Research on alternating magnetic treatment to diamond segments by experiment and numerical simulation

The heated test pieces of diamond segments were treated by alternating magnetic field,the influences of magnetic treatment on microstructure densification of diamond segments were studied through metallurgical structure analysis.The experiment results indicated that,the densification of diamond segments was further improved after magnetized.The alternating magnetic force distributions in the diamond segments were calculated by numerical simulation according to the coupled field theory.In alternating magnetic field,a prodigious swirl current field appeared in the component.The magnetic vibrating due to alternating magnetic force was obvious,which was in favor of microcosmic structure compacter.The numerical analysis results provided direct evidences for that the alternating magnetic treatment can act as an effective technique to improve the microstructure densification of diamond segments.

Blade Segment with a 3D Lattice of Diamond Grits Fabricated via an Additive Manufacturing Process

Diamond tools with orderly arrangements of diamond grits have drawn considerable attention in the machining field owing to their outstanding advantages of high sharpness and long service life.This diamond super tool,as well as the manufacturing equipment,has been unavailable to Chinese enterprises for a long time due to patents.In this paper,a diamond blade segment with a 3D lattice of diamond grits was additively manufactured using a new type of cold pressing equipment(AME100).The equipment,designed with a rotary working platform and 16 molding stations,can be used to additively manufacture segments with diamond grits arranged in an orderly fashion,layer by layer;under this additive manufacturing process,at least 216000 pcs of diamond green segments with five orderly arranged grit layers can be produced per month.The microstructure of the segment was observed via SEM and the diamond blade fabricated using these segments was compared to other commercial cutting tools.The experimental results showed that the 3D lattice of diamond grits was formed in the green segment.The filling rate of diamond grits in the lattice could be guaranteed to be above 95%;this is much higher than the 90%filling rate of the automatic array system(ARIX).When used to cut stone,the cutting amount of the blade with segments made by AME100 is two times that of ordinary tools,with the same diamond concentration.When used to dry cut reinforced concrete,its cutting speed is 10%faster than that of ARIX.Under wet cutting conditions,its service life is twice that of ARIX.By applying the machine vision online inspection system and a special needle jig with a negative pressure system,this study developed a piece of additive manufacturing equipment for efficiently fabricating blade segments with a 3D lattice of diamond grits.

Influences of magnetic treatment on microstructure densification of diamond saw segments

The heated test pieces were treated with alternating magnetic field by self-made experimental facility firstly. And influences of magnetic treatment on microstructure densification of Diamond Saw Segments were studied through hardness testing, ultrasonic testing, metallurgical structure and fracture pattern analysis by comparative method. The mechanism of magnetic treatment is analyzed and discussed in the end. The results show that the hardness of test pieces after magnetized are harder than before, that HRB hardness is improved by 3.58 on average. The sound path and amplitude of echo wave both decrease in test pieces after magnetized. The relative pad value of echo wave is regularly related with the microstructure densification, what is profound to further establish the regularity studying the degree of matrices densification using ultrasonic testing. The pores become few and pore shape gradually spheroidizing with the magnetic treatment, and matrices are more homogeneous and compact than the without by metallographic microscope. The degree of matrices densification is further improved after magnetized. The average crystal grain size is finer than the without, and the reason of grain refining is that densification of diamond saw blade improved. Magnetic treatment can act as one kind of effective technique to improve the microstructure densification of diamond saw segments.

