《磨具知识》翻译

freemanfly |浏览3548次
| 2009-05-24 15:27

磨具是用以磨削、研磨和抛光的工具。大部分的磨具是用磨料加上结合剂制成的人造磨具,也有用天然矿岩直接加工成的天然磨具。磨具除在机械制造和其他金属加工工业中被广泛采用外,还用于粮食加工、造纸工业和陶瓷、玻璃、石材、塑料、橡胶、木材等非金属材料的加工。

  磨具在使用过程中,当磨粒磨钝时,由于磨粒自身部分碎裂或结合剂断裂,磨粒从磨具上局部或完全脱落,而磨具工作面上的磨料不断出现新的切削刃口,或不断露出新的锋利磨粒,使磨具在一定时间内能保持切削性能。磨具的这种自锐性,是磨具与一般刀具相比突出的特点。

  早在新石器时代,人类就已经开始应用天然的磨石来加工石刀、石斧、骨器、角器和牙器等工具了;1872年,在美国出现了用天然磨料与粘土相结合烧成的陶瓷砂轮;1900年前后,人造磨料问世,采用人造磨料制造的各种磨具相继产生,为磨削和磨床的快速发展创造了条件。此后,天然磨具在磨具中所占比例逐渐减少。

  磨具按其原料来源分,有天然磨具和人造磨具两类。机械工业中常用的天然磨具只有油石。人造磨具按基本形状和结构特征区分,有砂轮、磨头、油石,砂瓦(以上统称固结磨具)和涂附磨具五类。此外,习惯上也把研磨剂列为磨具的一类。

  固结磨具按所用磨料的不同,可分为普通磨料固结磨具和超硬磨料固结磨具。前者用刚玉和碳化硅等普通磨料,后者用金刚石和立方氮化硼等超硬磨料制成。此外,还有一些特殊品种,如烧结刚玉磨具等。

  普通磨料固结磨具是由结合剂将普通磨料固结成一定形状,并具有一定强度的磨具。一般由磨料、结合剂和气孔构成,这三部分常称为固结磨具的三要素。

  磨料在磨具中起切削作用。结合剂是把松散的磨料固结成磨具的材料,有无机的和有机的两类。无机结合剂有陶瓷、菱苦土和硅酸钠等;有机的有树脂、橡胶和虫胶等。其中最常用的是陶瓷、树脂和橡胶结合剂。

  气孔在磨削时对磨屑起容屑和排屑作用,并可容纳冷却液,有助于磨削热量的散逸。为满足某些特殊加工要求,气孔内还可以浸渍某些填充剂,如硫黄和石蜡等,以改善磨具的使用性能。这种填充剂,也被称为磨具的第四要素。

  表示普通磨料固结磨具特征的项目有:形状、尺寸磨料、粒度、硬度、组织和结合剂。磨具硬度是指磨粒在外力作用下,从磨具表面脱落的难易程度,它反映了结合剂把持磨粒的强度。

  磨具的硬度主要取决于结合剂加入量的多少和磨具的密度,磨粒容易脱落的表示磨具硬度低;反之,表示硬度高。硬度的等级一般分为超软、软、中软、中、中硬、硬和超硬七大级,从这些等级中还可再细分出若干小级。测定磨具硬度的方法,较常用的有手锥法、机械锥法、洛氏硬度计测定法和喷砂硬度计测定法。

  磨具的硬度与其动态弹性模量具有对应关系,这有利于用音频法测定磨具的动弹性模量来表示磨具硬度。在磨削加工中,若被磨工件的材质硬度高,一般选用硬度低的磨具;反之,则选用硬度高的磨具。

  磨具组织粗分为紧密、中等和疏松三类。每类又可再细分数等,用组织号来区分。磨具组织号越大,磨料在磨具中所占的体积百分率越小,磨粒之间的间隙越宽,表示组织越松。反之,组织号越小表示组织越紧。较松组织的磨具使用时不易钝化,在磨削过程中发热少,能减少工件的发热变形和烧伤。较紧组织的磨具磨粒不易脱落,有利于保持磨具的几何形状。磨具的组织只在制造时按磨具配方予以控制,一般不作测定。

  超硬磨料固结磨具主要是由金刚石、立方氮化硼等与结合剂固结成的磨具。由于金刚石、立方氮化硼的价格高、具有很好的耐磨性能,用它们制造的固结磨具与普通磨料固结磨具不同,除超硬磨料层外,还有过渡层和基体。

  超硬磨料层是起切削作用的部分,由超硬磨料和结合剂组成。基体是在磨削中起支托作用的,由金属、电木或陶瓷等材料组成。过渡层用于连接基体和超硬磨料层,由结合剂构成,有时也可省去。常用的结合剂有树脂、金属、电镀金属和陶瓷等。

