SS400 Hot Rolled Carbon Steel Plate
SS400 is a classic general structural steel complying with Japanese Industrial Standard JIS G3101. Grade definition: "SS" stands for Structural Steel, while "400" refers to a minimum tensile strength of 400 MPa. As a dominant structural steel for engineering projects in Japan, Southeast Asia, South Korea and the Middle East, it is commonly supplied as hot-rolled steel plates, coils, section steel and flat bars. It features a broad allowable range for chemical composition and stable tensile strength performance.
Q235B Hot Rolled Carbon Steel Plate
Q235B is the primary carbon structural steel under Chinese national standard GB/T 700-2006. The letter "Q" denotes yield strength, "235" indicates a minimum yield strength of 235 MPa, and Grade B mandates a qualified Charpy V-notch impact test at 20°C. Compared with Q235A (no mandatory impact test), Q235B adopts stricter control over impurity elements and delivers superior low-temperature toughness. It is widely adopted for domestic construction, machinery manufacturing and large-scale exported structural engineering projects.
Although the two grades are often treated as interchangeable equivalent steel for non-critical informal applications, discrepancies in standard specifications, chemical composition control, impact toughness and market applicability will directly affect project acceptance, welding stability and overall procurement cost.
If you have confusion over steel grade selection for JIS-standard projects or bidding for domestic general structural works, please forward your project drawings and technical requirements to our technical engineers. We will provide free material substitution verification and formal quotation proposals within two working days.
Please send your project drawings and technical requirements
SS400 vs Q235B Carbon Steel Plate: Quick Overview Comparison
| Comparison Item | SS400 (JIS G3101) | Q235B (GB/T 700-2006) |
|---|---|---|
| Executive Standard | Japanese JIS G3101 | Chinese GB/T 700-2006 |
| Core Index Basis | Minimum tensile strength ≥400MPa | Minimum yield strength ≥235MPa |
| Impact Toughness Test | No mandatory impact test requirement | Mandatory 20℃ V-notch impact ≥27J |
| Chemical Composition Control | Only limit S≤0.050%, P≤0.050%; C, Mn, Si only factory internal control | Clear upper & lower limits for C, Mn, Si; S≤0.045%, P≤0.045% |
| Yield Strength Variation | Thickness-dependent: ≤16mm≥245MPa; 16–40mm≥235MPa; ＞40mm≥215MPa | Stable ≥235MPa for all thickness specifications |
| Main Target Market | Japan, Vietnam, Thailand, Malaysia, Middle East JIS standard projects | Domestic construction, Central Asia, Africa, European general structural export |
| Spot Supply Characteristic | Custom order dominated, small spot stock | Abundant spot coils & plates, small-batch urgent delivery supported |
| Direct Substitution Restriction | Cannot replace Q235B for low-temperature outdoor structures | Cannot replace SS400 for JIS certified bidding projects |
| Post-Welding Stability | Slightly higher cold crack risk for thick plate | Lower welding defect rate for medium & thick plate |
SS400 Q235B Hot Rolled Carbon Steel Plate Specification
| Product Name | SS400 Q235B Hot Rolled Carbon Steel Plate |
| Standard | JIS G3101; GB/T 700 |
| Manufacturing Process | Hot Rolled |
| Delivery Condition | As Rolled (AR) |
| Thickness Range | 6–300 mm |
| Width Range | 1000–3500 mm |
| Length Range | 3000–18000 mm |
SS400 vs Q235B Hot Rolled Steel Plate: Chemical Composition
| Element | SS400 JIS G3101 Limit | Q235B GB/T 700-2006 Limit |
|---|---|---|
| Carbon (C) | ≤0.25 | 0.12–0.22 |
| Silicon (Si) | ≤0.50 | ≤0.30 |
| Manganese (Mn) | ≤1.40 | 0.30–0.70 |
| Sulfur (S) | ≤0.050 | ≤0.045 |
| Phosphorus (P) | ≤0.050 | ≤0.045 |
SS400 vs Q235B Hot Rolled Steel Plate: Mechanical Property
| Performance Index | Plate Thickness | SS400 | Q235B |
|---|---|---|---|
| Yield Strength (MPa) | ≤16mm | ≥245 | ≥235 |
| 16–40mm | ≥235 | ≥235 | |
| ＞40mm | ≥215 | ≥235 | |
| Tensile Strength (MPa) | Full thickness | 400–510 | 375–500 |
| Elongation A5 (%) | Full thickness | ≥17–21 | ≥21 |
| Charpy V-notch Impact Energy | 20℃ | No mandatory requirement | ≥27J |
SS400 vs Q235B Hot Rolled Carbon Plate: Welding Performance
| Welding Evaluation Dimension | SS400 | Q235B |
|---|---|---|
| Carbon Equivalent (Ceq) | Fluctuating (C upper limit 0.25%) | Stable low carbon equivalent |
| Thick Plate Cold Crack Risk | Medium (unstable C content) | Low |
| Hot Crack Sensitivity | Higher (higher S/P upper limit) | Low |
| Applicable Welding Process | SMAW, MIG, SAW, gas cutting | SMAW, MIG, SAW, argon arc welding |
| Post-Weld Deformation | Slightly larger | Easy to calibrate |
SS400 vs Q235B Hot Rolled Plate: Typical Application Scenarios
SS400 Typical Application
- Japanese-funded factory steel structure, JIS-standard factory beams, columns, roof trusses and platform steel plates;
- Container side panels, logistics truck frame, van body structural parts (Southeast Asian container manufacturers widely adopt SS400);
- General mechanical equipment base, support bracket, non-load-bearing shell, ordinary hardware stamping parts;
- Auxiliary structural components for shipbuilding, bridge guardrail, port machinery auxiliary frame;
- Civil engineering projects in Japan, Thailand, Indonesia, Pakistan and other countries requiring JIS material certification.
