What is the basic knowledge of rebar

by Zhi shang Metallic material

There are many kinds of rebar, usually classified by chemical composition, mechanical properties, production technology, etc.

1. Carbon steel reinforcement bar and ordinary low alloy reinforcement bar are divided by chemical composition. Carbon steel reinforcement according to the amount of carbon, and is divided into low carbon steel reinforcement (carbon content less than 0.25%, such as I steel), carbon steel reinforcement (carbon content 0.25%~0.7%, such as IV steel), high carbon steel reinforcement (carbon content 0.70%~1.4%, such as carbon steel wire), carbon steel in addition to containing iron and carbon elements, There is also a small amount of silicon, manganese, phosphorus, sulfur and other impurities in the smelting process.

Ordinary low alloy steel bar is in low carbon steel and medium carbon steel to add a small amount of alloy element, high strength and good comprehensive performance of steel, commonly used in steel alloy elements such as silicon, manganese, vanadium, titanium, ordinary low alloy steel bar main varieties are: 20MnSi, 40Si2MnV, 45SiMnTi and so on. The content of various chemical components has great influence on the mechanical properties and weldability of steel bars.

General building reinforcement under normal circumstances do not make the chemical composition of the test, but in the selection of reinforcement, still need to pay attention to the chemical composition of the reinforcement. The following describes the influence of five main elements in the steel bar on its properties.

Carbon (C) : carbon and iron form compound carburizing (Fe3C), hard and brittle, steel carbon content increases carburizing volume, steel hardness and strength is increased, and the plasticity and toughness is reduced, the material becomes brittle, its weldability is also poorer. Manganese (Mn) : It is steelmaking as a deoxidizer added to the steel, can make the steel plasticity and toughness decrease, so the content should be appropriate, the general content is below 1.5%.

Silicon (Si) : It is also used as a deoxidizer added to steel, can make steel strength and hardness increase. Sometimes it is deliberately added to make it more than 0.4%, but not more than 0.6%, because it works as well as carbon (C) when it is high.

Sulfur (S) : It is a harmful impurity that causes hot brittleness in steel and causes hot cracks in steel during welding. Its presence in steel reduces the plasticity and toughness of steel.

It is generally required that the content should not exceed 0.045%. Phosphorus (P) : It is also a harmful substance.

Phosphorus makes steel prone to cold brittleness and deteriorates the welding performance of steel, especially at 200℃, it can cause cold cracks in steel or weld. It is generally required that the content is less than 0.045%, even some low alloy steel must be controlled between 0.050% and 0.120%.

Two, according to the mechanical properties of reinforced concrete structure with hot rolled steel bars, most of the past carbon steel. With the development of ordinary low alloy steel, the current hot rolled steel bar, except for carbon steel No. 3 steel, are all ordinary low alloy steel.

According to the mechanical properties of the steel is divided into four levels: I steel, 235/370, II steel, 335/510, Ⅲ steel, 370/570, Ⅳ steel, 540/835, the molecule is the yield strength, the denominator is tensile strength, the unit is MPa. 3. According to the production process and rolling shape, reinforced concrete steel bars are divided into hot rolled ribbed steel bars (GB1499-91), waste heat treatment steel bars (GB13014-91), hot rolled round steel bars (GB13013-91) and ordinary mild steel hot rolled disc bars.

1. Hot rolled ribbed rebar Hot rolled ribbed rebar is a finished steel bar formed by hot rolling and naturally cooled. Its cross section is usually circular, and the surface with two longitudinal ribs and along the length direction of uniform distribution of the transverse rib, when the longitudinal section of the transverse rib is crescent shape, and the longitudinal rib does not intersect, called crescent steel; When the longitudinal section of the transverse rib is the same height and intersects with the longitudinal rib, it is called the equiheight ribbed steel bar. Its shape is shown in Figure 1-1 and Figure 1-2. Grade Ⅱ and Ⅲ ribbed steel bar adopts the surface shape of the crescent rib, and its size and allowable deviation should conform to the provisions in Table 1-1.

2, waste heat treatment of steel reinforcement refers to the steel hot rolled molding immediately through water, surface cooling control, and then the core of the waste heat itself to complete tempering treatment of the finished steel bar, it is also with ribbed steel, at present only the crescental steel, the steel surface and section shape and hot rolled ribbed steel bar the same, waste heat treatment with ribbed steel grade Ⅲ.