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山東建筑大學(xué)課程設(shè)計(jì)說(shuō)明書(shū)(論文)
山東建筑大學(xué)
課 程 設(shè) 計(jì) 說(shuō) 明 書(shū)(論 文)
題 目: 卸扣鍛造工藝分析與模具設(shè)計(jì)
課 程: 鍛造工藝學(xué)與模具設(shè)計(jì)
院 (部): 機(jī)電工程學(xué)院
專 業(yè): 機(jī)械工程及自動(dòng)化
班 級(jí): 機(jī)械122
學(xué)生姓名: 陳建源
學(xué) 號(hào): 20120711074
指導(dǎo)教師: 袁文生
完成日期: 2016.6.1
目錄
摘 要 1
正 文 2
1、零件分析及工藝方案確定 2
1.1零件分析 2
1.2工藝方案的確定 2
2、繪制鍛件圖 3
2.1確定分模位置 3
2.2確定模鍛件加工余量及公差 3
2.3模鍛斜度 3
2.4確定鍛件圓角半徑? 3
2.5技術(shù)條件: 4
3、計(jì)算鍛件的主要參數(shù) 4
4、確定鍛錘噸位 4
5、確定毛邊槽形式和尺寸 5
6、確定終鍛型槽 5
7、設(shè)計(jì)預(yù)鍛型槽 6
8、繪制計(jì)算毛坯圖 6
9、制坯工步選擇 8
10、確定坯料尺寸 8
11、制坯型槽設(shè)計(jì) 9
12、鍛模結(jié)構(gòu)設(shè)計(jì) 10
13、鍛前加熱、鍛后冷卻及熱處理要求的確定?? 11
13.1確定加熱方式,及鍛造溫度范圍? 11
13.2確定加熱時(shí)間? 12
13.3確定冷卻方式及規(guī)范? 12
13.4確定鍛后熱處理方式及要求? 12
14、卸扣件的模鍛工藝流程 12
15、課程設(shè)計(jì)感悟 13
16、參考資料 13
摘 要
本次課程設(shè)計(jì)主要是對(duì)卸扣的鍛造模具進(jìn)行設(shè)計(jì),根據(jù)相應(yīng)的尺寸經(jīng)過(guò)計(jì)算得出合理的數(shù)據(jù),再依據(jù)數(shù)據(jù)設(shè)計(jì)鍛造用的模具。
鍛造是借助模具在沖擊壓力作用下加工金屬機(jī)械零件或零件毛坯的方法。與其它制造方法相比,鍛造加工生產(chǎn)的生產(chǎn)率最高,鍛件的尺寸形狀穩(wěn)定,并有最佳的綜合力學(xué)性能。鍛件的最大優(yōu)勢(shì)是韌性高,纖維組織合理,件與件之間的性能變化小,并且其內(nèi)部質(zhì)量與加工歷史有關(guān),不會(huì)被任何一種金屬加工工藝超過(guò)。鍛造是模具三大行業(yè)之一,并且隨著國(guó)內(nèi)以及國(guó)外的機(jī)械化加工的越來(lái)越被重視,鍛造正在發(fā)揮著不可替代的作用。卸扣因體積小承載重量大而廣泛應(yīng)用于各行各業(yè)。
關(guān)鍵字:鍛造工藝學(xué);鍛造模具;CAD制圖;
正 文
1、零件分析及工藝方案確定
1.1零件分析
卸扣,索具的一種。國(guó)內(nèi)市場(chǎng)上常用的卸扣,按生產(chǎn)標(biāo)準(zhǔn)一般分為國(guó)標(biāo)、美標(biāo)、日標(biāo)三類;其中美標(biāo)的最常用,因?yàn)槠潴w積小承載重量大而被廣泛運(yùn)用。卸扣由于承受重力較高所以對(duì)強(qiáng)度要求比較高;對(duì)外形要求并不高,目前較好的卸扣一般都是用合金鋼材質(zhì)。
如圖1.1.1對(duì)零件的整體形狀尺寸,表面粗糙度進(jìn)行分析,此零件的材料為45號(hào)鋼,材料性能穩(wěn)定。
圖1.1.1
1.2工藝方案的確定
根據(jù)上述分析,結(jié)合生產(chǎn)批量要求,生產(chǎn)設(shè)備,制模能力等進(jìn)行全面分析,初步確定出模鍛設(shè)計(jì)步驟:
①選擇鍛造方式:錘上模鍛;②選用設(shè)備類型:模鍛錘;③采用模鍛形式:開(kāi)式模鍛;④確定變形工步:下料—加熱—拔長(zhǎng)—滾擠—預(yù)鍛—終鍛。
2、繪制鍛件圖
2.1確定分模位置
確定分模面位置最基本的原則是保證鍛件形狀盡可能與零件形狀相同。使鍛件容易從鍛模型槽中取出,因此鍛件的側(cè)表面不得有內(nèi)凹的形狀,并且使模膛的寬度大而深度小。鍛件分模位置應(yīng)選在具有最大水平投影尺寸的位置上。應(yīng)使飛邊能切除干凈,不至產(chǎn)生飛刺。對(duì)金屬流線有要求的鍛件,應(yīng)保證鍛件有最好的纖維分布。
根據(jù)卸扣零件形狀,采用厚度方向上下對(duì)稱的直線分型模。
2.2確定模鍛件加工余量及公差
根據(jù)表中可知,鍛件的質(zhì)量為2.7kg,鍛件的材料為45號(hào)鋼,所以材質(zhì)系數(shù)為M1級(jí)。鍛件形狀復(fù)雜系數(shù):,經(jīng)計(jì)算為3級(jí)復(fù)雜系數(shù)。
由有關(guān)手冊(cè)查得:高度公差為;長(zhǎng)度公差為;寬度公差為。
零件需磨削加工,加工精度為,查得高度及水平尺寸的單邊余量約為,取。
2.3模鍛斜度
為便于模鍛件從型槽中取出,必須將型槽壁做成一定的斜度,稱為模鍛斜度或出模角。為了使鍛件容易從模膛中取出,一般鍛件均有脫模斜度或脫模角,它分為外斜度和內(nèi)斜度,常常內(nèi)斜度比外斜度大2~3?度。?
