塑料瓶蓋注射模具設(shè)計(jì)【說(shuō)明書(shū)+CAD】

塑料瓶蓋注射模具設(shè)計(jì)【說(shuō)明書(shū)+CAD】,說(shuō)明書(shū)+CAD,塑料瓶蓋注射模具設(shè)計(jì)【說(shuō)明書(shū)+CAD】,塑料,瓶蓋,注射,模具設(shè)計(jì),說(shuō)明書(shū),仿單,cad 目 錄 緒論-----------------------------------2 第1章 對(duì)塑料成型模具設(shè)計(jì)的認(rèn)識(shí)---------------3 1.1 模具工業(yè)現(xiàn)狀------------------------4 1.2 發(fā)展模具的積極意義--------------------4 1.3 我國(guó)的模具將呈現(xiàn)十大發(fā)展趨勢(shì)------------5 第2章 設(shè)計(jì)過(guò)程---------------------------7 2.1 塑料成型制品的分析---------------------------7 2.2 注射成型工藝的設(shè)計(jì)---------------------------8 2.3 注射機(jī)的技術(shù)規(guī)范-----------------------------12 第3章 模具的結(jié)構(gòu)設(shè)計(jì)-------------------------------14 3.1 注射機(jī)的鎖模力-------------------------------14 3.2 成型零件的設(shè)計(jì)-------------------------------16 第4章 模具結(jié)構(gòu)零件設(shè)計(jì)-----------------------------17 4.1 導(dǎo)柱和導(dǎo)套---------------------------------- 17 4.2 推桿、復(fù)位桿及拉料桿-------------------------17 4.3 限位釘、墊塊---------------------------------18 4.4 定位圈與澆口套-------------------------------18 4.5 模板-----------------------------------------18 4.6 擋塊、限位塊---------------------------------18 參考資料-------------------------------19 體會(huì)與感受--------------------- 19 緒 論 模具工業(yè)是制造業(yè)中的一項(xiàng)基礎(chǔ)產(chǎn)業(yè)，是技術(shù)成果轉(zhuǎn)化的基礎(chǔ)，同時(shí)本身又是高新技術(shù)產(chǎn)業(yè)的重要領(lǐng)域，在歐美等工業(yè)發(fā)達(dá)國(guó)家被稱(chēng)為“點(diǎn)鐵成金”的“磁力工業(yè)”。美國(guó)工業(yè)界認(rèn)為“模具工業(yè)是美國(guó)工業(yè)的基石”；德國(guó)則認(rèn)為是所有工業(yè)中的“關(guān)鍵工業(yè)”；日本模具協(xié)會(huì)也認(rèn)為“模具是促進(jìn)社會(huì)繁榮富裕的動(dòng)力”，同時(shí)也是“整個(gè)工業(yè)發(fā)展的秘密”，是“進(jìn)入富裕社會(huì)的原動(dòng)力”。日本模具產(chǎn)業(yè)年產(chǎn)值達(dá)到13000億日元，遠(yuǎn)遠(yuǎn)超過(guò)日本機(jī)床總產(chǎn)值9000億日元。如今，世界模具工業(yè)的發(fā)展甚至已超過(guò)了新興的電子工業(yè)。 　　我國(guó)國(guó)民經(jīng)濟(jì)的高速發(fā)展對(duì)模具工業(yè)提出了越來(lái)越高的要求，預(yù)計(jì)到2005年，僅汽車(chē)行業(yè)將需要各種塑料制件36萬(wàn)噸；電冰箱、洗衣機(jī)和空調(diào)的年產(chǎn)量均超過(guò)1000萬(wàn)臺(tái)；彩電的年產(chǎn)量已超過(guò)3000萬(wàn)臺(tái)。 　　近年來(lái)，我國(guó)的模具工業(yè)一直以每年13%左右的增長(zhǎng)速度快速發(fā)展。據(jù)預(yù)測(cè)，我國(guó)模具行業(yè)在“十五”期間的增長(zhǎng)速度將達(dá)到13%～15%。