立式不銹鋼管穿(擴)孔機的工模具配置取決于穿(擴)孔機的結構形式,穿(擴)孔過程的工藝要求,以及穿(擴)孔時坯料金屬變形時的流動特點。和臥式擠壓機的工模具配置一樣,穿(擴)孔機工模具配置的基本形式由穿(擴)孔筒(內襯和外套)、鐓粗桿、鐓粗頭、穿(擴)孔頭、支承桿、支承頭、剪切環以及連接件組成,如圖7-50所示。
一、穿(擴)孔(kong)筒
當不銹鋼管坯料進行穿和擴孔時,穿孔筒內襯承受相當小的單位壓力(不大于590MPa).因為從坯料穿孔或擴孔方向的垂直滑移摩擦力實際上是沒有的。但是,因與加熱到高溫的坯料直接接觸時間長達30s,引起穿孔筒內襯劇烈受熱。長久使用后的穿孔筒內襯以焊瘤的形式引起變形而損壞,或使穿孔坯料取出產生困難。因此,當其在高速工作時應采取強制冷卻的方法來降低穿孔筒內襯的溫度。通常在穿孔筒外套的內壁車有螺旋冷卻水槽(圖7-51)來冷卻內襯。
一般穿(chuan)孔筒的內(nei)襯(chen)與外(wai)套之間(jian)以1.0%~1.5%的錐(zhui)度(du)相配(pei)合(he),而內(nei)襯(chen)的內(nei)孔也制成約有1%~3%的錐(zhui)度(du),這樣使取出(chu)坯料(liao)時能比較順利地頂出(chu)。
另外(wai),穿孔筒內(nei)襯(chen)的內(nei)表面(mian)光(guang)潔度(du)要(yao)求(qiu)比(bi)較(jiao)高(gao),熱處理后要(yao)進(jin)行磨削。其(qi)熱處理后的硬度(du)約(yue)為HRC42~45,以提高(gao)其(qi)耐(nai)磨性。
穿(chuan)孔筒的內襯采用和(he)擠壓筒內襯相(xiang)同的材(cai)料制(zhi)造,如5CrW2Si或Ni11.一般穿(chuan)孔筒內襯的使用壽命(ming)大約(yue)為1000~3000次(ci)。
從穿孔(kong)筒內(nei)襯的(de)工(gong)作條件(jian)來考(kao)量,采用具有雙(shuang)穿孔(kong)筒旋轉輪換工(gong)作結(jie)構的(de)穿孔(kong)機(ji)最為合適。
原因為除(chu)了(le)能使穿(chuan)孔筒(tong)(tong)得到及時而充分的冷卻(que)之(zhi)外,輪流使用(yong)的穿(chuan)孔筒(tong)(tong)有利于內襯很好地清除(chu)玻璃潤滑(hua)劑殘渣(zha),提高內襯的使用(yong)壽命。
二(er)、鐓(dui)粗(cu)桿和(he)穿孔桿
1. 鐓粗(cu)桿和(he)穿孔桿的結構
鐓粗桿(gan)在結(jie)構(gou)上(shang),上(shang)端用銷子或夾(jia)緊裝置固定在鐓粗梁上(shang),下端用螺紋(wen)連接鐓粗頭(圖7-52),其內孔(kong)設有導向滑槽(cao)與穿(chuan)孔(kong)桿(gan)相配合。
鐓粗桿的(de)外徑比(bi)穿孔筒小(xiao)10~30mm,而內徑比(bi)穿孔桿大5~25mm.但考慮到鐓粗桿的(de)共(gong)用性,可在保證強(qiang)度(du)的(de)條件下超出上(shang)述范圍。
鐓(dui)粗桿的長度(du)應根據穿孔筒(tong)的長度(du)和生產最(zui)短的坯料(liao)長度(du)來決定。
根據穿(chuan)孔(kong)桿和穿(chuan)孔(kong)頭(tou)的(de)規格,可(ke)以(yi)(yi)更(geng)換鐓粗頭(tou),以(yi)(yi)擴大鐓粗桿的(de)使用范圍,鐓粗頭(tou)的(de)外徑(jing)與(yu)穿(chuan)孔(kong)筒(tong)的(de)內(nei)徑(jing)之(zhi)間間隙(xi)要小,約比穿(chuan)孔(kong)筒(tong)的(de)小頭(tou)直徑(jing)小0.5~1.5mm,其內(nei)孔(kong)帶有花鍵式導向槽。
2. 穿孔桿的穩定性強度校核