查有關(guān)手冊(cè)確定型槽的外斜度為7°,內(nèi)斜度為10°。
2.4確定鍛件圓角半徑?
鍛件上的圓角可使金屬容易充滿模膛,起模方便和延長(zhǎng)模具使用壽命。圓角半徑太小會(huì)使鍛模在熱處理或使用中產(chǎn)生裂紋或壓塌變形,在鍛件上也容易產(chǎn)生折紋。同時(shí)為了加工方便同一鍛件圓角的選取要與銑刀相配。?
為了使金屬易于流動(dòng)和充滿型槽,提高鍛件質(zhì)量并延長(zhǎng)鍛模壽命,模鍛件上的所有轉(zhuǎn)接出都用圓弧連接。?
r=余量+零件相應(yīng)處圓角半徑或倒角?
鍛件上內(nèi)圓角半徑R應(yīng)比外圓角半徑r大,一般取R=(2~3)r?
所以外圓角半徑為1.5mm,內(nèi)圓角半徑為R=(2~3)r,所以內(nèi)圓角半徑為3mm.?
2.5技術(shù)條件:
(1)未注明的模鍛斜度為7°,內(nèi)斜度為10°;
(2)圖上未標(biāo)注的圓角半徑R=1.5mm;
(3)允許的錯(cuò)移量0.6mm;
(4)允許的殘留毛邊量0.7mm;
(5)允許的表面缺陷深度0.5mm;
(6)鍛件熱處理:調(diào)質(zhì);
(7)鍛件表面清理:為便于檢查淬火裂紋,采用酸洗。
3、計(jì)算鍛件的主要參數(shù)
(1)鍛件在平面上的投影面積為9300;
(2)鍛件周邊長(zhǎng)度為730;
(3)鍛件的體積為344000;
(4)鍛件的質(zhì)量為2.7kg。
4、確定鍛錘噸位
總變形面積為鍛件在平面圖上的投影面積與毛邊面積之和,參考表4-14,按1~2t錘毛邊槽尺寸考慮,假定毛邊橋部寬度為18mm,總面積,按雙作用模鍛錘噸位確定的經(jīng)驗(yàn)公式確定鍛錘噸位,因卸扣件為大量生產(chǎn),需要高生產(chǎn)率,取較大的系數(shù)6.3,取,于是,選用1.5t錘。
5、確定毛邊槽形式和尺寸
圖5.1.1
選用圖5.1.1毛邊槽形式Ⅰ,其尺寸按表4-14確定;選定毛邊槽尺寸為,,,,,。
鍛件毛邊體積,其中(鍛件毛邊平均截面積)。
6、確定終鍛型槽
(1)型槽排布?
模鍛一種鍛件,往往要采用多個(gè)工步來(lái)完成。因此鍛模分模面上的型槽布置要根據(jù)型槽數(shù)、各型槽的作用以及操作方便來(lái)確定,原則上應(yīng)使型槽中心與理論上的打擊中心重合,以使錘擊力與鍛件的反作用力處于同一垂直線上從而減少錘桿承受的偏心力距,有利于延長(zhǎng)錘桿壽命,使鍛件精度增高。?
(2)兩個(gè)制坯型槽分布?
這時(shí)應(yīng)將第一道制坯工步安排在吹風(fēng)管的對(duì)面,以避免氧化皮落到終鍛型槽里。布排型槽應(yīng)以終鍛型槽為中心,左右對(duì)稱布排,并盡可能使型槽中心與打擊中心重合。
(3)終鍛型槽是按照熱鍛件圖加工和檢驗(yàn)的,卸扣材料為45鋼,考慮收縮率為1.5%。根據(jù)生產(chǎn)經(jīng)驗(yàn)總結(jié),考慮到鍛模使用后承擊面下陷,型槽深度減小及精壓時(shí)變形不均,橫向尺寸增大等因素,修改了幾處尺寸:如軸孔處高度是31mm,修改后的尺寸是31.5mm。
7、設(shè)計(jì)預(yù)鍛型槽
預(yù)鍛的主要目的是在終鍛前進(jìn)一步分配金屬,分配金屬是為了:
(1)確保金屬無(wú)缺陷流動(dòng),易于充填型槽;
(2)減少材料流向毛邊的損失;
(3)減少終鍛型槽磨損;
(4)取得所希望的流線和便于控制鍛件的力學(xué)性能。
但采用預(yù)鍛也會(huì)帶來(lái)不利的影響,由于模塊上附加預(yù)鍛型槽,容易造成偏心打擊,影響錘桿的壽命,容易使上下模錯(cuò)移,增大模塊尺寸,降低生產(chǎn)率。
預(yù)鍛型槽是以終鍛型槽或熱鍛件圖為基礎(chǔ)進(jìn)行設(shè)計(jì)的,設(shè)計(jì)的原則是經(jīng)預(yù)鍛型槽成形的坯料,在終鍛型槽中最終成型時(shí),金屬變形均勻,充填性好,產(chǎn)生的毛邊最小。為此,須具體考慮如下問(wèn)題:
①預(yù)鍛型槽的寬與高
當(dāng)預(yù)鍛后的坯料在終鍛型槽中是以鐓粗方式成形時(shí),預(yù)鍛型槽的高度尺寸應(yīng)比終鍛型槽大2~5mm,寬度則比終鍛型槽小1~2mm,橫截面面積應(yīng)比終鍛型槽相應(yīng)處截面積大1%~3%。
②模鍛斜度
預(yù)鍛型槽的模鍛斜度一般與終鍛模具型槽相同。
③圓角半徑
預(yù)鍛型槽周邊不設(shè)毛邊槽,而是在型槽分模面轉(zhuǎn)角處用較大的圓??;型槽內(nèi)的圓角半徑比終鍛型槽對(duì)應(yīng)處稍大。增大肋根部圓角半徑的目的是減小金屬流動(dòng)阻力,促進(jìn)預(yù)鍛件成形,同時(shí)也能補(bǔ)償終鍛時(shí)金屬的不足,還可防止產(chǎn)生折疊。