模具鋼的需求量也將以年12%的速度遞增，全國(guó)年需求量約70萬(wàn)噸左右，而國(guó)產(chǎn)模具鋼的品種只占現(xiàn)有國(guó)外模具鋼品種的60%，每年進(jìn)口模具鋼約6萬(wàn)噸。我國(guó)每年進(jìn)口模具約占市場(chǎng)總量的20%左右，已超過(guò)10億美元，其中塑料與橡膠模具占全部進(jìn)口模具的50%以上；沖壓模具占全部進(jìn)口模具約40%。 　　目前，全世界模具的年產(chǎn)值約為650億美元，我國(guó)模具工業(yè)的產(chǎn)值在國(guó)際上排名位居第三位，僅次于日本和美國(guó)。雖然近幾年來(lái)，我國(guó)模具工業(yè)的技術(shù)水平已取得了很大的進(jìn)步，但總體上與工業(yè)發(fā)達(dá)的國(guó)家相比仍有較大的差距。例如，精密加工設(shè)備還很少，許多先進(jìn)的技術(shù)如CAD/CAE/CAM技術(shù)的普及率還不高，特別是大型、精密、復(fù)雜和長(zhǎng)壽命模具遠(yuǎn)遠(yuǎn)不能滿(mǎn)足國(guó)民經(jīng)濟(jì)各行業(yè)的發(fā)展需要。 　　縱觀(guān)發(fā)達(dá)國(guó)家對(duì)模具工業(yè)的認(rèn)識(shí)與重視，我們感受到制造理念陳舊則是我國(guó)模具工業(yè)發(fā)展滯后的直接原因。模具技術(shù)水平的高低，決定著產(chǎn)品的質(zhì)量、效益和新產(chǎn)品開(kāi)發(fā)能力，它已成為衡量一個(gè)國(guó)家制造業(yè)水平高低的重要標(biāo)志。目前，我國(guó)模具工業(yè)的當(dāng)務(wù)之急是加快技術(shù)進(jìn)步，調(diào)整產(chǎn)品結(jié)構(gòu)，增加高檔模具的比重，質(zhì)中求效益，提高模具的國(guó)產(chǎn)化程度，減少對(duì)進(jìn)口模具的依賴(lài)。 現(xiàn)代模具技術(shù)的發(fā)展，在很大程度上依賴(lài)于模具標(biāo)準(zhǔn)化、優(yōu)質(zhì)模具材料的研究、先進(jìn)的設(shè)計(jì)與制造技術(shù)、專(zhuān)用的機(jī)床設(shè)備，更重要的是生產(chǎn)技術(shù)的管理等。21世紀(jì)模具行業(yè)的基本特征是高度集成化、智能化、柔性化和網(wǎng)絡(luò)化。追求的目標(biāo)是提高產(chǎn)品的質(zhì)量及生產(chǎn)效率，縮短設(shè)計(jì)及制造周期，降低生產(chǎn)成本，最大限度地提高模具行業(yè)的應(yīng)變能力，滿(mǎn)足用戶(hù)需要?？梢?jiàn)，未來(lái)我國(guó)模具工業(yè)和技術(shù)的主要發(fā)展方向?qū)⑹牵? 　——大力普及、廣泛應(yīng)用CAD/CAE/CAM技術(shù)，逐步走向集成化?，F(xiàn)代模具設(shè)計(jì)制造不僅應(yīng)強(qiáng)調(diào)信息的集成，更應(yīng)該強(qiáng)調(diào)技術(shù)、人和管理的集成。 　　——提高大型、精密、復(fù)雜與長(zhǎng)壽命模具的設(shè)計(jì)與制造技術(shù)，逐步減少模具的進(jìn)口量，增加模具的出口量。 　 ——在塑料注射成型模具中，積極應(yīng)用熱流道，推廣氣輔或水輔注射成型，以及高壓注射成型技術(shù)，滿(mǎn)足產(chǎn)品的成型需要。 　　——提高模具標(biāo)準(zhǔn)化水平和模具標(biāo)準(zhǔn)件的使用率。模具標(biāo)準(zhǔn)件是模具基礎(chǔ)，其大量應(yīng)用可縮短模具設(shè)計(jì)制造周期，同時(shí)也顯著提高模具的制造精度和使用性能，大大地提高模具質(zhì)量。我國(guó)模具商品化、標(biāo)準(zhǔn)化率均低于30%，而先進(jìn)國(guó)家均高于70%，每年我們要從國(guó)外進(jìn)口相當(dāng)數(shù)量的模具標(biāo)準(zhǔn)件，其費(fèi)用約占年模具進(jìn)口額的3%～8%。 　　——發(fā)展快速制造成型和快速制造模具，即快速成型制造技術(shù)，迅速制造出產(chǎn)品的原型與模具，降低成本推向市場(chǎng)。 　　——積極研究與開(kāi)發(fā)模具的拋光技術(shù)、設(shè)備與材料，滿(mǎn)足特殊產(chǎn)品的需要。 　　——推廣應(yīng)用高速銑削、超精度加工和復(fù)雜加工技術(shù)與工藝，滿(mǎn)足模具制造的需要。 　　