方形垫片落料冲孔复合模设计【芯片的冷冲模设计】【矩形垫板】【说明书+CAD】
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郑 州 航 空 工 业 管 理 学 院 课 程 设 计 方 形 垫 片 落 料 冲 孔 复 合 模 专 业 : 材 料 成 型 及 控 制 工 程 姓 名 : 张 兵 点 学 号 : 110609136 指 导 教 师 : 程 俊 伟 刘 长 红 目 录 第一章 冲压工艺分析及工艺方案的制定 .1 1.1 工艺分析 .1 1.2 工艺方案的制定 .2 第二章 冲裁模间隙 .3 2.1 间隙对冲裁工作的影响 .3 2.2 合理间隙值的确定 .4 第三章 排样设计与计算 .6 3.1 排样方法与原则 .6 3.2 确定搭边值 .6 3.3 送料步距与条料宽度的计算 .7 3.4 材料利用率的计算 .8 第四章 冲裁力计算 .9 4.1 落料力、冲孔力、卸料力、推件力的计算 .9 4.2 确定模具压力中心 .11 第五章 凸凹模的设计 .11 5.1 凸、凹模刃口尺寸计算原则 .11 5.2 凸、凹模刃口尺寸计算 .12 5.3 凸模、凹模、凸凹模的结构设计 .13 第六章 冲压设备的选择 .16 第七章 模具主要零部件设计 .17 7.1 定位方式的选择 .17 7.2 卸料出件方式的选择 .17 7.3 卸料橡胶的设计计算 .18 7.4 模架的选择 .18 第八章 模具的装配、调试和检测 .19 8.1 模具的装配 .19 8.2 冲裁模具的调试 .20 8.3 模具的检测 .20 第九章 模具材料的选用要求和选择原则 .22 9.1 冷冲模材料的选用要求 .22 9.2 材料的选择原则 .23 第十章 绘制模具总装图及零件图 .23 10.1 装配图绘制 .24 10.2 模具零件图的绘制 .24 参考文献 .25 第 0 页 共 25 页 第一章 冲压工艺分析及工艺方案的制定 1.1 工艺分析 零件简图:如图 1-1 所示 生产批量:大批量 材料:10 钢 材料厚度:0.5mm 该零件形状简单、对称,是由圆弧和直线组成。由表查出,冲裁件内外形所能达到 的经济精度为 IT12-IT13,孔中心距离尺寸公差为0.1mm。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,故决定采用冲孔落料复合 冲裁模进行加工。 图 1-1 选择复合模的原因: 从总体来看,由于大批量生产,零件的要求比较高, 冲压 工件尺寸精度较高,工件平整,对称度及位置度误差小,在一次行程内可完成两个以 上工序,大大提高了生产率,但对模具制造精度要求较高,由于复合模要在一副模具 第 1 页 共 25 页 中完成几道冲压工序,结构一般要比单工序模复杂,同时模具的强度、刚度、可靠性 也将随之下降。而且各零部件在动作时要求相互不干涉,准确可靠。因此模具的制造 成本也就提高了,制造周期相对延长,维修也不如单工序模简便。外形有直线组成,用 冲裁方法速度快,质量好,比其它加工方法(如铣削,切削)成本要低,效率要高,排样也较 为方便。由于大批量生产,在保证质量的情况下,可以采用冲裁,对冲裁的凸,凹模要求 就要提高,特别是凸模,要进行热处理,渗碳,淬火加回火等来提高强度和耐磨性,当凸模 磨损产生误差时,要及时更換,来保证工件精度要求.对于冲压过程中产品的开裂、起 皱等问题,利用理论知识计算分析。模具材料在保证质量的情况下,采用性能低的材 料来节约成本。模具自动化程度高,操作方便,劳动强度低。对凸模的安裝和拆卸要 方便,直接关系到凸模的更换。模具结构要设计合理,防止冲压时小孔的开裂。 1.2 工艺方案的制定 通过对该工件的冲压工艺性进行分析,考虑到制件生产批量和产品的质量、生产 效率、模具寿命、材料消耗及操作方便安全等因素,由冲压制件外观形状分析,该制 件有落料、冲孔两道工序,所以确定此连接板的生产中可以采用下面的几套方案: 方案一:先落料模后冲孔模 方案二:先冲孔模 后落料模 方案三:采用落料冲孔复合模 分析: 方案一,定位不方便,操作起来非常的麻烦,此方案不可取; 方案二,定位简单可靠,但要用手钳放置毛坯,多次进出危险区域,很不安全, 所以此方案不可取; 方案三,冲裁的孔与外形的位置精度较高,工件较平整,具有校形的作用,模 具制造复杂,可适用大批量生产,从以上比较多來看,在保证冲裁件质量的情况下, 应尽可能降低成本,提高经济效益,工人操作方便、安全的情况下考虑,选择复合 模比较合适。 