Q345NQR2, Q345NQR3, and Q345NQR4 are all Chinese atmospheric corrosion-resistant (weathering) structural steels, specifically designed for use in harsh environments-particularly within the field of railway vehicle manufacturing.
These steels are typically supplied in a hot-rolled or normalized condition and possess excellent weldability as well as superior resistance to high-temperature corrosion. According to the provisions of the TB/T 1979-2014 standard, the primary distinctions among them lie in their respective specific grades of low-temperature toughness and their designated applications within railway components.
Introduction To Q345NQR2 vs. Q345NQR3 vs. Q345NQR4
Q345NQR2 is a Chinese-produced atmospheric corrosion-resistant steel that complies with the TB/T 1979-2014 standard and is specifically designed for railway rolling stock. This steel grade exhibits superior atmospheric corrosion resistance compared to carbon steel. It is frequently utilized in the manufacture of transportation components that demand high levels of strength, durability, and low maintenance.
Q345NQR3 is a specialized Chinese-manufactured atmospheric corrosion-resistant steel, designed to ensure exceptional durability in harsh and exposed environments. Classified as a high-strength low-alloy steel, it has been specially modified to enhance its corrosion resistance, making it an ideal choice for the fabrication of shipping containers, railway rolling stock, and outdoor structures.
Q345NQR4 is a high-strength, atmospheric-corrosion-resistant steel widely utilized in specialized fields that impose rigorous requirements on both durability and environmental resistance. Classified within China's series of weather-resistant structural steels, this grade is frequently employed in the manufacturing of rail vehicles and railway freight cars, owing to its exceptional comprehensive performance.
Q345NQR2 vs. Q345NQR3 vs. Q345NQR4:Chmical Composition Compration
The primary distinction lies in the specific alloying elements added to enhance corrosion resistance-typically comprising titanium (Ti), copper (Cu), and rare earth elements (RE)-which are designed to improve atmospheric corrosion performance, making them particularly suitable for the high-end rail transit sector.
| Element | Q345NQR2 (Common Grade) | Q345NQR3 (Enhanced) | Q345NQR4 (Higher Resistance) |
|---|---|---|---|
| C | ≤ 0.18% | ≤ 0.16% | ≤ 0.16% |
| Si | ≤ 0.55% | ≤ 0.55% | ≤ 0.55% |
| Mn | 1.00-1.60% | 1.00-1.60% | 1.00-1.60% |
| P | 0.07-0.15% | 0.07-0.15% | 0.07-0.15% |
| S | ≤ 0.035% | ≤ 0.030% | ≤ 0.030% |
| Cu | 0.20-0.40% | 0.30-0.50% | ≥ 0.30% (often higher) |
| Cr | 0.30-0.65% | 0.40-0.80% | 0.50-1.00% |
| Ni | Trace/Added | Added | Often Added |
| Ti/RE | Added | Added | Added |
Q345NQR2 vs. Q345NQR3 vs. Q345NQR4:Mechanical Properties Compration
Q345NQR2, Q345NQR3, and Q345NQR4 all belong to the Q345 series, characterized by high strength, good weldability, and resistance to atmospheric corrosion. The primary difference among them lies in their low-temperature impact toughness.
| Feature | Q345NQR2 | Q345NQR3 | Q345NQR4 |
| Yield Strength | ≥345 MPa | ≥345 MPa | ≥345 MPa |
| Tensile Strength | 490-630 MPa | 490-630 MPa | 490-630 MPa |
| Elongation A(%, min) | ≥24 | ≥24 | ≥24 |
| Impact Temp | +20°C | 0°C | -20°C |
| Cold Resistance | Standard | High | Very High |
Q345NQR2 vs. Q345NQR3 vs. Q345NQR4:Main Applications Compration
The differences among Q345NQR2, Q345NQR3, and Q345NQR4 typically lie in their requirements for impact toughness under various low-temperature environments-a characteristic that determines their suitability for specific climatic conditions and application scenarios.
Q345NQR2: Standard / Warm Climate Applications
Regional Rail Vehicles: Passenger and freight vehicles operating exclusively in tropical or subtropical regions.
Urban Rail Transit: Subway cars and light rail vehicles operating within underground tunnels or indoor environments where temperatures remain stable.
Static Containers: Shipping containers utilized in ports situated in warm waters or within indoor storage facilities.
General Machinery: Components and structural brackets for small-scale vehicles operating in temperate climates.
Q345NQR3: Temperate / Transitional Zone Applications
Inter-provincial Freight Vehicles: Standard railway freight cars traveling between southern and central regions, where winter temperatures frequently hover near the freezing point.
Container Infrastructure: Shipping containers utilized for intermodal (sea-to-land) transport within temperate regions.