立式穿(chuan)(chuan)孔(kong)(kong)(kong)機的(de)(de)穿(chuan)(chuan)孔(kong)(kong)(kong)桿(gan)(gan)作(zuo)為連(lian)桿(gan)(gan),連(lian)接(jie)(jie)(jie)穿(chuan)(chuan)孔(kong)(kong)(kong)頭及(ji)芯棒(bang)支承,穿(chuan)(chuan)孔(kong)(kong)(kong)并不和(he)變形屬直(zhi)接(jie)(jie)(jie)接(jie)(jie)(jie)觸。在穿(chuan)(chuan)孔(kong)(kong)(kong)過程(cheng)中,穿(chuan)(chuan)孔(kong)(kong)(kong)桿(gan)(gan)連(lian)接(jie)(jie)(jie)并支承著穿(chuan)(chuan)孔(kong)(kong)(kong)頭及(ji)擴孔(kong)(kong)(kong)頭。一(yi)般穿(chuan)(chuan)孔(kong)(kong)(kong)桿(gan)(gan)的(de)(de)直(zhi)徑比穿(chuan)(chuan)孔(kong)(kong)(kong)頭工作(zuo)帶(dai)的(de)(de)直(zhi)徑小10~30mm.穿(chuan)(chuan)孔(kong)(kong)(kong)桿(gan)(gan)的(de)(de)長(chang)度(du)取(qu)決于穿(chuan)(chuan)孔(kong)(kong)(kong)筒的(de)(de)長(chang)度(du)。
由于在(zai)不銹鋼管穿孔(kong)時(shi)穿孔(kong)桿承受壓縮應力,且因穿孔(kong)桿的(de)長度較長,工作(zuo)時(shi)上端(duan)相當于固定。因此,其(qi)彎曲的(de)危險性要比壓縮變形的(de)危險性更大。
所以,穿(chuan)孔(kong)桿的強度校(xiao)核是按照壓桿穩定的方法(fa)來(lai)計算。
穿孔桿上(shang)所承(cheng)受的應力(li)為(wei):
3. 穿孔頭(tou)和擴孔頭(tou)
a. 穿(chuan)孔(kong)頭(tou)和擴(kuo)孔(kong)頭(tou)的(de)結構
在立式穿(chuan)孔(kong)(kong)(kong)機對實心坯料進行穿(chuan)孔(kong)(kong)(kong)時(shi)(shi),采用(yong)(yong)穿(chuan)孔(kong)(kong)(kong)工藝(yi)(yi),需用(yong)(yong)穿(chuan)孔(kong)(kong)(kong)頭(tou);而(er)對帶預鉆孔(kong)(kong)(kong)的(de)空心坯料進行擴(kuo)(kuo)孔(kong)(kong)(kong)時(shi)(shi),采用(yong)(yong)擴(kuo)(kuo)孔(kong)(kong)(kong)工藝(yi)(yi),則需用(yong)(yong)擴(kuo)(kuo)孔(kong)(kong)(kong)頭(tou)。在采用(yong)(yong)穿(chuan)(擴(kuo)(kuo))孔(kong)(kong)(kong)工藝(yi)(yi)時(shi)(shi),穿(chuan)孔(kong)(kong)(kong)頭(tou)和擴(kuo)(kuo)孔(kong)(kong)(kong)頭(tou)都安(an)裝在穿(chuan)孔(kong)(kong)(kong)桿上。對于穿(chuan)孔(kong)(kong)(kong)機的(de)工模具(ju)而(er)言,穿(chuan)孔(kong)(kong)(kong)頭(tou)的(de)工作條件(jian)最為(wei)(wei)嚴(yan)酷,受到(dao)最為(wei)(wei)強烈的(de)磨損(sun);而(er)擴(kuo)(kuo)孔(kong)(kong)(kong)頭(tou)的(de)工作條件(jian)相對會好一(yi)(yi)些(xie)。因此,擴(kuo)(kuo)孔(kong)(kong)(kong)頭(tou)的(de)使(shi)(shi)用(yong)(yong)壽(shou)命要比穿(chuan)孔(kong)(kong)(kong)頭(tou)長。一(yi)(yi)般在生產(chan)不銹鋼管時(shi)(shi),穿(chuan)孔(kong)(kong)(kong)頭(tou)的(de)使(shi)(shi)用(yong)(yong)壽(shou)命不超過(guo)30~40次/只,而(er)擴(kuo)(kuo)孔(kong)(kong)(kong)頭(tou)的(de)使(shi)(shi)用(yong)(yong)壽(shou)命可以(yi)達到(dao)80~100次/只(材(cai)質為(wei)(wei)3Cr2W8V).