结论:经过全面分析、综合考虑,以零件质量、生产效益及经济性几个方面衡量, 第 2 页 共 25 页 认为三种方案中方案三为最佳的方案,即采用落料冲孔复合模完成此制件的成品。 第二章 冲裁模间隙 2.1 间隙对冲裁工作的影响 间隙值影响到冲裁件时弯曲、拉深、挤压等附加变形的大小,因而对冲裁件工序 影响大,主要有以下几方面: 1)间隙对零件质量的影响 由资料分析知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间隙。此外间隙又是影响尺 寸精度的主要因素。间隙对零件质量也有很大影响,当间隙过小时,凸模刃口附件的 裂纹比正常间隙时向外错开一段距离,上、下裂纹产生后,各自进入凸、凹模断面的 压应力区而停止发展,不重合。由于间隙小,弯曲、拉深小,裂纹产生迟,光亮带变 宽,且零件穹弯小,断面斜度和圆角小,只要中间撕裂不是很深,仍可应用。 当间隙过大时,凸模刃口处的裂纹较正常间隙向里错开一段距离,上、下裂纹也 不重合。裂纹间的材料产生第二次拉裂,零件断面出现两个斜度,这时材料的弯曲和 拉深大,拉应力大,材料的塑性变形阶段结束较早,致使光亮带较窄,圆角和斜度较 大,弯穹厉害,毛刺大。 当间隙不均匀时,在间隙不合理处将出现毛刺,断面质量差。因此模具设计制造 与安装时必须保证间隙均匀。 2)间隙对冲裁力的影响 间隙增大时,材料所受的拉应力增大,材料容易断裂分离,冲裁力可得到一定程 度的降低,继续增大间隙值,会因从凸、凹模刃口处产生的裂纹不相重合的影响,冲 裁力下降变缓。当单面间隙介于料厚的 5%20%时,冲裁力的降低并不显著(不超过 5%10%)。间隙减小,材料所受拉应力减小,压应力增大,材料不易产生撕裂,使冲 裁力增大,在间隙合理情况下,冲裁力最小。 第 3 页 共 25 页 间隙对卸料力、推件力、或顶件力的影响比较显著。间隙增大后,从凸模卸料或 从凹模孔中推料都省力。一般当单面间隙增大到料厚的 15%25%时,卸料力几乎为零, 但当间隙继续增大时,因毛刺增大等因素,会引起卸料力、顶件力迅速增大。 3)间隙对模具寿命的影响 冲裁过程中,凸、凹模刃口收到材料对它的作用力,其方向与图中的方向相反。 在这些力的作用下模具的实效方式一般有:磨损、崩刃、变形、胀裂、断裂等。间隙 主要对模具的磨损和胀裂有影响。 模具受到制造误差和装配精度的限制,间隙不会绝对均匀分布。过小的间隙会引 起冲裁力、侧压力、摩擦力、卸料力、推件力增大,甚至会使材料粘连刃口,这就加 剧了刃口的磨损;如果出现二次剪切,产生的碎屑也会使磨损加剧。间隙小,落料件 或废料往往梗塞在凹模洞口,导致凹模胀裂。因此过小的间隙对模具寿命极为不利。 间隙增大,可使冲裁力、卸料力等减小,从而刃口磨损减小。但是间隙过大,零件毛 刺增大,卸料力增大,反而使刃口磨损加大。所以间隙应增大得适当。适当大的间隙 还可补偿因模具制造精度不够及动态间隙不匀所造成的不足,不至于啃伤刃口,起到 延长模具寿命的作用。 综上所述,凸、凹模之间的间隙值对零件质量、冲裁力和模具寿命都有很大的影 响,它是冲裁工件与模具设计中的一个主要工艺参数。 2.2 合理间隙值的确定 设计模具时一定要选择合理的间隙,使冲裁件的断面质量较好,所需冲裁力较小, 模具寿命高。但分别按质量、精度、模具寿命、冲裁力等方面的要求,各自确定的合 理间隙值并不相同,考虑到模具制造中的偏差及使用中的磨损,生产中通常是选择一 个适当的范围作为合理间隙,只要间隙在这个范围内,就能得到合格的产品和较长的 模具寿命。这个范围的最小值为最小合理间隙 Z ,最大值称为最大合理间隙 Z 。min max 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应采用最小合理 间隙值。确定凸、凹模合理间隙值有理论确定法和查表确定法。 第 4 页 共 25 页 1)理论确定法 理论确定法的主要根据是保证上、下裂纹重合,以获得良好的冲裁断面。但由于 影响间隙值的主要因素是材料的性质和厚度。材料愈硬愈厚,所需合理间隙值愈大。 