The quality standards of Chinese deformed steel bars in China mainly follow GB1499.2 – 2024 “Steel for the Reinforcement of Concrete – Part 2: Hot – Rolled Ribbed Bars”. The main quality standards include the following aspects:
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Chemical Composition
- The main elements include carbon (C), silicon (Si), manganese (Mn), phosphorus (P), and sulfur (S), etc. The carbon content affects the strength of steel. An appropriate amount of carbon can increase strength, but too much carbon will reduce toughness. Silicon can improve the strength and hardness of steel, and manganese can increase the toughness and strength of steel. The standard strictly limits the content of these elements. For example, the carbon content should not exceed a certain proportion, and the content of phosphorus and sulfur should not exceed 0.045%. According to requirements, elements such as vanadium (V), niobium (Nb), and titanium (Ti) can also be added to the steel.
- Different grades of deformed steel bars have different carbon equivalent requirements. For example, the carbon equivalent of HRB400, HRB400E, HRBF400, and HRBF400E should not exceed 0.54%; the carbon equivalent of HRB500, HRB500E, HRBF500, and HRBF500E should not exceed 0.55%; and the carbon equivalent of HRB600 should not exceed 0.58%.
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Mechanical Properties
- Tensile Strength: It is an important indicator to measure the ability of deformed steel bars to resist tensile failure. Different grades of deformed steel bars have different requirements for tensile strength. For example, the tensile strength of HRB400 – grade steel bars should be ≥540MPa, and the tensile strength of HRB500 – grade steel bars should be ≥630MPa.
- Yield Strength: It refers to the stress when the steel begins to produce obvious plastic deformation. The yield strength of HRB400 – grade steel bars should be ≥400MPa, and the yield strength of HRB500 – grade steel bars should be ≥500MPa, etc.
- Elongation: It reflects the plastic deformation ability of steel. Generally, the elongation of HRB400 – grade steel bars should be ≥16%, and the elongation of HRB500 – grade steel bars should be ≥15%.
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Dimensional Deviation
- Diameter: The diameter of deformed steel bars is allowed to have a certain deviation range. Different specifications of deformed steel bars have different diameter deviation standards to ensure that the size of deformed steel bars meets the design and construction requirements.
- Length: Usually, the fixed – length of deformed steel bars is 9 meters, 12 meters, etc., and the length deviation also needs to be within the specified range.
- Bending Degree: The bending degree of deformed steel bars is limited to ensure that it can be smoothly installed and stressed during use.
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Surface Quality
- There should be no cracks, folds, scabs, oil stains, and other defects that affect the use on the surface of deformed steel bars. The surface should have longitudinal ribs and transverse ribs, and the shape, size, and spacing of the ribs should meet the standard requirements.
- The grade mark, the serial number of the production enterprise (the last three – digit number of the license), and the nominal diameter in millimeters should be rolled on the surface of the steel bar for identification and traceability.
