Why should rebar be rolled with negative tolerance?

1. Why should rebar be rolled with negative tolerance?


Within the allowable range of the standard, the closer to the negative tolerance, the fewer raw materials will be lost within the qualified specifications, and the rebar rolling speed is fast, and the transaction is in tons, so the controlled raw materials add up. It is of great significance to its cost control. Under the current severe situation in the steel industry, steel mills are reducing costs and increasing efficiency, and negative tolerance rolling is even more important.


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2. Factors affecting negative tolerance of rebar


The main factors for controlling the negative deviation of threaded steel bars to meet the requirements of national standards are optimization of hole design, on-site process control and standard bundle count points.


3. Rolling diameter gauge helps in negative tolerance rolling of rebar


1) Accurate detection


The rolling steel diameter gauge can carry out accurate detection, with high detection accuracy and comprehensive detection data. The measurement accuracy of rebar can reach ±0.05mm. In negative tolerance rolling, it can provide real-time and accurate detection values of various required geometric dimensions and can set positive and negative tolerances. When the measured value exceeds the tolerance, an out-of-tolerance prompt will be issued.

2) Provide data for trial rolling


When changing the specifications of the rebar, a trial rolling must be carried out. The purpose of the trial rolling is to ensure that there are no problems with the rolling parts and to produce qualified products as a reference for subsequent production. During the trial rolling, a steel rolling calliper is used to determine Each data is detected in real-time. According to the detection data, the rolling line can be adjusted to reduce the number of trial rolling and enter production mode as soon as possible.


3) Influence of thermal expansion coefficient


Affected by front slip and thermal expansion, the distance between the transverse ribs of the rolled product is larger than the designed value. As the number of roll turning times increases, the roll diameter gradually decreases and the distance between transverse ribs also gradually becomes smaller. Therefore, in order to ensure that the roll diameter is within the range The spacing between transverse ribs meets the standard requirements. The number of transverse ribs of different specifications should be determined during design while taking into account the effects of forward slip and thermal expansion coefficient. There are functions related to the thermal expansion coefficient in the calliper: correction function – automatic/manual, calibrated after inputting the thermal expansion coefficient; automatic correction of the temperature coefficient – with a temperature acquisition interface, which can be connected to an external on-site pyrometer and automatically use the collected temperature Adjust the thermal expansion coefficient (need to configure a thermometer). This brings greater convenience to rolling.


4) Comprehensive site inspection


The rolling steel calliper can detect various dimensions such as inner diameter, transverse rib height, longitudinal rib height, cross-sectional area, etc., which are all information required for its quality. Therefore, when comprehensive testing of this information is carried out, the operator can quickly perform inspections based on the testing data. Adjustment, even with negative tolerance rolling, can better ensure quality.


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