由于该计算方法在生产中使用不便,故目前常用的是查表确定法。 2)查表确定法 下表所提供的经验数据为落料、冲孔模的初始间隙,可用于一般条件下的冲 裁。表中初始间隙的最小值 Z ,相当于最小合理间隙数值,而初始间隙的最大 Zmin 是考虑到凸模和凹模的制造公差,在 Z 的基础上所增加的数值。在使用过程中,max min 由于模具工作部分的磨损,间隙将有所增加,因而间隙的使用最大值(即最大合理间 隙)要超过表列数值。 材料 名称 45 钢 T7、T8(退火) 65Mn(退火) 磷青铜(硬) 10、15、20 冷轧钢 带 30 钢板 H62、H68(硬) 2AL2(硬铝) 硅钢片 Q215、Q235、08、10、1 5 钢板 H62、H68(半硬) 纯铜(硬) 磷青铜(软) 铍青铜(软) 力学 性能 硬度 190HBW 600MPab 硬度=140190HBW =400600MPab 硬度=70140HBW =300400MPab 初始间隙 Z/mm 厚度 t/mm Zmin Zmax Zmin Z max Z in Z max 0.1 0.015 0.035 0.01 0.03 * - 0.2 0.025 0.045 0.015 0.035 0.01 0.03 0.3 0.04 0.06 0.03 0.05 0.02 0.04 第 5 页 共 25 页 0.5 0.08 0.10 0.06 0.08 0.04 0.06 0.8 0.13 0.16 0.10 0.23 0.07 0.10 1.0 0.17 0.20 0.13 0.26 0.10 0.13 1.2 0.21 0.24 0.16 0.19 0.13 0.16 1.5 0.27 0.31 0.21 0.25 0.15 0.19 1.8 0.34 0.38 0.27 0.31 0.20 0.24 2.0 0.38 0.42 0.30 0.34 0.20 0.26 由表可知,取最小合理间隙值为 Z =0.06mm,最大合理间隙值为 Z =0.08mm。min max 第三章 排样设计与计算 3.1 排样方法与原则 冲裁件在条料、带料或板料上的布置方法叫排样。排样合理就能用同样的材料 冲出更多的零件来,降低材料消耗。大批量生产时,材料费用一般占冲裁件的成本 60%以上。因此材料的经济利用是一个重要问题,特别对贵重的有色金属。排样的 合理与否将影响到材料的经济利用、冲裁质量、生产率、模具结构与寿命、生产操 作方便与安全等。由于产量大,材料利用率是一项很重要的经济指标,要提高材料 利用率就必须减小废料面积,条料在冲裁过程中翻动要少,使工人操作方便、安全, 减轻劳动强度,排样应保证冲裁件的质量,无论是采用有废料或少、无废料的排样, 根据冲裁件在条料上的不同布置方法,排样方法有直排、斜排、对排、多排等多种 形式的排列方式,可以根据不同的冲裁件形状加以选出用。现工件外形为圆形,采 用有废料的直排法,比较方便、合理。 3.2 确定搭边值 搭边起补偿条料的剪裁误差,送料步距误差以及补偿于条料与导料板之间有间隙 第 6 页 共 25 页 所造成的送料歪斜误差的作用。使凸,凹模刃口双边受力,受力平衡,合理间隙一易 破坏,模具寿命与工件断面质量都能提高。对于利用搭边自动送料模具,搭边使条料 有一定的刚度,以保证条料的连续送进。搭边的合理数值主要决定于材料厚度、材料 种类、冲裁件的大小以及冲裁件的轮廓形状等。一般板料愈厚,材料愈软以及冲裁件 尺寸愈大,形状愈复杂,则搭边值也应愈大。搭边的作用是使条料定位,保证零件的 质量和精度,补偿定位误差,确保冲出合格的零件,并使条料有一定的刚度,不弯曲, 便于送进,并能使冲模寿命提高。 手送料 圆形 非圆形 往复送料 自动 送料 料厚 a a 1 a a1 a a1 a a1 1 1.5 1.5 2 1.5 3 2 12 2 1.5 2.5 2 3.5 2.5 3 2 23 2.5 2 3 2.5 4 3.5 34 3 2.5 3.5 3 5 4 4 3 45 4 3 5 4 6 5 5 4 56 5 4 6 5 7 6 6 5 由查表得工件间侧搭边 a=2mm、工件件距离 a =1.5mm。