Concerning the phenomenon of high residual Cr in steel bar

the influence of the mass fraction of Cr

Mn alloy elements on the mechanical properties and microstructure of HRB400 test steel bars in laboratory conditions is studied. The relationship between mechanical properties and the content of pearlite

and the microstructure of precipitated particles was also analyzed by transmission electron microscopy. The experimental results are as follows. At low

medium and high Mn content of 1.15%

1.25% and 1.35% respectively

the yield strength and tensile strength of test steel bars raised with the increase of Cr. Cr played a certain strengthening role

which can reduce Mn addition. The content of pearlite raised with increasinhg Cr from 0.1% to 0.3%

the average grain size was 8 ~9

Meanwhile

Cr-Fe-Mn composite alloy cementite and Cr carbide have been precipitated from steel. The microstructure and mechanical properties of the reinforced rebar with 0.125% _0.135%Mn

0.20% Cr meet the requirements of international standard. Based on the test results and the current price of alloying elements

the cost per ton of steel can be reduced by about 20 yuan.