另(ling)外,穿(chuan)(chuan)(chuan)孔(kong)頭(tou)(tou)工作(zuo)表面的(de)(de)不均(jun)勻磨損,將(jiang)引起(qi)穿(chuan)(chuan)(chuan)孔(kong)后空心坯的(de)(de)壁(bi)厚不均(jun)。穿(chuan)(chuan)(chuan)孔(kong)時,將(jiang)穿(chuan)(chuan)(chuan)孔(kong)頭(tou)(tou)輪流安(an)裝在(zai)穿(chuan)(chuan)(chuan)孔(kong)桿上,由10~15穿(chuan)(chuan)(chuan)孔(kong)頭(tou)(tou)組成為一(yi)組,循環輪流使用的(de)(de)效果最(zui)好。
圖(tu)(tu)7-53所(suo)示為(wei)立式穿孔(kong)(kong)機(ji)的穿孔(kong)(kong)頭和擴孔(kong)(kong)頭。穿孔(kong)(kong)頭既(ji)可使(shi)用有柄的(圖(tu)(tu)7-53(a)),也可以(yi)使(shi)用無(wu)柄平(ping)端面的(圖(tu)(tu)7-53(b)).這種固(gu)定方法,可以(yi)允(yun)許穿孔(kong)(kong)頭冷卻,檢查(cha)或更換(huan),不占穿孔(kong)(kong)的周期(qi)時間。
穿孔頭與穿孔坯料的接觸端面被做成(cheng)帶有(you)圓弧半徑(jing)的凹(ao)面,是(shi)為(wei)了(le)保證在整個(ge)穿孔周(zhou)期中,玻(bo)璃滑劑(ji)能夠(gou)均(jun)勻地進(jin)入變(bian)形區。
b. 穿孔頭和擴孔頭的設計
穿(chuan)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)和擴(kuo)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)的(de)(de)(de)設計(ji)數據(ju)(ju)來自于多年(nian)的(de)(de)(de)實(shi)際技術工作經驗(yan)數據(ju)(ju)。穿(chuan)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)(圖(tu)7-54)和擴(kuo)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)(圖(tu)7-55)定徑帶的(de)(de)(de)直(zhi)(zhi)徑,要根據(ju)(ju)產品的(de)(de)(de)規格而定。由于穿(chuan)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)和擴(kuo)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)在(zai)穿(chuan)(擴(kuo))孔(kong)(kong)(kong)(kong)(kong)過程中(zhong)直(zhi)(zhi)接與變形金(jin)屬接觸,因此(ci),其表面(mian)光(guang)潔度(du)應達到7~8級,且倒角要圓滑。穿(chuan)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)下端的(de)(de)(de)倒角半(ban)徑R應約為穿(chuan)孔(kong)(kong)(kong)(kong)(kong)頭(tou)(tou)直(zhi)(zhi)徑的(de)(de)(de)10%~20%。
穿(chuan)(chuan)孔(kong)頭(tou)上端過渡段的角度不宜過大,以(yi)防止(zhi)穿(chuan)(chuan)孔(kong)頭(tou)回程(cheng)時(shi)刮傷空心坯的內表面,其角度一般為5°~25°.穿(chuan)(chuan)孔(kong)筒和穿(chuan)(chuan)孔(kong)頭(tou)較(jiao)小(xiao)時(shi),采用較(jiao)小(xiao)值。
擴孔(kong)頭(tou)(tou)的下錐頭(tou)(tou)直(zhi)徑(jing)應等于坯(pi)料預鉆孔(kong)的直(zhi)徑(jing)。
擴孔(kong)頭(tou)的成(cheng)形錐角一般(ban)為(wei)30°~60°,太大時擴孔(kong)坯的內壁容易刮傷,且擴孔(kong)開始時導向不(bu)好。其過渡段要平(ping)滑,以便使金屬流動(dong)均勻。
一般(ban)穿(chuan)孔頭的直徑要(yao)比(bi)穿(chuan)孔桿(gan)的直徑大10~30mm,但是(shi)有(you)時考慮到穿(chuan)孔桿(gan)的共(gong)用性,而擴大這一數值的范圍。
在(zai)穿(chuan)(chuan)(chuan)孔(kong)過程中(zhong),穿(chuan)(chuan)(chuan)孔(kong)頭嚴(yan)酷(ku)的(de)(de)(de)工作(zuo)條件(jian),往往會使其工作(zuo)帶和(he)沿外徑的(de)(de)(de)棱緣,即側面連接端(duan)面的(de)(de)(de)圓(yuan)角半(ban)徑處,承(cheng)受最大的(de)(de)(de)加熱(re)和(he)磨損。棱緣的(de)(de)(de)磨損引(yin)起穿(chuan)(chuan)(chuan)孔(kong)后空心坯的(de)(de)(de)壁(bi)厚不(bu)(bu)均(jun)(jun)(jun),導致擠壓鋼管(guan)的(de)(de)(de)壁(bi)厚不(bu)(bu)均(jun)(jun)(jun)。