1 3.3 送料步距与条料宽度的计算 采用直排的排样方案,如图 3-1 所示: 计算冲压件的毛坯面积(利用 cad 测量): A=1928mm2 送料步距 A:送料步距的大小应为条料上两个对应冲裁件的对应点之间的距离, 每次只冲一个零件的步距按式: ADa ,A(441.5)mm45.5mm1 第 7 页 共 25 页 确定条料宽度的原则是: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。 B=(D+2a)mm 式中 D零件垂直于送料方向的最大尺寸(mm ); a侧搭边最小值( mm)。 把 D=44mm,a=2mm 代入到上式中有: B(44+22 )mm=48mm 即条料宽度为 B=48mm。 图 3-1 排样图 3.4 材料利用率的计算 排样是否合理,经济性是否好,可用材料利用率来衡量,材料利用率通常是以一 个步距内零件的实际面积与所用毛坯面积的百分率來表示, = 100%= 100%01SAB1 式中 一个步距内零件的实际面积( );1S 2m 第 8 页 共 25 页 一个步距内所需毛坯面积( );0S 2m A送料步距(mm); B条料宽度(mm)。 带入数据可得: = 100%= 100%=88.3%ABS 219845.m 即一个送料步距内的材料利用率 为 88.3%。 第四章 冲裁力计算 4.1 落料力、冲孔力、卸料力、推件力的计算 计算冲裁力的目的是为了选用合理的压力机,设计模具以及检验模具的强度。压 力机的吨位必须大于所计算的冲裁力,以适应冲裁工艺的需求。一般可按下公式计算: bLtFP 式中 F P冲裁力(N); L冲裁周边长度(mm); t冲裁料厚(mm); b抗拉强度( MPa)。 (1)落料力计算 按上式: bLtF落 式中: F 落 落料力(N); L工件外轮廓周长(mm); t材料厚度(mm),t=0.5mm; b材料抗剪强度( MPa)。由查表, 。 MPa30b 根据零件图可算轮廓长度 L =171.3mm,t=0.5mm, 代入到上式中, 第 9 页 共 25 页 则 17.30.5325.7FmMPakN落 (2)冲孔力 bLtF冲 式中 冲孔力(N);冲F L工件外轮廓周长(mm); t材料厚度(mm),t=0.5mm; b材料抗剪强度( MPa)。由查表, 。 MPa30b 根据零件图冲孔的总轮廓长度 L =(12.564+51.14)mm=101.38mm 则 10.38.53015.2FmakN冲 孔 1. 落料时的卸料力的计算 =KX 卸F落 式中 卸料力(N);卸F 落料力(N);落 KX卸料系数,查冲压模具简明设计手册表 3-11,P57 其值为 0.030.04(薄料取大值,厚料取小值),取 K=0.04。 则 =KX =( 0.0425.7)KN=1.028(KN)卸F落 2. 冲孔时的推件力的计算 =nkT 推 冲F 式中 推料力(N);推F K1推料系数,查冲压模具简明设计手册表 3-11,其值为 0.05; n梗塞在凹模内的制件或废料数量,n=h/t,h 为刃口部分的高(mm), t 为材料厚度(mm),其中,h=4mm,t=0.5mm,取 n=8, 则 第 10 页 共 25 页 =nkT =(80.0515.2)KN=6.08(KN)推F冲 冲裁时,压力机的公称压力必须大于或等于各冲裁工艺力的总和 = + + +总 落 冲F卸 推 式中:冲裁力 =25.7KN,冲孔力 =15.2KN,卸料力 =1.028KN,推料力落F冲 卸F =6.08KN,则: 推F = + + + 48 kN总 落 冲F卸 推 4.2 确定模具压力中心 由于工件完全对称,所以该模具的压力中心即为工件的几何中心。 第五章 凸凹模的设计 冲裁件的尺寸精度取决于凸,凹模刃口部分的尺寸。冲裁的合理间隙也要靠凸, 凹模刃口部分的尺寸来实现的保证。正确地确定刃口部分尺寸是相当重要的。 5.1 凸、凹模刃口尺寸计算原则 1)落料件的尺寸取决于凹模尺寸,冲孔件的尺寸取决于凸模尺寸。因此, 设计落料模时,以凹模为基准,间隙取在凸模上,设计冲孔模时,以凸模为基准, 间隙取在凹模上。 2)考虑到冲裁时凸,凹模的磨损,在设计凸,凹模刃口尺寸时,对基准 件刃口尺寸在磨损后增大的,应取工件尺寸公差范围内较小的数值。对基准件刃口 尺寸在磨损后减小,应取工件尺寸公差范围内较大的数值,在凸,凹模磨损到一定 程度的情况下,仍能冲出合格的零件。 