Cold-rolled Ribbed Steel Bar Chemical Components and Specification (GB 13788-2000)
Ribbed bars are formed by mats rolling or cold drawn of round steel bar. As an important reinforcement bar in the field of construction,they are widely used, such as concrete structures, bridges, tunnels and others. In 2000, National GB13788 Standard was promulgated, and suppliers have to strictly abide by the standard producing ribbed bars in China.
Ribbed bars are divided into five groups by metalic elements. Group A, B, C, D and E. Each ribbed bar needs two code to specify its diameter, metalic element, grade and other detailed information. For example, when the code is 12HRB400, “12” indicates the diameter of ribbed bar is 12mm and “HRB400” illustrates that the grade of metalic elements is HRB400.
Group A:
Group A is composed of the metalic elements of Carbon Steel and Low Alloy steel and falls into three sub-groups: A1, A3 and A5. A1 is plain carbon steel without any alloy components. It can be further divided into three sub-grade and each of them has different tensile strength: HRB335 (yr395MPa), HRB400(yr450MPa) and HRB500 (yr540MPa). A3 is low alloy steel with little alloy components. It can be divided into two sub-grades: HRB335(yr335MPa) and HRB400(yr400MPa). A5 is low alloy steel with much more alloy componentsthan A3, which is often used to make rebars for special projects. It includes two sub-grade of HRB400 (yr400MPa) and HRB500 (yr500MPa).
The chemical composition of Group A steel are listed as following:
Chemical components:
Group A1
C：≤0.22%
Mn：≤1.75%
Si：≤0.55%
P：≤0.05
S：≤0.05%
Group A3
C：≤0.19%
Mn：≤1.60%
Si：≤0.55%
P：≤0.045
S：≤0.045
Cr：－
Ni：－
Group A5
C：≤0.18%
Mn：≤1.60%
Si：≤0.55%
P：≤0.042
S：≤0.042
Cr：≤0.20%
Ni：≤1.60%
Group B:
Group B is stainless steel and falls into two subgroup: B1 and B3. It refers to ordinary stainless steel which contains carbon while B3 refers to austenite/martensite stainless steel. B1 includes two sub-grades of HRB335(yr395MPa) and HRB400(yr450MPa). B3 includes two sub-grades of HRB400(yr400MPa) and HRB500(yr500MPa).
The chemical component of Group B are listed as following:
Group B1
C：≤0.22%
Mn：≤1.75%
Si：≤0.50%
P：≤0.06
S：≤0.06
Cr：≤16.50%
Ni：≤10.50%
Group B3
C：≤0.15%
Mn：≤1.60%
Si：≤0.60%
P：≤0.06
S：≤0.06
Cr：≤30.50%
Ni：≤9.50%
Group C:
Group C is made up of alloy steel and can be divided into two subgroup: C1 and C4. C1 includes two sub-grade of HRB335(yr395MPa) and HRB400(yr450MPa). C4 includes two sub-grade of HRB400(yr400MPa) and HRB500(yr500MPa).
The chemical component of Group C are listed as following:
Group C1
C：≤0.19%
Mn：≤1.60%
Si：≤0.50%
P：≤0.045
S：≤0.045
Cr：≤0.30%
Ni：≤0.60%
Group C4
C：≤0.19%
Mn：≤1.60%
Si：≤0.50%
P：≤0.045
S：≤0.045
Cr：≤1.60%
Ni：≤2.60%
Group D:
Group D is composed of low alloy steel and can be further divided into two subgroup: D1 and D4. D1 includes two sub-grade of HRB335(yr395MPa) and HRB400(yr450MPa). D4 includes two sub-grade of HRB400(yr400MPa) and HRB500(yr500MPa).
The chemical component of Group D are listed as following:
Group D1
C：≤0.20%
Mn：≤1.30%
Si：≤1.00%
P：≤0.075
S：≤0.045
Cr：≤0.30%
Ni：≤0.60%
Group D4
C：≤0.19%
Mn：≤1.60%
Si：≤1.00%
P：≤0.045
S：≤0.045
Cr：≤1.21%
Ni：≤2.00%
Group E:
Group E is composed of high alloy steel and can be further divided into two subgroup: E1 and E4. E1 includes two sub-grade of HRB335(yr395MPa) and HRB400(yr450MPa). E4 includes two sub-grade of HRB400(yr400MPa) and HRB500(yr500MPa).
The chemical component of Group E are listed as following:
Group E1
C：≤0.17%
Mn：≤1.50%
Si：≤0.60%
P：≤0.06
S：≤0.06
Cr：≤2.00%
Ni：≤2.00%
Group E4
C：≤0.17%
Mn：≤1.50%
Si：≤0.60%
P：≤0.06
S：≤0.06
Cr：≤3.50%
Ni：≤3.50%
In summary, ribbed bars are divided into five groups by metalic elements. Each ribbed bar needs two code to specify its diameter, metalic element, grade and other detailed information. Group A, B, C, D and E ribbed bars have different chemical components and different tensile strength grades. Suppliers have to strictly abide by the National GB13788 Standard producing ribbed bars in China.