——開(kāi)發(fā)優(yōu)質(zhì)模具材料和先進(jìn)的表面處理技術(shù)，提高模具的可靠性。 　　——研究和應(yīng)用模具的高速測(cè)量技術(shù)、逆向工程與并行工程，最大限度地提高模具的開(kāi)發(fā)效率與成功率。 在科技發(fā)展中，人是第一因素，因此我們要特別注重人才的培養(yǎng)，實(shí)現(xiàn)產(chǎn)、學(xué)、研相結(jié)合，培養(yǎng)更多的模具人才，搞好技術(shù)創(chuàng)新，提高模具設(shè)計(jì)制造水平。在制造中積極采用多媒體與虛擬現(xiàn)實(shí)技術(shù)，逐步走向網(wǎng)絡(luò)化、智能化環(huán)境，實(shí)現(xiàn)模具企業(yè)的敏捷制造、動(dòng)態(tài)聯(lián)盟與系統(tǒng)集成。 第一章 對(duì)塑料成型模具設(shè)計(jì)的認(rèn)識(shí) 隨著工業(yè)的發(fā)展，模具所占的地位越來(lái)越重要，尤其是塑料模具，其應(yīng)用更加廣泛，技術(shù)含量更高，我們每天都在享用這它帶來(lái)的成果。 塑料制件在工業(yè)中的應(yīng)用日趨普遍，這是由于他們具有一系列特殊優(yōu)點(diǎn)所決定的。塑料密度小，質(zhì)量輕，大多數(shù)塑料密度在1.0－1.4之間，相當(dāng)于鋼材密度的0.11和鋁材的0.5左右，即在同樣的體積下，塑料制件要比金屬制件輕得多，這就是以塑代鋼的優(yōu)點(diǎn)。 模具是工業(yè)生產(chǎn)中的重要工藝裝備，模具工業(yè)是國(guó)民經(jīng)濟(jì)各部門(mén)的重要基礎(chǔ)之一，塑料模是指用于成型塑料制件的模具，它是型腔的一種類(lèi)型。模具設(shè)計(jì)水平的高低，加工設(shè)備的好壞，制造力量的強(qiáng)弱，模具質(zhì)量的優(yōu)劣，直接影響著許多新產(chǎn)品的開(kāi)發(fā)和老產(chǎn)品的更新?lián)Q代，影響著產(chǎn)品的質(zhì)量和經(jīng)濟(jì)效益的提高。 5模具工業(yè)現(xiàn)狀 由于歷史原因形成的封閉式、“大而全”的企業(yè)特征，我國(guó)大部分企業(yè)均設(shè)有模具車(chē)間，處于本廠(chǎng)的配套地位，自70年代末才有了模具工業(yè)化和生產(chǎn)專(zhuān)業(yè)化這個(gè)概念。模具工業(yè)主要生產(chǎn)能力分散在各部門(mén)主要產(chǎn)品廠(chǎng)內(nèi)的工模具車(chē)間，所生產(chǎn)的模具基本自產(chǎn)自用。據(jù)粗略估計(jì)，產(chǎn)品廠(chǎng)的模具生產(chǎn)能力占全國(guó)模具生產(chǎn)能力的75％，他們的裝備水平較好，技術(shù)力量較強(qiáng)，生產(chǎn)潛力較大，但主要為本廠(chǎng)產(chǎn)品服務(wù)，與市場(chǎng)聯(lián)系較少，經(jīng)營(yíng)機(jī)制不靈活，不能發(fā)揮人力物力的潛力。模具專(zhuān)業(yè)廠(chǎng)全國(guó)只有二百家左右，商品模具只占總數(shù)的20％左右，模具標(biāo)準(zhǔn)件的商品率也不到20％。由于受舊管理體制的影響較深，缺乏統(tǒng)籌規(guī)劃和組織協(xié)調(diào)，存在著“中而全”，“小而全”的結(jié)構(gòu)缺陷，生產(chǎn)效率不高，經(jīng)濟(jì)效益較差。 一、 發(fā)展模具的積極意義 中國(guó)經(jīng)濟(jì)的持續(xù)高速發(fā)展，為模具工業(yè)的發(fā)展提供了廣闊的空間。模具行業(yè)在今后的發(fā)展中，首先要更加注意其產(chǎn)品結(jié)構(gòu)的戰(zhàn)略性調(diào)整，使結(jié)構(gòu)復(fù)雜、精密度高的高檔模具得到更快的發(fā)展。我們的模具行業(yè)要緊緊地跟著市場(chǎng)的需求來(lái)發(fā)展。沒(méi)有產(chǎn)品的需求、產(chǎn)品的更新?lián)Q代，就沒(méi)有模具行業(yè)的技術(shù)進(jìn)步，也就沒(méi)有模具產(chǎn)品的上規(guī)模、上檔次。如汽車(chē)生產(chǎn)中90%以上的零部件，都要依靠模具成形，在珠三角和長(zhǎng)三角，為汽車(chē)行業(yè)配套的模具產(chǎn)值增長(zhǎng)達(dá)40%左右。 其次，要積極推進(jìn)中西部地區(qū)模具產(chǎn)業(yè)的發(fā)展，努力縮小發(fā)達(dá)地區(qū)和不發(fā)達(dá)地區(qū)的差距。