  固结磨具的制造工序有:分配料、混料、成型、热处理、加工和检查等。随结合剂不同,制造工艺也不尽一样。陶瓷结合剂磨具主要采用压型法,将磨料和结合剂按配方的重量比例称量后,置于混料机内混合均匀,投入金属模具内,在压力机上成型出磨具毛坯。毛坯经干燥再装入窑内焙烧,烧成温度一般为1300℃左右。当采用低熔点烧熔结合剂时,烧成温度低于1000℃。再按规定尺寸形状精确加工,最后检查产品。

  树脂结合剂磨具一般是在室温条件下在压力机上成型,也有采用在加热条件下边加热边加压的热压工艺。成型后在硬化炉内硬化。以酚醛树脂为结合剂时,硬化温度为180~200℃。

  橡胶结合剂磨具主要采用对辊机混料,并滚压成薄片,然后用冲刀冲裁成型;也有的用松散料,投入金属模具内在压力机上成型。成型后在硫化罐内硫化,温度为168~180℃。

  金属结合剂磨具的制造工艺有粉末冶金法和电镀法两种,主要用于超硬磨料固结磨具。粉末冶金法以青铜等为结合剂,混料后采用热压或在室温条件下加压成型,然后烧结加工。电镀法以镍或镍钴合金等为电镀金属,按电镀工艺将磨料固结在基体上,制成固结磨具。

  特殊品种的磨具有烧结刚玉磨具和纤维磨具等。烧结刚玉磨具是用氧化铝微粉和适量的氧化铬混合、成型,在1800℃左右烧结制成。这种磨具结构紧密,有较高强度,主要用于加工钟表、仪表等零件。纤维磨具是用含有或粘附有磨料的纤维丝(如尼龙丝)作原料制成的,它的弹性好,主要用于金属材料及其制品的抛光。