3) 确定模具刃口制造公差时,要既能保证工件的精度要求,又能保证有合理 的间隙数值,一般模具制造精度比工件精度高 3-4 级。 第 11 页 共 25 页 5.2 凸、凹模刃口尺寸计算 查表得间隙值 mm, mm。min0.6Zmax0.8Z 通过查表得凸、凹模制造公差: mm, mm2.凸.2凹 通过校核: maxin0. 0.4Z凸 凹 不能满足 的条件,所以无法采用分开加工的方法,只能采用凹凸 ia 配合加工的方法。 工件冲孔尺寸未注公差的为圆孔的尺寸,查表得: 0.164 所有冲孔尺寸中,以凸模为基准: 属于磨损后减小的尺寸0.164 属于磨损后减小的尺寸.5 属于磨损后减小的尺寸180.7 查表得磨损因数 x=0.75 磨损后增大尺寸的计算公式: 4max0()A 磨损后减小尺寸的计算公式: in4B 式中:x磨损系数; 为尺寸公差。 带入公式得: 00.16.444(.75)=200. .3518. 8.10.240(.507) 冲孔凹模刃口与冲孔凸模刃口配作,保证间隙 , 。min.6Zmax0.8 对于外轮廓的落料,也采用配合加工的方法,其凸、凹模刃口尺寸计算如下: 工件图中未注公差可查表,尺寸偏差数值如下,以凹模为基准: 第 12 页 共 25 页 44mm mm 为磨损后增大尺寸0.624 查表得:当 时,磨损系数为 x=0.5;5 当 时,磨损系数为 x=0.75. 代入公式: 40max )( AJ .620.134(.5)9凹 落料凸模刃口与冲孔凸模刃口配作,保证间隙 , 。min.6Zmax0.8 5.3 凸模、凹模、凸凹模的结构设计 冲孔凸模的结构设计,由于模具需要在凸模外面装推件块,因此设计成直柱的形 状。凸模示意图如图 5-1 所示。 凹模的刃口形式,考虑到本例生产批量较大,所以采用刃口强度较高的凹模,即 图 所示的刃口形式。 根据公式(7-1)可计算落料凹模板的尺寸: 凹模厚度: H=Kb2 =0.344 =10.56(mm) 根据公式(7-2)可计算凹模边壁厚: c=(1.52)H =1.510.56210.56 =15.8421.12(mm) 为了设计方便,取凹模厚度为16mm,凹模壁厚为25mm。 根据凹模厚度和边壁厚可确定凹模板的长、宽的尺寸。 可计算凹模长: L=b1+2c =44+225 =94(mm) 第 13 页 共 25 页 可计算凹模宽: L=b1+2c =44+225 =94(mm) 即:LBH=94mm94mm15mm 最终取整,选择凹模的外形尺寸为LBH=100mm100mm16mm 本模具为复合冲裁模,因此除冲孔凸模和落料凹模外,必然还有一个凸凹模。凸 凹模的结构简图如图 5-2 所示。校核凸凹模的强度:按公式得凸凹模的最小壁厚 m1.5t0.75mm,而实际最小壁厚为 4mm,故符合强度要求。凸凹模的外刃口尺寸 按凹模尺寸配制,并保证双面间隙 0.060.08。凸凹模上孔中心距离尺寸 32 的公差, 应比零件图所标精度高 3-4 级,即定为 320.025mm。 凸模、凹模、凸凹模三个零件的示意图如图 5-1、图 5-2、图 5-3、图 5-4 所示: 图 5-1 冲圆形孔凸模 第 14 页 共 25 页 图 5-2 冲中心孔孔凸模 图 5-3 凹模 第 15 页 共 25 页 图 5-4 凸凹模 第六章 冲压设备的选择 由于复合模的特点,为防止设备超载,可按公称压力 选择压力机。参总压 F3.1 照设计手册选取公称压力为的压力机,压力机型号为 J23-10。 表 6-1 为压力机 J23-40 技术参数:(冲压模具简明设计手册表 13.10,P389 表 6-1 型 号 J23-10 公称压力/kN 100 滑块行程/mm 45 公称压力行程/mm 35 最大倾斜角度 35 最大闭合高度/mm 180 闭合高度调节量/mm 35 垫板尺寸(厚度 mm孔径 mm) 35170 模柄孔尺寸(直径 mm深度 mm) 3055 工作台尺寸 前后 240 第 16 页 共 25 页 左右 370 第七章 模具主要零部件设计 7.1 定位方式的选择 定位方式的选择通俗的说既是选择定位零件。定位零件的作用是使坯料或工序件 在模具上有正确的位置,定位零件的结构形式很多,用于对条料进行定位的定位零件 有挡料销、导料销、导料板、侧压装置、导正销、侧刃等,用于对工序进行定位的定 位零件有定位销、定位板等。 