Q235B Typical Application
- Domestic industrial plant steel structure, steel truss, stair platform, steel pipe support;
- Outdoor municipal engineering, road guardrail, lighting pole base, outdoor pipeline support (relying on impact toughness to avoid cold brittle fracture in winter);
- General pressure vessel outer shell, low-pressure pipe flange, water tank steel plate;
- Domestic machinery manufacturing, agricultural machinery frame, engineering machinery counterweight plate;
- Bulk carbon steel export to Central Asia, Africa, Eastern Europe for general construction steel.
GNEE Steel can provide tailored SS400 / Q235B steel plate cutting, drilling and bending processing services, one-stop finished structural steel delivery to shorten your workshop processing cycle by 30%. Contact our processing business manager for drawing quotation.
Key Points for Steel Procurement
Strictly comply with drawing specification requirements
If JIS G3101 is clearly specified on construction drawings, Q235B shall never be used to replace SS400; otherwise, the cargo may be rejected by the end client or third-party inspection authorities. For drawings designed in accordance with Chinese GB standards, Q235B can be adopted to cut project costs.
SS400 is prohibited for low-temperature service conditions
For projects with ambient temperature staying below 0°C all year round, outdoor steel structures and equipment foundations bearing dynamic loads, Q235B with qualified impact test certification is mandatory. SS400 has no guaranteed toughness indicator and carries a high risk of brittle fracture.
Confirm welding procedure for thick steel plates
For plates thicker than 25 mm, a formal preheating welding procedure shall be prepared in advance for SS400 fabrication to prevent cold cracking defects during welding.
Verify the type of mill certificates before shipment
Official JIS-compliant Mill Test Certificates (MTC) for SS400 are compulsory for exports to Japan. General material certificates issued by GNEE Steel are acceptable for other regular export destinations.
Clarify dimensional tolerances and surface finish requirements
The default delivery surface is standard hot-rolled black scale. If pickled surface or shot blasting rust removal is required, processing specifications shall be clearly stipulated in the procurement contract.
Reasonably confirm the Minimum Order Quantity (MOQ)
Spot supply of Q235B is available for small orders ranging from 1 ton to 5 tons. Custom production of SS400 normally requires an MOQ of 10 tons to achieve lower unit cost.
Comprehensive Services for Q235B and SS400 from GNEE Steel
Professional Technical Matching Service
Our senior steel technical engineers review construction drawings and issue steel grade substitution feasibility reports to prevent economic losses arising from material rejection caused by improper grade selection.
One-Stop Deep Processing Service
Available processing items include flame cutting, plasma cutting, CNC cutting, bending, punching, surface shot blasting, hot-dip galvanizing, and delivery of tailor-made finished components.
Full-Set Export Documentation Support
We supply JIS certification documents, GB-standard Mill Test Certificates (MTC), commercial invoices, packing lists and ocean bills of lading. We assist in arranging third-party inspection by SGS/BV and offer professional customs clearance guidance for destination countries.
Flexible Payment Terms
Payment options include Telegraphic Transfer (T/T) and Irrevocable Letter of Credit (L/C). Open Account (OA) deferred payment service is available for long-term partners to ease their capital occupation pressure on procurement.
Factories and engineering contractors with long-term cooperation qualifications are eligible to sign an annual framework supply agreement with GNEE Steel, entitled to monthly fixed settlement prices, priority stock reservation and complimentary third-party inspection quota. Please consult our sales managers for detailed framework cooperation terms.
FAQ
Can SS400 be directly replaced with Q235B for construction projects?
Yes, SS400 and Q235B can be directly replaced in most general structural and construction applications because their mechanical strengths and chemical profiles are very similar. SS400 has a slightly higher tensile strength requirement (400 MPa), while Q235B guarantees a minimum yield point (235 MPa) with controlled impact test quality.
What is the essential difference between SS400 and Q235A & Q235B?
The essential difference lies in their governing regional standards (JIS G3101 for SS400 vs. GB/T 700 for Q235), how they specify mechanical properties (tensile strength vs. yield point), and how strictly chemical impurities and quality/toughness grades (A vs. B) are controlled.
Which steel grade has better welding performance, SS400 or Q235B?
SS400 and Q235B have practically the same great welding performance. Both are low-carbon structural steels with low carbon equivalents. You can weld them easily with standard methods like MIG, TIG, or stick welding without special pre-heating.
Which one is cheaper for bulk procurement Q235B or SS400?
Q235B and SS400 are nearly identical commodity carbon steels with base mill prices that are very close to each other, typically averaging around $450 to $600 per ton depending on global market conditions. However, Q235B is generally slightly cheaper or more cost-effective when sourced globally, particularly through Asian and Chinese supply chains.
