At present, the main building steel bars are hot-rolled ribbed steel bars (commonly known as threaded steel bars), with a nominal diameter of Φ 6mm ~ Φ 5mm, and hot-rolled round steel bars with a nominal diameter of Φ 8mm ~ Φ 2mm. High-quality steel bar has smooth surface, no crack, no scar and no folding. The thickness of the whole steel bar is uniform, and the deviation between the measured inner diameter and the nominal diameter is not more than 1 mm. There are marks on the surface of the threaded steel bar, such as "2LG14", where 2-indicates the brand of the steel bar, that is, the tensile strength is 49MPa. The larger the brand, the greater the tensile strength. LG-indicates that the manufacturer is Liugang. 14 —— Indicates that the nominal diameter of steel bar is φ 14 mm.. Consumers should carefully check the appearance and signs of steel bars when purchasing steel bars, and better measure the inner diameter of steel bars with vernier card and compare it with the nominal diameter, so as to make a better choice. Suggestions are as follows: 1. Go to the distribution department or specialty store of large steel bar production enterprises to buy the steel bars in these sales departments, which are directly provided by the production enterprises, and the quality of the steel bars is guaranteed. You can also buy from merchants with a certain sales history and scale, and check whether these merchants are authorized to sell by regular steel bar manufacturers. 2. Don't buy in unfamiliar small shops at will. Some small shops operate inferior steel bars in a hidden way. The steel bars displayed in the store are bought from regular manufacturers, but what they sell may be fake and shoddy steel bars produced by small rolling mills. 3. When purchasing steel bars, check whether there is a product quality certificate issued by the steel bar manufacturer and the production license number of the manufacturer. 4. It depends on the surface quality and signs of steel bars. Defects such as cracks, scarring and folding are not allowed on the surface of steel bars. Steel bars shall be rolled with brand mark, factory name (or trademark) and diameter on their surfaces.