Hot rolled ribbed steel bar

Rebar

Rebar is the common name of hot rolled ribbed steel bar. The grade of ordinary hot rolled steel bar consists of HRB and the minimum yield point of the grade. H, R and B are the first letters of Hotrolled, Ribbed and Bars respectively.

Hot rolled ribbed steel bar is divided into two grades HRB335 (old grade 20MnSi), three grades HRB400 (old grade 20MnSiV, 20MnSiNb, 20Mnti) and four grades HRB500.

Rebar is medium and above building components must be used steel, China has a certain number of imports every year. The main producing countries and regions are Japan and Western Europe. The number of rebar exports has increased, and the main domestic export manufacturers are iron and steel enterprises in Beijing, Tianjin, Shanghai, Wuhan, Sichuan, Liaoning and other provinces and cities. The main export areas are Hong Kong, Macao and Southeast Asia.

The transverse rib geometry of imported bar is mainly common square thread or common oblique square thread. The transverse rib geometry of domestic rebar mainly has spiral shape, herringbone shape, crescent shape three. The order principle of rebar is generally based on meeting the requirements of grip performance required by engineering design, based on the mechanical process performance or mechanical strength index.

There are three main factors affecting the price change of steel bar: one is the production cost; The second is the relationship between supply and demand, which is affected by complicated factors. Third, speculative factors, which sometimes lead to irrational price rises or falls. Factors affecting production cost include raw material cost and energy cost, while factors affecting supply and demand relationship include macroeconomic operation cycle, output and consumption, inventory, import and export policies.

Anti-dumping investigation

On July 1, 2015, Australia launched an anti-dumping investigation into rebar products of Chinese origin.

On December 23, 2015, the Australian Anti-dumping Commission issued a notice to initiate an anti-subsidy investigation into rebar products from China.

There are two commonly used classification methods for spiral steel: one is geometric shape classification, according to the cross section shape of the rib and rib spacing for classification or classification, such as the British standard (BS4449), the spiral steel is divided into type I, type II. This classification method mainly reflects the grip property of rebar. Second, performance classification (grade), such as Chinese current implementation standard, screw steel for (G B1499.2-2007) wire 1499.1-2008, according to strength levels (yield point/tensile strength) are divided into three grades; According to the Japanese Industrial standard (JI SG3112), rebar is divided into 5 types according to the comprehensive performance. The British Standard (BS4461) also specifies a number of grades for the performance test of rebar. In addition, the rebar can be classified according to its purpose, such as ordinary steel bars for reinforced concrete and heat treatment bars for prestressed reinforced concrete.

specification

The specifications of rebar should be specified in the import and export trade contract. Generally, it should include the standard grade (type code), the nominal diameter of the steel bar, the nominal weight (mass), the specified length and the tolerance value of the above indicators. Our country standard recommended diameter are 6, 8, 10, 12, 16, 20, 25, 32, 40 and 50mm spiral steel series. The length of the supply is divided into two kinds: fixed scale and double scale. The selection range of spiral steel set for export of our country is 6 ~ 12m and the selection range of spiral steel set for Japan is 3.5 ~ 10m. If the contract does not indicate the requirements of domestic sales of rebar steel, usually the size of 9m, 12m two lengths.

Appearance quality

① Surface quality. The surface quality of the bar steel is stipulated in the relevant standards, requiring that the end should be cut flat and straight, the surface should not have cracks, scars and folds, and there should be no harmful defects in use.

(2) Allowable size deviation. The requirements for bending degree of rebar and geometry of steel bar are specified in the relevant standards.

Standard number

GB1499.2-2007 (Steel for reinforced concrete -- Part 2: Hot rolled ribbed bars)

GB1499.2-2007/XG1-2009 "reinforced concrete steel part 2: Hot rolled ribbed bar" national standard No. 1 amendment; GB/T 2101 -- 2008 (General Requirements for section steel acceptance, packaging, marking and Quality Certificate); GB1499.1 ~ GB1499.3 (reinforcement for concrete); Bar steel for reinforced concrete; JISG3191 -- 66 (94) (Shape, Size, Weight and tolerances of hot rolled bar and coil steel); BS4449 -- 97 (hot rolled steel bars for concrete structures).

