Investigation of the wear mechanism of cubic boron nitride tools used for the machining of compacted graphite iron and grey cast iron

Various experiments were performed to investigate the wear mechanism of cubic boron nitride (cBN) tools used for the machining of compacted graphite iron (CGI). Comparative studies for tools used to machine grey cast iron (CI) were also performed in order to find out why in this case the tool lifetime is significantly higher. Two main effects were found that are responsible for tool wear, namely: (1) oxidation of the tool, and (2) interdiffusion of constituting elements between tool and CGI. These wear mechanisms are more or less the same for the machining of CGI and grey CI. The difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI. The MnS layer acts as a lubricant and as a diffusion barrier and is the reason for the reduced wear in the case of grey CI.     

Analytical investigations concerning the wear behaviour of cutting tools used for the machining of compacted graphite iron and grey cast iron

Compacted graphite iron (CGI) is the material for the upcoming new generation of high-power diesel engines. Due to its increased strength compared to grey cast iron (CI) it allows an increase in the cylinder-pressures and therefore a better fuel economy and a higher power output are possible. First examples of such engines are the 3.3 L Audi V8 TDI and the 4.0 L BMW V8. The reason why CGI is not used to a larger extent in large scale production up to now is its much more difficult machinability as compared to conventional CI, especially at high cutting speeds. In modern transfer lines high cutting speeds are used in the cylinder-boring operation. And especially in these continuous cutting operations the tool life decreased due to the change from CI to CGI by about a factor of 20. As was found out previously by us, the difference in tool lifetime can be explained by the formation of a MnS-layer on the tool surface in the case of CI. This layer cannot form when machining CGI because the formation of MnS-inclusions is not possible in this material due to the higher magnesium content which in turn is responsible for the formation of the graphite vermicles. The MnS-layer acts as a lubricant and prevents the adhesion of workpiece particles. This is the reason for the greatly reduced wear of CI in high speed machining operations. This MnS-layer is inspected closer by X-ray diffraction, X-ray induced photoelectron spectrometry, atomic force microscopy and secondary ion mass spectrometry in this work. Furthermore, available information on the performance of MnS as lubricant in PM-steels is comparatively discussed. This knowledge led to an economic solution of high productivity machining of CGI. The key was to reduce the cutting speed, replacing single insert tools with multiple insert tools. This allowed to increase the feed rate. By increasing the feed rate in the same amount as decreasing the cutting speed, the same productivity can be realized. This concept is leading to a number of multiple insert tools thus realizing a high productivity machining of CGI cylinder-bores with multi-layer-coated carbide tools.     

核电站反应堆冷却剂系统波动管安装焊接技术

论述了核电站反应堆冷却剂系统波动管的安装、焊接技术,详细阐述了波动管安装前的方案、焊接工艺评定等的准备工作要求,安装工序和具体实施过程及要点,焊接技术要求和焊接参数控制,焊接质量检验方法以及焊接变形的控制等,并对波动管焊接工作的重点进行了经验总结和反馈,对后续核电站反应堆冷却剂系统波动管的安装焊接及质量控制具有借鉴作用...     

A camera-based support system with augmented reality functions for manual tasks in radioactive production environments

This paper presents a support system dedicated to the improvement of the often unfavorable working conditions for manual tasks in radioactive production environments. Its main goals are to increase operational safety and comfort, to diminish costly mistakes and to improve the radiation protection for the operators, thus to reduce the permanent threat of nuclear radiation. The support system consists of a steerable camera system with intuitive control in combination with the information technology augmented reality that supplies the user with necessary data, required details and working instructions. Additionally to its ability to ease the adverse operating conditions, the support system offers a variety of additional features that create further benefit, like the possibility to have a closer look on tiny parts due to the zoom function, the excellent quality of the view and helpful extra information superimposed directly into the view of the operator.     

Production of iron castings with altered graphite morphology by a modified Inmold process

A new melt combination process which can control the graphite morphology from spheroidal, compacted-vermicular to flake in cast iron has been developed by a modified Inmold process. Two reaction chambers were prepared in one sand mould. One reaction chamber was for spheroidizing and the other was for inoculating. After being poured into the sprue, the molten iron, of a given chemical composition, was separated in the runner and passed through each reaction chamber. The separated metal streams then collided with each other and filled the cavity. As a result, a new iron, with one side having the properties of spheroidal graphite cast iron and the other the properties of flake graphite cast iron, was produced. The graphite structure has usually been controlled using filters, dams or chillers.     

