六边形垫片复合冲压模设计【说明书+CAD】
六边形垫片复合冲压模设计【说明书+CAD】,说明书+CAD,六边形垫片复合冲压模设计【说明书+CAD】,六边形,垫片,复合,冲压,设计,说明书,仿单,cad
六边形垫片冲压复合模模具设计专业:学生姓名:学生学号:指导教师:完成时间:目录目录2一、冲裁件的工艺分析3二、 冲压工艺方案的确定4三、冲裁间隙5四、 凸模与凹模刃口尺寸的计算6(一) 凸、凹模刃口尺寸计算的基本原则6(二) 刃口尺寸计算方法6(三) 刃口尺寸计算9五、排样设计10(一) 排样形式的确定10(二) 条料宽度的确定11 (三) 材料利用率13六、冲裁力相关的计算14(一)冲裁力的计算14(二)总冲裁力、推料力、卸料力、顶件力和总冲压力15(三)压力机公称压力的选取17七、模具压力中心的确定19八、 模具总体设计20(一) 模具类型的选择20(二)定位方式的选择201. 送进导料方式的选择202. 送料定距方式的选用213. 卸料、出件方式的选择21九、冲模主要零件的设计22(一) 工作零件的设计221. 凸凹模的设计222. 冲孔凸模的设计233. 落料凹模的设计24(二) 卸料板的设计26(三) 定位零件的设计27(四) 模架及其它零件的设计28十、模具总装图29十一、结论31十二、致谢31参考文献32一、冲裁件的工艺分析由零件图11可知,该零件形状简单、对称,是由圆弧和直线组成。冲裁件内外形所能达到的精度要求不高为IT12。将以上精度与零件简图中所标注的尺寸公差相比较,可认为该零件的精度要求能够在冲裁加工中得到保证。其它尺寸标注、生产批量等情况,也均符合冲裁的工艺要求,故决定采用冲裁落料复合模进行加工,且一次冲压成形。材料:08钢具有良好的塑性、焊接性、可锻性及良好的冲压性能,常用来制造焊接结构件和冲压件。工件结构形状:冲裁件外形应尽量避免有尖角,为了提高模具寿命,在所有60倾角改为R2的倒角。零件精度的选择:本文所设计的冲裁零件是板件如图1-1,该冲裁件的材料为08钢,具有较好的可冲压性能。该冲裁件的结构较简单,比较适合冲裁,零件图上所有尺寸均未注公差,属于自由尺寸,可参考几何量公差与检测确定冲裁件公差等级,根据查表,该零件的公差等级取IT12级确定零件的尺寸公差。 图1-1零件简图 2、 冲压工艺方案的确定该工件包括落料、冲孔两个基本工序,可以有以下三种工艺方案:方案一:先落料,后冲孔,采用单工序模生产。方案二:冲孔落料复合冲压,采用复合模生产。方案三:冲孔落料级进冲压。采用级进模生产。方案一单工序冲裁模指在压力机一次行程内只完成一个冲压工序的冲裁模。该模具结构简单,但需要两道工序两副模具,成本高而生产效率低,难以满足中批量生产的要求。方案二复合冲裁模是指在一次工作行程中,在模具同一部位同时完成数道冲压工序的模具。该模具只需要一副模具,工件的精度及生产效率都很高,但工件最小壁厚2.0mm接近凸凹模许用最小壁厚2.2mm,模具强度较差,制造难度大,并且冲压后成品件留在模具上,在清理模具上的物料时会影响冲压速度,操作不方便。方案三级进模:是指压力机在一次行程中,依次在模具几个不同的位置上同时完成多道冲压工序的模具。它也只需要在一副模具内可以完成多道不同的工序,可包括冲裁、弯曲、拉深等,具有比复合更好的生产效率。它的制件和废料均可以实现自然漏料,所以操作安全、方便,易于实现自动化。难以保证制件内、外相对位置的准确性因此制件精度不高。通过对上述三种方案的的分析比较,因为该制件的精度要求不高,用于批量生产。所以该制件的冲压生产采用方案二为佳。三、冲裁间隙1. 间隙对冲裁工作的影响间隙值影响到冲裁时弯曲、拉伸、挤压等附加变形的的大小,因而对冲裁工序的影响大,主要有以下几个方面: (1)间隙对零件质量的影响 模具间隙是影响断面质量的主要因素,提高断面质量的关键在于推迟裂纹的产生,以增大光亮带宽度,其主要途径就是减小模具间隙。此外间隙又是影响尺寸精度的主要因素。 (2)间隙对冲裁力的影响 间隙越小,变形区内压应力成分趟大,拉应力成分越小,材料变形抗力增加,冲裁力就越大。反之,间隙越大,变形区内拉应力成分就越大,变形抗力降低,冲裁力就校间隙达材料厚的5%-20%时,冲裁力下降不明显。当单边间隙Z增大到材料厚度的15%-20%时,卸料力为0。 (3)间隙对模具寿命的影响 由于工件与凸、凹模侧壁之间有磨擦的存在,间隙小,磨擦大,模具寿命短。冲裁过程中,凸模与被冲孔之闻,凹模与落料件之阀均有摩擦,而且闻隙越小,摩擦越严重。所以过小的间隙对模具寿命极为不利,而较大的间隙可使凸模与凹模的侧面与材料间的摩擦减小,井能减缓间隙不均匀的影响,从而提高模具的寿命。综上所述,设计模具时一定要选择合理的间隙,以保证冲裁件的断面质量、尺寸精度满足产品的要求,所需冲裁力小、模具寿命高,但分别从质量,冲裁力、模具寿命等方面的要求确定的合理间隙并不是同一个数值,只是彼此接近。考虑到制造中的偏差及使用中的磨损、生产中通常只选择一个适当的范围作为合理间隙,只要间隙在这个范围内,就可以冲出良好的制件,这个范围的最小值称为最小合理间隙Zmin,最大值称为最大合理间隙Zmax。考虑到模具在使用过程中的磨损使间隙增大,故设计与制造新模具时要采用最小合理间隙值Zmin。确定凸凹模合理间隙有理论确定法和查表确定法。根据实用间隙表查得:材料08钢的最小双面间隙2Zmin=0.246mm,最大双面间隙2Zmax=0.360mm,4、 凸模与凹模刃口尺寸的计算 凸凹模刃口尺寸精度决定的合理与否,直接影响冲裁件的尺寸精度及合理间隙值能否保证,也关系模具加工成本和寿命。因此,计算凹凸模刃口尺寸是一项重要工作。(1) 凸、凹模刃口尺寸计算的基本原则 计算冲裁凸凹模刃口尺寸的依据为1)冲裁变形规律,记落料件尺寸与凹模刃口尺寸相等,冲孔尺寸与凸模刃口尺寸相同2)零件的尺寸精度。3)合理的间隙值。4)磨损规律5)冲模的加工制造方法。因而在计算刃口尺寸时应按下属原则进行 1.保证冲出合格的零件。 根据冲裁变形规律,冲孔尺寸等于凸模刃口尺寸,落料件尺寸等于凹模刃口尺寸。因而冲孔时,应以凸模为基准件。落料时应以凹模为基准件。基准件的尺寸应在零件的公差范围内。冲孔时间隙取在凹模上,落料时间隙取在凸模上。 2.保证模具具有一定的使用寿命。 新磨具的间隙应是最小的合理间隙,磨损后达到最大合理间隙,考虑到冲裁时凸凹模的磨损,再设计凸凹模刃口尺寸时,对基件刃口尺寸在磨损后增大的,其刃口公称尺寸应取工减尺寸范围内较小的数值。对基准件刃口尺寸在磨损后减小的,其刃口公称尺寸应取工件尺寸公差范围内较大的数值。 3.考虑冲模制造修理方便,降低成本。 为使新磨具的间隙值不小于最小合理间隙,一般凹模公差标准成,凸模公差标注成。间隙能保证的条件下不要把制造公差定的太紧。一般模具制造精度比工件精度高24级。若零件没有标注公差,对于非缘形件按国家标准“非配合尺寸的公差数值”IT14精度处理,冲模则可按IT11级制造;对于圆形件,一般可按IT79级制造模具。冲压件的尺寸公差应按“入体”原则标注为单向公差,落料件上偏差为零,下偏差为负;冲孔件上偏差为正,下偏差为零。 (二) 刃口尺寸计算方法由于模具的加工方法不同,凸模与凹模刃口部分尺寸的计算公式与制造公差的标注也不同,刃口尺寸的计算方法可以分为两种情况。1)凸模与凹模分开加工。这种方法适用于圆形或简单规则形状的冲裁件。2)凸模与凹模配合加工。对于形状复杂或薄料的冲裁件的冲裁,为了保证凸凹模之间的间隙值,一般采用配合加工。 对该制件应该选用凸模和凹模分别加工的方法,按图纸加工之尺寸。要分别标注凸模和凹模刃口尺寸和制造公差(凸模p、凹模d)。为了保证初始间隙值小于最大合理间隙2Zmin,必须满足下列条件: p+d2Zmax-2Zmin 或取p=0.4(2Zmax-2Zmin) d=0.6(2Zmax-2Zmin)也就是说,新制造的模具应该是p+d+2Zmin2Zmax。否则制造的模具间隙已经超过允许的变动的范围2CZax-2Zmin。下面对落料和冲孔两种情况进行讨论。1、落料: 设工件的尺寸,根据计算原则,落料时以凹模为设计基准。首先确定凹模尺寸,使凹模基本尺寸接近或等于制件的轮廓的最小极限尺寸,再减小凸模尺寸以保证最小合理间隙值2Zmin。其计算公式如下: 2、冲孔:设冲孔尺寸为根据以上原则,冲孔时以凸模设计为基准,首先确定凸模刃口尺寸,使凸模基本尺寸接近或等于工件孔的最大极限尺寸,再增大凹模尺寸以保证最小合理间隙2Zmin。凸模制造偏差取负偏差,凹模取正偏差。