中西部很多地區(qū)已經(jīng)意識(shí)到模具產(chǎn)業(yè)的發(fā)展對(duì)制造業(yè)的重要作用。如陜西、四川、河北等模具生產(chǎn)企業(yè)的生產(chǎn)規(guī)模、技術(shù)水平都有了很大的發(fā)展。 第三，要積極推進(jìn)模具企業(yè)特別是國(guó)有企業(yè)的體制創(chuàng)新，轉(zhuǎn)換經(jīng)營(yíng)機(jī)制，大力發(fā)展混合所有制經(jīng)濟(jì)，明晰產(chǎn)權(quán)和完善法人治理結(jié)構(gòu)。充分發(fā)掘企業(yè)發(fā)展的內(nèi)在動(dòng)力。要積極推進(jìn)中、西部工業(yè)基礎(chǔ)較好地區(qū)的制造業(yè)大中型企業(yè)主輔分離，使其模具車(chē)間、分廠(chǎng)在不太長(zhǎng)的時(shí)間里，采用多種有效實(shí)現(xiàn)形式，轉(zhuǎn)換機(jī)制，大力發(fā)展產(chǎn)權(quán)明晰、獨(dú)立自主經(jīng)營(yíng)，適應(yīng)市場(chǎng)運(yùn)作和模具生產(chǎn)快速反應(yīng)的現(xiàn)代專(zhuān)業(yè)模具企業(yè)，培養(yǎng)能代表行業(yè)水平的“龍頭”企業(yè)，帶動(dòng)地區(qū)產(chǎn)業(yè)鏈的發(fā)展。 二、 我國(guó)的模具將呈現(xiàn)十大發(fā)展趨勢(shì) 一是模具日趨大型化。這是由于用模具成型的零件日漸大型化 和高生產(chǎn)效率要求發(fā)展的“一模多腔”所造成的。 二是模具的精度將越來(lái)越高。10年前精密模具的精度一般為5微米，現(xiàn)在已達(dá)到2-3微米，不久1微米精度的模具將上市。這要求超精加工。 三是多功能復(fù)合模具將進(jìn)一部發(fā)展。新型多功能復(fù)合模具除了沖壓成型零件外，還擔(dān)負(fù)疊壓、攻絲、鉚接和鎖緊等組裝任務(wù)，對(duì)鋼材的性能也要求越來(lái)越高。 四是熱流道模具在塑料模具中的比重也將逐漸提高。由于采用熱流道技術(shù)的模具可提高制件的生產(chǎn)率和質(zhì)量，并能大幅度節(jié)約制作的原材料，因此熱流道技術(shù)的應(yīng)用在國(guó)外發(fā)展很快，許多塑料模具廠(chǎng)所生產(chǎn)的塑料模具一半以上采用了熱流道技術(shù)，有的廠(chǎng)家使用率達(dá)到80%以上，效果十分明顯。熱流道模具在我國(guó)也已生產(chǎn)，有些企業(yè)使用率上升到20%—30%。 五是隨著塑料成型工藝的不斷改進(jìn)與發(fā)展，氣輔模具及適應(yīng)高壓注塑成型等工藝的模具將隨之發(fā)展。這類(lèi)模具要求剛性好，耐高壓，特別是精密模具的型腔應(yīng)淬火，澆口密封性好，模溫能準(zhǔn)確控制，所以對(duì)模具鋼的性能要求很強(qiáng)。 六是標(biāo)準(zhǔn)件的應(yīng)用將日益廣泛。模具標(biāo)準(zhǔn)化及模具標(biāo)準(zhǔn)件的應(yīng)用將極大地影響模具制造周期，且還能提高模具的質(zhì)量和降低模具制造成本。因此，模具標(biāo)準(zhǔn)件的應(yīng)用在“十五”期間必將得到較大的發(fā)展。 第2章 設(shè)計(jì)過(guò)程 塑料模具分類(lèi)的方法很多，按照塑料制作的成型方法不同可分為以下幾類(lèi)： 注射模，壓縮模，擠出模，氣動(dòng)成型模 本次設(shè)計(jì)主要是注射模，又叫注塑模，注射成型是根據(jù)金屬壓鑄成型原理發(fā)展起來(lái)的，首先將粒狀或粉末狀的塑料原料加入到注射機(jī)的料筒中，經(jīng)過(guò)加熱熔融成粘流態(tài)，然后在柱塞或螺桿的推動(dòng)下，以一定的流速通過(guò)料筒前端的噴嘴和模具的澆注系統(tǒng)，注射入閉合的模具型腔中，經(jīng)過(guò)一定的時(shí)間后，模具在模內(nèi)硬化成型，近幾年來(lái)，熱固性塑料注射成型的應(yīng)用也在逐漸增加。 塑料制件主要是靠成型模具獲得的，而它的質(zhì)量是靠模具的正確結(jié)構(gòu)和模具成型零件的正確形狀，精確尺寸及較低的表面粗糙度來(lái)保證的。由于塑料成型工藝的飛速發(fā)展，模具的結(jié)構(gòu)也日益趨于多功能和復(fù)雜化，這對(duì)模具的設(shè)計(jì)工作提出了更高的要求。