垫圈产品冲裁模设计【冲压模具设计】【说明书+CAD+STP三维】
垫圈产品冲裁模设计【冲压模具设计】【说明书+CAD+STP三维】,冲压模具设计,说明书+CAD+STP三维,垫圈产品冲裁模设计【冲压模具设计】【说明书+CAD+STP三维】,垫圈,产品,冲裁模,设计,冲压,模具设计,说明书,仿单,cad,stp,三维
摘要本次设计了垫圈的复合冲压模具。首先要对冲压模具进行工艺分析,经过工艺分析和对比确定模具架及压力机,确定压力机的型号。再分析对冲压件加工的模具适用类型选择所需设计的模具。得出将设计的模具类型后将模具的各工作零部件设计过程表达出来。在说明书中第一部分,主要叙述了冲压模具的发展状况,说明了冲压模具的重要性与本次设计的意义,对冲压件的工艺分析,工艺方案的确定。通过,对零件排样图的设计,完成了材料利用率的计算。再进行冲裁工艺力的计算和冲裁模工作部分的设计计算。最后对主要零部件的设计和标准件的选择,为本次设计模具的绘制和模具的成形提供依据,以及为装配图各尺寸提供依据。通过前面的设计方案画出模具各零件图和装配图。关键字:冲压;工艺:模具结构AbstractA molding tool for designing a set ofly hurtling bore, falling anticipating.Want to proceed the craft analysis to the washer first, analyze through craft with contrast certain molding tool a model number for and pressure machine, making sure pressure machine.Analyze again to wash to press a molding tool for processing apply the type the choice a molding tool for needing design.Get a molding tool for will designing type empress expresses out each work zero parts design process of the molding tool.In text file the first part, described to wash the development condition that press the molding tool primarily, explain to wash the importance that press the molding tool and the meaning of this design, to craft that washing and pressing the piece analyzes, the craft project really settles.Pass, line up the design of the kind diagram to the spare parts, complete the calculation of the material utilization.Proceed again the calculation that wash cut the craft dint with wash to cut mold work part of designs calculation.Finally to the design of the main the parts of zero with the choice of the standard piece, draw for this design molding tool to take shape the offering with the molding tool according to, and for assemble each size of diagram offering according to.The design project passing before draws an each spare parts of molding tool diagram with assemble the diagram.Keyword:Wash to press;Fall to anticipate to hurtle the bore;Molding tool construction目录摘要1Abstract2第1章 零件的分析51.1 零件的工艺性分析51.1.1 设计题目内容51.1.2 材料的性能51.1.3 冲压成型工艺分析61.2 工艺方案分析61.2.1 方案种类61.2.2 方案比较6第2章 冲压工艺计算72.1 落料力的计算72.2 冲孔力的计算82.3 卸料力的计算92.4 推件力的计算92.5 顶件力的计算92.6 选择压力机92.7 压力中心计算11第3章 排样设计计算12第4章 工作零件的设计134.1 模具间隙的确定134.2 冲孔刃口尺寸计算164.3 落料刃口尺寸计算16第5章 辅助结构零件的设计及选用175.1 模具总体结构设计175.2 凸凹模固定板175.3凸模固定板175.4 垫板185.5 卸料板185.6 操作与定位方式19第6章 模具的装配图的设计206.1 零件的技术要求206.2 装配技术要求206.3 模具安装要求216.4 复合模的调试要求216.5 主要组件的装配21第8章 模具工作过程23结论与展望24致谢25参考文献26第1章 零件的分析1.1 零件的工艺性分析1.1.1 设计题目内容图2-1 工件图原始资料:如图2-1所示零件材料:为紫铜;厚度:为0.8mm;生产批量:属于大批量生产根据图1可以知道,零件为落料冲孔垫圈。根据GB/T15055-2007f冲压件未注公差尺寸极限偏差可查得,分别是落料,冲孔。这2个工序可以在一副模具上完成,也可以在两、三或者四副模具上完成,其需要在几副上完成主要根据零件的外型来确定1.1.2 材料的性能紫铜并会随着材质的厚度的增加而使其屈服值减小。保证机械性能,不保证化学成分,不能热处理,机械性能较低,比较常用,价格便宜。1.1.3 冲压成型工艺分析此工件为紫铜,厚度为0.8mm, 具有良好的冲压性能,适合冲裁,具有良好的冲压工艺性。主要工艺难点在于两个精度要求,及其零件的形状不规则,在大批量的生产条件下,要保证生产效率。选取合理的模具类型、结构,采用最经济的制模工艺。因为该零件包含了落料、冲孔这2道工序1.2 工艺方案分析1.2.1 方案种类根据制件工艺性分析,要加工此零件,分析出以下两种方案。方案一:落料,冲孔单工序,共2道工序 方案二:落料,冲孔,复合冲裁模方案一次性实现冲孔1.2.2 方案比较 方案1属于单工序模。模具结构简单,制造方便,但需要2道工序,再加之此制件生产批量大,尺寸较小,这种方案生产率低,一般不宜采用。方案2为复合冲裁模,在同一部位同时完成了零件的生产,对于这种大批量生产零件,大大的提高了生产效率。故选用方案二。第2章 冲压工艺计算由于该零件的生产过程要经过落料,冲孔2道工序,且是落料冲孔其模具类型选择复合模形式。所以在选设备的时候要先计算哪个工序需要的力大些,其次还需考虑最大的力是否在压力机安全范围内等等,以下是压力机选择要考虑的基本因素:1 冲压设备的类型和工作形式是否使用于应完成的的工序;是否适合安全生产和环保的要求;2 冲压设备的压力和功率是否满足应完成工序的需要;3 冲压设备的装模高度,台面尺寸,行程等是否适合完成工序所用的模具;4 冲压设备的行程次数是否满足生产率的要求等。2.1 落料力的计算1 冲裁力的计算 =Lt其中 -冲裁力,单位为N;t-材料厚度,单位为mm;-材料抗剪强度,单位为MPa;对紫铜 取350MPa;L-冲裁周长,单位为mm。考虑到模具刃口的磨损,凸凹模间隙的波动,材料机械性能的变化,材料厚度的偏差等因素,实际所需冲裁力还必须增加30%,即 F=1.3=1.3LtF=1.3=1.3Lt=1.3x61.77x0.8x350=22.48KN2.2 冲孔力的计算冲裁力 =Lt 其中-冲裁力,单位为N;t-材料厚度,单位为mm;-材料抗剪强度,单位为MPa;对紫铜取350MPa;L-冲裁周长,单位为mm。考虑到模具刃口的磨损,凸凹模间隙的波动,材料机械性能的变化,材料厚度的偏差等因素,实际所需冲裁力还必须增加30%,即F=1.3=1.3Lt=1.3x20.42x350*0.8=7.43KN2.3 卸料力的计算由2得卸料力的计算公式F卸料=K卸料F落料 (3.3)式中: K卸料卸料力系数,查表3.1。F卸料=K卸料F落料 =0.03422.48=0.76(kN)2.4 推件力的计算由2中推件力的计算公式F推件=nK推件F冲孔(3.4) 式中: K推件推件力系数,查表3.1。