其计算公式如下: 在同一工步中出制件两个以上孔时,凹模型孔中心距Ld 按下式确定: Ld=(Lmin+0.5)0.125式中Dd落料凹模基本尺寸(mm);Dp落料凸模基本尺寸(mm);D落料件最大极限尺寸(mm);dd冲孔凹模基本尺寸(mm);dp冲孔凸模基本尺寸(mm);d冲孔件孔的最小极限尺寸(mm);Ld同一工步中凹模孔距基本尺寸(mm);Lmin制件孔距最小极限尺寸(mm);制件公差(mm) 可查表41;2Zmin凸、凹模最小初始双面间隙(mm);d凸模下偏差,可按IT6选用(mm);p凹模上偏差,可按IT7选用(mm);X 磨损系数,当制件公差为IT10以上,取X=1;当工件公差为IT11IT13,取X=0.75;当工件差为IT14者,取X=0.5。表4-1标准公差数值公差等级IT12IT13IT14IT15IT16IT17IT18基本尺寸/mm/mm3366101018183030505080801201201801802502503153154004005000.10.120.150.180.210.250.30.350.40.460.520.570.630.140.180.220.270.330.390.460.540.630.720.810.890.970.250.30.360.430.520.620.740.871.01.151.31.41.550.40.480.580.70.841.01.21.41.61.852.12.32.50.60.750.91.11.316.019.02.22.52.93.23.64.011.21.51.82.12.53.03.54.04.65.25.76.31.41.82.22.73.33.94.65.46.37.28.18.99.7(3) 刃口尺寸计算根据计算原则,落料时以凹模为设计基准。首先确定凹模尺寸,使凹模基本尺寸接近或等于制件的轮廓的最小极限尺寸,再减小凸模尺寸以保证最小合理间隙值2Zmin。 校核 p+d2Zmax-2Zmin 0.016+0.025 0.360-0.246 0.041 0.114(满足间隙要求)根据计算原则,冲孔时以凸模设计为基准,首先确定凸模刃口尺寸,使凸模基本尺寸接近或等于工件孔的最大极限尺寸,再增大凹模尺寸以保证最小合理间隙2Zmin。 校核 p+d2Zmax-2Zmin 0.013+0.021 0.360-0.246 0.034 0.114在同一工步中出制件两个以上孔时,凹模型孔中心距Ld 按下式确定: Ld=(Lmin+0.5)0.125 =(40+0.50.39) 0.1250.39 =40.1950.049五、排样设计(一) 排样形式的确定1.排样的分类1)按材料利用情况分类1 有废料排样 沿零件全部外形冲裁,零件周边都有生料。2 少废料排样 沿零件部分外形切断或冲裁,只局部又生料。3 无废料排样 除料头料尾外无任何生料。2) 安冲裁件在条料上的布置防水,排样又可分为 直排、单排、多排、斜排、对排、混合排、少废料、无废料、裁搭边等。 此处选用如图5-1所示排样方式 搭边值、条料宽度的确定 2. 搭边值的确定排样时零件之间以及零件与条料侧边间留下的工艺余料,称为搭边。搭边的作用是补偿定位误差,保持条料有一定的刚度,以保证零件质量和送料方便。搭边过大,浪费材料、搭边过小,冲裁时容易翘曲或被拉断,不仅会增大冲件毛刺,有时还有拉入凸、凹模间隙中损坏模具刃口,降低模具寿命或影响送料工作。图5-1 排样图搭边值通常由经验确定,表所列搭边值为普通冲裁时经验数据之一。表5-1 搭边a和a1数值材料厚度圆件及r2t的工件矩形工件边长L50mm矩形工件边长L50mm或r2t的工件工件间a侧面a1工件间a侧面a1工件间a侧面a10.250.250.50.50.80.81.21.21.61.62.02.02.52.53.03.03.53.54.04.05.05.0121.81.21.00.81.01.21.51.82.22.53.00.6t2.01.51.21.01.21.51.82.22.52.83.50.7t2.21.81.51.21.51.82.02.22.52.53.50.7t2.52.01.81.51.82.02.22.52.83.24.00.8t2.82.21.81.51.82.02.22.52.83.24.00.8t3.02.52.01.82.02.22.52.83.23.54.50.9t根据制件厚度与制件的排样方法可以查表51得:搭边值工件间a为2.0mm 侧面a1 为2.2mm(二) 条料宽度的确定排样方式和搭边值确定以后,条料的宽度和进距也就可以设计出。