雖然模具制作的質(zhì)量與許多因素有關(guān)，但合格的塑料制作首先取決于模具的設(shè)計(jì)與制造的質(zhì)量，其次取決與合理的成型工藝。塑料成型加工技術(shù)發(fā)展很快，塑料模具的各種結(jié)構(gòu)也在不斷的創(chuàng)新，我們?cè)趯W(xué)習(xí)成型的同時(shí)，還應(yīng)注意了解塑料模具的新技術(shù)、新工藝和新材料的發(fā)展動(dòng)態(tài)，學(xué)習(xí)和掌握新知識(shí)，為振興我國(guó)的塑料成型加工技術(shù)做出貢獻(xiàn)。 一、 塑料成型制品的分析 1、 制品的設(shè)計(jì)要求 本次設(shè)計(jì)制品的用途是塑料瓶蓋，形狀較復(fù)雜，但基本對(duì)稱(chēng)，精度要求中等。 2、 制品的生產(chǎn)批量 本制品為大批量生產(chǎn)，為了縮短周期，提高生產(chǎn)率，制品使用一模兩腔和全自動(dòng)化生產(chǎn)，利用模具的頂出機(jī)構(gòu)，將制品推出模腔，再利用拉料桿和二次脫模機(jī)構(gòu)使制品流道凝料脫落。為了提高生產(chǎn)率，制品在模具中直接成型。 3、 制品成型設(shè)計(jì) 按照與以往的設(shè)計(jì)經(jīng)驗(yàn)，該瓶蓋制品使用二次分型機(jī)構(gòu)，采用點(diǎn)澆口形式，雖然其他的澆口形式還有直接澆口、側(cè)澆口、扇形澆口、薄片式澆口、環(huán)行澆口、輪輻澆口、爪形澆口、潛伏澆口、護(hù)耳澆口等，但他們都不容易在開(kāi)模時(shí)實(shí)現(xiàn)自動(dòng)切斷，而點(diǎn)澆口就具有這個(gè)優(yōu)點(diǎn)，而且其留于塑件的疤痕較小，不影響塑件外觀(guān)。 4、 抽芯機(jī)構(gòu)的設(shè)計(jì) 在塑件中間有兩個(gè)用于翻蓋時(shí)起旋轉(zhuǎn)固定作用的半圓球，如果設(shè)計(jì)一抽芯機(jī)構(gòu)用于該球的成型，則在抽出時(shí)易于產(chǎn)生干涉現(xiàn)象，而且由于該處的尺寸形狀比較小，模具的抽芯機(jī)構(gòu)制造比較困難，對(duì)模具的制造工藝要求比較高，從而影響了模具的成本，為了簡(jiǎn)化該處抽芯問(wèn)題，考慮到制品是塑料制品，具有一定的收縮性，同時(shí)為了更好的控制制造成本，將模具機(jī)構(gòu)合理的簡(jiǎn)化，故本機(jī)構(gòu)不采用側(cè)向抽芯，改為由頂桿直接將模具頂出。 5、 制品的質(zhì)量和體積 塑件質(zhì)量：m=10.5 g ABS密度：=1.04 g/cm 所以 V=m/=10.09 cm 二、 注射成型工藝的設(shè)計(jì) 1、塑料制品分析 本制品采用ABS為原料（模具與制造簡(jiǎn)明手冊(cè)P272）苯乙烯—丁二烯—丙烯氰共聚物。 （1） 無(wú)定性料，流動(dòng)性中等，比聚苯乙烯、AS差，但比聚氯乙烯好，溢邊值為0.04 mm左右。 （2） 吸濕性強(qiáng)，必須充分干燥，表面要求光澤的塑料須經(jīng)長(zhǎng)時(shí)間的預(yù)熱干燥。 （3） 成型時(shí)宜取高料溫，但料溫過(guò)高易分解（分解溫度≥250℃），對(duì)精度較高的塑料，模溫宜取50～60℃，對(duì)光澤要求較高的耐熱塑料模溫宜取60～80℃，注射壓力高于聚苯乙烯。用柱塞式注射機(jī)成型時(shí)，料溫為180～200℃，注射壓力為1000～1400MPa，用螺桿式注射機(jī)成型時(shí)，料溫為160～220℃，注射壓力為700～1000×10MPa。 （4） ABS的其他成型工藝參數(shù) 注射機(jī)類(lèi)型：螺桿式 制品收縮率：0.3～0.8% 預(yù)熱溫度：80～85℃ 時(shí)間：2～3 h 料筒溫度： 后段 150～170℃ 中段 165～180℃ 前段 180～200℃ 噴嘴溫度：170～180℃ 模具溫度：50～80℃ 注射壓力：60～100 MPa 成型時(shí)間： 注射時(shí)間20～90 s 保壓時(shí)間0～5 s 冷卻時(shí)間20～120 s 總周期50～220 s 螺桿轉(zhuǎn)速：30 r/min 適用注射機(jī)類(lèi)型：螺桿、柱塞均可 后處理方法：紅外線(xiàn)燈、鼓風(fēng)烘箱 溫度70℃ 時(shí)間2～4 h 2、制品成型方法及工藝流程 本制品采用注射成型，工藝流程包括模前準(zhǔn)備，模塑成型和后處理及二次加工工藝流程步驟如下： （1）預(yù)熱 ABS吸濕性強(qiáng)，必須充分干燥，表面要求光澤的塑料須經(jīng)長(zhǎng)時(shí)間的預(yù)熱干燥。 （2）注射 注射過(guò)程包括加料、塑化、注射冷卻和脫模幾個(gè)步驟。 l 加料 由于注射成型是一個(gè)間歇過(guò)程，因而須定量（定容）加料，以保證操作穩(wěn)定，塑料塑化均勻，最終獲得良好的塑件。加料過(guò)多。受熱的時(shí)間過(guò)長(zhǎng)等容易引起物料的熱降解，同時(shí)注射及功率損耗增多；加料過(guò)少，料筒內(nèi)缺少傳壓介質(zhì)，型腔中塑料融化壓力降低，難于補(bǔ)料，容易引起塑件出現(xiàn)收縮、凹陷、空洞等缺陷。 l 塑化 加入的塑料在料筒中進(jìn)行加熱，由固體顆粒轉(zhuǎn)化成粘流態(tài)，并且受到良好的剪切力作用。通過(guò)料筒對(duì)物料加熱，使聚合物分子松弛，出現(xiàn)由固體向液體轉(zhuǎn)變；一定的溫度使塑料得到變形、熔融和塑化的必要條件，螺桿的剪切作用能在塑料中產(chǎn)生更多的摩擦熱，促進(jìn)了塑料的塑化，因而螺桿式注射機(jī)對(duì)塑料的溫度盡量均勻一致，還有使熱分解物的含量達(dá)到最小值，并且能提供上述質(zhì)量的足夠的熔融塑料以保證產(chǎn)生連續(xù)并順利的進(jìn)行，這些要求與塑料的特性、工藝條件的控制及注射機(jī)的塑化裝置的結(jié)構(gòu)等密切相關(guān)。 l 注射 不論何種形式的注射機(jī)，注射的過(guò)程可分為充模，保壓倒流，澆口凍結(jié)后的冷卻和脫模等幾個(gè)階段 （3）塑件的后處理 注射成型的塑件經(jīng)脫模或機(jī)械加工之后，常需要進(jìn)行適當(dāng)?shù)暮筇幚硪韵嬖诘膬?nèi)應(yīng)力，改善塑件的性能和提高尺寸穩(wěn)定性。其主要方法是退火和調(diào)濕處理。退火處理是將注射塑件在定溫的加熱液體介質(zhì)或熱烘箱中靜置一段時(shí)間，塑料制件的氧化，加快吸濕平衡速度的一種處理方法，其目的是使制作的顏色、性能以及尺寸得到穩(wěn)定。本次設(shè)計(jì)采用退火后處理。 工藝流程圖解： 3、成型工藝條件 注射成型的核心問(wèn)題，就是采用一切措施得到塑化良好的塑料 熔體，并把它注射到型腔中去，在控制條件下冷卻定型，使塑件 達(dá)到所要求的質(zhì)量，影響注射成型工藝的重要參數(shù)是塑化流動(dòng)和 冷卻的溫度、壓力以及影響的各個(gè)作用時(shí)間。 （1）注射成型過(guò)程需要控制的溫度有料筒溫度，噴嘴溫度和模具溫度等。前兩個(gè)溫度主要影響塑件的塑化和流動(dòng)，而后一個(gè)溫度主要是影響塑件的流動(dòng)和冷卻，料筒溫度的選擇與各種塑料的特性有關(guān)。每種塑料都具有不同的粘流態(tài)溫度，為了保證塑件溶體的正常流動(dòng)不使物料發(fā)生質(zhì)分解，料筒最合適的溫度范圍應(yīng)在粘流態(tài)溫度和熱分解溫度之間。 柱塞式和螺桿式柱塞注射機(jī)由于其塑化過(guò)程不同，因而選擇料筒也不同，通常后者選擇的溫度低一點(diǎn)，料筒溫度在70～93℃之間，噴嘴溫度稍低于料筒溫度，在65～90℃之間，模溫在要求塑件光澤時(shí)控制在60～80℃之間。 （2）壓力包括塑化壓力和注射壓力兩種，他們直接影響塑料的塑化和塑料質(zhì)量。塑化壓力是指背壓，是指采用螺桿式注射機(jī)時(shí)，螺桿頭部熔體在螺桿轉(zhuǎn)動(dòng)后退時(shí)所受到的壓力，塑化壓力在保證塑件質(zhì)量的前提下越低越好，其具體數(shù)值時(shí)隨所用塑料的品種而異的，但通常很少超過(guò)20MP，注射壓力是指柱塞式螺桿頭部對(duì)塑件熔體所施加的壓力。在注射機(jī)上常用表壓指示注射壓力的大小，一般在40～130MP之間。其作用式克服塑料熔體從料筒流向型腔的流動(dòng)阻力，給予熔體一定的充型速率以及對(duì)熔體進(jìn)行壓實(shí)等。 （3）完成一次注射成型過(guò)程所需要的時(shí)間稱(chēng)成型周期，成型周期直接影響到勞動(dòng)生產(chǎn)率和注射機(jī)使用率，因此在生產(chǎn)中，在保證質(zhì)量的前提下，盡量縮短成型周期中各個(gè)階段的有關(guān)時(shí)間，一般生產(chǎn)中，充模時(shí)間為3～5S，保壓時(shí)間為20～25S，冷沖壓時(shí)間一般在30～120S。 三、 注射機(jī)的技術(shù)規(guī)范 1、 注射機(jī)的選用 注射機(jī)的選用包括兩方面的內(nèi)容：一是要確定注射機(jī)的型號(hào)，使塑料、塑件、注射模、注射工藝等所要求的注射機(jī)的規(guī)格參數(shù)點(diǎn)在所選注射機(jī)的規(guī)格參數(shù)可調(diào)范圍之內(nèi)，即要滿(mǎn)足所需的參數(shù)在額定的范圍之內(nèi)；二是調(diào)整注射機(jī)的技術(shù)參數(shù)至所需的參數(shù)點(diǎn)。 