Outdoor Electrical Equipment: Components for power transmission towers or outdoor equipment enclosures situated in regions with mild winter climates.
Road Transport: Specialized truck bodies or trailers requiring a high degree of both lightweight construction and corrosion resistance.
Q345NQR4: Extreme Cold & Heavy-Load Applications
Heavy-Load Coal Freight Cars (C70/C80): This constitutes the primary application domain for this specific steel grade.
High-Altitude Railways: Railway vehicles deployed on high-altitude lines, such as the Qinghai–Tibet Railway.
Arctic / Sub-Arctic Infrastructure: Railway bridges, signal towers, and structural components utilized in high-latitude regions.
Mining Equipment: Heavy-duty transport vehicles utilized in open-pit mines located in cold-climate regions.
How To Select:Q345NQR2 vs. Q345NQR3 vs. Q345NQR4
The choice between Q345NQR2, Q345NQR3, and Q345NQR4 depends primarily on the low-temperature impact toughness and specific level of atmospheric corrosion resistance required by your project.
Analysis of Temperature Environment:For harsh northern or polar environments, Q345NQR4 must be selected to prevent brittle fracture; conversely, for temperate regions with mild climates, Q345NQR2 or Q345NQR3 is sufficient.
Assessment of Structural Stress:For structures subject to vibration or high fatigue loads, priority should be given to steel grades with higher toughness levels (R3/R4) to effectively resist crack propagation.
Welding and Processing:These steel grades generally exhibit good weldability; however, for higher grades with greater alloy content (such as NQR4)-particularly when dealing with thicker sections-strict preheating and welding process controls may be required to prevent cold cracking.
Cost Considerations:Steel grades with higher specifications and superior performance (such as NQR4) typically entail relatively higher costs.
Packaging & Logistics Description
Standard Export Packaging: Waterproof paper + Steel strapping + Wooden pallets.
Flexible Options: OEM customized packaging or bulk shipment.
Global Logistics: Supports FOB and CIF trade terms, or offers door-to-door delivery services with real-time tracking.
If you are interested in Q345NQR2, Q345NQR3, or Q345NQR4 atmospheric corrosion-resistant steel, please feel free to contact us at any time.
As a leading Chinese manufacturer of Q345NQR2, Q345NQR3, and Q345NQR4 atmospheric corrosion-resistant steel, GNEE boasts a wealth of industry experience spanning 20 years. Our warehouses maintain a standing inventory of over 50,000 tons, ensuring that orders can be dispatched in as little as seven days. Regarding quality assurance, we are a dual-certified supplier holding both API and ISO certifications, and we welcome inspections by third-party agencies such as SGS, BV, and Lloyd's.
By choosing our Q345NQR2, Q345NQR3, or Q345NQR4 atmospheric corrosion-resistant steel products, you will benefit from our comprehensive, customer-centric support services as well as our extensive value-added processing capabilities. We would be delighted to provide full-spectrum support and assistance for your project.
Contact now to get Q345NQR2 atmospheric corrosion-resistant steel
| Product Name | Weather Resistant Steel Plate |
| Length | 4m-12m or as required |
| Width | 0.6m-3m or as required |
| Thickness | 0.1mm-300mm or as required |
| Standard | AISI,ASTM,DIN,JIS,GB,JIS,SUS,EN,etc. |
| Technique | Hot rolled |
| Surface Treatment | Clean, blasting and painting according to customer requirement |
| Thickness tolerance | ±0.1mm |
| Material | Q345NQR2/Q345NQR3/Q345NQR4 |
| Application | It is mainly used to make structural parts such as car girder, beam, transmission shaft and car chassis parts, which can reduce the weight of the parts. |
| MOQ | 1tons.We also can accept sample order. |
| Shipment time | Within 15-20 workdays after receiving deposit or L/C |
| Export packing | Waterproof paper, and steel strip packed. Standard Export Seaworthy Package.Suit for all kinds of transport,or as required |
| Capacity | 250,000 tons/year |
How does Q345NQR2 achieve atmospheric corrosion resistance?
By adding elements like Copper (Cu), Chromium (Cr), and Nickel (Ni), the steel forms a dense protective patina that prevents deep rusting.
Can Q345NQR2 be replaced by Q345NQR4?
Yes. Q345NQR4 is a higher-quality grade with better low-temperature toughness. It can replace Q345NQR2 safely, though it may be more expensive.
Does Q345NQR steel need painting?
It can be used unpainted to develop a natural rusted look, but in the railway industry, it is often painted for double protection against harsh chemicals and environments.
What is the yield strength of the Q345NQR3 series?
The minimum yield strength is 345 MPa for thicknesses up to 16mm. Strength may slightly decrease for thicker plates.