确定1条料宽度的原则是:最小条料宽度要保证冲裁时零件周围有足够的搭边值;最大条料宽度能在导料板间送进,并与导料板间有一定的间隙。条料宽度的大小还与模具是否有侧压装置或侧刃有关。计算条料宽度有三种情况需要考虑:1、有侧压装置时条料的宽度。2、无侧压装置时条料的宽度。3、有定距侧刃时条料的宽度。该零件采用无侧压装置的模具,其条料宽度应考虑在送料过程中因条料的摆动而使侧面搭边减少。为了补偿面搭边的减少部分,条料宽度应增加一个条料的摆动量。故条料宽度为: (5-1)导尺间距 (5-2)式中:B条料宽度的基本尺寸;D条料宽度方向冲裁件的最大尺寸;a侧搭边值。c1条料与导料板之间的间隙(即条料的可能摆动量):B100, c1=0.51.0; B100, c1=1.01.5.表5-2 剪料公差及条料与导料板之间隙(mm)条料宽度B/mm材料厚度t/mm112233550501001001501502202203000.40.50.60.70.80.50.60.70.80.90.70.80.91.01.10.91.01.11.21.3导料板之间的距离,应使条料与导料板之间保持一定的间隙查表53,以保证送料畅通。表5-3 条料宽度偏差(mm)条料宽度B|mm材料厚度0.50.5112200.050.080.120300.080.10.1530500.10.150.2D取值由设计条料宽度方向冲裁件的最大尺寸为50 (mm)侧搭边值a可以从表51中查出为2.2 (mm)条料与导料板之间的间隙c1取查表52可得条料宽度偏差下偏差为0.8(mm)故带入条料宽度公式得; =50+2(2.2+0.8)+0.5=56.5(mm)(三) 材料利用率 材料利用率通常以一个进距内制件的实际面积与所用毛坯面积的百分率表示;=(nA1/hB)100% (3-2)式中 材料利用率(%);n 冲裁件的数目;A1 冲裁件的实际面积(mm2);B 板料宽度(mm);h进距;计算冲压件的面积;A1=2521.653-3.141515 =1834(mm2)条料宽度计算:B=50+22.2=54.4 (mm)送进距离计算:h=43.3+2=45.3 (mm)一个进距的材料利用率;=(nA1/hB)100% =11834(45.354.4)100%=74.42%由此可之,值越大,材料的利用率就越高,废料越少。工艺废料的多少决定于搭边和余量的大小,也决定于排样的形式和冲压方式。因此,要提高材料利用率,就要合理排样,减少工艺废料。六、冲裁力相关的计算(一)冲裁力的计算冲裁力是冲裁过程中凸模对材料的压力。冲裁力是选用压力机、模具设计以及强度校核的重要依据。冲裁在理论上可以近似认为是剪切断裂,所以最大冲裁力可以按板料的抗剪强度来计算。普通平刃冲裁模,其冲裁力F p一般可以按下式计算: 式中 材料抗剪强度,见附表(MPa); L零件剪切周长(mm); t材料厚度(mm) K-系数系数K是考虑到冲裁模刃口的磨损,凸模与凹模间隙之波动(数值的变化或分布不均),润滑情况,材料力学性能与厚度公差的变化等因数而设置的安全系数K,一般取1.3。为了简便,也可用材料的抗拉强度,按下式估算冲裁力:表61常用冲压材料的力学性能材料名称牌号材料状态抗剪强度抗拉强度申长率屈服强度电工用纯铁C0.025DT1、DT2、DT3已退火18023026普通碳素钢Q195火未退2603203204002833200Q2353103803804702125240Q2754005005006201519280优质碳素结构钢08F已退火22031028039032180082603603304503220010260340300440292102028040036051025250454405605507001636065Mn60075012400不锈钢1Cr13已退火600400470211Cr18Ni9Ti热处理退软32038054070040200铝L2、L3、L5已退火8075110255080冷作硬化1001201504铝锰合金LF21已退火701101101451950硬铝LY12已退火10515015021512淬硬后冷作硬化28032040060010340纯铜T1、T2、T3软态1602003007硬态2403003黄铜H62软态26030035半硬态30038020200H68软态24030040100半硬态28035025由于材料08钢的力学性能查(表61)可得:抗剪强度=260360,故取起抗拉强度b代替抗剪强度,查表可知b=360(MPa)。