n同时梗塞在凹模内的工件数(废料数);F推件=nK推件F冲孔 =0.0457.43=0.334(kN)2.5 顶件力的计算由2中顶件力的计算公式F顶件=K顶件F落料 (3.5)式中: K顶件顶件力系数,查表3.1。 F顶件=K顶件F落料 =0.0622.48=1.35(kN)2.6 选择压力机根据以上几个工序所计算的结果,落料的冲裁力最大,且该冲压件选择的模具类型为复合模,这类模具在工作的时候是一道工序一道工序完成,在受力的时候各个工序所受的力不和其他的工序重叠,就是说在选设备的时候根据在各个工序里的最大力来选,且所受的力在安全范围内。所以此副模具就是根据落料工序的总工艺力来初选压力机。1 对于落料冲裁工序,压力机的公称力应大于或等于冲裁时总冲压力的1.1-1.3倍 P(1.1-1.3) 其中P-压力机的公称力F-冲裁力的总冲压力P 1800.11KN 2 冲压设备的选择 冲压设备选择的要求:1) 压力机的行程大小,应能保证成型零件的取出与毛坯的放入。2) 压力机的工作台面尺寸应大于冲模的平面尺寸,还需留有安装固定的余地,但是在过大的工作台上安装很小尺寸的冲模时,工作台的受力条件也是不理想的。所选的压力机的工作台面尺寸应与冲模的平面尺寸相适应。3) 模具的闭合高度:模具在闭合时,上模座的上表面到下模座的下表面之间的距离。压力机的闭合高度H:滑块在下死点时,工作台面到滑块下端面的距离。该距离一般是可以调整的,故一般的压力机均由最大闭合高度和最小闭合高度。4) 压力机的吨位要与总的冲压力相适应。根据所计算出的总冲压力。初步选择公称压力为2500kN的闭式单点单动压力机J31-250。其基本参数如下表1:表1 J31-250基本参数公称压力2500kN滑块行程315mm标准行程次数20次/min最大闭合高度 490mm闭合高度调节量200mm工作台尺寸(左右)1000mm工作台尺寸(前后)950mm标称压力行程10.4mm导轨间距离900mm滑快底面前后尺寸850mm拉深垫压紧力400KN2.7 压力中心计算因为该零件是对称图形,并按照如下式进行计算得:冲孔:(3.8) (3.9)冲裁边:(3.10) (4.11)式中:冲孔时指各种孔的中心位置;冲裁边时指各线段中心坐标; 冲各孔时所用压力; 各线段长度; 压力中心坐标。由于零件是对称图形,即压力中心在中心.第3章 排样设计计算根据工件的开关,确定采用无废料的排样方法不可能做到,但能采用有废料和少废料的排样方法。经多次排样计算决定采用, 1)搭边设计 板料厚度t=0.8mm, 所以a=1mm, a=1.4mm。送料步距A=15mm, 条料宽度B=25mm。 2)排样布局3)材料利用率计算:S=206.23mm=100%=100%=100%=55%式中,材料利用率;S工件的实际面积;S所用材料面积,包括工件面积与废料面积;A步距(相邻两个制件对应点的距离)B条料宽度。第4章 工作零件的设计4.1 模具间隙的确定冲裁件的工艺性分析是指冲裁件对冲裁的适应性,即冲裁件的形状结构、尺寸的大小及偏差等是否符合加工的工艺要求。冲裁件的工艺性是否合理对冲裁件的质量、模具的寿命和生产率有很大影响。 冲裁间隙指凸、凹模刃口间隙的距离。冲裁间隙是冲压工艺和模具设计中的重要参数,它直接影响冲裁件的质量、模具寿命和力能的消耗,应根据实际情况和需要合理的选用。冲裁间隙有单面间隙和双面间隙之分。根据冲裁件尺寸精度、剪切质量、模具寿命和力能消耗等主要因素,将金属材料冲裁间隙分成三种类型3:类(小间隙),类(中等间隙),类(大间隙)。1、间隙过小时,由凹模刃口处产生的裂纹在继续加压的情况下将产生二次剪切,继而被挤入凹模。这样,制件端面中部留下撕裂面,而两头出现光亮带,在端面出现挤长的毛刺。毛刺虽长单易去除,只要中间撕裂不是很深,仍可用。2、间隙过大时,材料的拉深与拉伸增大,拉伸应力增大,材料容易被撕裂,使制件的光亮代减小,圆角与断裂都增大,毛刺大而厚,难去除。所以随着间隙的增大,制件的断裂面的倾斜度的增大,毛刺增高。 冲裁件的尺寸精度是指冲裁件的实际尺寸与公差尺寸的差值。这个差值包含两个方面的偏差,一是冲裁件相对于凸模或凹模尺寸的偏差,一是模具本身的制造偏差。其中凸、凹模间隙是影响凸模或凹模尺寸的偏差的主要因素。当凸、凹模的间隙较大时,材料所受拉伸作用增大。冲裁完后,材料的弹性恢复使落料尺寸小于凹模尺寸,冲孔孔径大于凸模直径。此时穹弯的弹性恢复方向与其相反,鼓薄板冲裁时制件尺寸偏差减小。在间隙较小时,由于材料受凸、凹模挤压力大,故冲裁完后,材料的弹性恢复使落料件尺寸增大,冲孔孔径减小。 随着间隙的增大,材料所受的拉力增大,材料容易断裂分离,因此冲裁力减小。但是继续增大间隙时,会因从凸、凹模刃口处产生的裂纹不重合,冲裁力减小。由于间隙的增大,使冲裁件的光亮面变小,落料尺寸小于凹模尺寸,冲孔尺寸大于凸模尺寸,因而使卸料力、推件力或顶件力也随之减小。但是,间隙继续增大时,因为毛刺增大,引起卸料力、顶件力也迅速增大。 冲裁模具的寿命通常以保证获得合格产品时的冲裁次数来表示。冲裁过程中模具的失效形式一般有:磨损、变形、崩刃和凹模刃口涨裂四种。 间隙增大时可使冲裁力、卸料力等减小,因而模具的磨损也减小;但当间隙继续增大时,卸料力增加,又影响模具磨损,一般间隙为(10%-15%)t时磨损最小模具寿命较高。间隙小时,落料件梗塞在凹模洞口的涨裂力也大。由以上分析可见,凸、凹模对冲裁件质量、冲裁力、模具寿命等都有很大的影响。因此,在设计和制造模具时有一个合理的间隙值,以保证冲裁件的断面质量好,尺寸精度高,所需冲裁力小,模具寿命高。生产中常选用一个适当的范围作为合理间隙。这个范围的最小值称为最小合理间隙,最大值称为最大合理间隙。设计与制造新模具时采用最小合理间隙值。 确定合理间隙的理论根据是以凸、凹模刃口处产生的裂纹相重合为依据。可以计算得到合理间隙值,计算公式如下:Z=2t(1- )tan2-5由上式可看出,间隙z与材料厚度t、相对切入深度/t及破裂角有关。对硬而脆的材料, /t有较小值时,则合理间隙值较大。对软而韧的材料,/t有较大值,则合理间隙值较小。板厚越大,合理间隙越大。由于理论计算在生产中不便使用,故目前广泛使用的是经验数据。 表2-1冲裁模较大单面间隙材料厚度08、10、35、09Mn、Q235、B3紫铜40、5065Mn最小值最大值最小值最大值最小值最大值最小值最大值0.50.0200.0300.0200.0300.0200.0300.0200.0300.60.0240.0360.0240.0360.0240.0360.0240.0360.80.0360.0520.0360.0520.0360.0520.0360.0520.90.0450.0630.0450.0630.0450.0630.0450.0631.00.0500.0700.0500.0700.0500.0700.04500.0631.20.0630.0900.660.0900.0660.0901.50.0660.1200.0850.1200.0850.1202.00.1230.1800.1300.1900.1300.190间隙的选择可以按照如下原则:对于断面垂直度与尺寸公差要求较高的工件,选择较小的合理间隙值。这时冲裁力与模具寿命作为次要因素来考虑。对于断面垂直度与尺寸公差要求的前提下,应以降低冲裁力、提高模具寿命为主,采用较大的合理间隙值。 落料部分以落料凹模为基准计算,落料凸模按间隙值配制;冲孔部分明中孔凸模为基准计算,冲孔凹模按间隙值配制。既以落料凹模、冲孔凸模为基准,凸凹模按间隙值配制。零件外形为异形,为便于凸凹模加工,保证凸凹模之间的间隙,采用凸凹模配合加工。公式:冲孔时: d= (d+x) (310)d= (d+x+Z) (311)落料时: D= (D-x) (312)D= (D+x+Z) (313)孔距尺寸:L= (L+0.5+)8 (314)式中 d, d分别为冲孔凸模和凹模的刃口尺寸;D ,D分别为落料凸模和凹模的刃口尺寸;d,D分别为冲孔件和落料件的最小和最大极限尺寸;L两孔中心距的最小极限尺寸;工件公差;Z最小合理间隙;X磨损系数。4.2 冲孔刃口尺寸计算=0.36X=0.5s=/4d(6.5) mm=(d+x)=(6.5+0.50.36)-s0=6.684.3 落料刃口尺寸计算D1(22.3)mm = (D-x)=(22.3-0.50.25)0+0.063=22.175D1(14)mm = (D-x)=(14-0.50.25)0+0.063=13.875D1(6)mm = (D-x)=(6-0.50.25)0+0.063=5.875第5章 辅助结构零件的设计及选用5.1 模具总体结构设计废料由凸模入凹模洞口中,积累到一定数量,由下模漏料孔排出,不必清除废料,操作方便,应用很广,但工件表面平直度较差,凸凹模承受的张力较大,因此凸凹模的壁厚应严格控制,以免强度不足。5.2 凸凹模固定板凸凹模固定板形状与凹模板一致,如图所示: 5.3凸模固定板凸模固定板将凸模固定在模座上,其平面轮廓尺寸与凹模板外形尺寸相同,但还应考虑紧固螺钉及销钉的位置。