合金元素含量波动对U78CrV钢轨珠光体转变临界冷却速率的影响

Effect of alloying elements in U78CrV rail on critical cooling rate of pearlite

珠光体转变临界冷却速率(ν_(c))是U78CrV钢轨热处理过程中的重要参数,但其值并不固定,而是随着合金元素含量的波动而变化。研究了主要合金元素含量对U78CrV钢轨ν_(c)的影响,建立了基于C、Mn、Si、Cr和V元素含量的ν_(c)动态预测模型。随着合金元素含量的波动,U78CrV钢轨的ν_(c)在3~6℃/s范围内变化,若不明确所生产批次钢轨的具体合金元素含量,则其热处理的冷却速率应不大于3℃/s。合金元素含量对ν_(c)的影响程度为ω(Si)>ω(Mn)>ω(Cr)>ω(V)=ω(C)。生产时,检测钢轨的实际合金成分含量,将含量带入预测模型中得到预测的ν_(c),以接近但不超过预测ν_(c)的速度进行冷却,有助于得到更高性能的热处理钢轨。

A critical cooling rate(ν_(c))plays a crucial role in a heat treatment process of U78CrV steel rails,as it significantly impacts an austenite to pearlite transformation.The u.is not a fixed parameter;rather,it varies with a fluctuation of alloying element content.The influence of the major alloying elements(C,Mn,Si,Cr,and V)on the ν_(c) of U78CrV steel rails was investigated.Moreover,a dynamic prediction model for ν_(c) based on the alloying content of C,Mn,Si,Cr,and V was established.It was found that the ν_(c) of U78CrV steel rails ranged between 3 and 6 ℃/s,corresponding to variations in alloying element content.In cases where the specific alloying element content of the steel rails of a batch was unknown,it was advisable to keep the cooling rate below 3 ℃/s.The order of influence of alloying element content on ν_(c)was as follows:ω(Si)>ω(Mn)>ω(Cr)>ω(V)=ω(C).During production,the actual alloy composition of the steel rails was determined,which was subsequently introduced into the predictive model presented to derive the anticipated ν_(c).Cooling was conducted at a rate close to,but not exceeding,the predicted Ue.This approach aided in producing heat-treated steel rails with higher performance.