(二)总冲裁力、推料力、卸料力、顶件力和总冲压力由于冲裁模具采用弹性卸料装置和上出件方式。 F总冲压力。 Fp总冲裁力。 FQ卸料力 FQ1推料力。 FQ2顶件力计算总冲裁力 Fp=F1+F2 F1落料时的冲裁力。 F2冲孔时的冲裁力。冲裁周边的总长(mm)落料周长为: L2=256 =150 (mm)冲孔周长为: L1=3.1430 =94.2(mm)落料冲裁力为: F1=KtL2 =1.31503602 =140400 (N)冲孔冲裁力为: F2=KtL1 =1.3294.2360 = 88171.2 (N)所以可求总冲裁力为: Fp=F1+F2 =140400+88171.2 =228571.2(N)表6-2 卸料力、推件力和顶件力系数料厚t/mmKxKtKd钢0.10.10.50.52.52.56.56.50.0650.0750.0450.0550.040.050.030.040.020.030.10.0630.0550.0450.0250.140.080.060.050.03铝、铝合金纯铜,黄铜0.0250.080.020.060.030.070.030.09按卸料力公式计算卸料力FQFQ=KxFp查表62得Kx=0.04根据公式得FQ=KxFp=0.04228571.2=9142.848 (N)按推料力公式计算推料力FQ1 FQ1=nKtFp取n=2查表62得Kt=0.055n梗塞在凹模内的制件或度料数量(n=h/t h直刃口部分的高度,t材料厚度)根据公式得 FQ1=nKtFp =20.055228571.2 =25142.832按顶件力公式算顶件力FQ2FQ2=KdFpKd查表62得0.06根据公式得FQ2=KdFp=0.06228571.2 =13714.272 (N)(三)压力机公称压力的选取 冲裁时,压力机的公称压力必须大于或等于冲裁各工艺力的总和。采用弹压卸料装置和上出件的模具表63 常用冷冲压设备的工作原理和特点类型设备名称工作原理特点机械式压力机摩擦压力机利用摩擦盘与飞轮之间相互接触传递动力,皆助螺杆与螺母相对运动原理而工作。结构简单,当超负荷时,只会引起飞轮与摩擦盘之间的滑动,而不致损坏机件。但飞轮轮缘摩擦损坏大,生产率低。适用于中小件的冲压加工,对于校正、亚印和成形等冲压工序尤为适宜。曲柄式压力机利用曲柄连杆机构进行工作,电机通过皮带轮及齿轮带动曲轴传动,经连杆使滑块作直线往复运动。曲柄压力机分为偏心压力机和曲轴压力机,二者区别主要在主轴,前者主轴是偏心轴,后者主轴是曲轴。偏心压力机一般是开式压力机,而曲轴压力机有开式和闭式之分。生产率高,适用于各类冲压加工。高速压力机工作原理与曲柄压力机相同,但其刚度、精度、行程次数都比较高,一般带有自动送料装置、安全检测装置等辅助装置。生产率很高,适用于大批量生产,模具一般采用多工为级进模。液压机油压机水压机利用帕斯卡原理,以水或油为工作介质,采用静压 力传递进行工作,使滑块上、下往复运动。压力大,而且是静压力,但生产率低。适用于拉深、挤压等成形工序。根据公式得 F=Fp+FQ+FQ2 =228571.2 +25142.832+13714.272 =267428.304 (N)冲压设备属锻压机械。常见的冷冲压设备有机械压力机(以Jxx表示其型号)和液压机(以Yxx表示其型号)。冲压设备分类:1、 机械压力机按驱动滑块机构的种类可以分为曲柄式和摩擦式;2、 按滑块个数可分为单动和双动;3、 按床身机构形式可分为开式(C型床身)和闭式(型床身);4、 按自动化程度可分为普通压力机和高速压力机等;常用冷冲压设备的工作原理和特点如表63根据综上所计算出来的总压力与常用冷冲压设备的工作原理和特点选取开式可倾压力机型号为J2335。七、模具压力中心的确定模具压力中心是指冲压时诸冲压力合力的作用点位置。