固定板的凸模安装孔与凸模采用过渡配合H7/m6、H7/n6,压装后将凸模端面与固定板一起磨平。凸模固定板为圆形,厚度一般取凹模厚度的0.60.8倍。5.4 垫板冲裁时,如果凸模的端部对模座的压应力超过模座材料的许用压应力,这时需要在凸模端部与模座之间加上一块强度较高的垫板。即下列情况下雨加垫板。式中 凸模端面的压应力,其数值为; 模座材料下雨压应力,其数值:铸铁约为100MPa,钢约为200 MPa;冲裁力;凸模上端面面积。垫板的下载与凸模固定板一致,厚度一般取412mm。垫板淬硬后两面应磨平,表面粗糙度Ra0.320.63。由于本套模具选用压入式模柄,在上模座与凸模固定板之间也必须安装垫板5.5 卸料板卸料板同样为和凹模板一致,卸料板材料选A3或(45)钢,不用热处理淬硬。取卸料板与凸凹模的双面间隙为0.10.3mm.卸料板上设置几个卸料螺钉。卸料钉尾部应留有足够的行程空间。卸料螺钉拧紧后,应使卸料板超出凸模端面lmm,有误差时通过在螺钉与卸料板之间安装垫片来调整。如下图所示:5.6 操作与定位方式零件中批量生产,安排生产可采用手工送料方式能够达到批量生产,且能降低模具成本,因此采用手工送料方式.零件尺寸较大,厚度较高,保证孔的精度及较好的定位,宜采用导料板导向,导正销导正,为了提高材料利用率采用始用挡料销和固定挡料销。第6章 模具的装配图的设计6.1 零件的技术要求1冲模零件不允许有裂纹,工作表面不允许有划痕、机械损伤、锈蚀等表面缺陷。经热处理后的零件硬度应均匀、不允许有软点和脱碳区,并清除氧化物等。2冲模各零件的材料和热处理硬度应优先按模具设计手册中标准选用,允许采用性能高于两表规定的其他钢种。3零件图中普通螺纹的基本尺寸应符合GB/T196的规定,选用极限与配合应符合GB/T197的规定。4固定板、凹模、垫板、卸料板的形状和位置公差按GB/T1182-1996等的规定。5冲模各零件的几何形状、尺寸精度、表面粗糙度等应符合设计图样的要求。6零件图中未注公差尺寸的极限偏差按GB/T1804的规定。7零件图中未注的形状和位置公差按GB/T1184-1996的规定。8冲裁模之凸、凹模刃口及侧刃必须锋利,不允许有崩刃、缺刃和机械损坏。9冲裁模凹模工作孔不允许有倒锥度。6.2 装配技术要求1装配时应保证凸、凹模之间的间隙均匀一致,配合间隙符合设计要注,不允许采用使凸、凹模变形的方法来修正间隙。2推料、卸料机构必须灵活,卸料板或推件器在冲模开启状态时,一般应突出凸凹模表面0.5-1mm。4各接合面保证密合。5冲压的凹模刃口的高度,按设计要求制造,其漏料孔应保证畅通,一般应比刃口大0.2-2mm6.冲模所有活动部分的移动应平稳灵活,无滞止现象,滑块、楔埠在固定滑动面移动时,其最小面积不少于其面积的一半。7各紧固用的螺钉、锁钉不得松动,并保证螺钉和销钉的端面不突出上、下模座平面。8各卸料螺钉沉孔深度应保证一致。9各卸料螺钉、顶杆的长度应保证一致。10凸模的垂直度必须在凸凹模间隙值允许范围内。11冲模的装配必须符合模具装配图、明细表及技术条件规定。12凸模、凸凹模等与固定板的配合一般按H7/h6或H7/m6,保证工作稳定可靠。6.3 模具安装要求1.上模座上平面对下模座下平面的平行度,导柱轴心线对下模座下平面的垂直度和导套孔轴心线对上模座上平面的垂直度均应达到规定的精度要求。2.模架的上模沿导柱上、下移动应平稳,无阻滞现象。3.装配好的模具,其封闭高度应符合图样规定的要求。6.4 复合模的调试要求模具按图纸技术要求加工与装配后,必须在符合实际生产条件的环境中进行试模,可以发现模具设计与制造的缺陷,发现问题必须及时解决。找出产生的原因,进行改正。对模具进行适当的调整和修理后再进行试模,直到模具能正常工作,才能将模具正式交付生产使用。6.5 主要组件的装配1模柄的装配,在安装凸模固定板和垫板之前,应先把模柄装好,用角尺检查模柄与上模座上平面的垂直度。2. 凸模和凸模固定板的装配配合要求为H7/m6。装配时,先在压力机上将凸模压入凸模固定板内,检查凸模的垂直度,然后将固定板的上平面与凸模尾部一起磨平,为了保持凸模刃口锋利还应将凸模的端面磨平。3. 导柱与导套的技术要求及装配,组成模架各零件均应符合相应的技术条件,其中特别重要的是每对导柱,导套的配合间隙应符合要求。压入上、下模座的导柱、导柱离其它安装表面应有1-2 mm的距离,压入后就应牢固。装配成套的模架,各零件的工作表不应有碰伤,裂纹以及其它机械损伤。第8章 模具工作过程有上面可知模具为复合冲裁模。上模部分有凹模与冲孔凸模,通过冲孔凸模固定板、垫板由销钉定位、螺钉固定装在上模座上。凸凹模通过凸凹模固定、垫板装在下模座上。采用导柱导套导向,导柱布置在两侧。为防止装反,两个导柱的直径有同。为了推件与卸料,上模装有由推杆、推板、推杆与推件板组成的刚性系统。下模装有由卸料、卸料螺钉与橡皮组成的弹性卸料系统。弹性卸料对条料起校平作用。冲载时,落料凹模将弹性卸料板压下,冲孔凸模也进入冲孔凹模孔中,同时完成冲孔与落料。当上模回程时,弹性卸料板在橡作用下将条料从凸凹模上卸下,而推杆受到横杆的推动,通过推板、推杆与推件板将冲件从凹中推出,冲孔废料由凸凹模孔中漏出。条料的定位依靠左侧的两个活动导料的方法在复合模中的应用较多,它不影响弹性卸料板对条料的压平作用。而倒装复合模的主要的优点是废料能直接从压力机漏料孔落下,冲载件从上模落下,比较容易取出这些排出件,因此操作方便安全,有利于倒装复合模的安装送料装置,生产效率较高,所以应用比较广泛。结论与展望本次冲压模具的设计历时几个月,系统综合应用了大学期间所学的相关知识。通过本次设计,基本上已经掌握了冲压模具的设计过程和方法,查阅文献收集资料途径,培养了良好的设计思路,为以后从事模具设计工作打下了坚实的基础。为了提高生产效率和降低成本,在设计中尽量对模具进行设计。但这也带来如模具内部结构复杂,不便于安装等问题。原模存在着最小壁厚的问题,最小壁厚取值大,浪费材料,取值小模具的强度不能保证,设计时解决了最小壁厚与搭边值之间的矛盾;使用定位装置,避免了毛坯的偏移;凸模在工作时保证其强度时存在问题;给清理工作带来不便,应该改进。致谢本设计的撰写是在我的指导教师的精心指导和关心下完成的。从课题的选择、方案制定、工作实施到设计的撰写、修改无不渗透着老师的心血。老师以他们渊博的学识、卓越的才智、严谨的治学精神和求实创新的工作作风使我受益非浅,在学习和设计过程中给予我很大的启迪与帮助,给我留下了极为深刻的印象,使我对以后的工作充满信心。在此设计完成之际,谨向几年来关心我的工程技术学院所有老师致以崇高的敬意和衷心的感谢!同时在设计过程中得到了同组同学的大力帮助和支持,在此一并致谢。参考文献1冲模设计手册编写组.模具设计手册M.北京:机械工业出版社,19992冷冲压模具设计M.北京: 化学工业出版社,20103王芳.冷冲模具指导书M.北京:机械工业出版社,19984王以真.实用扬器技术手册M.北京:国防工业出版社,20035王新华,袁联富.冲模结构图册M.北京:机械工业出版社,20036陈锦昌,刘就女等.计算机工程制图M.广州:华南理工大学出版社,19997刘鸿文.材料力学M.北京:高等教育出版社,19998黄毅宏,李明辉.模具制造工艺M.北京:机械工业出版社,19999模具实用技术丛书编委会.冲模设计应用实例M.北京:机械工业出版社,199910廖念钉,古莹奄等.互换性与技术测量M.北京:中国计量出版社,200111王焕庭,李茅华、徐善国.工机械工程材料M.大连:大连理工大学出版社,200212党根茂,骆志斌等.模具设计与制造M.西安:西安电子科技大学出版社,2001INEEL/CON-2000-00104 PREPRINT Spray-Formed Tooling for Injection Molding and Die Casting Applications K. M. McHugh B. R. Wickham June 26, 2000 June 28, 2000 International Conference on Spray Deposition and Melt Atomization This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint should not be cited or reproduced without permission of the author. This document was prepared as a account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third partys use, or the results of such use, of any information, apparatus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights. The views expressed in this