Spiral steel pipe technology and performance
1) Bending performance After the bending center diameter specified in the table below is bent by 180 degrees, the surface of the bending part of the steel bar must not be cracked. Grade Nominal diameter a Bend test mm Bend diameter HRB335 6-25 3a 28-50 4a HRB400 6-25 4a 28-50 5a HRB500 6-25 6a 28-50 7a
(2) Reverse bending performance
According to the buyer's requirements, the rebar can be tested for reverse bending performance.
In the reverse bending test, the diameter of the bending center is increased by one bar diameter compared to the bending test. It is bent 45 degrees forward, 23 degrees backward, and 23 degrees backward. After the reverse bending test, no cracks may form on the surface of the steel bar subjected to bending.
4. Surface quality:
The surface of the rebar allows no cracks, scabs, and folds.
The surface of the steel bar is allowed to have a bump, but it must not exceed the height of the transverse rib. 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.
5. Size, shape, weight and allowable deviation:
1) nominal diameter range and recommended diameter
The nominal diameter range of steel bars is 6 to 25mm, and the standard nominal bar diameters recommended are 6, 8, 10, 12, 16, 20, 25, 32, 40, and 50mm.
2) Surface shape and size tolerances of ribbed steel discs
Ribbed bar cross ribs should meet the following basic requirements: elbows
The angle β between the transverse ribs and the axis of the steel plate shall not be less than 45 degrees. When the included angle is not more than 70 degrees, the direction of the transverse ribs on the opposite sides of the steel bar shall be opposite;
The transverse rib and spacing l shall not be greater than 0.7 times the nominal diameter of the steel bar;
The angle between the side of the transverse rib and the surface of the steel bar shall not be less than 45 degrees; butt weld fittings
The sum of the gap (including the width of the longitudinal ribs) between the ends of the transverse ribs on the opposite sides of the reinforcing bar shall not exceed 20% of the nominal circumference of the reinforcing bar.
When the nominal diameter of the steel bar is not more than 12mm, the relative rib area shall not be less than 0.055; the nominal diameter shall be 14mm and 16mm; the relative rib area shall not be less than 0.060; when the nominal diameter exceeds 16mm, the relative rib area shall not be less than 0.065.
(3) length and allowable deviation
a. Length: The steel bars are usually delivered according to the length of the fixed length. The specific delivery length should be specified in the contract. When the steel bars are delivered in coils, each plate should be a steel bar. The number of discs per batch of 5% is allowed. (There are two plates when there are less than two plates.) It consists of two steel bars. Its disk weight and disk diameter are negotiated between supply and demand parties.
b. Permissible length deviation: The allowable deviation of the length of steel bars delivered by fixed length shall not be greater than +50 mm.
c. Bend and end: The bending of the straight bar should not affect the normal use, the total bending is not more than 40% of the total length of the bar; the end of the bar should be cut straight, and the local deformation should not affect the use