8、繪制計(jì)算毛坯圖
根據(jù)卸扣的形狀特點(diǎn),選取9個(gè)截面,分別計(jì)算,,列于下表中,并畫(huà)出卸扣的截面圖和直徑圖。為設(shè)計(jì)滾擠型槽方便,計(jì)算毛坯圖按熱鍛件尺寸計(jì)算。
截面圖所圍面積即為計(jì)算毛坯體積,得:
,縮尺比M通常取為,這里取為20。
(與對(duì)比,相差2.4%。)
平均截面積 ;
平均截面直徑 。
按體積相等修正截面圖和直徑圖,修正后的最大截面積為,則最大截面直徑為。
圖8.1.1
表8.1卸扣計(jì)算毛坯的計(jì)算數(shù)據(jù)
截面號(hào)
1
0
252
252
15.9
2
1411
176
1587
39.8
3
1984
176
2160
46.5
4
755
176
931
30.5
5
855
176
1031
32.1
6
755
176
931
30.5
7
1308
176
1484
38.5
8
1411
176
1587
39.8
9
0
252
252
15.9
9、制坯工步選擇
計(jì)算毛坯為兩頭一桿,應(yīng)簡(jiǎn)化成兩個(gè)簡(jiǎn)單的一頭一桿計(jì)算毛坯來(lái)選擇制坯工步。
可知此鍛件應(yīng)采用拔長(zhǎng)、滾擠制坯工步。為易于充滿型槽,應(yīng)選圓形坯料,先拔長(zhǎng),再開(kāi)式滾擠。模鍛工藝方案為:拔長(zhǎng)—開(kāi)式滾擠—預(yù)鍛—終鍛。
10、確定坯料尺寸
根據(jù)公式拔長(zhǎng)加滾擠聯(lián)合制坯:
—毛坯截面積;—計(jì)算毛坯頭部最大尺寸處截面積,。
根據(jù)坯料的制坯工步采用圓形坯料
其直徑,經(jīng)計(jì)算,取直徑為65mm。
查表取燒損率d=3%,在室內(nèi)電爐中加熱。
坯料體積為:
鉗頭長(zhǎng)度:。
所以坯料長(zhǎng)度:,取200mm。
11、制坯型槽設(shè)計(jì)
11.1拔長(zhǎng)型槽設(shè)計(jì)
拔長(zhǎng)型槽的主要作用是使批表局部截面積減小,長(zhǎng)度增加,還兼有清除氧化皮的作用,拔長(zhǎng)型槽的位置在模塊邊緣,有坎部,倉(cāng)部和鉗口三部分組成。
①拔長(zhǎng)坎高度。
②拔長(zhǎng)坎長(zhǎng)度。
③圓角半徑R=0.25C=0.25×97.5=24,。
④型槽寬度。取B=95mm。
⑤倉(cāng)部深度。
⑥拔長(zhǎng)型槽長(zhǎng)度。
按上述設(shè)計(jì)可鍛出合格鍛件,但為了提高生產(chǎn)率,可將型槽的高度h減小,增大。
11.2滾擠型槽設(shè)計(jì)
滾擠型槽可認(rèn)為是由鉗口、本體、毛刺槽三部分組成,鉗口用來(lái)容納夾鉗并卡細(xì)坯料,毛刺槽是用來(lái)容納滾擠時(shí)產(chǎn)生的端部毛刺,本體使坯料變形。
(1)滾擠型槽設(shè)計(jì):采用開(kāi)式滾擠。
(2)滾擠型槽高度
由于滾擠時(shí),上下模不一定打靠,實(shí)際采用的型槽高度應(yīng)比計(jì)算值小一些,按下式計(jì)算:
綜上所述,滾擠型槽高度h為:
(3)滾擠型槽寬度B
滾擠型槽寬度B應(yīng)根據(jù)所選型槽形式和坯料的狀態(tài)來(lái)確定。型槽B過(guò)大會(huì)減少聚集效率,并增大模塊尺寸;B過(guò)小,在滾擠過(guò)程中金屬流進(jìn)分模面會(huì)形成毛邊,當(dāng)翻轉(zhuǎn)90度再滾擠時(shí),就會(huì)形成折疊。
經(jīng)過(guò)拔長(zhǎng)的坯料再進(jìn)行滾擠時(shí),桿部金屬富裕量要小得多,不會(huì)再有大量金屬流入頭部,因此,經(jīng)過(guò)拔長(zhǎng)過(guò)的坯料再滾擠時(shí),滾擠型槽桿部寬度應(yīng)比前述的小,根據(jù)經(jīng)驗(yàn)可得
因?yàn)殚_(kāi)式滾擠型槽頭部與桿部寬度一致,經(jīng)試生產(chǎn)寬度調(diào)整取為80mm
(4)滾擠型槽長(zhǎng)度L?
滾擠型槽長(zhǎng)度L應(yīng)根據(jù)熱鍛件圖尺寸確定。?直鍛件
(5)鉗口與毛刺槽尺寸
鉗口處:,經(jīng)計(jì)算:。
查表得:。
12、鍛模結(jié)構(gòu)設(shè)計(jì)
(1)鍛模緊固方法?
錘上鍛模緊固在下模座和錘頭上,采用楔鐵和定位鍵配合燕尾緊固的方法。?