paper are not necessarily those of the U.S. Government or the sponsoring agency. BECHTEL BWXT IDAHO, LLC 1 Spray-Formed Tooling For Injection Molding and Die Casting Applications Kevin M. McHugh and Bruce R. Wickham Idaho National Engineering and Environmental Laboratory P.O. Box 1625 Idaho Falls, ID 83415-2050 e-mail: kmm4inel.gov Abstract Rapid Solidification Process (RSP) Tooling is a spray forming technology tailored for producing molds and dies. The approach combines rapid solidification processing and net-shape materials processing in a single step. The ability of the sprayed deposit to capture features of the tool pattern eliminates costly machining operations in conventional mold making and reduces turnaround time. Moreover, rapid solidification suppresses carbide precipitation and growth, allowing many ferritic tool steels to be artificially aged, an alternative to conventional heat treatment that offers unique benefits. Material properties and microstructure transformation during heat treatment of spray-formed H13 tool steel are described. Introduction Molds, dies, and related tooling are used to shape many of the plastic and metal components we use every day at home or at work. The process involves machining the negative of a desired part shape (core and cavity) from a forged tool steel or a rough metal casting, adding cooling channels, vents, and other mechanical features, followed by grinding. Many molds and dies undergo heat treatment (austenitization/quench/temper) to improve the properties of the steel, followed by final grinding and polishing to achieve the desired finish 1. Conventional fabrication of molds and dies is very expensive and time consuming because: Each is custom made, reflecting the shape and texture of the desired part. The materials used to make tooling are difficult to machine and work with. Tool steels are the workhorse of industry for long production runs. Machining tool steels is capital equipment intensive because specialized equipment is often needed for individual machining steps. Tooling must be machined accurately. Oftentimes many individual components must fit together correctly for the final product to function properly. 2 Costs for plastic injection molds vary with size and complexity, ranging from about $10,000 to over $300,000 (U.S.), and have lead times of 3 to 6 months. Tool checking and part qualification may require an additional 3 months. Large die-casting dies for transmissions and sheet metal stamping dies for making automobile body panels may cost more than $1million (U.S.). Lead times are usually greater than 40 weeks. A large automobile company invests about $1 billion (U.S.) in new tooling each year to manufacture the components that go into their new line of cars and trucks. Spray forming offers great potential for reducing the cost and lead time for tooling by eliminating many of the machining, grinding, and polishing unit operations. In addition, spray forming provides a powerful means to control segregation of alloying elements during solidification and carbide formation, and the ability to create beneficial metastable phases in many popular ferritic tool steels. As a result, relatively low temperature precipitation hardening heat treatment can be used to tailor properties such as hardness, toughness, thermal fatigue resistance, and strength. This paper describes the application of spray forming technology for producing H13 tooling for injection molding and die casting applications, and the benefits of low temperature heat treatment. RSP Tooling Rapid Solidification Process (RSP) Tooling, is a spray forming technology tailored for producing molds and dies 2-4. The approach combines rapid solidification processing and net- shape materials processing in a single step. The general concept