Hot rolled steel plate for structural load-bearing and heavy manufacturing purposes
Product Name: Hot Rolled Carbon Structural Steel Plate/Low Alloy High Strength Steel Plate
Execution standard: GB/T 709 (Dimensions, Appearance, and Weight) GB/T 3274、GB/T 1591
Common materials: Q235B, Q355B, Q355C, Q355ND
Core positioning: welded structural components, heavy machinery chassis, building steel structures
1、 What is' hot rolling '? Craftsmanship determines its character
Hot rolled steel plate refers to a steel plate that is rolled above the recrystallization temperature (usually above 1000 ℃). At this time, the steel is in an austenitic state, with excellent plasticity and low deformation resistance.
This process endows hot-rolled plates with two distinct "personality" characteristics:
Balance between strength and toughness: Through controlled rolling and controlled cooling (TMCP) technology, good comprehensive mechanical properties can be obtained without adding too many alloying elements.
Surface Inclusiveness: Due to high temperature oxidation, a layer of blue gray oxide skin (Fe ∝ O ₄) will form on the surface, which makes it unsuitable for direct use as an appearance part, but very suitable for subsequent sandblasting, shot blasting, and painting.
Hot rolled plates have always been the main material in fields such as bridges, building steel structures, and construction machinery arm frames due to their excellent welding performance and cost advantages.
2、 Material spectrum: from ordinary carbon to low alloy
According to the design load and ambient temperature, hot-rolled plates provide a rich material gradient:
Material Classification
Representative brand
yield strength
impact temperature
Typical application scenarios
carbon steel
Q235B
≥235MPa
20℃
Factory columns, platform steel plates, and general supports
low-alloy steel
Q355B
≥355MPa
20℃
Crane main beam, excavator track plate, H-beam web plate
low-temperature steel
Q355C/D/E
≥355MPa
0℃ / -20℃ / -40℃
Outdoor steel structures, low-temperature storage tanks, and wind turbine towers in northern China
weathering steel
Q355NH
≥355MPa
20℃
Railway containers, outdoor sculptures, landscape bridges
Material selection suggestion:
If the project is located in a northern region with lower temperatures, it is recommended to upgrade the material from Q355B to Q355D or Q355E to prevent brittle fracture of the steel at low temperatures.
3、 Dimensional accuracy and cutting processing
The dimensional tolerance of hot-rolled plates is slightly wider than that of cold-rolled plates, but this does not affect their structural safety.
Thickness deviation: Implement Class N (positive deviation) or Class A (symmetrical deviation) in GB/T 709 standard. For example, for a 20mm thick regular board, the actual thickness may fluctuate between 19.7mm-20.3mm.
Cutting method:
Flame cutting: Low cost, suitable for heavy plates with a thickness greater than 50mm, but with a large heat affected zone.
Plasma cutting: fast speed, vertical incision, suitable for medium and thin plates (10mm -50mm).
Laser cutting: High precision, suitable for cutting complex shaped parts, but has certain limitations on thickness (usually<25mm).
Attention: When flame cutting plates with a thickness exceeding 25mm, it is recommended to preheat the steel plate to prevent microcracks from forming at the cut due to rapid cooling.
4、 Welding performance and pretreatment
Hot rolled plates are materials made for welding, but attention to details is still necessary during welding:
Pre weld cleaning: The oxide scale and rust in the area to be welded must be thoroughly removed, otherwise it is easy to cause slag inclusion and porosity in the weld seam.
Welding parameters: For low-alloy steels such as Q355B, due to their slightly higher carbon equivalent, it is recommended to preheat them appropriately (80 ℃ -120 ℃) during high constraint welding. After welding, stress can be released by hammering.
Pre treatment: Before painting, it is recommended to perform sandblasting treatment (Sa2.5 grade) on the hot-rolled plate to thoroughly remove the oxide scale, so as to ensure the long-term adhesion of the paint and prevent "peeling" phenomenon.
5、 The complementary relationship between hot-rolled plate and cold-rolled plate
dimension
hot-rolled plate
cold-rolled sheet
surface state
Rough, with oxidized skin
Smooth, silver bright color
thickness range
1.5mm-200mm+(wide range)
0.15mm-3.0mm (thinner)
Intensity level
High (up to 1000MPa or above)
Medium to low (usually<800MPa)
main purpose
Structural components, welded components
Stamping parts, appearance parts
Summary in one sentence: Find hot rolling for strength and cold rolling for beauty.
6、 Supply and Service Description
We have stock of hot-rolled plain and low-alloy plates with a thickness of 6mm to 100mm, covering commonly used specifications such as 2000mm, 2200mm, and 2500mm in width. Support integrated services such as CNC cutting, drilling, and groove processing.
For large-scale steel structure projects, we can provide customized rolling services with controllable delivery time and quality. All products come with the original steel mill warranty certificate (MTC) and support third-party inspection.
During storage, the surface oxide scale of hot-rolled plates may continue to rust (yellow spots), which is a normal phenomenon and does not affect the internal material properties. If there are appearance requirements, it is recommended to perform shot blasting and rust removal treatment.