电解加工中管理系统的开发和实现

论述了电解加工中参数数据库的功能，设计要点和编程方法，该系统在Windows平台下，以Visual Basic6.0为开发工具，界面友好，操作方便，可满足电解加工的基本应用。     

Development of a virtual machining system, part 2: prediction and analysis of a machined surface error

In part 2 of this three-part paper, a newly developed method that predicts the three-dimensional machined surface errors generated during the peripheral end milling process is presented. From the cutting force prediction system of Part 1, since the uncut chip thickness is calculated by tracing the movement of the cutter, the positions at which the cutting edges pass over the workpiece surface can readily be obtained. In this part of the paper these positions are used to construct surface error maps. In addition, by using the estimated locations of the peak and valley values of the cutting force component normal to the machined surface, a quantitative analysis of the machined surface error is given and followed by theoretical explanations. A series of machining tests on aluminum workpieces were conducted to validate the effectiveness of the model. The predicted cutting forces and surface errors were found in good agreement with their measured counterparts.     

Thermodynamic analysis of Na-S-Fe-H2O system for Bayer process

Thermodynamic diagrams of Na-S-Fe-H₂O system were constructed to analyze the behavior of sulfur and iron in the Bayer process. After digestion, iron mainly exists as Fe₃O₄ and Fe₂O₃ in red mud, and partial iron transfers into solution as Fe(OH)₃^-, HFeO₂^-, Fe(OH)₄^- and Fe(OH)₄^2-. The dominant species of sulfur is S^2-, followed by SO₄^2-, and then SO₃^2- and S₂O₃^2-. The thermodynamic analysis is consistent with the iron and sulfur species distribution in the solution obtained by experiments. When the temperature decreases, sulfur and iron can combine and precipitate. Controlling low potential and reducing temperature are beneficial to removing them from the solution. XRD patterns show that NaFeS₂·2H₂O, FeS and FeS₂ widely appear in red mud and precipitates of pyrite and high-sulfur bauxite digestion solution. Thermodynamic analysis can be utilized to guide the simultaneous removal of sulfur and iron in the Bayer process.     

CO2激光切割系统中防反射技术的研究

在CO2激光切割铝、铜等有色金属过程中,经常发生工件反射现象。为防止在激光切割系统中由于光束反射导致的不稳定和损坏,光路系统中必须设计防反射装置进行隔离。本文从理论上阐述了该装置的设计原理、结构形式以及安装方法。     

Increasing the stability of the CO2 welding process with a long arc

A CO₂-shielded long arc welding stability increase technique is suggested, which is attainable by pulsed arc welding application. At pulse pile-up, power dispensing is carried out on the droplets melting, starting from the moment of droplet detachment, which is registered by the voltage spike at the arc space. This allows for keeping up equal sizes of the droplets, favours higher process stability and weld upgrading.     

Automated system for controlling the process of CO2 welding with pulsed wire feed and welding current modulation

An automated system for consumable electrode welding with pulsed wire feed and arc current modulation is proposed. The circuit diagram and operating principle of automated control of the welding process and also welding equipment are described.     

中凸变椭圆活塞加工数控车床数控系统的研究

重点探讨了中凸变椭圆活塞加工数控车床数控系统设计中的几个重要问题 ,指出 ,必须从运动学和动力学两个方面考虑活塞加工过程。本文依据上述原则成功地设计了活塞加工数控车床的数控系统 ,实验结果表明 ,对活塞加工可以达到较高转速和± 10 μm的加工精度     

基于PIC单片机的CO_2焊机数字化送丝控制系统

本文介绍了一种基于PIC单片机的CO2焊机数字化送丝控制系统,分析了系统的硬件构成原理和软件流程。试验结果表明,该控制系统达到了设计的目标,送丝系统运行平稳,抗干扰能力强,可靠性高。     

Development of a virtual machining system, part 1: approximation of the size effect for cutting force prediction

In this three-part paper, components of a virtual machining system for evaluating and optimizing cutting performance in -axis NC machining are presented. Part 1 describes a new method of calculating cutting-condition-independent coefficient and its application to the prediction of cutting forces over a wide range of cutting conditions. The prediction of the surface form error and transient cutting simulations, described in Parts 2 and 3, respectively, can be effectively performed based on the cutting force model with the improved size effect model that is presented in Part 1.

The relationship between the instantaneous uncut chip thickness and the cutting coefficients is calculated by following the movement of the center position of the cutter, which varies with nominal feed, cutter deflection and runout. The salient feature of the presented method is that it determines the cutting-condition-independent coefficients using experimental data processed for one cutting condition. The direct application of instantaneous cutting coefficient with size effects provides more accurate predictions of the cutting forces. A systematic comparison of the predicted and measured cutting forces over a wide range of cutting conditions confirms the validity of the proposed mechanistic cutting force and size effect models.     