involves converting a mold design described by a CAD file to a tooling master using a suitable rapid prototyping (RP) technology such as stereolithography. A pattern transfer is made to a castable ceramic, typically alumina or fused silica (Figure 1). This is followed by spray forming a thick deposit of tool steel (or other alloy) on the pattern to capture the desired shape, surface texture and detail. The resultant metal block is cooled to room temperature and separated from the pattern. Typically, the deposits exterior walls are machined square, allowing it to be used as an insert in a holding block such as a MUD frame 5. The overall turnaround time for tooling is about three days, stating with a master. Molds and dies produced in this way have been used for prototype and production runs in plastic injection molding and die casting. Figure 1. RSP Tooling processing steps. 3 An important benefit of RSP Tooling is that it allows molds and dies to be made early in the design cycle for a component. True prototype parts can be manufactured to assess form, fit, and function using the same process planned for production. If the part is qualified, the tooling can be run in production as conventional tooling would. Use of a digital database and RP technology allows design modifications to be easily made. Experimental Procedure An alumina-base ceramic (Cotronics 780 6) was slurry cast using a silicone rubber master die, or freeze cast using a stereolithography master. After setting up, ceramic patterns were demolded, fired in a kiln, and cooled to room temperature. H13 tool steel was induction melted under a nitrogen atmosphere, superheated about 100C, and pressure-fed into a bench-scale converging/diverging spray nozzle, designed and constructed in-house. An inert gas atmosphere within the spray apparatus minimized in-flight oxidation of the atomized droplets as they deposited onto the tool pattern at a rate of about 200 kg/h. Gas-to-metal mass flow ratio was approximately 0.5. For tensile property and hardness evaluation, the spray-formed material was sectioned using a wire EDM and surface ground to remove a 0.05 mm thick heat-affected zone. Samples were heat treated in a furnace that was purged with nitrogen. Each sample was coated with BN and placed in a sealed metal foil packet as a precautionary measure to prevent decarburization. Artificially aged samples were soaked for 1 hour at temperatures ranging from 400 to 700C, and air cooled. Conventionally heat treated H13 was austenitized at 1010C for 30 min., air quenched, and double tempered (2 hr plus 2 hr) at 538C. Microhardness was measured at room temperature using a Shimadzu Type M Vickers Hardness Tester by averaging ten microindentation readings. Microstructure of the etched (3% nital) tool steel was evaluated optically using an Olympus Model PME-3 metallograph and an Amray Model 1830 scanning electron microscope. Phase composition was analyzed via energy- dispersive spectroscopy (EDS). The size distribution of overspray powder was analyzed using a Microtrac Full Range Particle Analyzer after powder samples were sieved at 200 m to remove coarse flakes. Sample density was evaluated by water displacement using Archimedes principle and a Mettler balance (Model AE100). A quasi 1-D computer code developed at INEEL was used to evaluate multiphase flow behavior inside the nozzle and free jet regions. The codes basic numerical technique solves the steady- state gas flow field through an adaptive grid, conservative variables approach and treats the droplet phase in a Lagrangian manner with full aerodynamic and energetic coupling between the droplets and transport gas. The liquid metal injection system is coupled to the throat gas dynamics, and effects of heat transfer and wall friction are included. The code also includes a nonequilibrium solidification model that permits droplet undercooling and recalescence. The code was used to map out the temperature and velocity profile of the gas and atomized droplets within the nozzle and free jet regions. 