Microstructure And Property Research Of Screw Bar During Controlled Rolling And Controlled Cooling After Rolling

Controlled rolling and controlled cooling(CRCC) technique is a advanced technology, which is not only economize alloy,but also predigest working procedure.This kind of technology can fully realise steel products' potential,extremely improve the comprehensive property of the steel products, as well as eminent economic benefit and social benefit.The basic point is to connect steel products hot strain with transformation, improve the stress and toughness between low carbon steel and low alloy steel.Since the hole shape in the rolling mill has been fixed, ,the main technique of hot rolling screw bar during CRCC is controlled temperature rolling and controlled cooling after rolling.This paper is aim to improve the stress and toughness of screw bar by CRCC technique,and instituting a reasonable technique ,produce suitably , requirement screw bar. First part in this paper tell the present study state and development in the CRCC technique; Second ,analyze the theoretic mechanism about controlled rolling,several rolling ways,as well as the effect to the microsruction by the rolling temperature ,strain, and microalloy; Third ,analyze the theoretic mechanism about controlled cooling,the end of rolling temperature,as well as the effect to the microstructure by cooling rate; Fourth, the summarize of the high speed wire plant; Fifth is the concrete theory about screw bar during CRCC ,analyze the effect to the controlled temperature rolling and controlled cooling after rolling; Sixth is the test study on screw bar by CRCC technique; Seventh is the conclusion.In the experiment part, I have done a lot of work to analyze the effect to the microstructure by controlling the end of rolling temperature,cooling rate,and the final cooling temperature, with the optical microscope and the yield strength and tensile strength experiment analysis,we got the result, the screw bar after the end of rolling was quenched in the state of austenite(A or y ), then the sample is self annealed by the heatwhich was released from inner center ,produce such microstructure: the outer of the sample is anneal martensite(M),the transition layer is grain bainite(B) and qushiti(Q),the ceter is the microstructure of ferrite(F or a ) and pearlite(P).Such microstructure is benefit to improve the comprehensive property of screw bar,and provide the theoretic evidence for the screw bar production.