Research on a New Type of Diamond Saw Plate

With the developing of stone material, diamond saw pl ate is used widely, and in order to increase cutting efficiency and life-span o f diamond saw plate, there are a lot of research jobs of segment for diamond saw plate. Layered segment for diamond saw plate is to divide single segment into s everal cutting tools by its structure, then increases rock-cutting faces. For i mpregnated man-made diamond saw plate, the bonding strength of diamonds with ma trix material has great effect on its life and service. Diamond is a kind of non metal and there is such high interface energy between diamond and common metals or alloys that diamond surface can’t be soaked by low melt-point metal or allo y. Diamonds are hold in metal matrix of working layer only mechanically, rather than bonded chemically, so the usage rate of diamonds in working layer is very l ow. Weakly impregnated method refers to covering diamonds with a thin layer of tu ngsten carbide mechanically by physical method, and chemical plating membrane re fers to coating a layer of carbide, which can react with the carbon atoms on the surface of diamond by chemical method and be soaked by matrix metal. In this pa per it analyses working mechanism and sintering process of layered segment of di amond saw plate by means of resistor hot-pressing sintering, it points out shor tages of layered structure, and raises using weakly impregnated layer instead of pure matrix layer, then overcomes the pure matrix layer slipping by pulling out diamonds earlier to improve cutting efficiency of saw plate, in the same time u ses diamond grains of chemical plating membrane proposed then preventing the hea t-hurting to diamond grains in working layer during the process of welding and sintering and improving the bonding strength of diamond with matrix, then improv ing life-span and aging of diamond saw. The theory of the design of mixed holding of diamonds by matrix of saw plate assures that chemical plating diamonds in working layer cut rock and weakly impr egnated diamonds in weakly impregnated layer make segment expose, then design a new type of layered segment for diamond saw plate.

用于隧道位移监测的菱形布设新方法

提出了一种基于弱光栅传感器特性的监测方法,用于长期监测运营期盾构地铁隧道中存在的不均匀沉降和管片水平错动位移。将缆状弱光栅传感器经过预拉伸后,呈菱形固定在盾构隧道的壁面,通过监测弱光栅传感器的形变量,可以判别隧道结构变形的不同模式并计算出隧道变形量,满足工程所需的实时性和精度要求。依据相似比原则,设计制造了1∶5的隧道位移模型,模拟隧道管片的局部伸缩、沉降、水平位移,将光栅传感器固定在壁面上,开展了弱光栅监测灵敏度试验、不同菱形布设角度下弱光栅监测结果对比试验和竖直沉降与水平位移试验,对比监测结果与实际位移量。研究结果表明:(1)在相同沉降情况下,弱光栅菱形布设时的光栅应变量要大于直线型布设时光栅的应变量,菱形布设方法对沉降量的变化敏感度优于传统直线型布设;(2)10°~20°为弱光栅菱形布设较优的倾斜角度区间,监测结果误差较低;(3)以光缆布设倾角为15°的试验数据为基础,建立了弱光栅波长变化与管片位移的反演方程。

常泰长江大桥主航道桥5号桥塔中塔柱钢筋部品装配化施工关键技术

常泰长江大桥主航道桥为主跨1208 m的公铁两用双塔钢桁梁斜拉桥,5号桥塔采用钢-混混合空间钻石型桥塔,高352 m,分为上、中、下塔柱,中塔柱单塔肢为正八边形截面。5号桥塔中塔柱采用“装配化设计、工业化生产、快速化安装”的钢筋部品装配化施工方案。在钢筋厂内,首先采用研发的钢筋片体和钢筋块体柔性制造生产线进行钢筋片体自动化成型和钢筋块体机械化成型;然后将钢筋块体运输至塔下施工平台,通过步履式组拼胎架组拼成钢筋部品;最后采用塔吊将部品整体吊装上塔,通过锥套锁紧钢筋接头进行快速连接。采用钢筋部品装配化施工技术,减少塔上高空作业人数60%~70%,降低了劳动强度和高空作业安全风险,每节段塔上钢筋施工时间缩短至1~1.5 d,提升了钢筋施工效率,塔柱浇筑后钢筋保护层厚度合格率超过97%,保证了工程施工品质。

花岗石加工用金刚石-金属复合材料磨损机理研究

本文通过大量实验过程，跟踪观察了花岗石锯切过程中金刚石－金属复合材料在各种加工条件下的磨损状态；探讨了花岗石种类、金刚石、金属合金结合剂等因素对磨损状态的影响。最后，分析了磨、抛过程中金刚石的磨损特点，并提出了相应的解决措施。

金刚石框架锯锯切研究(Ⅲ)——单个金刚石结块锯切力的特征与影响因素分析

在对金刚石框架锯锯切加工动力学和锯切破碎机理模型的研究基础上,通过单颗粒金刚石划痕、单个金刚石结块切削石材的系列实验,测量并分析了金刚石框架锯锯切加工时的切削力特征及其影响因素。结果表明,单颗粒金刚石和单个金刚石结块以不同切削路径切削时的切削力不同的特征,反映了切削断裂过程性质的变化;金刚石浓度低和金刚石颗粒直径小时金刚石磨粒形状和切削方位对切削力有较大的影响。减小切削深度、使用切削液、在已切削表面上切削时,切削力下降。在框架锯锯切中,单颗粒金刚石承受载荷不高,考虑到磨粒切削干涉和重复切削的影响,单颗粒金刚石承载大约在5～15N之间。