4 Results and Discussion Spray forming is a robust rapid tooling technology that allows tool steel molds and dies to be produced in a straightforward manner. Examples of die inserts are given in Figure 2. Each was spray formed using a ceramic pattern generated from a RP master. Figure 2. Spray-formed mold inserts. (a) Ceramic pattern and H13 tool steel insert. (b) P20 tool steel insert. Particle and Gas Behavior Particle mass frequency and cumulative mass distribution plots for H13 tool steel sprays are given in Figure 3. The mass median diameter was determined to be 56 m by interpolation of size corresponding to 50% cumulative mass. The area mean diameter and volume mean diameter were calculated to be 53 m and 139 m, respectively. Geometric standard deviation, d =(d 84 /d 16 ) , is 1.8, where d 84 and d 16 are particle diameters corresponding to 84% and 16% cumulative mass in Figure 3. 5 Figure 3. Cumulative mass and mass frequency plots of particles in H13 tool step sprays. Figure 4 gives computational results for the multiphase velocity flow field (Figure 4a), and H13 tool steel solid fraction (Figure 4b), inside the nozzle and free jet regions. Gas velocity increases until reaching the location of the shock front, at which point it precipitously decreases, eventually decaying exponentially outside the nozzle. Small droplets are easily perturbed by the velocity field, accelerating inside the nozzle and decelerating outside. After reaching their terminal velocity, larger droplets (150 m) are less perturbed by the flow field due to their greater momentum. It is well known that high particle cooling rates in the spray jet (10 3 -10 6 K/s) and bulk deposit (1- 100 K/min) are present during spray forming 7. Most of the particles in the spray have undergone recalescence, resulting in a solid fraction of about 0.75. Calculated solid fraction profiles of small (30 m) and large (150 m) droplets with distance from the nozzle inlet, are shown in Figure 4b. Spray-Formed Deposits This high heat extraction rate reduces erosion effects at the surface of the tool pattern. This allows relatively soft, castable ceramic pattern materials to be used that would not be satisfactory candidates for conventional metal casting processes. With suitable processing conditions, fine 6 Figure 4. Calculated particle and gas behavior in nozzle and free jet regions. (a) Velocity profile. (b) Solid fraction. 7 surface detail can be successfully transferred from the pattern to spray-formed mold. Surface roughness at the molding surface is pattern dependent. Slurry-cast commercial ceramics yield a surface roughness of about 1 m Ra, suitable for many molding applications. Deposition of tool steel onto glass plates has yielded a specular surface finish of about 0.076 m Ra. At the current state of development, dimensional repeatability of spray-formed molds, starting with a common master, is about 0.2%. Chemistry The chemistry of H13 tool steel is designed to allow the material to withstand the temperature, pressure, abrasion, and thermal cycling associated with demanding applications such as die casting. It is the most popular die casting alloy worldwide and second most popular tool steel for plastic injection molding. The steel has low carbon content (0.4 wt.