Composition test

(1) Inspection methods: The standard inspection methods often used for the inspection and analysis of the above chemical components are as follows: GB/T223, JISG1211? 1215, BS1837, BS Manual 19, etc.

(2) Composition index: The main indicators to assess the composition content of bar steel are: C, Mn, P, S, Si and other items, brand is different, content

The general range is: C (0.10-0.40%), Mn< 1.80%, P< 0.050%, S< 0.050%, Si (0.60-1.00%).

Surface quality

Cracks, scarring and folding are not allowed on the surface of the steel bar.

Convex blocks are allowed on the surface of the steel bar, but shall not exceed the height of the transverse ribs. The depth and height of other defects on the steel bar surface shall not be greater than the permissible deviation of the size of the location.

Dimensional shape

1) Nominal diameter range and recommended diameter

The nominal diameter range of the steel bar is 6 ~ 50mm, and the standard recommended nominal diameter of the steel bar is 6, 8, 10, 12, 14, 16, 20, 25, 32, 40, 50mm.

2) Allowable deviation of surface shape and size of ribbed steel bar

The design principle of ribbed bar transverse rib shall comply with the following provisions:

Transverse rib and reinforcement axis of the included Angle β should not be less than 45 degrees, when the included Angle is not greater than 70 degrees, the steel bar relative to the two sides of the transverse rib direction should be opposite;

The nominal distance between transverse ribs l shall not be greater than 0.7 times of the nominal diameter of the reinforcement;

The Angle α between transverse rib side and reinforcement surface shall not be less than 45 degrees;

The sum of the gaps between the ends of the upper transverse ribs (including the width of the longitudinal ribs) of the adjacent two sides of the steel bar shall not be greater than 20% of the nominal perimeter of the steel bar;

When the nominal diameter of the reinforcement is less than 12mm, the relative rib area should not be less than 0.055;  nominal diameter is 14 mm and 16 mm, relative costal area should not be less than 0.060; When the nominal diameter is greater than 16mm, the relative rib area should not be less than 0.065. The relative costal area can be calculated by reference to Appendix C.

Ribbed bars usually have or do not have longitudinal ribs;

3) Length and allowable deviation

A. Length

The steel bar is usually delivered according to the specified length, the specific length of delivery should be indicated in the contract; 

Steel coil can delivery, each dish should be a steel bar, allow 5% per batch  plate number (less than two sets can have two sets) consists of two steel. The disk weight and disk diameter shall be determined by negotiation between the supply and demand parties.

b. Allowable deviation of length

The allowable deviation of the length of the steel bar shall not be greater than ±25mm when it is delivered according to the fixed size;

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

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

C. Curvature and end

The end of the steel bar should be shear straight, local deformation should not affect the use of.

Performance test

1. Mechanical properties

(1) Performance index: Test items to evaluate the mechanical properties of rebar include tensile test (tensile strength, yield strength, elongation), bending test (primary bending and reverse bending).

(2) Tensile test methods: The commonly used standard test methods are GB/T228.1-2010, JISZ2201, JI SZ2241, ASTMA370, Ti, (2) Bending test methods: The commonly used standard inspection methods are GB/T232-88, YB/T5126-2003, JISZ2248, ASTME290, and Tip1401 9, respectively.

(3) Bending property

After bending 180 degrees according to the specified bending center diameter, the surface of the bending part of the steel bar shall not produce cracks.

(4) Reverse bending performance

According to the requirements of the buyer, the steel bar can be tested for reverse bending performance.

The diameter of the bending center in the reverse bending test is increased by one bar diameter. First bend 90 degrees forward, then bend 20 degrees backward. After the reverse bending test, no cracks should occur on the surface of the bending part of the steel bar.

2. Surface quality

The surface of the steel bar shall not be cracked, scarred or folded.

Bumps are allowed on the surface of the steel bar.

Rebar is widely used in housing, Bridges, roads and other civil engineering construction. Large to highways, railways, Bridges, culverts, tunnels, flood control, DAMS and other public facilities, small to the building of the foundation, beam, column, wall, plate, screw steel are indispensable structural materials. With the deepening of China's urbanization, infrastructure construction and the booming development of real estate have a strong demand for rebar.