Control method for reducing specified non-proportional extension strength fluctuation

Abstract

The invention discloses a control method for reducing specified non-proportional extension strength fluctuation, and belongs to the technical field of steel production for anti-seismic coiled reinforced bars. A traditional technology is used for conducting a series of optimization on the microalloy added amount, rolling and the air cooling process through small batch trial manufacture for four times, and the same position (3) of non-lap joint points is selected in stretching sampling positions of different batches as shown in the first picture; according to the test result as shown in the first picture, the Rop0.2 fluctuation is still very large, the Rop0.2 testing range of a phi 8 mm anti-seismic coiled reinforced bar HRB400E on the same day is 394-527 MPa, and the fluctuation range is 133 MPa; after natural aging of seven days, the Rop0.2 range is 396-489 MPa, and the fluctuation range still reaches up to 93 MPa; at last, the bainite content of the center part is controlled to be smaller than or equal to 3%, and the temperature difference of the lap joint and the non-lap joint is smaller than or equal to 15 DEG C. Consequently, it is guaranteed that the same circle Rop0.2 fluctuation of a 400 MPa anti-seismic coiled reinforced bar can be smaller than or equal to 50 MPa, and the same circle Rop0.2 fluctuation of a 500 MPa anti-seismic coiled reinforced bar can be smaller than or equal to 55 MPa.

Description

technical field [0001] The invention belongs to the technical field of production of steel for anti-seismic coils and snails. In particular it relates to a specified non-proportional tensile strength R p0.2 The fluctuation control method is suitable for reducing the non-proportional extension strength R of the anti-seismic coil screw p0.2 volatility control. Background technique [0002] Flex ratio (R o el / R el ≤1.30), strength ratio (R o m / R o el ≥1.25), uniform elongation (A gt ≥9.0%) are three important indicators to measure the anti-seismic performance of the coiled snail. The reason for the yield strength is mainly due to the interaction between the Coriolis air mass formed by the solute atoms and the dislocation. The movement of the air mass is hindered by the dislocation line and additional work is performed, which shows the upper yield point. When the air mass leaves the dislocation line, the stress begins to decrease, showing is the lower yield point R ...

AI Technical Summary

Problems solved by technology

[0004] 1)R o p0.2 The fluctuation is large, not only the fluctuation between the non-lapping point and the lapping point is large, but also the fluctuation range of the non-lapping point at the same position is more than 100MPa, resulting in part of the yield strength being lower than the lower limit, and some exceeding the upper limit. R o p0.2 / R el unqualified

[0005] 2)R o p0.2 The fluctuation is large. In order to ensure that the minimum value is not lower than the lower limit, it is necessary to increase the amount of microalloy added or increase the air-cooled strength, which results in a uniform elongation A gt lowered, resulting in part A gt unqualified;

[0006] 3)R o p0.2 The fluctuation is large. If in order to ensure that the maximum value is not greater than the upper limit, it is necessary to reduce the amount of microalloy added or reduce the air-cooling strength, which causes the tensile strength R o m reduced, partially unqualified, resulting in a stronger yield ratio than R m o / R o p0.2 unqualified

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