Folding is a variety of folding lines formed on the surface of the steel, this defect often runs through the entire product longitudinally. The reason for folding is due to the pursuit of high efficiency by shoddy manufacturers, the amount of press down is on the high side, producing ears and folding in the next rolling, the folded product will crack after bending and the strength of the steel is greatly reduced
The hemp surface is a defect caused by the severe wear of the rolling groove causing irregular unevenness on the surface of the steel. As shoddy steel manufacturers want to pursue profits, it is often the case that the rolling groove is most over-rolled.
There are two reasons: a, shoddy steel material is not uniform, impurities. b, shoddy material manufacturers guide guard equipment is rudimentary, easy to stick steel, these impurities bite people after the rolls easy to produce scars.
The reason for this is that it is made of adobe, which has many air holes, and the adobe is cracked during the cooling process due to the thermal stresses, and is cracked after rolling.
The reason for this is that substandard steel manufacturers have poor equipment and are prone to producing burrs that scratch the surface of the steel. Deep scratches reduce the strength of the steel.
There are two reasons for this: a. It is made from adobe. b. The temperature at which the shoddy steel is rolled is not standard. Their steel temperature is measured visually, so that it cannot be rolled in the required austenitic zone and the properties of the steel are naturally not up to standard.
The reason for this is that in order to achieve large negative tolerances, the finished product is pressed down in the first few passes in a large amount, the iron type is small and the holes are not filled.
The reason for this is that in order to save material, the manufacturer’s first two passes of the finished rolls are pressed down by a large amount. The strength of this rebar is greatly reduced and it does not meet the standards for rebar shape and size.
The quality of the steel is uniform, the tonnage of the cold shear is high, and the end face of the cutting head is smooth and neat, while the shoddy material is poor, and the end face of the cutting head often has the phenomenon of falling meat, i.e. unevenness, and no metallic lustre. And because of the shoddy material manufacturers products cut head less, the head and tail will appear large ears.
The substandard steel material contains many impurities, the density of the steel is small and the size is super poor, so in the absence of vernier calipers, it can be weighed for verification. For example, for rebar 20, the national standard stipulates that the maximum negative tolerance is 5%, and the theoretical weight of a single rebar is 120kg at 9M.
If the actual weight of a single piece is less than 114 kg, it is a shoddy steel, because it has a negative tolerance of more than 5%. Generally speaking, the whole phase weighing is better, mainly due to the cumulative error and probability theory of the problem.
The reasons for this are; l. Unstable steel temperature with yin and yang. 2. Uneven composition of the steel. 3. Large bounce in the mill due to rudimentary equipment and low strength foundations. There will be a large change in the inner diameter of the same week, so that the steel is not uniformly stressed prone to fracture.
The trademark and printing of high-quality material are more standardized.
Three steel diameter 16 above the large thread, the spacing between the two trademarks are in IM above.
The longitudinal bars of shoddy steel rebar are often wavy.
Fake steel manufacturers pack more loosely as they do not have a line drive. The sides are oval-shaped.