脉冲电流处理对ZG25SiMn2CrB钢组织及性能的影响

发布时间：2018-04-02 01:39

本文选题：低合金铸钢　切入点：脉冲电流　出处：《吉林大学》2017年硕士论文

【摘要】：低合金高强度钢是现今社会使用量大且应用范围广泛的重要金属材料,但其传统热处理工序复杂,资源消耗量大,难以充分发挥材料的潜能。为了降低资源消耗,开发能够提高资源利用率、缩短钢铁生产过程的新工艺势在必行。电脉冲处理技术是在改善金属材料的显微组织和力学性能、提高能源利用率的背景下提出的一种新兴技术,已在材料加工的各领域内有所应用,并取得了显著的效果。本论文将脉冲电流处理技术应用于ZG25SiMn2Cr B钢的固态相变和回火过程,通过检测其显微组织和力学性能的变化,系统地研究了脉冲电流处理对三种不同初始组织ZG25Si Mn2CrB钢固态相变过程的影响规律及作用机制。对比不同初始状态下的试样,研究了电脉冲处理马氏体逆相变机理,得到不同初始状态下ZG25SiMn2CrB钢的最佳脉冲电流处理工艺参数。(1)以退火态为初始状态的试样奥氏体化升温过程为扩散型转变,随脉冲电流处理时间的增加,室温显微组织由铁素体/珠光体逐渐转变为板条马氏体组织,并于500 ms脉冲电流淬火处理后的组织达到最细,力学性能最佳;以正火态为初始状态的试样奥氏体升温转变过程既有扩散型转变又有非扩散型转变,钢的室温组织逐渐由贝氏体/铁素体和马氏体的混相组织转变为板条马氏体和隐晶马氏体组织,最佳淬火工艺参数为480 ms脉冲电流淬火处理;以淬火态为初始组织的试样逆相变有位移型逆相变的特征,在380 ms脉冲电流处理后晶粒尺寸最细,综合力学性能最好。与退火态和正火态初始组织相比,淬火所得到的马氏体初始组织更有利于脉冲电流处理工艺实现奥氏体晶粒超细化。(2)分别利用脉冲电流和传统热处理对电脉冲淬火态ZG25SiMn2CrB钢进行回火处理,研究ZG25Si Mn2CrB钢回火后组织的演变过程和力学性能变化,研究发现瞬时脉冲电流回火处理可以避免回火脆性现象的产生。(3)在最佳参数脉冲电流淬、回火处理下ZG25SiMn2CrB钢获得比传统箱式电阻炉热处理更好的力学性能。高密度脉冲电流处理ZG25SiMn2Cr B钢的相变是热效应和非热效应相耦合作用的结果,非热效应可以降低奥氏体的形核势垒,瞬时升温过程能够提高形核率,抑制奥氏体晶粒的长大,最终使组织细化。
[Abstract]:High strength low alloy steel is an important metal materials in modern society and the use of a large quantity of a wide range of applications, but the traditional heat treatment process is complex, the consumption of resources, to give full play to the potential of material. In order to reduce the consumption of resources, development can improve the utilization rate of resources, it is imperative to shorten the process of steel production process. The electric pulse treatment technology is to improve the microstructure and mechanical properties of metal materials, a new technique is proposed to improve the energy utilization rate of the background, has been applied in the field of material processing, and achieved remarkable results. The solid phase and the tempering process the pulse current treatment technology application in ZG25SiMn2Cr B steel. By detecting the changes of the microstructure and mechanical properties of the system, to study the effect of electric current pulse on three different initial microstructure of ZG25Si Mn2CrB steel solid phase change process The law and mechanism. The sample comparison under different initial conditions, the electric pulse reverse martensitic transformation mechanism, obtained under different initial conditions of ZG25SiMn2CrB steel. The optimum pulse current treatment parameters (1) in the annealed samples for the initial state of austenite of the heating process for the diffusion transformation, with the increase of pulse current treatment the microstructure consists of ferrite / pearlite gradually transformed into lath martensite, and the microstructure after quenching pulse current to achieve the most fine at 500 ms, the optimum mechanical properties; normalizing state is the initial state, the sample temperature of austenite transformation process is diffusion transformation and change the diffusion type. The microstructure of steel gradually from bainite / ferrite and martensite mixed phase organization into lath martensite and martensite microstructure, the optimum process parameters for the 480 MS power flow quenching quenching pulse In the quenched samples for processing; the initial organization characteristic of inverse transformation of displacement inverse transformation, at 380 ms after electropulsing treatment the fine grain size, the best comprehensive mechanical properties. Compared with the annealed and normalized initial microstructure, quenching are martensite initial microstructure is more conducive to the current process of implementation of the austenite grain detailed pulse. (2) according to the pulse current and the traditional heat treatment on the electrical pulse quenched ZG25SiMn2CrB steel tempering, changes of evolution and mechanical properties of ZG25Si Mn2CrB steel after tempering organization, found that instantaneous pulse current can avoid the phenomenon of tempering temper brittleness. (3) the optimal parameters of pulse current quenching ZG25SiMn2CrB, tempering steel to obtain mechanical properties than the traditional box type resistance furnace heat treatment better. High density pulse current transformation processing ZG25SiMn2Cr B steel is thermal effect Due to the coupling effect with non thermal effect, the non thermal effect can reduce the nucleation barrier of austenite. The instantaneous heating process can improve the nucleation rate, inhibit the growth of austenite grain, and finally make the microstructure refined.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1;TG161

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