金刚石框架锯锯切研究(2)──锯切破碎机理

在对金刚石框架锯锯切加工动力学研究的基础上 ,通过单颗粒划痕和单个金刚石结块切削大理石试验 ,模拟金刚石框架锯锯切过程中 ,金刚石颗粒和结块在不同加工条件下的切削过程 ;测量分析了切削力、表面沟槽轮廓和有效切削磨粒数 ;观察并分析了加工表面形貌 ;运用岩石脆性断裂力学理论 ,分析了单颗粒金刚石切削机理。通过金刚石框架锯锯切加工大理石的切屑粒度分布分析 ,指出了实际加工切削条件对锯切破碎机理的影响。研究结果证实了金刚石框架锯锯切加工动力学研究的一些基本结论 ,最后提出了金刚石框架锯锯切大理石破碎机理模型。

金刚石框架锯锯切研究(Ⅳ)—金刚石框架锯锯切力

在对金刚石框架锯锯切加工动力学和锯切破碎机理模型的研究基础上 ,通过金刚石锯条切削石材的实验 ,测量并分析了金刚石框架锯锯切加工石材时的切削力特征以及切削力与进给速度、石材种类、金刚石结块性能、金刚石结块分布距离等因素的关系 ,提供了几种石材的切削力值 。

不同烧结工艺制备的Fe基孕镶金刚石磨头结构和摩擦磨损性能

采用真空热压烧结法,以Fe基元素混合粉末和MBD8人造金刚石为原材料,通过改变工艺参数,制备锯切花岗岩用Fe基孕镶金刚石锯片磨头。采用SEM、XRD、布氏硬度仪、万能力学试验机和MRH-3销盘式摩擦试验机研究不同烧结工艺制备的磨头结构、力学性能和摩擦磨损行为。结果表明:提高烧结温度或烧结压力可使磨头胎体合金化程度增大,金刚石和胎体由机械包镶变为冶金结合,力学性能得到提高。与680℃/15 MPa/4 min和760℃/23 MPa/4 min烧结工艺相比,760℃/15 MPa/4 min工艺所得磨头胎体与金刚石具有最佳的耐磨匹配性和界面结合特性,摩擦磨损性能最好。

锯切花岗石过程中金刚石节块磨损特征及影响因素分析

在已有的节块磨损规律的基础上，对锯切花岗石过程中的金刚石及其固位载体——粘合剂的磨损规律进行了研究．通过实验，跟踪观察了不同金刚石节块在各种加工条件下的磨损状态．结果表明：金刚石的工作状态与节块的使用性能有良好的对应关系，金刚石的微破碎和完整晶型比例越高节块耐磨性越好；宏观破碎和脱落比例越高节块耐磨性越差．金刚石的粒度、含量、品级，粘合剂和金刚石的匹配以及锯切用量组合等均明显影响锯切效果．

稀土夹杂物对D6AC超高强度钢力学性能的影响

本文研究了稀土夹杂物含量对Ｄ６ＡＣ钢强度和塑性的影响，得出了夹杂物的体积百分率与断面收缩率的定量关系式。从夹杂物尺寸和数量方面探讨了对Ｄ６ＡＣ钢韧性的影响。并提出了改善性能的途径。

电镀金刚石复合齿锯片的研究

为了克服金刚石锯片生产中采用高频焊接时锯片基体变形大和激光焊接一次性投入高的不足 ,本文综合利用热压法和电镀法的优势 ,介绍了一种成本较低且不影响基体性能的金刚石锯片制造方法 :用电镀法将金刚石复合齿镶在锯片基体上以形成锯片。文中对金刚石复合齿的两种制作方法 :热压法和电镀法 ,进行了详细介绍 ,讨论了热压法涉及到的胎体配方和烧结工艺以及电镀法中的复合齿模具设计、镀液配方和电镀工艺参数条件等问题。并对金刚石锯片电镀的三个步骤 :基体铣槽、镶齿和入槽电镀作了介绍 ;给出了锯片电化学除油液的配方和除油工艺条件。该法具有焊接牢固、对金刚石热损伤小、锯片性能调节方便等优点 ,主要适用于 60 0mm以下的金刚石锯片的生产。

