YORGEE INSPECTION 

Hot-rolled Ribbed Steel Bar Used for GB1499—1998 Reinforced Concrete
Ribbed Steel Bar: usually its cross section is round, and there are two longitudinal ribs and even distributed transverse ribs along a direction of length in its surface.
Crescent Ribbed Bar: the longitudinal section of cross rib is crescent and the cross rib will not cross with longitudinal rib.
Longitudinal Rib: even and continuous rib paralleling to axial line of bar.
Lateral Rib: other ribs not paralleling to longitudinal rib.
Nominal Diameter：diameter of round equaling to nominal cross section area of bar.
Relative Projection Rib Area: ratio between the projection area of lateral rib on vertical plane of bar axial line and multiplied value of nominal perimeter of bar and interspaces between lateral rib.
Rib Height：Distance between the rib top and the core point vertical to plane of axial line. 
Interspaces between Ribs: Distance between two centers of two contiguous lateral ribs measured paralleling to axial line of bar.
The brand of hot-rolled ribbed bar is made up of HRB and minimum yield point of brand. H, R, B refer to first letter of following three words: Hot-rolled, Ribbed and bars respectively. Hot-rolled ribbed bar is classified as following brand: HRB335, HRB400, HRB500.
 (I) Dimensions, shape, weight and tolerances 
1. Scope of nominal diameter and recommended diameter
The scope for nominal diameter of steel bars is 6-50mm while its recommended diameters are 6, 8, 10, 12, 16, 20, 25, 32, 40 and 50mm.
2. Nominal cross-section area and theoretical weight
See following Table 4-1-66 for nominal cross-section area and theoretical weight of steel bar.
Table 4-1-166

Note: the nominal weight is calculated basing on density is subject to 7.85g/cm3
3. Surface shape and dimensional tolerance of ribbed bar
(1) Cross rib of ribbed bar should accord with following provisions:
①Angular separationβbetween the cross rib and the axial line of bar should be less than 45 degree, when it is more than 70 degree, the direction of both sides cross ribs on the bar should be in reverse.
②The interspaces between cross ribs should be less than 0.7 times of nominal diameter of bar.
③Angular α between cross-rib sides and bar surface should not be less than 45 degree.
④The total interspaces (including cross-rib width) between cross-rib ends on relative two sides of bar should be less than 20% of nominal perimeter of bar.
⑤The relative rib area should not be less than 0.055 when the nominal diameter of bar is less than 12mm, 0.060 when nominal diameter of bar is 14mm and 16mm, and 0.065 when nominal diameter of bar is more than 16mm.
(2) When the crescent rib is adopted in the ribbed bar, refer to Figure 4-1-3 for its shape (omit here), and its dimension and tolerance should meet the provisions listed in Table 4-1-167. When the difference between actual weight and theoretical weight of bar meet the provisions in Table 4-1-168, bore diameter tolerance of bar could be excluded from delivery condition.
4. Length and tolerance
(1) Length
Usually, the length of delivered bar is appointed, and detailed length of delivered bar should be described in the contract.
Provided that the bar is delivered in coils, only single bar should be included in each coil with an exception of 5% coils (2 coils is allowed it less than 2) including two bars in each. For the weight and diameter of the bar coil should be decided by two parties.
（2）Length tolerance
Table 4-1-167

Note：① Longitudinal-rib angle is ranging from 0 to 30 degree.
　　  ② Dimensions of a, b are for reference.
The tolerance of delivered bar length as appointed should not be more than +50mm.
5. Curves and ends
The curves of straight bar should not affect its normal use, and its total curves should not exceed 0.4% of its total length.
The bar end should be cut straightly while its partial deformations is out of influence on normal use.
6. Weight and tolerance
1）Bar weight to be delivered could be subject to either actual weight or theoretical weight.
2）Weight and tolerance
The tolerance between the actual weight and theoretical weight of bar should accord with the provision in Table 4-1-168.
Table 4-1-168

(II) Brand & Chemical Composition
1. Steel brand should accord with the provision in Table 4-1-169, and its chemical composition in carbon equivalent (melting analysis) should not be more than those figures in Table 4-1-169. Such element as vanadium, niobium and titanium etc. could be added in steel according to needs.
Table 4-1-169

2. See Table 4-1-170 for referenced chemical composition (melting analysis) of HRB 335 and HRB 400 bar.
Table 4-1-170

3. Carbon equivalent Ceq(%) could be calculated basing on formula (1):
　　　　Ceq=C+Mn/6+(Cr+V+Mo)/5+(Cu+Ni)/15..............................(1)
4. Nitrogen content in steel should not be more than 0.012%. No further analysis is needed if the supplier could offer relative guarantee.
Limitation on Nitrogen content could be wider provided there is enough combination element of nitrogen in steel.
5. The tolerance of chemical composition of bar should accord with the provision in GB/T 222 Method of Sampling Steel for Determination of Chemical Composition and Permissible Variations for Product Analysis, and the tolerance of carbon equivalent Ceq should be +0.03%.
(III) Delivery Status
Delivery status of bars should be hot rolled. 
(IV) Mechanical property
1. The mechanical property of bar should accord with the provisions listed in Table 4-1-171
Table 4-1-171

2. Total elongation rate (δgt) of bar under maximum force should not be less than 2.5%. No inspection is needed if the supplier could offer guarantee related.
3. Bars meeting following provision are available as per request of customer:
① Ratio between measured tension strength and measured yield point of bar should be more than 1.25. 
② Ratio between measured yield point of bar ant minimum yield point listed in Table 4-1-171 should be less than 1.30.
(V)Technical properties
1. Bending property
After bending 180 degree as per bending diameter listed in Table 4-1-172, the bending surface of bar should be free from any crackle.
Table 4-1-172

2. Reverse bending property
It is possible to carry out reverse bending test on bar as per request of purchaser.
An extra bar diameter is needed in bending diameter of reverse bending test compared with bending test. Firstly positive bending to 45 degree, then bending to 23 degree in reverse, after which the bending surface of bar should be free from any crackle.
(VI) Surface Quality
Bar surface should be free from any crackle, dog’s ear and folds.
Bump less than lateral rib on the bar surface is allowed, and the depth and height of other defects on the bar surface should be less than the allowable deviation related.
(VII) Sign
1. Brand sigh should be rolled on the surface of ribbed bar, as well as its manufacturer (trade mark) and diameter (unit: mm)
2. Bar band number should be expressed in Arabic cipher, corresponding number for HRB 335, HRB 400 and HRB 500 are 2, 3 and 4. Manufacturer name should be expressed in Chinese phonetic letters. Diameter (mm) is expressed with Arabic number. Bars with a diameter less than 10mm is not needed to be rolled with sign, but a label is needed.