塑件的直徑：d=66 mm 所以塑件的投影面積s=П×(d/2)=3.14×(66÷2)≈3419.46 mm 澆道凝料的質(zhì)量大約為20 g，澆注系統(tǒng)的投影面積大約為300 mm l 擬定一次成型8個(gè)塑件 （1）注射量的校核 根據(jù)公式K×G=Q+Q’ K—注射機(jī)公稱(chēng)質(zhì)量注射量(g） G—注射機(jī)最大注射量的利用系數(shù)，一般取0.75～0.85 Q—塑件的質(zhì)量(g） Q’—澆注系統(tǒng)等廢料的質(zhì)量(g） 所以所需注射機(jī)的注射量K=(Q+Q’)/G=(2.5×8+20)÷0.85 ≈47.1 g （2）鎖模力的校核 鎖模力必須大于模具在模具在開(kāi)模方向得投影面積上的總注射壓力。根據(jù)要求，鎖模力不小于總注射壓力的1.2倍，即要取一安全系數(shù)，以保證安全生產(chǎn)。 所以F≥A×P×S F—注射機(jī)的鎖模力（KN） P—型腔單位面積的注射壓力（MPa），ABS的壓力值約為80MPa S—型腔（包括澆注系統(tǒng)）的投影面積（mm） A—安全系數(shù)，本設(shè)計(jì)取1.4 即F≥)≈15000 KN 根據(jù)要求選得的注射機(jī)型號(hào)為SZ—250/1250，但該注射機(jī)過(guò)于龐大，能源損耗大，用于生產(chǎn)本次設(shè)計(jì)塑件不合理，故修改生產(chǎn)方案。 l 擬定一次成型4個(gè)塑件 （1）注射量的校核 根據(jù)公式K×G=Q+Q’?得K=(Q+Q)/G=(2.5×4+20)÷0.85 =25.5 g （2）鎖模力的校核 根據(jù)公式F≥A×P×S 得F≥1600 根據(jù)要求選得的注射機(jī)型號(hào)為SZ—100/630，該型號(hào)的注射機(jī)比較經(jīng)濟(jì)合理，故本設(shè)計(jì)采用該注射機(jī)。 2、 注射機(jī)的確定 本次設(shè)計(jì)采用螺桿式注射機(jī)，型號(hào)是SZ-300/160 它的主要參數(shù)為： 理論注射容積：300 cm 螺桿直徑：45mm 注射壓力：150 MPa 注射速率：145g/s 塑化能力：82 g/s 螺桿轉(zhuǎn)速：0～180 r/min 鎖模力：1600KN 拉桿內(nèi)間距：450×450 mm 移模行程：L=380mm 模具定位孔直徑：160 mm 最大模具厚度：Hmax=450 mm 最小模具厚度：Hmin=250 mm 模具噴嘴球半徑：R=20mm ⒋ 三 模具結(jié)構(gòu)零件設(shè)計(jì) ㈠. 導(dǎo)柱和導(dǎo)套 用于動(dòng)模與定模間或推出機(jī)構(gòu)零件的定位和導(dǎo)向. ⒈ 導(dǎo)柱 導(dǎo)柱具有與動(dòng)模之間的導(dǎo)向作用,同時(shí)也具有保護(hù)模具的作用.導(dǎo)柱的導(dǎo)向部分應(yīng)具有較好的滑動(dòng)性能, 一般應(yīng)沒(méi)有潤(rùn)滑油槽. 其硬度應(yīng)在50HRC以上, 采用銅為原料,經(jīng)淬火后導(dǎo)柱的滑動(dòng)配合部分在進(jìn)行磨消加工,表面粗糙度到達(dá)Ra 0.63μm. ⒉導(dǎo)套 通常在模板上鑲配導(dǎo)套以減少導(dǎo)柱滑動(dòng)部分的磨損. 采用錫青銅為原料. ㈠ 推桿.復(fù)位桿及拉料桿 ⒈ 推桿 推桿用于推出塑件的桿類(lèi)零件, 通稱(chēng)為推桿.要求外觀(guān)無(wú)傷痕, 裂紋及銹斑等缺陷. 配合部分需進(jìn)行加工, 表面粗糙度到達(dá)Ra 0.63μm以下. 推桿前端部分淬火后硬度到達(dá)55HRC以上. ⒉ 復(fù)位桿也稱(chēng)回程桿, 它是用于使推出機(jī)構(gòu)復(fù)位的桿類(lèi)零件. 復(fù)位桿用材料與加工要求與推桿相同. ⒊ 拉料桿 用于拉出主流道凝料或分流道凝料的一類(lèi)桿狀零件. 通稱(chēng)為拉料桿. 根據(jù)其功能作用的不同,又可分為主道拉料桿和分道拉料桿兩種. 主道拉料桿是用來(lái)從澆口套中拉出主流道凝料的零件. 分道拉料桿是用來(lái)拉出針點(diǎn)澆口并使之與模塑件斷開(kāi)的桿類(lèi)零件,其前端形狀視樹(shù)脂種類(lèi)不同兒異. ㈡ 定位圖與澆口套 ⒈ 定位圖 定位圖的作用是使注射機(jī)的噴嘴與模具主流澆口保持同心. 