(2)模膛的布排?因?yàn)榇隋懩2恍桀A(yù)鍛模膛,且零件為中心對(duì)稱,故終鍛模膛中心位置應(yīng)在鍛模中心處。?
(3)鎖扣的設(shè)計(jì)?
H=25mm,b=35mm,δ=0.3mm,α=5°,R1=13mm,R2=25mm。
(4)確定模膛壁厚?
S1=1.2×62.5=75mm,S2=1.7×22.5=38.25mm,S3=2×15=30mm。
(5)模塊尺寸的確定?
由噸位設(shè)備1.5t,查得鍛模允許的最小承擊面積400,綜合考慮模膛布排、飛邊槽、鎖扣及鐓粗臺(tái)設(shè)計(jì)要求等方面的因素,可取模塊尺寸L=550mm,B=420mm。此時(shí)的承擊面積為:
,滿足要求。
(6)模塊高度?
上模塊高度:H=180mm
下模塊高度:H=180mm
模塊最小閉合高度:H=360mm
(7)檢驗(yàn)角b=5mm??h=50mm
?燕尾b=200mm??h=50.5mm?
鍵槽b1=50mm??l=60mm?
起重孔d×s=30×60mm?
13、鍛前加熱、鍛后冷卻及熱處理要求的確定??
13.1確定加熱方式,及鍛造溫度范圍?
在鍛造生產(chǎn)中,金屬坯料鍛前加熱的目的:提高金屬塑性,降低變形抗力,即增加金屬的可塑性,從而使金屬易于流動(dòng)成型,并使鍛件獲得良好的組織和力學(xué)性能。金屬坯料的加熱方法,按所采用的加熱源不同,可分為燃料加熱和電加熱兩大類。根據(jù)鍛件的形狀,材質(zhì)和體積,采用半連續(xù)爐加熱。?
金屬的鍛造溫度范圍是指開(kāi)始鍛造溫度(始鍛溫度)和金屬鍛造溫度(終鍛溫度)之間的一段溫度區(qū)間。確定鍛造溫度的原則是,應(yīng)能保證金屬在鍛造溫度范圍內(nèi)具有較高的塑性和較小的變形抗力。并能使制出的鍛件獲得所希望的組織和性能。查有關(guān)資料確定鍛件的始段鍛溫度為1200℃,終鍛溫度為750℃。
13.2確定加熱時(shí)間?
加熱時(shí)間是坯料裝爐后從開(kāi)始加熱到出爐所需的時(shí)間,包括加熱個(gè)階段的升溫時(shí)間和保溫時(shí)間。
13.3確定冷卻方式及規(guī)范?
按照冷卻速度的不同,鍛件的冷卻方法有3種:在空氣中冷卻,冷卻速度快;在灰沙中冷卻,冷卻速度較慢;在爐內(nèi)冷卻,冷卻速度最慢。根據(jù)本鍛件的形狀體積大小及鍛造溫度的影響,選擇在空氣中冷卻。?
13.4確定鍛后熱處理方式及要求?
鍛件在機(jī)加工前后均進(jìn)行熱處理,其目的是調(diào)整鍛件的硬度,以利鍛件進(jìn)行切削加工,消除鍛件內(nèi)應(yīng)力,細(xì)化晶粒等。根據(jù)鍛件的含碳量及鍛件的形狀大小,采用在連續(xù)熱處理爐中,調(diào)質(zhì)處理??墒瑰懠@得良好的綜合力性能。
14、卸扣件的模鍛工藝流程
(1)切料:5000kN型剪機(jī)冷切。?
(2)加熱:半連續(xù)式爐,1220-1240。?
(3)模鍛:1.5t模鍛錘,坺長(zhǎng)、開(kāi)滾、預(yù)鍛、終鍛,每班約生產(chǎn)1100件。
(4)熱切邊:1600kN切邊壓機(jī)。
(5)彎曲:折彎?rùn)C(jī)彎曲。
(6)沖孔:沖床沖孔。?
(7)磨毛邊:砂輪機(jī)。
(8)熱處理:連續(xù)熱處理爐,調(diào)質(zhì)。?
(9)酸洗:酸洗槽。?
(10)冷校正:1t夾板錘。?
(11)冷精壓:10000kN精壓機(jī)。?
