What is Carbon Structural Steel?
Carbon structural steel is a type of steel material. The “Q” represents the yield strength of this material, and the following “235” indicates that the yield value of this material is around 235 MPa. This yield value decreases as the material thickness increases. Due to its moderate carbon content, it offers good comprehensive properties, with a favorable balance of strength, plasticity, and weldability, making it the most widely used grade. It is often rolled into wire rod, or steel sections such as round steel, square steel, flat steel, angle steel, I-beam, channel steel, window frame steel, as well as medium and heavy steel plates. It is extensively used in building and engineering structures. It is used to make reinforcing bars or to build factory building frames, high-voltage transmission towers, bridges, vehicles, boilers, containers, ships, etc., and is also widely used for mechanical parts where performance requirements are not exceptionally high. Grades C and D can also be used for certain specialized steel applications.
Q235 Carbon Structural Steel Grades
Q235A, Q235B, Q235C, Q235D. These are grade distinctions, primarily indicating different impact test temperatures.
The difference between A, B, C, and D lies in the impact test temperature specified in their properties. Specifically: Q235A grade requires no impact test; Q235B grade requires impact test at 20°C (room temperature); Q235C grade requires impact test at 0°C; Q235D grade requires impact test at -20°C. The impact energy values also differ at these various impact temperatures.
Element Content: The sulfur content decreases sequentially from A, B, C, to D; The phosphorus content is the same for A and B, lower for C, and the lowest for D.
Chemical Composition of Q235 Various Grades
Low Alloy Steel Plate
Q235 Chemical Composition (Mass Fraction, %)
| Grade | C (max) | Mn (max) | Si (max) | S (max) | P (max) |
| Q235A | 0.14~0.22 | 0.30~0.65 | ≤0.30 | ≤0.050 | ≤0.045 |
| Q235B | 0.12~0.20 | 0.30~0.67 | ≤0.30 | ≤0.045 | ≤0.045 |
| Q235C | ≤0.18 | 0.35~0.80 | ≤0.30 | ≤0.040 | ≤0.040 |
| Q235D | ≤0.17 | 0.35~0.80 | ≤0.35 | ≤0.040 | ≤0.035 |
Regarding deoxidation methods, they can be denoted by F, b, Z representing rimmed steel, semi-killed steel, and killed steel, respectively. Rimmed steel is incompletely deoxidized steel, with relatively poor plasticity and toughness. Welded structures made with this material are prone to cracking at the joints under dynamic loads. It is not suitable for low-temperature work and can sometimes exhibit hardening phenomena. In contrast, killed steel is of high and uniform quality, with good plasticity and toughness.
Mechanical Properties of Q235
Tensile Strength (σb/MPa): 375-500
Elongation (δ5/%):
Tensile Strength (σb/MPa)
| Material Thickness or Diameter (a) | Elongation (δ5/%) ≥ |
| a ≤ 16mm | 26 |
| a > 16-40mm | 25 |
| a > 40-60mm | 24 |
| a > 60-100mm | 23 |
| a > 100-150mm | 22 |
| a > 150mm | 21 |
In steel plates, this is the most common material, belonging to the common steel plate series. It was previously referred to as A3.
Execution Standards: External standard: GB/T709-2006 “Dimensions, Shape, Weight and Tolerances for Hot-Rolled Steel Plates and Strips”, Internal standard: GB/T3274-2007 “Hot-rolled thick steel plate and strip of carbon structural steel and low-alloy structural steel”
Q255 is a type of carbon structural steel.
【Chemical Composition】(mass fraction) (%)
C: 0.18-0.28
Mn: 0.40-0.70
Si: ≤0.30
S: ≤0.050 (Grade A), ≤0.045 (Grade B)
P: ≤0.045
Deoxidation Method: Z
【Mechanical Properties】
Tensile Strength (σb/MPa): 410-550
Elongation (δ5/%):
| Material Thickness or Diameter (a) | Elongation (δ5/%) ≥ |
| a ≤ 16mm | 24 |
| a > 16-40mm | 23 |
| a > 40-60mm | 22 |
| a > 60-100mm | 21 |
| a > 100-150mm | 20 |
| a > 150mm | 19 |
【Cold Bending Properties】
180° Cold Bend Test
| Specimen Width (B) / Material Thickness or Diameter (a) | Bend Diameter (d) |
| B=2a ≤ 60mm | d=2a |
| B=2a > 60～100mm | d=3a |
| B=2a > 100～200mm | d=3.5a |
Used for manufacturing parts that do not require very high strength, such as bolts, keys, levers, shafts, tie rods, and various steel sections and plates for steel structures.
Jiyuan Iron & Steel’s main process is the long process production route, with excellent ironmaking, steelmaking, rolling, and testing equipment, advanced technology, reaching international advanced levels. It is a base producing a wide variety and full specification range of special quality steel bars and wire rods. Our products, with their excellent performance, provide reliable, efficient, and safe solutions for various industries. If you have product needs, please feel free to contact us.
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