Low alloy high-strength plate · Q355 series bridge and vehicle manufacturing special
Product Name: Low alloy high-strength structural steel plate
Execution standard: GB/T 1591-2018 (Low alloy High strength Structural Steel)
Core materials: Q355B, Q355C, Q355D
Main applications: highway bridges, railway steel bridges, commercial vehicle chassis, rail vehicle bodies
1、 Why do bridges and vehicles prefer the Q355 series?
In the fields of bridge construction and vehicle manufacturing, reducing self weight and enhancing load-bearing capacity have always been a core contradiction. Although traditional Q235B plain carbon steel is low-cost, it appears inadequate under conditions of large spans and heavy loads.
The Q355 series low-alloy high-strength steel has achieved a significant increase in strength by adding trace alloying elements such as Mn, Si, V, Nb, etc. Compared to Q235B, the yield strength of Q355 has increased by about 50%. This means that thinner steel plates can be used when bearing the same load, significantly reducing the weight of bridges and vehicles, saving foundation costs or increasing the effective load of vehicles.
2、 Temperature adaptability: The meanings of suffixes B, C, and D
The letters after Q355 represent the impact test temperature, which is a key indicator for material selection:
Material Grade
Impact test temperature
Core Features
Typical application scenarios
Q355B
20℃
Room temperature impact energy ≥ 34J, mature process
Bridges and general engineering machinery in the southern region of the Yangtze River
Q355C
0℃
Better low-temperature toughness and strong resistance to brittle fracture
Outdoor steel structures and bus frames in Central and East China regions
Q355D
-20℃
Stable service performance in high-altitude regions
Northeast/Northwest bridges, railway freight cars, refrigerated trucks
Selection logic:
For bridges crossing rivers or located in areas with large temperature differences, it is recommended to use at least Q355C; If the vehicle operates in an environment below -20 ℃ (such as Russian export orders or extremely cold regions in China), Q355D is a reliable choice.
3、 Key performance requirements in bridge engineering
Bridges are not only load-bearing structures, but also durable components exposed to the atmosphere for a long time.
Resistance to layered tearing (Z-direction performance):
Large bridge node plates bear significant tensile forces in the thickness direction and are prone to layered tearing. Q355B-Z15/Z25/Z35 can be selected to change the morphology of inclusions through calcium treatment, significantly improving the thickness direction cross-sectional shrinkage rate.
Weldability:
The Q355 series carbon equivalent (Ceq) is strictly controlled (usually ≤ 0.45%), and with a reasonable preheating process, it can effectively avoid welding cold cracks.
Weather resistance:
If the bridge is designed to be paint free, a weather resistant version (such as Q355NHD) can be selected, which uses alloy elements to form a dense rust layer and block corrosion from deepening.
4、 Processing adaptability in vehicle manufacturing
In vehicle structures such as semi trailers, mixer trucks, and crane booms, the Q355 series exhibits excellent processing performance:
Bending Forming:
Q355B/D has good cold formability. When making U-shaped tanks or boxes, it is recommended to bend the inner radius ≥ 2 times the plate thickness to prevent cracks from appearing on the outer arc side.
Wear resistance considerations:
Although Q355 focuses on strength, it is often used in conjunction with NM series wear-resistant steel in worn parts such as mixer blades, forming a combination structure of "strong and tough skeleton+wear-resistant lining".
Lightweight design:
By replacing Q235B with Q355D, the plate thickness can be reduced by about 30%, and the overall weight reduction effect of the vehicle is significant, which directly translates into improved fuel economy.
5、 Performance comparison with ordinary carbon steel
performance metrics
Q235B
Q355B
Q355D
Yield strength (MPa)
≥235
≥355
≥355
Tensile strength (MPa)
370‑500
470‑630
470‑630
-20 ℃ impact energy (J)
not required
not required
≥34
Carbon equivalent Ceq (%)
≈0.17
≈0.40
≈0.40
comprehensive cost
benchmark
slightly higher
moderately high
6、 Supply and Service Description
We have stock of Q355B/C/D series low-alloy high-strength plates with a thickness ranging from 6mm to 60mm, covering widths of 2000mm, 2200mm, 2500mm, and other specifications. For bridge projects, we can provide Z-directional performance steel plates and recommended welding materials.
Support integrated services such as CNC cutting, groove processing, sandblasting rust removal, and anti-corrosion coating (such as epoxy zinc rich primer). All products come with third-party testing reports, including chemical analysis, mechanical properties, and impact test data.
Before welding construction, it is necessary to determine the appropriate preheating temperature based on the plate thickness and ambient temperature to ensure welding quality.
