Q345B Z15 / Z25 / Z35 Steel Plate: High-Performance Z-Direction Steel
Q345B Z-direction steel plate is a low-alloy high-strength structural steel specifically processed to improve its mechanical properties in the thickness direction (Z-axis). By reducing impurities like sulfur and oxygen through advanced refining techniques, Q345B Z-grade plates effectively prevent lamellar tearing in heavy-duty welded structures.
At Huaxiao Metal, we provide premium Q345B steel with guaranteed through-thickness ductility levels: Z15, Z25, and Z35.
Our Z Direction plates ensure structural integrity in critical projects, minimizing the risk of lamellar tearing and enhancing the safety and longevity of your structures.
Available Dimensions & Supply Range
Material: Q345B
Grades: Z15, Z25, Z35
Direction: Z Direction – optimized for lamellar tearing resistance
Standards: Compliant with GB / EN 10025-5 standards
Thickness: 10 mm – 200 mm
Width: up to 3,500 mm
Length: up to 18,000 mm
Surface Treatment: Hot rolled, sandblasted, or coated to prevent rust
Delivery: Available worldwide with packaging to ensure safe transit
Custom cutting and project-based supply are available.
What is Q345B Z-Direction Steel?
The “Z” grade refers to the reduction of area (RA) measured in a tensile test perpendicular to the surface of the sheet metal. Standard structural steel may contain internal inclusions that can lead to delamination under high weld stress. Q345B Z series steel is specially designed to withstand these stresses, making it ideal for critical load-bearing joints.
Z Grade Performance Levels:
Q345B Z15: Minimum average reduction of area ≥ 15%.
Q345B Z25: Minimum average reduction of area ≥ 25%.
Q345B Z35: Minimum average reduction of area ≥ 35%.
Worried about lamellar tearing or failure of thick plate structures during welding? Our Z-axis steel plates are designed to prevent cracking, giving engineers and purchasing teams peace of mind when using our products.
Technical Specifications & Chemical Composition
To achieve Z-direction properties, the sulfur (S) content in Q345B is strictly controlled, often below 0.005% – 0.010%, which is significantly lower than standard Q345B plates.
Mechanical Properties (GB/T 5313 Standard)
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Z-Axis RA (Avg %) |
| Q345B Z15 | ≥ 345 | 470 – 630 | ≥ 20 | ≥ 15% |
| Q345B Z25 | ≥ 345 | 470 – 630 | ≥ 20 | ≥ 25% |
| Q345B Z35 | ≥ 345 | 470 – 630 | ≥ 20 | ≥ 35% |
Note: Performance values may vary slightly based on the thickness of the plate. Contact our technical team for specific data sheets.
Our Z Direction Steel Plates are engineered to minimize lamellar tearing, ensuring safety under high-stress conditions.
Why Use Q345B Z-Direction Plates?
Anti-Lamellar Tearing: Prevents structural failure in T-joints and corner joints where heavy welding is required.
Internal Purity: Produced using Vacuum Degassing (VD) or Electroslag Remelting (ESR) to ensure minimal non-metallic inclusions.
Excellent Weldability: Low carbon equivalent ensures high weldability without pre-heating in many applications.
Uniform Strength: Consistent mechanical properties across all three axes (X, Y, and Z).
Core Applications
Q345B Z-direction steel is widely used in projects where safety and structural integrity are non-negotiable:
High-Rise Buildings: Critical beam-to-column connections in steel skyscraper frames.
Bridges: Large-span bridge components subjected to complex multi-directional loads.
Offshore Engineering: Oil platforms, wind turbine foundations, and marine structures.
Heavy Machinery: Large crane bases, hydraulic supports, and pressure vessel components.
Quality Assurance & Testing
Every Q345B Z15/Z25/Z35 plate from Huaxiao Metal undergoes rigorous inspection to ensure compliance with international standards:
Ultrasonic Testing (UT): Performed to detect internal defects (Level I, II, or III per ASTM A578).
Z-Direction Tensile Test: To verify the reduction of area (RA) meets the specified grade.
MTC Certification: All plates are shipped with a Mill Test Certificate (EN 10204 3.1 or 3.2).
Custom Processing
We don’t just supply raw plates; we provide precision processing to meet your exact engineering drawings:
Precision Cutting: CNC Flame, Plasma, and Laser cutting for complex shapes.
Beveling Services: Professional edge preparation for immediate welding upon arrival.
Surface Treatment: Sandblasting (Sa2.5) and shop priming to prevent corrosion.
Third-Party Inspection: We support inspections by SGS, BV, ABS, or LR to guarantee Z-axis performance.
Why Choose Huaxiao Metal
Global Shipping: Reliable delivery to Europe, North America, Asia, and Middle East
Custom Processing: Tailored thickness, dimensions, and steel grades
Quality Assurance: ISO 9001 certified, GB and EN compliant
Technical Support: Professional advice on material selection, welding, and applications
Fast Quotation: Short lead times for bulk orders
FAQ – Q345B Z-Direction Steel
What is the main difference between Q345B and Q345B Z35?
Although Q345B and Z35 have the same chemical composition and yield strength (≥345 MPa), Q345B and Z35 undergo additional refining processes (e.g., vacuum desulfurization/electroslag remelting) to ensure a reduction of area (ψ_z) ≥35% in the thickness direction. This gives Z35 steel extremely high resistance to lamellar tearing during re-welding.
Does Q345B Z-direction steel require Ultrasonic Testing (UT)?
Yes. To guarantee Z-grade performance, all plates must pass Ultrasonic Testing (UT). We typically provide Level I or Level II testing according to ASTM A578 or GB/T 2970 to ensure no internal voids or inclusions.
Can Q345B Z25/Z35 be used as an equivalent to S355J2+Z35?
Yes, in many structural applications, Q345B Z35 is often equivalent to European S355J2+Z35 steel due to its similar yield strength and Z-axis ductility. However, please be sure to confirm the low-temperature impact testing requirements (e.g., -20°C) with our technical team first.
What is the lead time for custom-sized Z-direction plates?
We maintain a large stock of standard Q345B Z15/Z25/Z35 plates (10mm – 150mm thickness). Stock items can be shipped within 3-7 days, while custom mill runs typically take 30-45 days.
Can you provide custom thickness and sizes?
Yes, we offer custom thickness from 15mm to 200mm, widths up to 3000mm, and lengths up to 12,000mm based on client requirements.
Are your plates certified?
All Q345B Z Direction steel plates from Huaxiao Metal comply with GB/EN standards and are available with ISO 9001 certification, ensuring quality and reliability.
Get a Quote for Q345B Z-Direction Steel
As a professional Z-Direction Steel Plate supplier, Huaxiao Metal offers a wide range of thicknesses and sizes for Q345B Z-grade plates. Whether you need standard stock or custom-cut components, we are ready to support your project.
Contact us today for the latest price and lead times.