定位零件基本上都已标准化,可根据坯料和工序件形状、尺寸、精度及模具的结 构形式与生产效率要求等选用相应的标准。 因为该模具采用是条料,控制条料的送进方向采用导料板,无侧压装置。控制条 料的送进步距采用固定挡料销定距,导料销精定位。而第一件的冲压位置因为条料长 度有一定余量,可以靠操作工目测来确定。 7.2 卸料出件方式的选择 卸料与出件装置的作用是当冲模完成一次冲压之后,把冲件或废料从模具工作零 件上卸下来,以便冲压工作继续进行。通常,把冲件或废料从凸模上卸下来称为卸料。 卸料装置按卸料的方式分为固定卸料装置弹性卸料装置和废料切刀三种。 固定 卸料装置 , 固定卸料装置仅由固定卸料板构成,一般安装在下模的凹模上;弹性卸料 装置由卸料板、卸料螺钉和弹性元件(弹簧或弹簧)组成;弹性卸料装置可安装于上 模或下模,依靠弹簧或弹簧的弹力来卸料,卸料力不太大但冲压时可兼起压料作用, 故多用于冲裁料薄及平面度要求较高的冲件;废料切刀是在冲裁过程中冲裁废料切断 成数块,从而实现卸料的一种卸料零件。 出件装置的作用是从凹模内卸下冲件或废料。我通常把超过上模内的出件装置称 第 17 页 共 25 页 为推件装置;把装在下模内的称为顶件装置。 综合考虑该模具的结构和使用方便,以及工件料厚为 2.2mm,相对较薄,卸料力也 比较小,故可采用弹性卸料装置,卸料装置由卸料板、卸料螺钉和弹簧组成。冲制的 工件由推板、推销和推件块组成的刚性推件装置,冲孔的废料可通过凸凹模的内孔从 冲床台面孔漏下。 7.3 卸料橡胶的设计计算 综合考虑该模具的结构和使用方便,以及工件料厚为 0.5mm,卸料力不是很大,故 可采用弹性卸料装置,卸料装置由卸料板、橡胶和卸料螺钉组成。冲制的工件通过凹 模的内孔从冲床台面孔漏下。 卸料橡胶的设计计算: 橡胶的自由高度为 (4-1)工 作自 由 )( s45.3H 其中 s1017mt工 作 修 模 量 ( ) 故 2.8自 由 橡胶的装配高度为: 0.59H( ) 选择橡胶的直径为 30,满足 5.1/.D自 由 7.4 模架的选择 模架是由上、下模座、模柄及导向装置(最常用的是导柱、导套)组成,模架是 整副模具的骨架,模具的全部零件都固定在它的上面,并且承受冲压过程中的全部载 荷。模架的上模座通过模柄与压力机滑块相连,下模座用螺钉压板固定在压力机工作 台面。上、下模之间靠模架的导向装置来保持其精确位置,以引导凸模的运动,保证 冲裁过程中间隙均匀。 上模座:L/mm =125mHB/1254 第 18 页 共 25 页 下模座:L/mm 125mHB/1253 导柱:d/mm L/mm=22 130 导套:d/mm L/mm D/mm=22 70 35 上、下垫板的厚度定为:6mm 卸料板厚度取:10mm 模具的闭合高度: H ( 35+6+12+15+0.5+10+20+12+6+45)mm=161.5mm模 第八章 模具的装配、调试和检测 8.1 模具的装配 根据复合模装配要点,选凹模作为装配基准件,先装下模,再装上模,并调整间 隙、试冲、返修,具体装配见表 7.1。 表 7.1 复合模的装配表 序 号 工序 工艺说明 1 凸、 凹模预配 (1)装配前仔细检查各凸模形状以及凹模形孔,是否符合图纸 要求尺寸精度、形状。 (2)将各凸模分别与相应的凹模孔相配,检查其间隙是否加工 均匀。不合适则应重新修磨或更换。 2 凸模 装配 以凹模孔定位,将各凸模分别压入凸模固定板的形孔中,并拧 紧牢固 3 装配 下模 (1) 在下模座上划中心线,按中心预装凹模、导料板; (2) 在下模座、导料上,用已加工好的凹模分别确定其螺孔位置, 并分别钻孔,攻丝 (3) 将下模座、导料板、凹模、活动挡料销、弹簧装在一起,并 用螺钉紧固,打入销钉 第 19 页 共 25 页 4 装配 上模 (1) 在已装好的下模上放等高垫铁,再在凹模中放入 0.12mm 片, 然后将凸模与固定板的组合装入凹模; (2) 预装上模座,划出与凸模固定板相应螺孔。销孔位置并钻绞 螺孔、销孔; (3) 用螺钉将固定板组合、垫板、上模座连接在一起,但不要拧 紧; (4) 将卸料板套装入固定板的凸模上,装上弹簧和卸料螺钉,调 节弹簧的预压量,使卸料板高出凸模下端约 1mm;复查凸、 凹模间隙并调整合适后,紧固螺钉; (5) 安装导正销、承料板; 8.2 冲裁模具的调试 模具装配以后,必须在生产条件下进行试冲。