金刚石框架锯锯切研究(Ⅵ)—在实验机上模拟框架锯锯切过程

测定金刚石框架锯锯切切削力、金刚石结块磨损和锯条变形等是十分重要也是非常困难的。在前面对锯切运动、锯切机理、锯切切削力和金刚石结块磨损研究的基础上,介绍了一种在实验室里用小型框架锯切实验机模拟框架锯锯切过程的实验方法,比较了用单锯条三节块和单锯条单结块锯切石材的实验结果.优选了结块分布间距。与金刚石框架锯锯切加工实验结果的比较表明,在实验机上用单锯条三节块锯切石材时,测量得到的处于中间的金刚石结块的切削性能,可以较好地反映实际加工中金刚石结块的切削状态。利用这一结果,可快速地通过简单的实验,评价金刚石锯条在实际加工中的切削力和金刚石结块磨损特性,其误差在20％之内。

金刚石框架锯锯切研究(Ⅷ)——计算机模拟框架锯锯切过程

计算机模拟了在框架锯锯切过程中石材和锯片的接触面积和有效切削刃数、单个金刚石颗粒、金刚石结块和整个金刚石锯条的切削力。结果表明 :在结块表面上出刃的金刚石颗粒中 ,只有半数金刚石颗粒在一个固定的切削区间内切削石材。金刚石在不同位置切削产生的断裂沟槽交错 ,形成了锯切沟槽的底部 ,切削力的试验结果与实际切削试验结果在数量级和变化趋势上是一致的。切削进给量和金刚石结块的切削性能是影响切削力和结块磨损的主要因素。石材和锯条结块间的最佳接触面积取决于结块间距、结块数目、结块尺寸 。

结合剂氧含量对金刚石锯片性能的影响

采用氮 /氧自动分析仪及SEM、XRD等手段分析了结合剂粉末中氧含量及其对锯片性能的影响。结果发现 :在烧结过程中 ,含氧量高的结合剂对金刚石形成了强烈的侵蚀 ,金刚石表面形成了许多凹坑 ,最终导致在切削过程中金刚石发生整体破碎的比例大幅度增加 ,工具的寿命和效率急剧下降。

真空液相活化烧结对金刚石孕镶体性能的影响

本文研究金刚石刀头真空热压烧结与普通热压烧结的烧结成型及结合性能。通过真空烧结采用含有强碳化物形成元素的低熔点预合金粉末作为粘结相 ,采用三点弯曲试验测试了普通热压烧结与真空液相活化烧结试样的抗弯强度 ,用SEM观察了断口金刚石表面的界面反应。结果表明 ,采用真空液相活化烧结使得钛元素在金刚石表面聚集 ,与碳原子形成碳化钛 ,提高了金刚石与基体金属的结合力以及基体自身的强度。切割实验表明真空液相活化烧结刀头锋利度及寿命明显提高。

造粒粉末在金刚石工具中的应用

本文介绍了国外滚动式和喷雾式两种造粒工艺。研究了造粒粉末的特性 ,经测试造粒粉末流动性大幅提高 ,而松装密度却下降。用SEM观察了造粒粉末的形貌。分析了造粒粉末在金刚石工具中的应用 ,指明了造粒粉末特别适用于容积投料冷压多层刀头的自动化生产 ,克服了金刚石在粉料中容易产生的分布不均匀现象。

金刚石框架锯锯切研究(VII)━计算机模拟框架锯锯切过程基础

基于框架锯锯切加工运动学分析、单颗粒和单结块切削力试验结果 ,讨论了采用计算机模拟框架锯锯切过程中所需的运动学、金刚石结块磨损和金刚石颗粒切削力模型 ,以及模拟过程图。采用简化方法计算了金刚石结块表面的理论金刚石颗粒数 ;结合对金刚石结块磨损的研究结果 ,用MontoCarlo方法生成了结块表面的金刚石颗粒的出刃高度、分布位置和磨损形态 ,生成了数字化的金刚石锯条 ,为计算机模拟框架锯锯切加工过程 ,提供了基础数据。