渗氮过程中轴套开裂原因

SKH51高速钢轴套在渗氮过程中发生开裂现象。采用宏观观察、化学成分分析、硬度测试、金相检验、扫描电镜分析等方法分析了轴套开裂的原因。结果表明:轴套基体中的共晶碳化物分布不均匀,在沿轴向方向上存在较为严重的条带状共晶碳化物;材料回火不充分使组织中存在残余奥氏体,在渗氮过程中残余奥氏体转变为马氏体,产生了组织应力;轴套开裂位置处倒角半径过小,产生了应力集中,最终导致轴套发生开裂。

气体渗氮工艺过程集散控制系统设计

阐述了气体渗氮工艺过程控制系统的设计原理。该系统采用了集散式的结构,构成了一个上、下位机系统。下位机采用智能数字控制仪进行现场控制。上位机软件采用VB进行设计,实现与下位机的通信,通信模块采用了RS-485标准。

1Cr11Ni2W2MoV不锈钢氮化表面磨削黑点原因分析

1Cr11Ni2W2MoV材料在渗氮后,对其氮化层表面磨削后会出现黑点,经过试验以及分析得出,是由于在600℃渗氮保温时候材料析出的沿晶界碳、氮化物,该碳、氮化物析出降低了晶界强度,并在晶界产生较大的应力集中,在随后加工时叠加磨削应力而产生的沿晶开裂。

Numerical modelling rock deformation subject to nitrogen cooling to study permeability evolution

How to model the permeability evolution of rock subjected to liquid nitrogen cooling is a key issue. This paper proposes a simple but practical method to study the permeability evolution of rocks subject to liquid nitrogen cooling. FLAC with FISH function was employed to numerically model the rock behavior under cooling. The enhanced perme- ability of the volumetric strain was defined, and the permeability was directly evaluated based on element＇s volumetric strain. Detailed procedures for implementing the evolution model of permeability in this paper were presented. A case study was carried out to simulate a coal bed where liquid nitrogen was injected in the bore hole. And a semi-submerged test of liquid nitrogen was performed. The method to model the permeability evolution of rocks subject to liquid nitrogen shock in this paper was proved to be right by the test results. This simulation results are discussed with the hope to provide some insight into understanding the nitrogen cooling practice.