通过试冲可以发现模具设计和制造 的不足,并找出原因给与纠正。并能够对模具进行适当的调整和修理,直到模具正常 工作中冲出合格的制件为止。 冲裁模具经试冲合格后,应在模具模座正面打上编号、冲模图号、制件号、使用 压力机型号、制造日期等。并涂油防锈后经检验合格入库。 在模具制造中,模具零件的检验与模具装配试模后的验收是模具加工过程中的重 要工艺环节。模具零件加工及装配质量好坏,对模具的使用寿命有着较大的影响。加 强模具装配后及模具零件加工各工序间质量检验,是确保模具质量的重要手段。因此, 模具生产单位在生产过程中,要健全模具零件及模具装配前后的检验与验收制度。即 根据本厂产品要求和工艺水平,编制切合实际的质量检验规程。实行以检验人员专职 检验与生产工人自检互检相互结合的检验方法,严格按图样技术条件和有关工艺文件 进行必要的检查。在检验中,除了进行工序间的检验和装配后的验收外,还加强各工 序实际操作的检查,以督促执行工艺规定,防止废品的产生。 8.3 模具的检测 模具的检验与验收和设计、制造一样是模具制造中不可分割的部分,在模具生产 第 20 页 共 25 页 中起着积极的作用,是满足现代模具制造业发展的需要。同时,在检测技术对于模具 制造质量的提高、延长模具的寿命和能生产出高效、优质制品零件,有着十分重要的 意义。模具的检测主要是检查在设计、制造或装配中出现的缺陷,并在交付客户前做 最后的验证,保证模具的合格性和安全性并能生产出合格的产品,模具零件加工及装 配质量好坏,对模具的使用寿命有着较大的影响。 加强模具装配后及模具零件加工各工序间质量检验,是确保模具质量的重要手段。 因此,模具生产单位在生产过程中,要健全模具零件及模具装配前后的检验与验收制 度。只有这样才能保证模具的合格性和安全性并能生产出合格的产品。其具体方法可 详细查 8.2 所示。 表 8.2 模具中常见缺陷和调整方法表 缺陷 产生原因 调整方法 冲件毛刺过大 1.刃口不锋利或淬火硬度不够 2间隙过大或过小,间隙不均 匀 1修磨刃口使其锋利 2重新调整间隙,使其均匀 冲件不平整 1凸模有倒锥,冲件从孔中通 过时被压弯 2顶出件与顶出器接触零件面 积 1修磨凹模孔,去除导锥现象 2更换顶出杆,加大与零件的接 触面积 尺寸超差和形 状不准确 凸模、凹模形状及尺寸精度差 修整凸模、凹模形状及尺寸,使其 达到形状及尺寸精度要求 凹模被胀裂 1凹模孔有倒锥度形象 2凹模孔内卡住废料 1修磨凹模孔,消除倒锥现象 2修抵凹模孔高度 凸、凹模刃口 相咬 1.上、下模座,固定板、凹模、 垫板等零件安装基面不平行 2.凸模、导柱、导套与安装基 面不垂直 1调整有关两件重新安装 2重新安装凸、凹模,使之对正 3调整其垂直度重新安装 4更换导柱、导套 第 21 页 共 25 页 送料不畅通, 有时被卡死 1两导料板之间的尺寸过小或 有斜度 2凸模与卸料板之间的间隙太 大,致使搭边翻转而堵塞 1粗修或重新调整装配导料板 2减小凸模与导料板之间的配合 间隙,或重新调整浇注卸料板孔 3重新调整装配导料板,使之平 行 第九章 模具材料的选用要求和选择原则 利用模具生产制品零件,其模具质量的好坏,寿命的长短,直接关系到产品制造 精度、性能和成本。是提高劳动生产率、降低消耗、创造效益,尽快使产品占领市场 的重要性条件。而模具的质量、使用寿命、制造精度及合格率很大程度上取决于设计 时对模具材料的选用、热处理工艺要求、模具零件配合精度及公差等级的选择和表面 质量要求。 9.1 冷冲模材料的选用要求 冷冲模材料应具有的性能: 冷冲模包括冲裁模、弯曲模、拉深模、成形模和冷挤压模等。冷冲模在工作中承 受冲击、拉深、压缩弯曲、疲劳磨擦等机械的作用。模具常常发生脆断、堆塌、磨损、 啃伤和软化等形成的失效。因此,作为冷冲模主要材料的钢材,应具有的性能。 1. 应具有较高的变形抗力:主要抗力指标包括淬火、回火抗压强度、弯强度等。 其中硬度是模具注意重要的抗力指标,高的硬度是保持模具耐磨性的必要条件。工作 零件热处理后的硬度在 60HRC 强度和抗弯强度才能保证模具具有较高的变形能力。 2. 应具有较高的断裂抗主要抗力指标有材料的抗冲击性能抗压强度、抗弯强度 断 裂抗力和冲击载荷下抵抗模具裂纹产生一个特性,也是作为防止断裂的一个重要依据。 