(12)檢驗(yàn)。
15、課程設(shè)計(jì)感悟
經(jīng)過(guò)本次的課程設(shè)計(jì),我又學(xué)到了很多的知識(shí),首先,非常感謝老師的細(xì)心指導(dǎo),讓我對(duì)有關(guān)鍛造工藝?yán)碚撝R(shí)進(jìn)行了鞏固和重新理解,同時(shí)提高了自己查閱相關(guān)資料和手冊(cè)的能力,解決了在課程設(shè)計(jì)中遇到的一些問(wèn)題,積極向老師和同學(xué)討論和請(qǐng)教,認(rèn)真研究了所有的實(shí)驗(yàn)項(xiàng)目,不僅提高了制圖能力,而且強(qiáng)化了專業(yè)知識(shí)的綜合能力。
在課程設(shè)計(jì)中發(fā)現(xiàn)自己平時(shí)學(xué)習(xí)的不足和薄弱環(huán)節(jié),從而加以彌補(bǔ)。 在此感謝我們的老師,老師嚴(yán)謹(jǐn)細(xì)致、一絲不茍的作風(fēng)一直是我工作、學(xué)習(xí)中的榜樣;老師循循善誘的教導(dǎo)和不拘一格的思路給予我無(wú)盡的啟迪;這次模具設(shè)計(jì)的每個(gè)實(shí)驗(yàn)細(xì)節(jié)和每個(gè)數(shù)據(jù),都離不開(kāi)老師您的細(xì)心指導(dǎo)。
16、參考資料
1. 《中國(guó)模具設(shè)計(jì)大典(第三卷)》,肖祥芷,王孝培編寫(xiě)。
2. 模具技術(shù)叢書(shū)編委會(huì).沖模設(shè)計(jì)應(yīng)用實(shí)例.北京:機(jī)械工業(yè)出版社,1994
3. 馮炳堯、韓泰榮、蔣文森編.模具設(shè)計(jì)與制造簡(jiǎn)明手冊(cè)(第二版).上海科學(xué)技術(shù)出版社,1998年
4. 模具設(shè)計(jì)與制造技術(shù)教育叢書(shū)編委會(huì).模具制造工藝與裝備.北京:機(jī)械工業(yè)出版社,2003年
5. 許發(fā)越主編.模具標(biāo)準(zhǔn)應(yīng)用手冊(cè).北京:機(jī)械工業(yè)出版社,1994年
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沖壓成形與板材沖壓
1. 概述
通過(guò)模具使板材產(chǎn)生塑性變形而獲得成品零件的一次成形工藝方法叫做沖壓。由于沖壓通常在冷態(tài)下進(jìn)行,因此也稱為冷沖壓。只有當(dāng)板材厚度超過(guò)8~100mm時(shí),才采用熱沖壓。沖壓加工的原材料一般為板材或帶材,故也稱板材沖壓。某些非金屬板材(如膠木板、云母片、石棉、皮革等)亦可采用沖壓成形工藝進(jìn)行加工。
沖壓廣泛應(yīng)用于金屬制品各行業(yè)中,尤其在汽車、儀表、軍工、家用電器等工業(yè)中占有極其重要的地位。沖壓成形需研究工藝設(shè)備和模具三類基本問(wèn)題。
? 板材沖壓具有下列特點(diǎn):
(1).高的材料利用率。
(2).可加工薄壁、形狀復(fù)雜的零件。
(3).沖壓件在形狀和尺寸方面的互換性好。
(4).能獲得質(zhì)量輕而強(qiáng)度高、剛性好的零件。
(5).生產(chǎn)率高,操作簡(jiǎn)單,容易實(shí)現(xiàn)機(jī)械化和自動(dòng)化。
沖壓模具制作成本高,因此適合大批量生產(chǎn)。對(duì)于小批量、多品種生產(chǎn),常采用簡(jiǎn)易沖模,同時(shí)引進(jìn)沖壓加工中心等新型設(shè)備,以滿足市場(chǎng)求新求變的需求。板材沖壓常用的金屬材料有低碳鋼、銅、鋁、鎂合金及高塑性的合金剛等。如前所述,材料形狀有板材和帶材。
沖壓生產(chǎn)設(shè)備有剪床和沖床。剪床是用來(lái)將板材剪切成具有一定寬度的條料,以供后續(xù)沖壓工序使用,沖床可用于剪切及成形。
2. 沖壓成形的特點(diǎn)
生產(chǎn)時(shí)間中所采用的沖壓成形工藝方法有很多,具有多種形式餓名稱,但塑性變形本質(zhì)是相同的。沖壓成形具有如下幾個(gè)非常突出的特點(diǎn)。
(1).垂直于板面方向的單位面積上的壓力,其數(shù)值不大便足以在板面方向上使??板材產(chǎn)生塑性變形。由于垂直于板面方向上的單位面積上壓力的素質(zhì)遠(yuǎn)小于板面方向上的內(nèi)應(yīng)力,所以大多數(shù)的沖壓變形都可以近似地當(dāng)作平面應(yīng)力狀態(tài)來(lái)處理,使其變形力學(xué)的分析和工藝參數(shù)的計(jì)算大呢感工作都得到很大的簡(jiǎn)化。
(2).由于沖壓成形用的板材毛胚的相對(duì)厚度很小,在壓應(yīng)力作用下的抗失穩(wěn)能力也很差,所以在沒(méi)有抗失穩(wěn)裝置(如壓邊圈等)的條件下,很難在自由狀態(tài)下順利地完成沖壓成形過(guò)程。因此,以拉應(yīng)力作用為主的伸長(zhǎng)類沖壓成形過(guò)程多于以壓應(yīng)力作用為主的壓縮類成形過(guò)程。
(3).沖壓成形時(shí),板材毛胚內(nèi)應(yīng)力的數(shù)值等于或小于材料的屈服應(yīng)力。在這一點(diǎn)上,沖壓成形與體積成形的差別很大。因此,在沖壓成形時(shí)變形區(qū)應(yīng)力狀態(tài)中的靜水壓力成分對(duì)成形極限與變形抗力的影響,已失去其在體積成形時(shí)的重要程度,有些情況下,甚至可以完全不予考慮,即使有必要考慮時(shí),其處理方法也不相同。
(4).在沖壓成形時(shí),模具對(duì)板材毛胚作用力所形成的約束作用較輕,不像體積成形(如模鍛)是靠與制件形狀完全相同的型腔對(duì)毛胚進(jìn)行全面接觸而實(shí)現(xiàn)的強(qiáng)制成形。在沖壓成形中,大多數(shù)情況下,板材毛胚都有某種程度的自由度,常常是只有一個(gè)表面與模具接觸,甚至有時(shí)存在板材兩側(cè)表面都有于模具接觸的變形部分。在這種情況下,這部分毛胚的變形是靠模具對(duì)其相鄰部分施加的外力實(shí)現(xiàn)其控制作用的。例如,球面和錐面零件成形時(shí)的懸空部分和管胚端部的卷邊成形都屬這種情況。
? ?由于沖壓成形具有上述一些在變形與力學(xué)方面的特點(diǎn),致使沖壓技術(shù)也形成了一些與體積成形不同的特點(diǎn)。由于不需要在板材毛的表面施加很大的單位壓力即可使其成形,所以在沖壓技術(shù)中關(guān)于模具強(qiáng)度與剛度的研究并不十分重要,相反卻發(fā)展了學(xué)多簡(jiǎn)易模具技術(shù)。
由于相同原因,也促使靠氣體或液體壓力成形的工藝方法得以發(fā)展。因沖壓成形時(shí)的平面應(yīng)力狀態(tài)或更為單純的應(yīng)變狀態(tài)(與體積成形相比),當(dāng)前對(duì)沖壓成形匯中毛胚的變形與 力能參數(shù)方面的研究較為深入,有條件運(yùn)用合理的科學(xué)方法進(jìn)行沖壓加工。借助于電子計(jì)算機(jī)與先進(jìn)的測(cè)試手段,在對(duì)板材性能與沖壓變形參數(shù)進(jìn)行實(shí)時(shí)測(cè)量與分析基礎(chǔ)上,實(shí)現(xiàn)沖壓過(guò)程智能化控制的研究工作也在開(kāi)展。人們?cè)趯?duì)沖壓成形過(guò)程有離開(kāi)較為深入的了解后,已經(jīng)認(rèn)識(shí)到?jīng)_壓成型與原材料有十分密切的關(guān)系。所以,對(duì)板材沖壓性能即成形性與形狀穩(wěn)定性的研究,目前已成為沖壓技術(shù)的一個(gè)重要內(nèi)容。對(duì)板材沖壓性能的研究工作不僅是沖壓技術(shù)發(fā)展的需要,而且也促進(jìn)了鋼鐵工業(yè)生產(chǎn)技術(shù)的發(fā)展,為其提高板材的質(zhì)量提供了一個(gè)可靠的基礎(chǔ)與依據(jù)。