为了确保压力机和模具正常工作,应使模具的压力中心与压力机滑块的中心相重合,否则,会使冲模和力机滑块产生偏心载荷,使滑块和导轨之间产生过大的摩擦,模具导向零件加速磨损,降低模具和压力机的使用寿命。冲裁模的压力中心,可按下述原则来确定:1、对称形状的单个冲裁件,冲模的压力中心就是冲裁件的几何中心。2、工件形状相同且分布位置对称时,冲模的压力中心与零件的对称中心相重合。3、形状复杂的零件、多孔冲模、级进模的压力中心可用解析计算法求出冲模的对称中心。根据制件图可以得出该工件形状相同且分布位置对称,所以冲模的压力中心与零件的对称中心相重合。7-1 制件图纸八、 模具总体设计(一) 模具类型的选择由冲压工艺分析可知,采用复合冲压,所以模具类型为复合模。(二)定位方式的选择为保证冲裁出外形完整的合格零件。毛坯在模具中应该有正确的位置。正确位置是依靠定位零件来保证的。由于毛坯形式和模具结构不同,所以定位零件的种类很多。设计时应根据毛坯形式、模具结构、零件公差大小、生产效率等进行选择。定位包括控制送料进距的挡料和送料定距的挡料。 1. 送进导料方式的选择送进导向方式有两种,在此我们选择复合模设计中最常用的一种,导料销导向,在模具中设计两个导料销,并位于条料的两侧,该模具是从右向左送料,所以导料销装在前后各一侧。形式为固定导料销。如图81所示。 图8-1 固定导料销 2. 送料定距方式的选用限位销用来限制条料送进的距离,在此我们根据国家标准选用活动挡料销如图8-2 所示,其结构简单、制造容易,用途广泛。 图8-2 活动挡料销 3. 卸料、出件方式的选择 卸料零件的目的,是将冲裁后卡箍在凸模上或凸凹模上的制件或废料卸掉,保证下次冲压压正常进行。常用的卸料方式有刚性卸料和弹性卸料两种。 因为工件料厚为2mm,相对较薄,卸料力也比较小,故可采用弹性卸料。又因为是复合模生产,所以采用上出件比较便于操作与提高生产效率。 4. 标准模架导向方式的选择按导柱在模架上的固定位置不同,导柱模架的基本型式有四种:对角导柱模架;后侧导柱模架;中间导柱模架;四导柱模架。为了提高模具寿命和工件质量,方便安装调整,该复合模采用后侧导柱的导向方式。九、冲模主要零件的设计设计主要零部件时,首先要考虑主要零部件用什么方法加工制造及总体装配方法。结合模具的特点,本模具适宜采用线切割加工凸模固定板、卸料板、凸凹固定板、凹模及冲孔凸模、凸凹模。除凸凹模外,在采用线切割后,还得采用数控车床加工其形腔锥度。这种加工方法可以保证这些零件各个内孔的同轴度,使装配工作简化。下面就分别介绍各个零部件的设计方法。 (1) 工作零件的设计 1.凸凹模的设计因为该制件形状复杂,所以将落料凸模与冲孔凹模设计成一个整体为凸凹模。直通式凸模工作部分和固定部分的形状做成一样,直通式凸模采用线切割机床加工。凹模和工作部分与凸模联在一起,为保证废料直接由凸模从凸凹模内孔推出。凹模洞口若采用直刃、则模内有积荐废料,胀力较大。若采用上直下斜的锥面式,可以解出积荐废料的问题,锥度先采用线切割加工后采用数控车床加工。通过固定板把凸凹模固定。固定板与凸凹模的配合按H7/m6。凸凹模材料应选T10A,热处理5860HRC,凸凹模与卸料板之间的间隙见表91查得凸凹模与卸料板的间隙选为0.035mm。凸凹模高度是固定板、卸料板和弹簧间隙组成。凸凹模高度为: H=H1+H2+(1520)mm H1固定板厚度;得H1=0.8H凹=0.816=12.8 mm(标准为15mm) H2卸料板厚度;查表94得H2=10 mm(1520)附加长度,包括凸凹模的修磨量,凸模进入凹模的深度及固定板与卸料板间的安全距离。(附加长度取18)H=15+10+18 =43 mm 表9-1 凸凹模与卸料板、导柱与导套的间隙序号模具冲裁间隙Z卸料板与凸模间隙Z1辅助小导柱与小导套间隙Z210.0150.0250.0050.007约为0.00320.0250.050.0070.015约为0.00630.050.100.0150.025约为0.0140.100.150.0250.035约为0.02 2. 冲孔凸模的设计因为冲孔凸模是由圆和非圆组合而成的凸模,结构复杂,对模具零件精度要求较高;模具装配精度也较高。将冲孔凸模设计成直通式,采用线切割加工。