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磨具是用来做什么的?一般有哪些?用在什么地方?

(2010-04-20 10:26:25)
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杂谈

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。 

  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。 

  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。 

  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。 

  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

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 working surface of the continuous emergence of new cutting abrasive edge, or constantly exposing new sharp abrasive, so abrasive in a certain period of time can keep cutting.
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.
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.
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.
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 of

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