【導(dǎo)讀】加工條件和材料的物理性能對(duì)材料的切削加工有直接影響。運(yùn)轉(zhuǎn)條件、刀具材料、幾何尺寸和加工工件的需求作業(yè)間接影響加工性能，并且經(jīng)常用于克服加工材料所呈現(xiàn)的復(fù)雜情況。這些因素可以導(dǎo)致出現(xiàn)增加加工難度的情況。分、制造、硬度、屈服強(qiáng)度、拉伸強(qiáng)度。具有相似晶粒顯微結(jié)構(gòu)的金屬由相似的加工性能特性，但是在同。寸中等大小的金屬呈現(xiàn)折中的金屬切削和拋光加工特性。相關(guān)，并且它是一般作為機(jī)械加工的指標(biāo)。金屬可以改善加工性能，如減少脆性、消除應(yīng)力、增強(qiáng)硬度或其他變化。因?yàn)槎喾N元素構(gòu)成的金屬合金，每種元素都對(duì)金屬加工性能有影響，而他們影響的疊加則不確定。“加工”是指用傳統(tǒng)的加工工藝，捶打或材料。加工金屬分為棒材、鋼坯、卷板、條料、板材。熱量使刀具邊緣磨損加速。的刀頭形狀和切削更小的切削尺寸來(lái)抵御加工區(qū)域增加的負(fù)荷。前角度數(shù)很大的刀具容易發(fā)生咬刀，產(chǎn)生材料的剪切。

　　

【正文】 hardening tendencies are subjected to increased temperature ,it acts like a catalyst to produce higher hardness levels in the workpiece . The machining of workpiece materiaks with work hardening properties should be undertaken with a generous amount of coolant .In additon ,cutting speed should correlate specifically to the material machined and should not be recklessly altered to meet a production rate .The excess heat created by unusually high cutting speeds could be extremely by detrimental to the machning process by promoting work hardening of the workpiece .Low chip thicknesses should be avoided on these materials ,since this type of inefficient machining practice creates heat due to friction ,which produces the same type effect mentioned earlier .Positive low force cutting geometries at moderate speeds and feeds are normally very effetive on these materials . Machining The term ‘machinability’is a relative measure of how easily a material can be machined when pared to 160 Brinell AISI B1112 free machining low carbon steel .The 14 American Iron and Steel Institute (AISI) ran turning tests of this material at 180 surface feet and pared their results for B1112 against several other materials .If B1112 represents a 100% rating ,then materials with a rating less than this level would be decidedly more difficult to machine ,while those that exceed 100% would be easier to machine . The machinability rating of a metal takes the normal cutting speed ,surface finish and tool life attained into consideration to arrive at a final machinability rating .The fllowing chart shows a variety of materials and their specific machinability Rating: MaterialHardness Machinability Rating 6061T Aluminum 190% 7075T Alumimum 120% B1112 Steel 160BHN 100% 416 Stainless Steel 200BHN 90% 1120 Steel 160BHN 80% 1020 Steel 148BHN Machinability The factors affecting machinability have been explained 。four methords used to judge machinability are discussed below: 15 Tool life :Metals which can be cut without rapid tool wear are generally thought of as being quite machinble ,and vice versa .A workpiece material with many small hard inclusions many appear to have the same mechanical properties as a less abrasive metal .It may require no greater power consumption during cutting . Yet ,machinability of this material would be lower because its abrasive properties are responsible for rapid wear on the tool ,resulting in higher machining costs. Tool Force and Power Consumption :The use of tool force or power consumption as a criterion of machinability of the workpiece material es about fow two reasons .First ,the concept of machinability as the case with which a metal is cut ,imples that a metal through which a tool is easily pushed should have a good machinability rating .Second ,the more practical concept of machinability in terms of minimum cost per part machined , relates to forces and power consumption ,and the overhead cost of a machine of property capacity . Surface Finish ： The quality of the surface finish left on the workpiece during a cutting opeeration is sometimes useful in determining machinability rating of matel 。 Some workpiece will not ‘ take a good finish’as well as others .The fundamental reason for surface roughness is the formation and sloughing off of parts of the builtup edge on the tool . Soft ,ductile materials tend to form a builtup edge rather easily .Stainless steeels ,gas turbine alloy ,and other metals with high strain hardening ability ,also tend to machine with builtup edges .Materials which machine with high shear zone angles tend to minimize buileup dege effects .These include the aluminum alloy ,cold worked steels ,freemachining steels ,brass , and titatnium allys .If surface finish alone is the chosen index of machinabiity ,these latter metals would rate higher than those in the first group . Chip Form :There have been machinability ratings based on the type of chip that is formed during the machining operation .The machinability might be judged by the case handling and disposing of chips .A material that produces long stringy chips would receive a low rating ,as would one which produces fine powdery chips .Materials which inherently from nicely broken chips ,a half or full turn of the normal chip helix ,would receive top rating . Chip handling and disposal can be quite expensive .Stringy chips are a menace to 16 the operator and to the finish on the freshly machined surface .However ,chip formation is a function of the machine variables as well as the workpiece material ,and the rationgs obtained by this method coould be changed by provision of a suitable chip breaker .