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  • Grinding is used to grinding, grinding and polishing tools. Most of the abrasive is bonded abrasive is made with artificial abrasive, but also useful for the direct processing of natural ore and rock into a natural abrasive. In addition to grinding and other metalworking machinery manufacturing industry has been widely used, but also for food processing, paper industry and ceramics, glass, stone, plastic, rubber, wood and other non-metallic materials processing.
    Abrasive during use, when the abrasive grinding dull, due to fragmentation or a combination of abrasive agent themselves part of the fracture, abrasive from the abrasive on the partial or complete loss, while the abrasive surface of the abrasive work of emerging new cutting edge, or continuously exposing new sharp abrasive, so abrasive in a certain period of time can keep cutting. This self-sharpening abrasive, and is the abrasive tool is underscored by comparing with the general characteristics.
    As early as the Neolithic Age, humans have already begun to process applications grindstone natural stone knives, stone axes, bone, and teeth, etc. Angle tool; in 1872 in the United States appeared to use a combination of natural abrasive and clay kiln ceramic grinding wheel; in 1900 before and after the advent of artificial abrasives, synthetic abrasives manufactured using a variety of abrasive products have generated, for grinding and grinding machines to create the conditions for rapid development. Since then, a natural abrasive in the abrasive in the proportion of reduced gradually.
    Abrasives source of their raw materials, there are two kinds of natural abrasive and artificial abrasives. Commonly used in machinery industry is only natural abrasives Whetstone. Artificial abrasives according to the basic shape and structural characteristics of the distinction between a grinding wheel, grinding head, Whetstone, sand tile (collectively Bonded Abrasives), and five types of coated abrasives. In addition, the abrasive used also as a class of abrasive.
    Bonded Abrasives used by the different abrasive can be divided into regular and super-hard abrasive abrasive Bonded Abrasives Bonded Abrasives. The former general with corundum and silicon carbide abrasive, while the latter such as diamond and cubic boron nitride superabrasive made. In addition, there are some special species, such as sintered corundum abrasives, etc..
    Ordinary abrasive Bonded Abrasives by the binding agent to form a certain shape ordinary abrasive solid and has a certain strength abrasives. Generally abrasive, bond and pore structure, these three parts are frequently referred to as consolidation of the three elements of abrasive.
    Abrasive in the abrasive cutting role to play. Binder is to form a loose abrasive grinding solid materials, there are two types of inorganic and organic. Inorganic binders are ceramics, magnesite and sodium silicate, etc.; organic with resin, rubber and shellac, etc.. One of the most commonly used is the ceramic, resin and rubber binder.
    Holes in the grinding capacity of wear debris from debris and chip removal, and could accommodate the coolant to help grinding heat dissipation. In order to meet some special processing requirements, can also be impregnated within the pores of certain fillers, such as sulfur and paraffin, so as to improve the use of abrasive performance. Such fillers, also known as the fourth element of abrasive.
    Abrasives Bonded Abrasives, said general characteristics include: shape, size abrasive, grain size, hardness, organization and binding agent. Abrasive hardness refers to the wear debris in the external force, and from the abrasive surface, ease of falling, which reflects the strength of bonded abrasive dominated.
    Abrasive hardness depends primarily on the amount of binding agent to join the number and density of abrasive, abrasive easy to fall off the expression of abrasive hardness is low; On the contrary, that high hardness. Hardness level is generally divided into super-soft, soft, medium soft, medium, medium hard, hard and superhard seven levels, from which the hierarchy can be subdivided into a number of small-class. Abrasive hardness measurement method, more commonly used are hand-cone method, mechanical cone method, Rockwell hardness tester hardness measurement method and blasting assay.
    Abrasive hardness and its dynamic elastic modulus with the corresponding relation, which is favorable to use the audio Determination of the dynamic elastic modulus abrasive to represent the abrasive hardness. In the grinding, if they are grinding the workpiece material, high hardness, low abrasive hardness is generally used; the contrary, the selection of high hardness of the abrasive.
    Abrasives organization roughly divided into the close, medium and loose categories. Each category can be further subdivided, etc., to use numbers to distinguish between organizations. Abrasives organization, the greater the share of abrasive in the abrasive volume percentage of the smaller, the wider the gap between the grit that the more loose organization. On the contrary, the smaller the number the organization, said the organization more closely. Than the loose organization of the abrasive used is not easy passivation, less heat in the grinding process can reduce the workpiece deformation and heat burns. Tight organization's not easy to come off abrasive grit, is conducive to maintaining the geometric shape of abrasive. The organization only in the manufacture of abrasive press the abrasive formula be controlled, generally no determination.
    Superabrasive grinding mainly by the consolidation of diamond, cubic boron nitride, etc. and combination of the abrasive agent solid form. As the diamond, cubic boron nitride of high prices, with good wear resistance, they are manufactured with ordinary abrasive Bonded abrasive Bonded abrasive different, in addition to super-hard abrasive layer, there are transition layer and matrix.
    Super-hard abrasive layer is part of the role played cutting by the composition of super-hard abrasive and binding agent. Matrix in the grinding care to play the role of support, from metal, Bakelite or ceramic materials such as composition. Buffer layer is used to connect the base body and super-hard abrasive layer, from the binder composition, and sometimes can be avoided. Commonly used binders are resins, metals, plating metals and ceramics.
    Bonded Abrasives manufacturing processes are: the allocation of material, mixing, forming, heat treatment, processing and inspection. With the combination of agents is different manufacturing processes are not the same. Ceramic binder grinding mainly uses profiling method, the abrasive and binding agent according to the weight ratio of formula, after weighing, place mixing machine mixing, input of metal mold, in press forming a rough abrasives. Blank after drying and then firing into the kiln, firing temperature is generally around 1300 ℃. When using low melting point Shaorong binder, the sintering temperature below 1000 ℃. Size shape and then provides accurate processing, and final inspection products.
    Resin-bonded abrasives are generally at room temperature under the condition of forming presses, there is also an edge in the heating conditions, heat below the hot pressing process. Hardening furnace hardened after forming. With phenolic resin as binder, the curing temperature of 180 ~ 200 ℃.
    Rubber bonding agent used mainly on the roller grinding machine mixing, and roll into thin slices, then use the red knife punching molding; while others with loose materials, presses into the inner metal mold forming. Forming curing tank after the curing temperature of 168 ~ 180 ℃.
    Metal-bonded grinding tools manufacturing process are two kinds of powder metallurgy and electroplating method is mainly used in super-hard abrasive Bonded Abrasives. Powder metallurgy bronze etc. binder after mixing with hot or at room temperature compression molding, and then sintering process. Plating method with nickel or nickel-cobalt alloy plating metals etc., by electroplating process will be abrasive consolidation in the matrix, making a consolidation of abrasives.
    Special varieties of grinding with sintered corundum abrasives such as abrasive and fiber. Sintered corundum abrasive is alumina powder and an appropriate amount of chromium oxide mixture, molding, sintering is made at about 1800 ℃. This abrasive compact, has high strength, mainly used for processing of clocks and watches, instruments and other components. Fiber containing or abrasive is used for chunks of abrasive filaments (eg, nylon) as raw material, its good elasticity, is mainly used for polishing metal materials and products.

    回答于 2009-10-05 16:32
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