According to specification of SCM435 steel hot rolled wire rod

the austenite grain size is ≥7 grade and the reduction of area is N≥ 35%. The test results show that in the original process the mixed grain size structure of 中12 mm SCM435 steel wire is distributed along the surface of the wire rod with depth 0. 5 mm

and the austenite grain size rating is 4(25% )+7. 5(75% ) ； the rating of austenite grain size at the rest of the core area is 7. 5. There is more martensite in the microstructure

and the reduction of area of steel is lower. Through analysis on the causes of mixed grain structure

and decreasing finishing rolling temperature from 935 Y to 850 °C

and outgoing temperature decreasing from 900 °C to 850 °C the rating of austenite grain size of 4)12 mm SCM435 steel hot rolled wire rod increases from 7. 5 to 8. 5 and the mixed grain structure on surface of wire rod disappeared

the proportion of martensite in the microstructure decreases

and the average reduction of area increases from 35% to 40% .<br />