Steel for boron micro-alloying waste heat treatment steel bar

Abstract

The invention provides a steel for a boron microalloying afterheat-treating steel bar, comprising the chemical compositions with the following mixture ratio (by weight percent): 0.15-0.25% of C, not higher than 0.80% of Si, 0.45-1.00% of Mn, not higher than 0.045% of P, not higher than 0.045% of S, 0.0005-0.006% of B, and the balance of Fe and impurity elements. The steel for the steel bar is smelted and continuously cast to a steel billet on common steelmaking equipment, and then is rolled on a common steel bar mill, which is followed by post-rolling afterheat treatment, rapid surface quenching is carried out by a cooling device and self tempering is implemented using the heat transmitting from inside to outside of the core of the steel bar. The steel bar produced by the invention can further lower alloy content of a 20MnSi afterheat-treating steel bar, save alloy resources, lower production cost, overcome the defects of high technical requirements to the cooling device, large control difficulty of cooling procedures and low production efficiency of a Q235 general carbon steel afterheat-treating steel bar.

Description

technical field [0001] The invention relates to a steel for hot-rolled ribbed steel bars for reinforced concrete, in particular to a steel for steel bars with boron microalloying waste heat treatment. Background technique [0002] When producing waste heat treated steel bars, heat treatment is carried out directly on the steel rolling line by utilizing the waste heat of rolling. The basic principle is that after the steel bar is rolled out from the finished product stand of the rolling mill, it is quickly surface quenched by the cooling device, and then self-tempering is carried out by using the heat from the core of the steel bar to transfer from the inside to the outside, and air-cooled to room temperature in the cooling bed. This technology can effectively develop the performance potential of the steel. Through the control of various process parameters, the performance of the steel bar can be improved. While the strength of the steel bar is greatly improved, the plastic t...

AI Technical Summary

Problems solved by technology

However, when using Q235B steel to produce 460MPa grade and above steel bars through waste heat treatment process, it requires high cooling intensity and high technical requirements for cooling devices; the rolling speed is limited, which affects production efficiency; the cooling process is difficult to control, and the rolling time It is easy to block steel, the yield is low, and even the industrial scale production cannot be realized because the production cannot be guaranteed to be stable and smooth.

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