3.沖壓變形的分類
? ?沖壓變形工藝可完成多種工序,其基本工序可分為分離工序和變形工序兩大類。分離工序是使胚料的一部分與另一部分相互分離的工藝方法,主要有落料、沖孔、切邊、剖切、修整等。其中又以沖孔、落料應(yīng)用最廣。變形工序是使胚料的一部分相對(duì)于另一部分產(chǎn)生位移而不破裂的工藝方法,主要有拉深、彎曲、局部成形、脹形、翻邊、縮徑、校形、旋壓等。
從本質(zhì)上看,沖壓成形就是毛胚的變形區(qū)在外力的作用下產(chǎn)生相應(yīng)的塑性變形,所以變形區(qū)內(nèi)的應(yīng)力狀態(tài)和變形特點(diǎn)景象的沖壓成形分類,可以把成形性質(zhì)相同的成形方法概括成同一個(gè)類型并進(jìn)行體系化的研究。
絕大多數(shù)沖壓成形時(shí)毛胚變形區(qū)均處于平面應(yīng)力狀態(tài)。通常認(rèn)為在板材表面上不受外力的作用,即使有外力作用,其數(shù)值也是較小的,所以可以認(rèn)為垂直于板面方向上的應(yīng)力為零,使板材毛胚產(chǎn)生塑性變形的是作用于板面方向上相互的兩個(gè)主應(yīng)力。由于板厚較小,通常都近似地認(rèn)為這兩個(gè)主應(yīng)力在厚度方向上是均勻分布的?;谶@樣的分析,可以把各種形式?jīng)_壓成型中的毛陪變形區(qū)的受力狀態(tài)與變形特點(diǎn),在平面應(yīng)力的應(yīng)力坐標(biāo)系中與相應(yīng)的兩向應(yīng)變坐標(biāo)系中以應(yīng)力與應(yīng)變坐標(biāo)決定的位置來(lái)表示。
4.沖壓用原材料
? ?沖壓加工用原材料有很多種,它們的性能也有很大的差別,所以必須根據(jù)原材料的性能與特點(diǎn),采用不同的沖壓成形方法、工藝參數(shù)和模具結(jié)構(gòu),才能達(dá)到?jīng)_壓加工的目的。由于人們對(duì)沖壓成形過(guò)程板材毛胚的變形行為有了較為深入的認(rèn)識(shí),已經(jīng)相當(dāng)清楚的建立了由原材料的化學(xué)成分、組織等因素所決定的材料性能與沖壓成形之間的關(guān)系,這就使原材料生產(chǎn)部門不但按照沖壓件的工作條件與使用要求進(jìn)行原材料的設(shè)計(jì)工作,而且也根據(jù)沖壓件加工過(guò)程對(duì)板材性能的要求進(jìn)行新型材料的開(kāi)發(fā)工作,這是沖壓技術(shù)在原材料研究方面的一個(gè)重要方向。對(duì)沖壓用原材料沖壓性能方面的研究工作有
(1)原材料沖壓性能的含義。
(2)判斷原材料沖壓性能的科學(xué)方法,確定可以確切反映材料沖壓性能的參數(shù),建立沖壓性能的參數(shù)與實(shí)際沖壓成形間的關(guān)系,以及沖壓性能參數(shù)的測(cè)試方法等。
(3)建立原材料的化學(xué)成分、組織和制造過(guò)程與沖壓性能之間的關(guān)系。沖壓用原材料主要是各種金屬與非金屬板材。金屬板材包括各種黑色技術(shù)和有色金屬板材。雖然在沖壓生產(chǎn)中所用金屬板材的種類很多,但最多的原材料蛀牙是鋼板、不銹鋼板、鋁合金板及各種復(fù)合金屬板。
5.板材沖壓性能及其鑒定方法
? ? 板材是指對(duì)沖壓加工的適應(yīng)能力。對(duì)板材沖壓性能的研究具有飛行重要的意義。為了能夠運(yùn)用最科學(xué)與最經(jīng)濟(jì)合理的沖壓工藝過(guò)程與工藝參數(shù)制造出沖壓零件,必須對(duì)作為加工對(duì)象的板材的性能具有十分清楚的了解,這樣才有可能充分地利用板材在加工方面的潛在能力。另一方面,為了能夠依據(jù)沖壓件的形狀與尺寸特點(diǎn)及其所需的成形工藝等基本因素,正確、合理地選用板材,也必須對(duì)板材的沖壓性能有一個(gè)科學(xué)的認(rèn)識(shí)與正確的判斷。評(píng)定板材沖壓性能的方法有直接試驗(yàn)法與間接試驗(yàn)法。
? ?實(shí)物沖壓試驗(yàn)是最直接的板材沖壓性能的評(píng)定方法。利用實(shí)際生產(chǎn)設(shè)備與模具,在與生產(chǎn)完全相同的條件下進(jìn)行實(shí)際沖壓零件的性能評(píng)定,當(dāng)然能夠的最可靠的結(jié)果。但是,這種評(píng)定方法不具有普遍意義,不能作為行業(yè)之間的通用標(biāo)準(zhǔn)進(jìn)行信息的交流。
? ?模擬試驗(yàn)是把生產(chǎn)中實(shí)際存在的沖壓成形方法進(jìn)行歸納與簡(jiǎn)單化處理,消除許多過(guò)于復(fù)雜的因素,利用軸對(duì)稱的簡(jiǎn)化了的成形方法,在保證試驗(yàn)中板材的變形性質(zhì)與應(yīng)力狀態(tài)都與實(shí)際沖壓成形相同的條件下進(jìn)行的沖壓性能的評(píng)定工作。為了保證模擬試驗(yàn)結(jié)果的可靠性與通用性,規(guī)定了私分具體的關(guān)于試驗(yàn)用工具的幾何形狀與尺寸、毛胚的尺寸、試驗(yàn)條件(沖壓速度、潤(rùn)滑方法、壓邊力等)。
? ?間接試驗(yàn)法也叫做基礎(chǔ)試驗(yàn)法。間接試驗(yàn)法的特點(diǎn)是:在對(duì)板材在塑性變形過(guò)程中所表現(xiàn)出的基本性質(zhì)與規(guī)律進(jìn)行分析與研究的基礎(chǔ)上,進(jìn)一步把它和具體的沖壓成形中板材的塑性變形參數(shù)聯(lián)系起來(lái),建立間接試驗(yàn)結(jié)果(間接試驗(yàn)值)與具體的沖壓成形性能(工藝參數(shù))之間的相關(guān)性。由于間接試驗(yàn)時(shí)所用試件的形狀與尺寸以及加載的方式等都不同于具體的沖壓成形過(guò)程,所以它的變形性質(zhì)和應(yīng)力狀態(tài)也不同于沖壓變形。因此間接試驗(yàn)所得的結(jié)果(試驗(yàn)值)并不是沖壓成形的工藝參數(shù),而是可以用來(lái)表示板材沖壓性能的基礎(chǔ)性參數(shù)。
Characteristics and Sheet Metal Forming
1. The article overview
Stamping is a kind of plastic forming process in which a part is produced by means of the plastic forming the material under the action of a die. Stamping is usually carried out under cold state, so it is also called stamping. Heat stamping is used only when the blank thickness is greater than 8~100mm. The blank material for stamping is usually in the form of sheet or strip, and therefore it is also called sheet metal forming. Some non-metal sheets (such as plywood, mica sheet, asbestos, leather)can also be formed by stamping.
?? Stamping is widely used in various fields of the metalworking industry, and it plays a crucial role in the industries for manufacturing automobiles, instruments, military parts and household electrical appliances, etc.
