As we all know, steel and cement are often used as building materials on construction sites. Many people know that these rebar is rebar, but they rarely understand why there are these threads on the rebar, and they rarely think about how these threads are processed. What are these threads full of steel bars designed for, and what can they do?
Rebar is the common name of hot rolled ribbed steel bar, usually with 2 longitudinal ribs and horizontal ribs evenly distributed along the length direction. The shape of the transverse rib is spiral shape, herringbone shape and crescent shape. Expressed in millimeters of nominal diameter. The nominal diameter of a ribbed bar is equivalent to the nominal diameter of a circular bar of equal cross-section.

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 the words Hotrolled, Ribbed and Bars respectively.
Hot rolled ribbed steel bars are divided into two grades HRB335 (old number 20MnSi), three grades HRB400 (old number 20MnSiV, 20MnSiNb, 20Mnti) and four grades HRB500.
Round steel is a long, solid steel bar with a round cross-section. Its specifications are expressed in diameter, unit millimeter (mm); Round steel is divided into hot rolled, forged and cold drawn three kinds. Hot rolled round steel is 5.5-250 mm in size. Among them:5.5-25 mm small round steel is mostly supplied in straight strips in bundles, commonly used as steel bars, bolts and various mechanical parts; Round steel larger than 25 mm, mainly used for the manufacture of mechanical parts, seamless steel pipe billets, etc.
The main differences between rebar and round steel are the following five points:
1. Different shapes. The outer surface of round steel is smooth; The outer surface of the rebar has a spiral rib;
2. Different production standards. In the current standard, round steel refers to HPB235 steel bar, its production standard is ' hot rolled smooth steel bar for reinforced concrete ' (GB13013); Rebar generally refers to HRB335 and HRB400 grade rebar, its production standard is ' hot rolled ribbed steel bar for reinforced concrete ' (GB1499);
3. Different levels of intensity. The design strength of round steel (HPB235) is 210MPa; The strength of rebar is higher than that of round steel, and the design strength of HRB335 is 300MPa; The design strength of HRB400 is 360MPa;
4. Different types of steel (chemical composition is different). Round steel (HPB235) is carbon steel, steel is Q235; Rebar is low alloy steel, HRB335 steel bar is 20MnSi(20 manganese silicon); HRB400 grade rebar is 20MnSiV or 20MnSiNb or 20MnTi, etc.
5. Different physical and mechanical properties. Due to the different chemical composition and strength of steel bars, there are differences in physical and mechanical properties. The cold bending performance of round steel is better, can be 180 degrees of bending hook, rebar can only be 90 degrees of straight hook; The weldability of round steel is better, and ordinary carbon electrode can be used, and low alloy electrode should be used for rebar.
1, a circle plus a vertical or diagonal line is round steel, that is, a grade steel; A circle with a vertical line and then a horizontal line under the vertical line is rebar, which is secondary steel; Then a circle plus a vertical line and then two horizontal lines below the vertical line are also rebar, but the level is one more level, that is, three levels of steel;
2, round steel bars are basically HPB235 steel bars (one level), the diameter is basically within 10MM (inclusive), commonly used Φ6, Φ8, Φ10; 2. Add a vertical line in the circle of this symbol, and add a horizontal line below for HRB335 steel bars (two levels), basically rebar, commonly used diameters:8, 10, 12, 14, 16, 18, 20, 22, 25, 28, 32;
Ribbed steel bars bear mainly tensile stress in concrete. The transverse rib on the steel bar is used to enhance the bonding performance between the steel bar and concrete, better transfer the stress, simply put, is to make the steel bar and concrete can better coordinate the work, jointly withstand the external force, ribbed steel bar due to the role of the rib, so that rebar and concrete bite together, and concrete has a greater bonding ability, so it can better withstand the external force. Improve the strength of concrete. Then the compressive strength and resistance of bending buildings will be better, and can also effectively resist earthquakes and other disasters, ribbed steel is widely used in a variety of building structures, especially large, heavy, light thin-walled and high-rise building structures.
Rebar is produced by small rolling mills, the main types of small rolling mills are divided into:continuous, semi-continuous and transverse. Most of the new and in use in the world are fully continuous small rolling mills. Popular steel mills include the universal high speed steel mill and the high yield steel mill.
New processes such as step heating furnace, high pressure water descaling, low temperature rolling and headless rolling are used in bar rolling. Rough rolling and middle rolling are developed to adapt to large billets and improve rolling accuracy. Finishing rolling is mainly to improve accuracy and speed (up to 18m/s).
Step heating furnace → roughing mill → medium mill → finishing mill → water cooling device → cold bed → cold shear → automatic counting device → baling machine → discharge