為(wei)了消除穿(chuan)(chuan)(chuan)孔(kong)頭的(de)(de)(de)不(bu)(bu)均(jun)(jun)(jun)勻磨損,避(bi)免因(yin)此而引(yin)起的(de)(de)(de)穿(chuan)(chuan)(chuan)孔(kong)空心坯的(de)(de)(de)壁(bi)厚不(bu)(bu)均(jun)(jun)(jun),在(zai)現代的(de)(de)(de)穿(chuan)(chuan)(chuan)孔(kong)機上(shang)采用了穿(chuan)(chuan)(chuan)孔(kong)桿和(he)穿(chuan)(chuan)(chuan)孔(kong)芯棒運動的(de)(de)(de)套管(guan)系統,即在(zai)坯料經(jing)鐓粗后穿(chuan)(chuan)(chuan)孔(kong)桿不(bu)(bu)立即返回,而是繼續壓在(zai)坯料上(shang),這樣可以使穿(chuan)(chuan)(chuan)孔(kong)頭精(jing)確地對準坯料的(de)(de)(de)中(zhong)心,并(bing)且減小了其自由長(chang)度。
采用(yong)帶圓弧(hu)半(ban)徑的(de)(de)(de)凹面穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)頭(tou)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong),實現了穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)桿(gan)和(he)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)頭(tou)對穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)坯料的(de)(de)(de)附加定心(xin),提(ti)高了穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)后空心(xin)坯的(de)(de)(de)壁(bi)厚(hou)均勻度。在穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)過程中,穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)頭(tou)處(chu)于(yu)最嚴(yan)酷的(de)(de)(de)工作條件(jian),其(qi)工作帶和(he)沿外徑的(de)(de)(de)棱緣(yuan),即側面和(he)端面的(de)(de)(de)圓角半(ban)徑,承受最大(da)(da)的(de)(de)(de)加熱和(he)磨(mo)損(sun)。觀察經多次使用(yong)后的(de)(de)(de)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)頭(tou),其(qi)棱緣(yuan)的(de)(de)(de)磨(mo)損(sun)引起穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)空心(xin)坯壁(bi)厚(hou)不均,當出(chu)現穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)頭(tou)棱緣(yuan)的(de)(de)(de)單(dan)邊磨(mo)損(sun)時,危險性更大(da)(da)。
穿(chuan)(chuan)孔(kong)桿,包括螺紋固定(ding)的(de)穿(chuan)(chuan)孔(kong)頭在內,具有通過(guo)沿(yan)軸線(xian)鉆孔(kong)的(de)冷卻(que)水孔(kong)槽。穿(chuan)(chuan)孔(kong)時用水冷卻(que)穿(chuan)(chuan)孔(kong)桿和穿(chuan)(chuan)孔(kong)頭。
采(cai)用(yong)組合(he)式(shi)的穿(chuan)孔(kong)(kong)工模具,允(yun)許用(yong)低合(he)金鋼制(zhi)作不受熱(re)的零件,如采(cai)用(yong)5CrNiW、50CrVA鋼制(zhi)造(zao)固定穿(chuan)孔(kong)(kong)桿的夾(jia)具,用(yong)5CrNiW、5CrNiMo鋼制(zhi)造(zao)穿(chuan)孔(kong)(kong)桿,用(yong)高合(he)金鋼和耐熱(re)合(he)金鋼制(zhi)造(zao)穿(chuan)孔(kong)(kong)頭。
擴孔(kong)過(guo)程中,擴孔(kong)頭的(de)(de)錐形表面(mian)受(shou)到最劇(ju)烈的(de)(de)磨損,并逐漸形成劃道(dao)和(he)凹陷。擴孔(kong)頭的(de)(de)工作負荷較穿(chuan)孔(kong)頭要(yao)輕許多,因此其使(shi)用壽命比穿(chuan)孔(kong)頭高得多,一(yi)般可達到80~100次。
擴孔(kong)頭(tou)的(de)長度取決于(yu)穿(chuan)(chuan)孔(kong)機(ji)的(de)結構形式,并且首先取決于(yu)穿(chuan)(chuan)孔(kong)桿和穿(chuan)(chuan)孔(kong)筒(tong)上平面之(zhi)間(jian)的(de)距離。如果其間(jian)隙大,為了減小成(cheng)形角度,擴孔(kong)頭(tou)可以做得(de)比(bi)較長。擴孔(kong)頭(tou)成(cheng)形角的(de)平均值一般等于(yu)15°~20°,而(er)在最大的(de)擴孔(kong)程度時,可以達到30°~32°.