? ?The process, equipment and die are the three foundational problems that needed to be studied in stamping.
? ?The characteristics of the sheet metal forming are as follows:
(1)? ? High material utilization
(2)? ? Capacity to produce thin-walled parts of complex shape.
(3)? ? Good interchangeability between stamping parts due to precision in shape??
and dimension.
(4)? ? Parts with lightweight, high-strength and fine rigidity can be obtained.
(5)? ? High productivity, easy to operate and to realize mechanization and? ? automatization.
? ? The manufacture of the stamping die is costly, and therefore it only fits to mass production. For the manufacture of products in small batch and rich variety, the simple stamping die and the new equipment such as a stamping machining center, are usually adopted to meet the market demands. The materials for sheet metal stamping include mild steel, copper, aluminum, magnesium alloy and high-plasticity alloy-steel, etc.??
Stamping equipment includes plate shear punching press. The former shears plate into strips with a definite width, which would be pressed later. The later can be used both in shearing and forming.
2.Characteristics of stamping forming
There are various processes of stamping forming with different working patterns and names. But these processes are similar to each other in plastic deformation. There are following conspicuous characteristics in stamping:
(1).The force per unit area perpendicular to the blank surface is not large but is enough to cause the material plastic deformation. It is much less than the inner stresses on the plate plane directions. In most cases stamping forming can be treated approximately as that of the plane stress state to simplify vastly the theoretical analysis and the calculation of the process parameters.
(2).Due to the small relative thickness, the anti-instability capability of the blank is weak under compressive stress. As a result, the stamping process is difficult to proceed successfully without using the anti-instability device (such as blank holder). Therefore the varieties of the stamping processes dominated by tensile stress are more than dominated by compressive stress.
(3).During stamping forming, the inner stress of the blank is equal to or sometimes less than the yield stress of the material. In this point, the stamping is different from the bulk forming. During stamping forming, the influence of the hydrostatic pressure of the stress state in the deformation zone to the forming limit and the deformation resistance is not so important as to the bulk forming. In some circumstances, such influence may be neglected. Even in the case when this influence should be considered, the treating method is also different from that of bulk forming.
(4).In stamping forming, the restrain action of the die to the blank is not severs as in the case of the bulk forming (such as die forging). In bulk forming, the constraint forming is proceeded by the die with exactly the same shape of the part. Whereas in stamping, in most cases, the blank has a certain degree of freedom, only one surface of the blank contacts with the die. In some extra cases, such as the forming of the blank on the deforming zone contact with the die. The deformation in these regions are caused and controlled by the die applying an external force to its adjacent area.