其基体中碳含量越高冲击韧性越高。故对韧性的要求应依据载荷较大的冷冲镦及剪切 模易受偏心弯曲载荷细长凸模或有应力集中的模具,都需要有较高的韧性。 3. 应具有较高的耐磨性和抗疲劳性能:对于在一定条件下工作的模具钢,为了提 第 22 页 共 25 页 高耐磨性,需要在硬度高的基体上均匀分布有大量细小硬的碳化物 相同硬度下,提高 钢的性能是模具在交变应力条件下产生的疲劳破坏,如模具长期使用有刮痕凹槽等。 4. 应具有较好的冷、热加工工艺性:钢材的加工性能包括可锻性、可加工性、淬 透性、淬硬性较小的脱碳敏感性和较小变形倾向等,以方便模具的加工,易于成形及 防止热处理后变形等。 9.2 材料的选择原则 1.要选择满足模具零件工作要求的最佳综合性能的材料:要选择满足模具零件工作 要求的最佳综合性能的材料; 2.要针对模具的失效形式选用钢材,钢材的失效是影响模具寿命的主要因素包括: 为防模具开裂,要选用韧性好的材料; 为防磨损,应选用合金元素高的材料; 对于大型冲模应选用淬透性好的材料; 为保持钢材硬度能力,要选用耐回火性高的含铬、钼合金钢; 为防热处理变形,对于形杂的零件应选用含碳量高、淬透性好的高合金材料。 3.要根据制品批量大小,以最低的成本的选材原则选用; 对于需冲压数量较多模具,一般采用优质合金钢,而数量少的则采用碳素钢,以 降低成本。 4要根据冲模零件的作用选择; 凸模凹模钢材选用,对于数量不多或厚度不大的可采用有色金属或黑色金属,而 对于支撑板、卸料零件、导向件应选用一般钢材。 5要根据冲模精密程度选用。 在制造小型精密模具而又复杂时可选用优质合金钢制作,而对于比较简单,形状、 精度有要求不高的模具应选用比较便宜的碳钢或低合金钢。 第十章 绘制模具总装图及零件图 运用 Auto CAD 软件,按照上述几章设计的尺寸,绘制模具装配总图及各零件图。 第 23 页 共 25 页 总装配图按照 0#图纸绘制,零件图则按照其它型号的图纸绘制。图样幅面应符合国家 (GB4457.1-84)。 先绘制装配草图,经指导老师认可,才进行正式图的绘制。绘图过程中严格按照 国标制图标准绘制。 10.1 装配图绘制 装配图应用足够说明模具构造的投影图及必要的剖面图、剖视图,一般主视图和 俯视图应对应绘制。还要注明必要尺寸,如模具高度、轮廓尺寸以及装配保证的有关 尺寸和精度。画出排样图,填写详细的零件明细表和技术要求。装配结构图如图 9-1: 图 10-1 模具总装图 10.2 模具零件图的绘制 见附图 第 24 页 共 25 页 参考文献 1 张超英.冲压模具与制造.北京:化学工业出版社,1999.7 2 罗学科.模具识图与制图.北京:化学工业出版社,2001.4 3 王新华.冲模设计与制造实用计算手册.北京: 机械工业出版社,2003.5 4 万本善.实用冲模结构图解与冲压新工艺详图及常用数据速查速用手册.北京: 科大电子出版社,2001.8 5 齐卫东.冷冲压模具图集.北京: 北京理工大学出版社,2000.9 6 王立刚.冲压工艺与模具设计.北京:机械工业出版社,1998.11 7 薛啟翔.冲压工艺与模具设计实例分析.北京:机械工业出版社,2001.5 8 郝滨海.冲压模具简明设计手册.北京:化学工业出版社,2002.6 9 宛强.冲压模具设计及实例精解.北京:化学工业出版社,2004.8 10 模具实用技术丛书编委会.冲模设计应用实例.北京:机械工业出版社,2005.4 11 成虹.冲压工艺与模具设计.北京:高等教育出版社,2006.7 12 高锦张.塑性成形工艺与模具设计.北京:机械工业出版社,1998.9 13 翁其金.冲压工艺及冲模设计.北京:机械工业出版社,2004.7 14 甄瑞麟.模具制造工艺课程设计指导与范例.北京:化学工业出版社, 2009.1 15 张水忠.挤压工艺及模具设计.北京:化学工业出版社, 2009.2 16 张如华.冲压工艺与模具设计.北京:清华大学出版社, 2006.3 第 25 页 共 25 页 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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