穿孔(kong)頭和擴孔(kong)頭必須具(ju)有良(liang)好的(de)綜合力學(xue)性能,工(gong)作(zuo)表面光潔圓滑(hua),與(yu)穿孔(kong)桿連接可靠,更(geng)換(huan)方(fang)便。
穿孔頭的形狀由端面圓角半徑R,工作帶l1和倒錐l2組成(圖7-54).各部分的尺寸,按以下經驗公式確定:
采用倒錐的(de)目(mu)的(de)是(shi)(shi)為(wei)了防止(zhi)穿(chuan)孔(kong)頭回程(cheng)時刮切金屬或帶出空心坯。穿(chuan)孔(kong)頭端面加工成凹面的(de)目(mu)的(de),是(shi)(shi)為(wei)了儲存潤滑劑,以使在整個穿(chuan)孔(kong)過程(cheng)中,保持潤滑劑的(de)連(lian)續(xu)供(gong)應。
擴孔頭由鼻尖l3、擴孔錐l4、工作帶l5和反向錐l6組成(圖7-55).鼻尖的作用是導向和定心,其直徑等于坯料鉆孔直徑,長度l3約為10~20mm,擴孔錐角α一般取15°~20°,當擴徑量大時,可達30°~32°,工作帶直徑dc由擠壓工藝表得到,其長度l5一般為6~10mm。
由于(yu)擴孔錐至(zhi)工作(zuo)帶處(chu)的磨(mo)損(sun)最為嚴重(zhong),故該處(chu)采(cai)用圓滑(hua)過渡,其他(ta)尺寸同上。
c. 剪切環組件
剪切環(huan)組件包括下支(zhi)承桿、支(zhi)承頭、剪切環(huan)和連接件等(deng)零部件。
支承(cheng)頭和(he)剪切環(huan)的作用是在穿(chuan)(chuan)孔(kong)過(guo)程(cheng)中封閉穿(chuan)(chuan)孔(kong)筒內襯(chen)的下端面(mian),以減小穿(chuan)(chuan)孔(kong)余料的高度,為空(kong)心坯下端面(mian)定形;在穿(chuan)(chuan)孔(kong)結束時,剪切環(huan)還要剪斷(duan)穿(chuan)(chuan)孔(kong)余料;支承(cheng)桿最后(hou)將穿(chuan)(chuan)孔(kong)空(kong)心坯從穿(chuan)(chuan)孔(kong)筒內襯(chen)中推出。
在整個(ge)穿(chuan)孔過程中,支(zhi)承頭(tou)和剪(jian)切(qie)環的(de)上端(duan)面和加熱到(dao)高溫的(de)坯料相接(jie)觸(chu),使其表面層金(jin)屬被加熱到(dao)650~700℃.使用(yong)過程中剪(jian)切(qie)環的(de)主(zhu)要(yao)破壞形式是端(duan)面棱緣翹曲和焊瘤(圖2-27).
剪(jian)切(qie)(qie)環與穿孔(kong)(kong)頭(tou)或(huo)擴孔(kong)(kong)頭(tou)之間的間隙不能過(guo)大,一(yi)般小于2mm.如果(guo)此間隙過(guo)大或(huo)剪(jian)切(qie)(qie)環過(guo)度磨損,則(ze)會導致在剪(jian)切(qie)(qie)穿孔(kong)(kong)或(huo)擴孔(kong)(kong)余料(liao)的過(guo)程(cheng)中(zhong),坯料(liao)前端內孔(kong)(kong)處產生飛邊缺(que)陷,并易(yi)引(yin)起擠(ji)壓筒和(he)擠(ji)壓模的損壞。