What are the mechanical properties of steel?
The mechanical properties of steel refer to the yield strength, tensile strength, elongation, cold bending properties and impact toughness of steel under standard conditions, also known as mechanical properties.
1. Yield strength
The strength corresponding to the yield platform in the unidirectional tensile stress-strain curve of steel is called yield strength, also known as yield point, which is an important mechanical characteristic of construction steel. The yield point is the end point of elastic deformation, and the stress does not increase over a large deformation range, forming an ideal elastoplastic model. Both mild and low-alloy steels have obvious yield platforms, while heat-treated steels and high-carbon steels do not.
2. Tensile strength
Unidirectional tensile stress-The strength corresponding to the high point in the strain curve is called tensile strength, which is the large stress value that steel can withstand. Since the steel has a large residual deformation after yielding, it has exceeded the normal use range of the structure, so the tensile strength can only be used as a safety reserve of the structure.
3. Elongation
Elongation is the percentage of the permanent deformation of the specimen at break to the original calibration length. Elongation represents the plastic deformation ability of steel before breaking, which allows the structure to be manufactured without significant damage even if the steel is subjected to shear, stamping, bending and pounding. The greater the elongation, the better the plasticity and ductility of the steel
Yield strength, tensile strength and elongation are the three important mechanical properties of steel. All steel in the steel structure should meet the specifications for these three indicators.
4. Cold bending performance
According to the thickness of the specimen, the specimen is bent 180° according to the specified bending diameter under normal temperature conditions, and its surface is qualified for cold bending without cracks and delamination. Cold bending performance is a comprehensive index, cold bending qualification on the one hand means that the plastic deformation ability of steel meets the requirements, on the other hand also means that the metallurgical quality of the steel (particle crystallization and non-metallic inclusions, etc.) meets the requirements. When steel needs to have good cold and hot processing process performance in important structures, there should be a cold bending test qualification guarantee.
5. Impact toughness
Impact toughness is the ability of steel to resist impact loads and is measured by the total energy absorbed when the steel breaks. The properties of steel shown in unidirectional tensile tests are static properties, and toughness is dynamic properties. Toughness is a comprehensive indicator of steel strength and plasticity, and the lower the toughness, the greater the possibility of brittle failure. The toughness value is greatly affected by temperature, and when the temperature is lower than a certain value, it will drop sharply, so the requirements should be made according to the corresponding temperature.