%) to promote toughness, medium chromium content (5 wt%) to provide good resistance to high temperature softening, 1 wt% Si to improve high temperature oxidation resistance, and small molybdenum and vanadium additions (about 1%) that form stable carbides to increase resistance to erosive wear 8. Composition analysis was performed on H13 tool steel before and after spray forming. Results, summarized in Table 1, indicate no significant variation in alloy additions. Table 1. Composition of H13 tool steel Element C Mn Cr Mo V Si Fe Stock H13 0.41 0.39 5.15 1.41 0.9 1.06 Bal. Spray Formed H13 0.41 0.38 5.10 1.42 0.9 1.08 Bal. Microstructure The size, shape, type, and distribution of carbides found in H13 tool steel is dictated by the processing method and heat treatment. Normally the commercial steel is machined in the mill annealed condition and heat treated (austenitized/quenched/tempered) prior to use. It is typically austenitized at about 1010C, quenched in air or oil, and carefully tempered two or three times at 540 to 650C to obtain the required combination of hardness, thermal fatigue resistance, and toughness. Commercial, forged, ferritic tool steels cannot be precipitation hardened because after electroslag remelting at the steel mill, ingots are cast that cool slowly and form coarse carbides. In contrast, rapid solidification of H13 tool steel causes alloying additions to remain largely in solution and to be more uniformly distributed in the matrix 9-11. Properties can be tailored by artificial aging or conventional heat treatment. A benefit of artificial aging is that it bypasses the specific volume changes that occur during conventional heat treatment that can lead to tool distortion. These specific volume changes occur as the matrix phase transforms from ferrite to austenite to tempered martensite and must be accounted for in the original mold design. However, they cannot always be reliably predicted. Thin sections in the insert, which may be desirable from a design and production standpoint, are oftentimes not included as the material has a tendency to slump during austenitization or distort 8 during quenching. Tool distortion is not observed during artificial aging of spray-formed tool steels because there is no phase transformation. An optical photomicrograph of spray-formed H13 is shown in Figure 5 together with an SEM image, in backscattered electron (BSE) mode. Energy dispersive spectroscopic (EDS) composition analysis of some features in the photomicrographs is also given. While exact quantitative data is not possible due to sampling volume limitations, results suggest that grain boundaries are particularly rich in V. Intragranular (matrix) regions are homogeneous and rich in Fe. X-ray diffraction analysis indicates that the matrix phase is primarily ferrite (bainite) with very little retained austenite, and that the alloying elements are largely in solution. Discrete intragranular carbides are relatively rare, very small (about 0.1 m) and predominately vanadium-rich MC carbides. M 2 C carbides are not observed. Element Si V Cr Mn Mo Fe Spot #1 (wt%) 0.61 32.13 6.68 0.17 2.05 58.36 Spot #2 (wt%) 1.59 0.79 5.35 0.28 2.28 89.72 Figure 5. Photomicrographs of as-deposited H13 tool steel. 3% nital etch. (a) Optical photomicrograph. (b) SEM image (BSE mode) near a grain boundary. Table gives EDS composition of numbered features. 9 Figure 6 illustrates the microstructure of spray-formed H13 aged at 500C for 1 hr. During aging, grain boundaries remain well defined, perhaps coarsening slightly compared to as- deposited H13 (Figure 5). The most prominent change is the appearance of very fine (0.1 m diameter) vanadium-rich MC carbide precipitates. The precipitates are uniformly distributed throughout the matrix and increase the hardness and wear resistance of the tool steel. Increasing the soak temperature to 700C results in prominent carbide coarsening, the formation of M 7 C 3 and M 6 C carbides, and a decrease in hardness. The photomicrographs of Figure 7 illustrate the dramatic change in carbide size. BSE imaging clearly differentiates Mo/Cr-rich carbides from V-rich carbides, shown as light and dark areas, respectively, in Figure 7. EDS analysis of these carbides is also given in Figure 7. Element Si V Cr Mn Mo Fe Spot #1 (wt%) 0.06 13.80 7.20 2.64 2.44 73.86 Spot #2 (wt%) 1.52 0.82 5.48 0.23 2.38 89.57 Figure 6. Photomicrographs of spray-formed/aged H13 tool steel. 