Due to the characteristics of stamping deformation and mechanics mentioned above, the stamping technique is different form the bulk metal forming: The importance or the strength and rigidity of the die in stamping forming is less than that in bulk forming because the blank can be formed without applying large pressure per unit area on its surface. Instead, the techniques of the simple die and the pneumatic and hydraulic forming are developed.
Due to the plane stress or simple strain state in comparison with bulk forming, more research on deformation or force and power parameters has been done. Stamping forming can be performed by more reasonable scientific methods. Based on the real time measurement and analysis on the sheet metal properties and stamping parameters, by means of computer and some modern testing apparatus, research on the intellectualized control of stamping process is also in proceeding. It is shown that there is a close relationship between stamping forming and raw material. The research on the properties of the stamping forming, that is, forming ability and shape stability, has become a key point in stamping technology development, but also enhances the manufacturing technique of iron and steel industry, and provides a reliable foundation for increasing sheet metal quality.
3.Categories of stamping forming
? ? Many deformation processes can be done by stamping, the basic processes of the stamping can be divided into two kinds: cutting and forming.Cutting is a shearing process that one part of the blank is cut from the other. It mainly includes blanking, punching, trimming, parting and shaving, where punching and blanking are the most widely used. Forming is a process that one part of the blank has some displacement from the other. It mainly includes deep drawing, bending, local forming, bulging, flanging, necking, sizing and spinning.
In substance, stamping forming is such that the plastic deformation occurs in the deformation zone of the stamping blank caused by the external force. The stress state and deformation characteristic of the deformation zone are the basic factors to decide the properties of the stamping forming. Based on the stress state and deformation characteristics of the deformation zone, the forming methods can be divided into several categories with the same forming properties and be studied systematically.
??The deformation zone in almost all types of stamping forming is in the plane stress state. Usually there is no force or only small force applied on the blank surface. When is assumed that the stress perpendicular to the blank surface equals to zero, two principal stresses perpendicular to each other and act on the blank surface produce the plastic deformation of the material. Due to the small thickness of the blank, it is assumed approximately the two principal stresses distribute uniformly along the thickness direction. Based on this analysis, the stress state and the deformation characteristics of the deformation zone in all kinds of stamping forming can be denoted by the points in the coordinates of the plane principal stresses and the coordinates of the corresponding plane principal strains.
4.Raw materials for stamping forming
There are a lot of raw materials used in stamping forming, and the properties of these materials may have large difference. The stamping forming can be succeeded only by determining the stamping method, the forming parameters and the die structures according to the properties and characteristics of the raw materials. The deformation of the blank during stamping forming has been investigated quite thoroughly. The relationships between the material properties decided by the chemistry component and structure of the material and the stamping forming has been established clearly. Not only the proper material can be selected based on the working condition and usage demand, but also the new material can be developed according to the demands of the blank properties during processing the stamping part. This is an important domain in stamping forming research. The research on the material properties for stamping forming is as follows:
(1).Definition of the stamping property of the material.
(2).Method to judge the stamping property of the material, find parameters to express the definitely material property of the stamping forming, establish the relationship between the property parameters and the practical stamping forming, and investigate the testing methods of the property parameters.
(3).Establish the relationship among the chemical component, structure, manufacturing process and stamping property.
?? The raw materials for stamping forming mainly include various metals and nonmetal plate. Sheet metal includes both ferrous and nonferrous metals. Although a lot of sheet metals are used in stamping forming, the most widely used materials are steel, stainless steel, aluminum alloy and various composite metal plates.
5.Stamping forming property of sheet metal and its assessing method
The stamping forming property of the sheet metal is the adaptation capability of the sheet metal to stamping forming. It has crucial meaning to the investigation of the stamping forming property of the sheet metal. In order to produce stamping forming parts with most scientific, economic and rational stamping forming process and forming parameters, it is necessary to understand clearly the properties of the sheet metal, so as to utilize the potential of the sheet metal fully in the production. On the other hand, to select plate material accurately and rationally in accordance with the characteristics of the shape and dimension of the stamping forming part and its forming technique is also necessary so that a scientific understanding and accurate judgment to the stamping forming properties of the sheet metal may be achieved.
There are direct and indirect testing methods to assess the stamping property of the sheet metal?.Practicality stamping test is the most direct method to assess stamping forming property of the sheet metal. This test is done exactly in the same condition as actual production by using the practical equipment and dies. Surely, this test result is most reliable. But this kind of assessing method is not comprehensively applicable, and cannot be shared as a commonly used standard between factories.
? ? The simulation test is a kind of assessing method that after simplifying and summing up actual stamping forming methods, as well as eliminating many trivial factors, the stamping properties of the sheet metal are assessed, based on simplified axial-symmetric forming method under the same deformation and stress states between the testing plate and the actual forming states. In order to guarantee the reliability and generality of simulation results, a lot of factors are regulated in detail, such as the shape and dimension of tools for test, blank dimension and testing conditions(stamping velocity, lubrication method and blank holding force, etc).???Indirect testing method is also called basic testing method its characteristic is to connect analysis and research on fundamental property and principle of the sheet metal during plastic deformation, and with the plastic deformation parameters of the sheet metal in actual stamping forming, and then to establish the relationship between the indirect testing results(indirect testing value) and the actual stamping forming property (forming parameters). Because the shape and dimension of the specimen and the loading pattern of the indirect testing are different from the actual stamping forming, the deformation characteristics and stress states of the indirect test are different from those of the actual one. So, the results obtained form the indirect test are not the stamping forming parameters, but are the fundamental parameters that can be used to represent the stamping forming property of the sheet metal.