Rebar
- May 15, 2018 -

Rebar is commonly known as rebar, also known as fine-grained hot-rolled rebar; its brand name is "fine" in the first letter of English after the abbreviation of hot-rolled ribbed steel. Such as: HRBF335, HRBF400, HRBF500. The higher-required anti-seismic structure is available in the following grades: E is added to existing grades (eg, HRB400E, HRBF400E).

I. Overview

Rebar is commonly known as rebar, also known as fine-grained hot-rolled rebar; its brand name is "fine" in the first letter of English after the abbreviation of hot-rolled ribbed steel. Such as: HRBF335, HRBF400, HRBF500. The higher-required anti-seismic structure is available in the following grades: E is added to existing grades (eg, HRB400E, HRBF400E).

Second, the type

(1) performance classification, according to China's implementation standards for rebar (G B1499.2-2007), according to the strength level (yield point / tensile strength) will be rebar is divided into 3 levels; (2) according to the use of thread Classification of steels, such as ordinary steel reinforced concrete and prestressed steel bars, concrete heat treatment steel bars, etc. (3) According to the appearance of points, divided into ribbed steel and light round steel bar.

Difference between rebar and light round bar

The difference between rebar and polished bar is that the surface has longitudinal and transverse ribs, usually with two longitudinal ribs and transverse ribs that are evenly distributed along the length. Rebar is a small steel steel, mainly used for the skeleton of reinforced concrete building components. In use requires a certain degree of mechanical strength, bending deformation and process welding performance. Raw material billets for rebar production are carbon structural steels or low alloy structural steels that are smelted and smelted, and finished steel products are delivered in hot rolled, normalized, or hot rolled state.

The main origins are: North China, East China and Northeast China, such as Shougang, Tangshan Iron and Steel, Xuanhua Steel, Chenggang, Xinxing Casting, Jianlong, Xilin, Beitai, Fushun, Shagang, and Hebei Iron and Steel.

Specifications

The specifications of rebar should be specified in the import and export trade contract. It should generally include standard grades (type codes), nominal diameters of steel bars, nominal weights (mass), specified lengths, and tolerance values for the above indicators. China's standard recommended nominal diameter of 6,8,10,12,16,20,25,32,40,50mm rebar series. The length of supply is divided into two types, length and size. China's export rebar length selection range is 6 ~ 12m, Japan rebar length selection range is 3.5 ~ 10m; domestic domestic rebar If the contract does not specify requirements, usually the length is 9m, 12m two lengths.

Third, use

Widely used in housing, bridges, roads and other civil engineering construction.

1) Surface quality. The relevant standards stipulate the surface quality of rebar, requiring that the tip should be cut straight, with no cracks, knots and folds on the surface, and no harmful defects in use.

2) Permissible value of external dimension deviation. The requirements for bending and reinforcing bar geometry of rebar are specified in the relevant standards. As stipulated in our country's standards, the straightness of steel bar should not affect the normal use, and the total bending is not more than 0.4% of the total length of the bar.

Fourth, technical standards

GB 1499.2-2007 (Steel for reinforced concrete Part 2: Hot rolled ribbed rebar)

GB1499.2-2007/XG1-2009 "Steel for reinforced concrete - Part 2: Hot-rolled ribbed rebar" National Standard Revision No. 1; GB700-2006 (carbon structural steel); GB/T 2101-2008 (form steel General requirements for acceptance, packaging, marking and quality certificates); GB1499.1-GB1499.3 (reinforcement for concrete); JIS G3112-87 (98) (bar steel for reinforced concrete); JISG3191-66 (94) (heat The shape, size, weight, and allowable difference of rolled bar and coil bar steel; BS4449-97 (hot rolled bar for concrete structures).

Fifth, chemical composition

Brand Chemical composition, 100% C Si Mn P S Ceq

HRB400 0.25 0.80 1.60 0.045 0.045 0.54

HRB500 0.25 0.80 1.60 0.045 0.045 0.55

(1) Composition inspection

1) Test method: The standard test methods commonly used for inspection and analysis of the above chemical components are as follows: GB/T223, JISG1211?1215, BS1837, BS manual 19, and so on.

2) Composition index: The indexes for checking the content of rebar components are: C, Mn, P, S, Si, etc. The grades are different and the contents are different. The approximate range is: C (0.10 to 0.40%), Mn< 1.80%, P<0.050 %, S<0.050%, Si (0.60-1.00%).

(2) Surface quality

Reinforced steel surfaces must not be allowed to crack, scab or fold. The surface of the steel bar is allowed to have bumps, but it must not exceed the height of the transverse ribs. The depth and height of other defects on the surface of the steel bar must not exceed the allowable deviation of the size of the site.

(3) Size and shape

1) nominal diameter range and recommended diameter

The nominal diameter of the steel bar is in the range of 6-50mm, and the standard bar nominal diameters recommended are 6, 8, 10, 12, 16, 20, 25, 32, 40, and 50mm.

2) Surface shape and size tolerances of ribbed bars

The angle β between the transverse rib and the axis of the steel bar shall not be less than 45 degrees. When the angle is not more than 70 degrees, the direction of the transverse rib on the opposite sides of the bar shall be opposite;

The nominal distance l between transverse ribs shall not be greater than 0.7 times the nominal diameter of the steel bars.

The angle between the side of the transverse rib and the surface of the steel bar shall not be less than 45 degrees;

The sum of the gaps (including the width of the longitudinal ribs) between the ends of the transverse ribs on the two adjacent reinforcing bars shall not exceed 20% of the nominal length of the reinforcing bar;

When the nominal diameter of the steel bar is not more than 12mm, the relative rib area should not be less than 0.055; when the nominal diameter is 14mm and 16mm, the relative rib area should not be less than 0.060; when the nominal diameter is larger than 16mm, the relative rib area should not be less than 0.065. Relative rib area calculation can refer to Appendix C.

Ribbed reinforcements usually have longitudinal ribs and may not have longitudinal ribs;

3) Length and tolerance

a, length, steel bars are usually delivered according to the length of the fixed length, the specific delivery length should be specified in the contract; steel bars can be coiled and delivered, each plate should be a steel bar, allowing each batch to have 5% of the number of discs (less than There are two plates for two plates. It consists of two rebars. Its disk weight and disk diameter are negotiated between the supplier and the buyer.

b. The allowable length deviation, the allowable deviation of the length of the delivery of steel bars according to the fixed length shall not be greater than ±25 mm;

When the minimum length is required, the deviation is 50mm;

When the maximum length is required, the deviation is -50mm.

c. Bend and end, the bending of the straight bar should not affect the normal use, the total bending is not more than 0.4% of the total length of the bar; the end of the bar should be cut and straight, and the local deformation should not affect the use.

Sixth, performance inspection

1) Performance indicators: The inspection items that examine the mechanical properties of rebar include tensile tests (tensile strength, yield strength, elongation), and bending tests (one bend and reverse bend). Specific indicators are listed in Table 6-7-7.

2) Test methods: 1 Tensile test methods: Commonly used standard test methods are GB/T228.1-2010, JISZ2201, JI SZ2241, ASTMA370, ГОСТ1497, BS18, etc.; 2 Bending test methods: Commonly used standard test methods are GB/ T232-88, YB/T5126-2003, JISZ2248, ASTME290, ГОСТ1401 9, and the like.