Steel bar introduction
Steel bar refers to steel for reinforced concrete and prestressed reinforced concrete. Its cross section is round, sometimes square with rounded corners. Including light round bars, ribbed bars, twisted bars.
Steel bar for reinforced concrete refers to straight or wire rod-shaped steel for reinforced concrete reinforcement. Its appearance is divided into two types: light round steel bar and deformed steel bar. The delivery status is two types: straight bar and round bar.
The light round steel bar is actually the small round steel and the round steel of ordinary low carbon steel. Deformed steel bars are ribbed bars on the surface, usually with two longitudinal ribs and horizontal ribs evenly distributed along the length. The shape of the horizontal ribs is spiral, herringbone, and crescent. Expressed in millimeters of the nominal diameter. The nominal diameter of the deformed steel bar is equivalent to the nominal diameter of the light round steel bar with the same cross section.
Steel bar performance
Reinforcement process performance includes many items. Different requirements can be put forward for the characteristics of different products. For example, ordinary steel bars require bending and reverse bending (reverse bending) tests, and some prestressed steels require repeated bending, torsion, and winding tests.
The form of all these tests simulates to different degrees the process of materials that may be involved in actual use. For example, ordinary steel bars need to be hooked or bent to form, and prestressed steel wires sometimes need to be wound. The ultimate bearing capacity of deformation, so the process performance is also a requirement for the plasticity of the material, and is consistent with the above requirements for ductility (elongation). Generally speaking, the steel with a large elongation has good process performance.
However, compared with the unidirectional stress state during stretching, the stress state of the process performance test is much more complicated. The deformation type and size of the sample are different in each direction (axial and radial). The structure and crystal structure of the steel are different. Particle size, harmful residual element content, especially any internal and surface defects that affect continuous deformation, such as cracks and inclusions, may affect and cause the test to fail. So in a sense, the process performance test can be said to be more stringent in assessing the quality of steel.
In addition, the reverse bending test of steel bars is essentially a strain aging sensitivity test. This is because molten steel generally contains a certain amount of free nitrogen (N), also known as residual nitrogen. When the content is too high, it can cause plastic deformation of the steel.