冲孔凸模与凸凹模中的落料凹模镶拼结构中的压入式固定。凸模的高度是凸模固定板、凹模及附加长度组成。凸模高度为: H=H1+H2+(1520)mm H1凸模固定板厚度;得H1=0.8H凹=0.816=12.8 mm(标准为15mm) H2凹模厚度; H2=16 mm(1520)附加长度,包括凸凹模的修磨量,凸模进入凹模的深度及固定板与卸料板间的安全距离。(附加长度取18)H=15+16+18 =49 mm 3. 落料凹模的设计凹模采用整体凹模,各种冲裁的凹模孔均采用线切割机床加工,安排凹模在模架上位置时,要依据计算压力中心的数据,将压力中心与模柄中心重合。模具的外形尺寸如下: 模具厚度的确定公式为: H=Kb式中:K92系数值,考虑板料厚度的影响;b 冲裁件的最大外形尺寸;表9-2系数值Ks/mm材料厚度t/mm1336501001002002000.300.400.200.300.150.200.100.150.350.500.220.350.180.220.120.180.450.600.300.450.220.300.150.22查表92得:K=0.30 H=0.3050 =15 mm查表取标准:H=16 mm模具壁厚的确定公式为: C=(1.52)H =1.520216 =3032 mm凹模壁厚取C=32 mm、凹模宽度的确定公式为: B=b+2C =44+232 =108 mm查表取标准取B=125 mm凹模长度的确定公式为: L=50+232 =114 mm凹模的长度要考虑导料板发挥的作用,保证送料粗定位精度。查表取标准L=125 mm。凹模轮廓尺寸为125mm125mm16mm。凹模材料选用T10A,热处理6062HRC。(二) 卸料板的设计卸料板不仅有卸料作用,还具有用外形凸模导向,对内孔凸模起保护作用,卸料板的边界尺寸与凹模的边界尺寸相同,卸料板的厚度按表94选择,卸料板厚度为10mm。卸料板与2个凸模的间隙以在凸模设计中确定了为0.035。卸料板上设置了4个螺钉。卸料板采用45钢制造,热处理淬火硬度4045HRC。表9-4固定卸料板厚度冲件厚度t卸料板宽度2000.866810120.81.5681012141.53810121416(三) 定位零件的设计 为了保证模具的正常工作和冲出合格的冲裁件,必须保证坯料或工序件对模具的工作刃口处于正确的相对位置,即必须定位。而模具送料平面中必须有两个方向的限位:一是送料方向垂直的方向上限位,保证条料沿正确的方向的送进,称为送进的导向,二是在送进方向上的限位,控制条料一次送进的距离(步距)称为送料定距。属于送料导向的定位零件有导料销,导料板、侧压板等,属于送料定距的定位零件有固定挡料销、始用挡料销、活动挡料销、导正销、侧刃等。属于块料或工序件的定位零件有定位销、定位板等。由于止动垫圈冲压所用的材料属于条料,厚度不大,零件精度且采用的是复合模进行冲裁。终上所述定位零件选用导料销,定位零件采用活动挡料销。活动挡料销的位置可以由公式确定B=A-D/2+d/2 式中A送料进距(mm);d挡料销直径(mm);D落料凸模直径(mm)。B= A-D/2+d/2 =45.3-50/2+8/2 =24.3 (mm)(四) 模架及其它零件的设计 根据国家标准,模架主要有两大类,一类是由上模座、下模座、导柱、导套组成的导柱模模架。另一类是由弹压导板、下模座、导柱、导套组成的导板模模架。考虑到经济效益以及加工的特点,选择后侧导柱模模架。本模具采用滑动导柱、导套来保证模具上、下模的精确导向。滑动导柱、导套都是圆柱形的,其加工方便,可采用车床加工,装配容易。导柱的长度应保证上模座最底位置时(闭合状态),导柱上端面与上模座顶面的距离15mm。而下模座底面与导柱底面的距离为5mm。导柱的下部与下模座导柱孔采用R7/h5的过盈配合,导套的外径与上模座导套孔采用R7/h5的过盈配合。导套的长度,需要保证冲压时导柱一定要进入导套10mm以上。导柱与导套之间采用H7/h6的间隙配合,导柱与导套均采用20钢,热处理硬度渗碳淬硬5660HRC。导柱的直径、长度,按标准选取。导柱:d/mmL/mm分别为32160;导套:d/mmL/mmDmm分别为3210545模座的的尺寸L/mmB/mm为160mm315mm。