定位圖為標(biāo)準(zhǔn)型與特殊型兩種. 由于此此模具為普通模具.因此選甲標(biāo)準(zhǔn)型. ⒉ 澆口套 通常澆口套與定位圖是配合使用的. 澆口套是塑料熔體熔入模具的入口,其尺寸與注塑機(jī)噴嘴尺寸有關(guān). 本模具選用標(biāo)準(zhǔn)澆口套中的A 型. ㈢ 限位釘, 墊塊 ⒈ 限位釘 限位釘安裝在動(dòng)模板上,用于確定推板下限位置. ⒉ 墊塊 墊塊用以決定推出模塑件的距離,調(diào)節(jié)高度一類(lèi)塊狀零件. ㈣ 斜銷(xiāo), 側(cè)滑塊, 導(dǎo)滑槽 ⒈ 斜銷(xiāo) 斜銷(xiāo)是用于驅(qū)動(dòng)側(cè)滑塊進(jìn)行側(cè)向分型或的構(gòu)件.選其傾斜角為20°,淬火后硬度在55HRC以上,并須進(jìn)行磨削加工. ⒉ 側(cè)滑塊 側(cè)滑塊通常有側(cè)型芯 ,滑動(dòng)部分及本體組成,其硬度在40HRC以上. ⒊ 導(dǎo)滑槽 導(dǎo)滑槽是用于支撐側(cè)滑塊進(jìn)行抽芯運(yùn)動(dòng)的機(jī)構(gòu) ㈤ 模板. 模板于固定凹凸槽,各類(lèi)桿件,導(dǎo)柱和導(dǎo)套等各類(lèi)成型零件的板類(lèi).多用45＃開(kāi)鋼制造,為拉提高模具壽命,加工后須要淬火. ㈥ 擋塊, 彈簧, 限位塊 ⒈ 擋塊 它是用于在模具開(kāi)模以后,防止側(cè)滑塊由于抽芯力的作用而脫離模具整體,一般將其固定在動(dòng)模板上. ⒉ 彈簧 彈簧它是用于在模具開(kāi)模以后, 防止側(cè)滑塊向塑件而破壞塑件的抽芯,將它固定在擋板塊的雙頭螺栓柱上. ⒊ 限位塊 限位塊是用來(lái)定位側(cè)滑塊,一般將其固定在定模板上整體加工出來(lái). 參考資料 在設(shè)計(jì)過(guò)程中所查閱的書(shū)籍如下： 《模具設(shè)計(jì)于制作技術(shù)基礎(chǔ)》 《典型模具設(shè)計(jì)圖例》 《實(shí)用塑料注射模設(shè)計(jì)與制造》 《機(jī)械原理》 《機(jī)械基礎(chǔ)》 體會(huì)與感受(宋小2號(hào)) （通過(guò)畢業(yè)設(shè)計(jì)自己的體會(huì)和感受，在哪些方面有經(jīng)驗(yàn)、教訓(xùn)和提高。） 在本次畢業(yè)設(shè)計(jì)中，我從指導(dǎo)老師身上學(xué)到了很多東西。老師認(rèn)真負(fù)責(zé)的工作態(tài)度，嚴(yán)謹(jǐn)?shù)闹螌W(xué)精神和深厚的理論水平都使我收益匪淺。他無(wú)論在理論上還是在實(shí)踐中，都給與我很大的幫助，使我得到不少的提高這對(duì)于我以后的工作和學(xué)習(xí)都有一種巨大的幫助，感謝他耐心的輔導(dǎo) 。 在設(shè)計(jì)期間由于模具設(shè)計(jì)是第一次有點(diǎn)無(wú)從下手的感覺(jué)，上學(xué)期學(xué)過(guò)《塑料模具的設(shè)計(jì)》一課，對(duì)模具的結(jié)構(gòu)不是太陌生，再加上老師的指導(dǎo)，數(shù)據(jù)的來(lái)源較快，畫(huà)圖的工作量太大，使我有些招架不住。還好由于我平時(shí)CAD學(xué)得還行，再加上系里同學(xué)提供方便，在這么多人的關(guān)心下，我的進(jìn)展很快，草圖在一天內(nèi)完成，兩天內(nèi)也完成了繪圖的三分之一，一周內(nèi)完成了畢業(yè)設(shè)計(jì)。一學(xué)期的任務(wù)讓我在一周內(nèi)完成了，工作量可想而知，但我沒(méi)有因?yàn)闀r(shí)間短而忽略了設(shè)計(jì)質(zhì)量。在老師的指導(dǎo)下，我精心的查手冊(cè)，認(rèn)真的計(jì)算和驗(yàn)算著每一個(gè)數(shù)據(jù)，并根據(jù)我所設(shè)計(jì)的零件的特性，找出了比較完整的設(shè)計(jì)方案，并得到了指導(dǎo)老師得認(rèn)可。嚴(yán)格的按照要求繪圖，終于在答辯之前完成了畢業(yè)設(shè)計(jì)。 總之，畢業(yè)設(shè)計(jì)期間，我體驗(yàn)到了許多以前少能體驗(yàn)到的東西。 21 級(jí)畢業(yè)設(shè)計(jì)（論文） 課題名稱(chēng)：塑料瓶蓋注射模設(shè)計(jì) 專(zhuān) 業(yè)：數(shù)控技術(shù)及應(yīng)用 設(shè) 計(jì) 人 指導(dǎo)老師: 職 稱(chēng)： 年 月 日 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