal pre- or post-heating.

Good Machinability: It can be readily drilled, cut, and sheared.

Cost-Effective: As a basic grade of steel, it is one of the most affordable options available.

Wide Availability: Produced in large quantities by mills worldwide, making it readily accessible.

Comparisons and Equivalents

Q215 vs. Q235: Q235 has a higher minimum yield strength (235 MPa) and slightly higher carbon content, making it stronger but slightly less ductile than Q215.

International Equivalents:

ASTM A36 (USA): While A36 has a similar yield strength, its chemical composition and tensile strength requirements are different. A36 is generally considered a closer match to China's Q235.

S235JR (Europe - EN 10025-2): This European grade is a more direct equivalent in terms of mechanical properties and application.

SS330 (Japan - JIS G3101): This Japanese standard grade has similar properties.