模座的厚度应为凹模厚度的1.52倍上模座的厚度为30mm,上垫板厚度取8mm,凸凹固定板厚度取20mm,下模座的厚度为40mm。那么该模具的闭合高度为: H闭=H上模+H垫+H凸+H凸凹+H下模-h2式中: H凸凸模长度,L=49 mm H凸凹凸凹模厚度,H=43 mmh2凸模冲裁后进入凹模的深度,h2=3 mm H闭=H上模+H垫+H凸+H凸凹+H下模-h2 =32+8+49+43+45-3 =174 mm可见该模具闭合高度小于所选压力机J2335的最大装模高度(220mm)可以使用。十、模具总装图通过以上的设计,可得到模具总装图。模具的上模部分由上模座、上模垫板、凸模、凸模固定板及凹模等组成。上模座、上模垫板、凸模、凸模固定板及凹模用4个M10螺钉和2个8圆柱销固定。螺钉选取:M1070mm的标准件。采用45钢,热处理淬火硬度4348HRC。圆柱销选取:870mm的标准件。采用45钢,热处理淬火硬度4348HRC。下模部分由下模座、凸凹模、卸料板及固定板等组成。下模座、凸凹模、卸料板及固定板用4个M10的螺钉和2个8的圆柱销固定。螺钉选取:M1070mm的标准件。采用45钢,热处理淬火硬度4348HRC。圆柱销选取:870mm的标准件。采用45钢,热处理淬火硬度4348HRC。冲孔废料由凸凹模的冲孔凹模漏料孔漏出。十一、压力机设备的选定通过校核,选择开式双柱可倾压力机J2335能够满足使用要求。其主要技术参数如下:公称压力:350KN;滑块行程:80mm; 最大闭合高度:270mm;最大装模高度;220mm;作台尺寸(前后左右):370mm560mm;垫板尺寸(厚度孔径):50mm200mm;模柄孔尺寸:40mm60mm;最大倾角高度:30。12、 结论通过这次毕业设计我收获颇多,指导老师的热心指导,耐心的为我讲解、分析,在设计的过程中所遇到的问题,同学们的热心帮助也让我感到了同学之间的情谊。这次从设计过程、加工过程和零件的加工分析过程,其实也是考验我大学来理论知识的掌握、实际操作和如何将书本上的理论知识怎么样运用到实际操作的一个过程。在毕业设计过程中我掌握了很多东西,冲裁件的工艺分析,制件的排样方法,冲裁力的相关计算,模具压力中心的计算,冲裁间隙的确定,凸模与凹模刃口尺寸的计算,模具的总体设计,主要零部件的设计,压力机的选择,总装配图的绘制等。总之,通过这次毕业设计让我掌握了很多东西,也有很多不足的地方,设计说明书格式的不太清楚,模具的公差不好给,图纸的绘制不熟练,但在老师和同学的帮助下我顺利的完成了设计。通过这次设计我让我全方位的知道模具的设计过程,真是受益匪浅。13、 致谢 本次课程设计离不开两位指导老师的帮助,老师总是耐心帮我看图,帮我指正,向我发送邮件,传达需要修改的地方和解决方案。感谢老师给我们这样一次机会,能够独立地完成一个课程设计,并在这个过程当中,给我们提供了许多相关资料,使我们在即将离校的最后一段时间里,能够更多学习一些实践应用知识,增强了我们实践操作和动手应用能力,提高了独立思考的能力。为了顺利帮我们完成课程设计,程老师披星戴月为我们修改作业,好感动。再一次对我们的程老师表示感谢。感谢在整个课程设计期间陪伴我的小伙伴,和曾经在各个方面给予过我帮助的同学们,在大学生活即将结束的最后的日子里,我们把一个庞大的,从来没有上手的课题,圆满地完成了。正是因为有了你们的帮助,才让我不仅学到了本次课题所涉及的新知识,更让我感觉到了知识以外的东西。最后,感谢所有在本次课程设计中给予过我帮助的人。参考文献 1 郝滨海.冲压模具简明设计手册.化学工业出版社.2 杨可桢、程光蕴、李仲生.机械设计基础.高等教育出版社3 机械制图. 高等教育出版社。4 翁其金.冲压工艺与冲模设计.清华大学出版社.5 冲模设计与制造实用计算手册.机械工业出版社.6 高锦张.塑性成形工艺与模具设计.机械工业出版社7 甘永立.几何量公差与检测.上海科学技术出版社.8 齐卫东.冷冲压模具图集.北京理工大学出版社9 史铁梁.冷冲模设计指导.机械工业出版社.10 张鼎承.冲模设计手册.北京.机械工业出版社.INEEL/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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