500C soak for 1 hr. 3% nital etch. (a) Optical photomicrograph. (b) SEM image (BSE mode) near a grain boundary. Table gives EDS composition of numbered features. 10 Element Si V Cr Mn Mo Fe Spot #1 (wt%) 0 82.27 9.01 0 4.33 4.39 Spot #2 (wt%) 0 5.30 25.70 0 55.55 13.45 Spot #3 (wt%) 1.60 0.88 6.32 0.28 2.92 88.00 Figure 7. SEM Photomicrograph (BSE mode) of spray-formed/aged H13 tool steel showing adjacent V-rich (dark) and Mo/Cr-rich (light) carbides. 700C soak for 1/2 hr, 3% nital etch. Table gives EDS composition of numbered features. Material Properties Porosity in spray-formed metals depends on processing conditions. The average as-deposited density of spray-formed H13 was 98-99% of theoretical, as measured by water displacement using Archimedes principle. As-deposited hardness was typically about 59 HRC, harder than commercial forged and heat treated material (28 to 53 HRC depending on tempering temperature), and significantly harder than annealed H13 (200 HB). The high hardness is attributable to lattice strain due to quenching stresses and supersaturation. As shown in Figure 8, hardness can be varied over a wide range by artificial aging. 59 HRC as- deposited samples were given isochronal (1 hr) soaks at 50C increments from 400 to 700C, air cooled, and evaluated for microhardness. At 400C, a small decrease in hardness was observed, presumably due to stress relieving. As the soak temperature was further increased, hardness rose to a peak hardness of approximately 62 HRC at 500C. Higher soak temperature resulted in a drop in hardness as carbide particles coarsened. Peak age hardness in spray-formed H13 tool steel is notably higher than that of commercial hardened material. Normally, commercial H13 dies used in die casting are tempered to about 40 to 45 HRC as a tradeoff since high hardness dies, while desirable for wear resistance, are prone to premature failure via thermal fatigue as the dies surface is rapidly cycled from 300C to 700C during aluminum production runs. 11 Figure 8. Hardness of artificially aged spray-formed H13 tool steel following one hour soaks at temperature. Hardness range of conventionally heat treated H13 included for comparison. As-deposited spray-formed material was also hardened following the conventional heat treatment cycle used with commercial material. Samples of forged/mill annealed commercial and spray- formed materials were austenitized at 1010C, air quenched, and double tempered (2 hr plus 2 hr) at (538C). The microstructure in both cases was found to be tempered martensite with a few spheroidal particles of alloy carbide. Hardness values for both materials were very nearly identical. Table 2 gives the ultimate tensile strength and yield strength of spray-formed, cast, and forged/heat treated H13 tool steel measured at test temperatures of 22 and 550C. Values for spray formed H13 are given in the as-deposited condition and following artificial aging and conventional heat treatments. Values for the spray-formed material are comparable to those of forged and are considerably higher than those of cast tool steel. The spray-formed material seems to retain its strength somewhat better than forged/heat treated H13 at higher temperatures. 12 Table 2. H13 tool steel mechanical properties. Sample/Heat Treatment Ultimate Tensile Strength (MPa) Yield Strength (MPa) Test Temperature (C) Spray formed/as-deposited 1061 951
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