基于数据驱动的航站楼碳浓度控制系统设计及应用仿真

碳浓度偏高是导致航站楼内空气质量不佳的主要原因之一,且航站楼内随旅客数量变化碳浓度呈现的非平稳性给其控制带了挑战.为了营造航站楼内良好的空气质量,本文设计基于数据驱动的碳浓度控制系统,该系统根据航站楼内碳浓度、新风量等环境数据组成的信息向量在基础数据库中选取邻元素,通过参数调节器对邻元素的PID参数进行有向学习修正,实现系统PID参数在线优化.利用MATLAB/Simulink平台根据航站楼实际环境建立碳浓度控制系统进行应用仿真,结果表明:该系统通过参数在线优化实现了非平稳碳浓度的良好控制,可保证航站楼内碳浓度低于800ppm,系统稳态误差小于1%,与定风量系统相比节约风量约30%.该系统在为旅客提供良好的空气质量的同时可为航站楼节能设计提供参考.     

5CrNiMo热作模具CO2气体保护焊修复用药芯焊丝研制

开发了用于5CrNiMo热作模具修复的药芯焊丝,用高速摄影观察NaF含量对焊接电弧稳定性的影响,并对堆焊层金属组织和力学性能进行测试分析。结果表明,当药芯粉中加入质量分数为1.5%的NaF作为稳弧剂时,焊接过程最稳定,产生的焊接飞溅最少且以小颗粒飞溅为主;优化后的焊丝堆焊获得的堆焊层表面无焊接缺陷;堆焊层金属主要为马氏体,硬度高于锻造5CrNiMo热作模具钢;在600 ℃高温环境下,堆焊层金属强度与室温强度相当,高温稳定性好;堆焊层金属在600 ℃的磨损率比锻造5CrNiMo热作模具钢低18.75%,可用于模具钢的堆焊修复。     

Characteristics and influence factors of mold filling process in permanent mold with a slot gating system

The main problems caused by improper gating are entrained aluminum oxide films and entrapped gas. In this study, the slot gating system is employed to improve mold filling behavior and therefore, to improve the quality of aluminum castings produced in permanent molds. An equipment as well as operation procedures for real-time X-ray radiography of molten aluminum flowing into permanent molds have been developed. Graphite molds transparent to X-rays are utilized which make it possible to observe the flow pattern through a number of vertically oriented gating systems. The investigation discovers that there are many influencing factors on the mold filling process. This paper focuses its research on some of the factors, such as the dimensions of the vertical riser and slot thickness, as well as roughness of the coating layer. The results indicate that molten metal can smoothly fill into casting cavity with a proper slot gating system. A bigger vertical riser, proper slot thickness and rougher coating can provide not only a better mold filling pattern, but also hot melt into the top of the cavity. A proper temperature gradient is obtainable, higher at the bottom and lower at the top of the casting cavity, which is in favor of feeding during casting solidification.     

细丝CO2自动焊机的单片机智能控制系统

针对目前细丝ＣＯ２焊自动焊机焊接电流和电弧电压－之间存在非线性调节关系,利用人工调节很难使两者达到最佳匹配的难点,研究了一种以１６位８０Ｃ１９６ＫＣ数字单片机为核心器件,通过自主开发的软件自动实现电弧电压与焊接电流最传真匹配的智能控制系统。系统设计了旨在补偿电弧电压寻优过程中焊接电流念头的模糊控制器,同时采髟优选法自动对电弧电压进行夺电流值下的以实现最高短路过渡频率为目标的自寻优。     

Development of real-time process control system for precision and flexible V-bending with an on-line database

An advanced process control system based on expertise is developed for the V-bending process. An experimental database and a fuzzy inference model are employed as the expertise for real-time process control. The punch force-stroke curves and other process parameters stored in the database are retrieved in-process and evaluated by the fuzzy model for precise prediction control. Also, a learning process, which is similar to the way craftsmen acquire knowledge, is applied for database and fuzzy model improvements in order to cope with new materials. Several experiments were carried out to confirm the validity of the developed control system. The results show that the process control is capable of coping with differences in the material properties and other forming parameters automatically even if the operator has no information on the material properties and the process.     

Synthesis of Cu2O nanowhiskers with CTAB as a template in water-in-oil microemulsion system

Dispersed cuprite （Cu2O） nanowhiskers were synthesized in a water/butanol/cyclohexane/cetyl trimethyl ammonium bromide （CTAB） water-in-oil microemulsion system at 25℃. The nanowhiskers with a diameter of about 8 am exhibit a well-crystallized one-dimensional （1D） structure over several hundreds nanometers in length and mainly grow along the 〈111〉 direction. However, without CTAB, only cubic and hexagonal bulks are obtained. Without emulsifier, short and thick nanowhiskers can be prepared but they are apt to agglomerate. The possible growth mechanism of Cu2O nanowhiskers is speculated. The surfactant and the microemulsion system are related to the 1D shape formation and the even dispersion of Cu2O nanomaterials, respectively.