Control points of HRB400, hrb400e and HRB500 steel bar rolling

　　1、 Preparation of raw materials

　　1. The feeding team shall do a good job in the classified stacking and identification of converter hrb400-hrb500 steel billets to avoid mixed numbers.

　　2. The lagging blanks shall be stored separately and shall not be mixed with other heat numbers.

　　3. The billet in the furnace shall be isolated with refractory bricks, and the sequence and quantity shall be recorded.

　　2、 Billet heating

　　1. The billet shall be heated in strict accordance with the heating system, and the temperature of the preheating section shall be controlled at 700 ± 50 ℃,

　　The temperature of heating section shall be controlled at 950 ℃ - 1100 ℃, and the temperature of soaking section shall be controlled at 1150 ± 50 ℃.

　　2. Strictly prevent the billet from overheating and overburning.

　　3. The heating temperature and gas pressure shall be recorded every two hours and shall be accurate.

　　3、 Rolling

　　1. Operation control shall be carried out in strict accordance with the process specification to ensure that the process dimension of each rolling piece meets the process requirements.

　　2. Ensure that the key points K19 and K13 and the finished product dimensions are qualified.

　　3. For the DC motor, it is necessary to ensure that the rolling pieces in the rolling mill can be rolled with slight tension. Under the condition that the cooling bed is not affected, the speed of the finished rolling mill shall be reduced as much as possible to improve the performance of the rolling pieces.

　　4. Avoid low temperature and high rolling, and ensure the uniformity of rolled piece temperature.

　　5. After the rolled piece is out of the finished product, it shall not pass through the water penetration device, nor shall there be strong cooling phenomenon.

　　6. Record the size of rolled piece and the speed of DC motor at key points, and ensure the authenticity and reliability. Each shift shall not be less than twice.

　　4、 Cooling and finishing

　　1. The rolled piece shall enter the cooling bed smoothly to ensure that the final rolling temperature is above 850 ℃.

　　2. The cooling bed surface shall ensure that the rolled piece has sufficient cooling time. When the cooling bed is lowered, the temperature of the rolled piece shall not exceed 300 ℃.

　　3. The hot inspection rebar shall be inspected and accepted according to gb1499.2-2007 standard, and it can be put into normal production after passing the inspection.

　　4. The sizing and bundling shall be carried out in strict accordance with the process specification.

　　5. Unqualified materials in cold inspection must be stacked separately and shall not be mixed.

　　6. Record the final rolling temperature (twice per shift) and the finished product inspection record (twice per heat number).