Overview
A36, Q235, and S235JR are globally recognized carbon steel grades extensively employed in structural and industrial applications. Governed by distinct regional standards, these materials exhibit overlapping mechanical characteristics while maintaining unique compositional and testing requirements. The following expanded analysis provides deeper insights into their specifications, performance, and suitability for diverse engineering scenarios.
1. ASTM A36 (USA Standard)
Composition:
Carbon (C): ≤0.26% (balanced for weldability and strength)
Manganese (Mn): 0.60–0.90% (enhances hardenability and tensile properties)
Phosphorus (P): ≤0.04% (controlled to minimize brittleness)
Sulfur (S): ≤0.05% (limited to improve hot workability)
Trace elements: Silicon (Si) ≤0.40%, Copper (Cu) ≥0.20% (for atmospheric corrosion resistance).
Mechanical Properties:
Yield Strength: ≥250 MPa (36 ksi) – measured at 0.2% offset
Tensile Strength: 400–550 MPa (58–80 ksi) – ensures structural integrity under load
Elongation: ≥20% in 200 mm gauge length (indicates ductility for forming operations)
Modulus of Elasticity: 200 GPa (29,000 ksi) – typical for low-carbon steels.
Thermal Processing:
Hot-rolled condition: Standard delivery state with normalized microstructure
Cold-working: Possible but requires annealing for severe deformations.
Applications:
Primary load-bearing members in skyscrapers, highway bridges, and transmission towers
Base plates, gussets, and connection components in steel structures
Machinery frames, truck chassis, and agricultural equipment.
Certification & Testing:
Mill test reports (MTRs) include chemical analysis and tensile results
Charpy V-notch testing optional unless specified for low-temperature service.
Fabrication Advantages:
Optimized for arc welding (SMAW, GMAW, FCAW) without preheating under moderate thicknesses
Suitable for bolting, riveting, and plasma cutting operations.
2. Q235 (GB/T 700, China Standard)
Composition:
Carbon (C): ≤0.22% (lower than A36 for improved formability)
Manganese (Mn): 0.30–0.65% (varies with thickness)
Silicon (Si): ≤0.35% (deoxidizing agent affecting surface quality)
Sulfur (S) & Phosphorus (P): ≤0.045% each (stricter control in higher subgrades)
Residual elements: Chromium (Cr), Nickel (Ni), and Copper (Cu) ≤0.30% combined.
Subgrade Classification:
Q235A: Basic grade with no impact requirements
Q235B: Room-temperature Charpy impact ≥27 J
Q235C: 0°C impact toughness ≥27 J
Q235D: -20°C impact toughness ≥27 J.
Mechanical Properties:
Yield Strength: ≥235 MPa (34 ksi) – consistent across thicknesses ≤16 mm
Tensile Strength: 370–500 MPa (54–72 ksi) – varies with processing route
Elongation: ≥26% in proportional specimen (5.65√S₀).
Processing & Supply:
Available in hot-rolled, controlled-rolled, or normalized conditions
Surface finishes: Black, pickled, or shot-blasted for specific applications.
Typical Use Cases:
Reinforcing elements in prefabricated building systems
Pressure vessel shells (non-critical service) and storage tanks
Railway rolling stock components and crane booms.
Standards Compliance:
Mandatory factory inspection certificates (FIC) for subgrades B/C/D
Complies with Chinese seismic design codes for construction.
3. S235JR (EN 10025-2, European Standard)
Composition:
Carbon (C): ≤0.17% (reduced for enhanced weldability, thickness-dependent)
Manganese (Mn): ≤1.40% (higher than Q235 for strength compensation)
Sulfur (S): ≤0.035% (improved machinability versus A36)
Phosphorus (P): ≤0.035% (tight control for cold-forming applications)
Nitrogen (N): ≤0.012% (prevents aging brittleness).
Impact Toughness:
Minimum Charpy V-notch energy: 27 J at -20°C (mandatory for JR designation)
Tested longitudinally from parent material or transverse for critical sections.
Mechanical Properties:
Yield Strength: ≥235 MPa (34 ksi) – valid up to 16 mm thickness
Tensile Strength: 360–510 MPa (52–74 ksi) – overlaps with A36 range
Elongation: ≥26% in proportional specimen (consistent with Q235).
Processing Standards:
Delivered in hot-rolled (AR) or normalized (N) conditions
Surface tolerances per EN 10029 Class A (standard) or Class B (precision).
Application Spectrum:
Offshore platform walkways and non-primary marine structures
Architectural cladding supports and greenhouse frameworks
Food processing equipment with hygienic surface requirements.
Certification:
CE marking compliant with EU Construction Products Regulation (CPR)
Third-party inspection options for critical infrastructure projects.
Key Similarities & Cross-Standard Compatibility
Strength Class: All grades fall within 235-250 MPa yield strength range, enabling substitution in non-critical global projects.
Fabrication Flexibility: Compatible with modern steel construction techniques including laser cutting and robotic welding.
Corrosion Management: Require protective coatings (galvanizing, painting) for outdoor exposure.
Availability: Widely stocked in thicknesses from 1.5 mm to 200 mm across international steel distributors.
Detailed Comparative Analysis
Parameter | A36 (ASTM) | Q235 (GB/T 700) | S235JR (EN 10025-2) |
Yield Strength | 250 MPa (≥36 ksi) | 235 MPa (≥34 ksi) | 235 MPa (≥34 ksi) |
Tensile Range | 400–550 MPa | 370–500 MPa | 360–510 MPa |
Impact Testing | Optional | Subgrade-dependent | Mandatory (-20°C) |
Max Carbon Content | 0.26% | 0.22% | 0.17% (thickness-based) |
Primary Market | North America | China | Europe/Global Projects |
Key Advantage | High tensile versatility | Cost-effectiveness | Low-temperature compliance |
Selection Guidelines & Engineering Considerations
Code Compliance: Adhere to local building codes (AISC, GB, Eurocode) for structural calculations.
Temperature Sensitivity: Specify S235JR for environments below 0°C; Q235D for moderate cold regions.
Welding Criticality: A36 offers wider filler metal compatibility; S235JR requires EN 499-compliant electrodes.
Cost Optimization: Q235 provides economical solutions for non-cyclic loading structures.
Surface Quality: S235JR’s tighter impurity control suits exposed architectural applications.
While A36, Q235, and S235JR demonstrate comparable baseline performance as mild carbon steels, their nuanced differences in chemistry, certification requirements, and regional availability dictate precise material selection. Engineers must evaluate operating temperatures, fabrication methodologies, and lifecycle costs while ensuring strict adherence to project-specific standardization bodies. These grades continue to serve as the backbone of modern structural engineering, balancing economic feasibility with mechanical reliability across continents.
| Product Name | A36/Q235/S235JR Carbon Steel Plate |
| Production Process | Hot Rolled &Cold Rolled |
| Material Standards | AISI,ASTM, ASME, DIN,BS, EN, ISO, JIS, GOST, SAE,etc. |
| Width | 45mm-2200mm |
| Length | Custom Size |
| Thickness | Hot Rolled:2.75mm-100mm |
| Cold Rolled:0.2mm-3mm |
| Delivery Conditions | Rolling,Annealing, Quenching,Tempered or Standard |
| Surface Process | Ordinary, Wire Drawing, Laminated Film |
|
Chemical Composition
| C | cu | Fe | Mn | P | Si | S |
| 0.25-0.290 | 0.2 | 98.0 | 1.03 | 0.040 | 0.280 | 0.05 |
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Mechanical Properties
