浙江至德鋼業有(you)限(xian)公司技術人(ren)員，根據(ju)公司車(che)間生產工(gong)藝及檢(jian)驗發現不銹鋼管擠壓時，使用的空心坯可以由以下三種(zhong)方法獲得：

 1. 在(zai)實心坯料上，直(zhi)(zhi)接鉆一個直(zhi)(zhi)徑(jing)比擠壓芯棒直(zhi)(zhi)徑(jing)略大的孔。這種方(fang)法用于得(de)到(dao)直(zhi)(zhi)徑(jing)為50mm以下的孔。

 2. 在(zai)實心坯(pi)料上，先預鉆(zhan)一個直徑為20~30mm的(de)(de)小孔，然后在(zai)擴(kuo)孔機上將(jiang)孔擴(kuo)大到指定的(de)(de)尺寸。這種(zhong)方(fang)法(fa)用(yong)于得(de)到50~100mm的(de)(de)孔。

 3. 實(shi)心坯料在(zai)穿(chuan)孔機上直接穿(chuan)孔，得到(dao)所要(yao)求尺(chi)寸的(de)孔。這(zhe)種方(fang)法用于大于100mm的(de)孔。

  無論以何種方法獲得的空心坯料，其主要的質量指標是空心壞料的同心度及其內孔的彎曲度。在坯料進行穿孔或擴孔時，影響穿孔空心坯同心度和內孔看曲度的，同時也是影響其擠壓鋼管壁厚均勻度極限值的參數，主要是坯料的長度Lz,與其內孔的直徑dg的比值。一般情況下，為了確保空心坯的同心度和擠壓管壁厚均勻度的極限值，將參數L2/ds限制在一定范圍內。實心坯料穿孔時，L,/d8=5~7(碳素鋼7,不銹(xiu)鋼 5~6);空心坯料擴孔時，L/dg=10~12(最大L/dg可達到15)。

  L,/d比值的選擇主要取決于材料的變形抗力以及對擠壓不銹鋼管壁厚精度的要求。06Cr18N111Ti不銹鋼坯料穿孔后空心坯壁厚不均影響的試驗結果顯示，隨著L/ds的比值從4.4增大至6.1,穿孔后空心坯的壁厚不均增大15%.根據奧地利原VEW公司在34MN擠壓機上所得到的數據，空心坯的獲得方法對不銹鋼擠壓鋼管壁厚均勻度的影響示于圖2-23。由圖2-23可知，擴孔工藝比穿孔工藝具有更高的空心坯壁厚精度。

 55MN擠壓機上，采(cai)用ф210mm、ф280mm和(he)ф315mm 擠壓筒(tong)時(shi)的(de)(de)(de)芯(xin)(xin)棒直徑(jing)空心坯長度(du)之間的(de)(de)(de)關系示(shi)于圖2-24。圖中有細線的(de)(de)(de)區(qu)域表示(shi)可能(neng)的(de)(de)(de)芯(xin)(xin)棒直徑(jing)與空心坯的(de)(de)(de)長度(du)的(de)(de)(de)比值。采(cai)用坯料的(de)(de)(de)孔工藝，將使這個區(qu)域向較(jiao)小(xiao)(xiao)的(de)(de)(de)空心坯長度(du)方面明(ming)顯(xian)地縮小(xiao)(xiao)。在許多(duo)情況下，不銹鋼管縮小(xiao)(xiao)到(dao)一半。

 不銹(xiu)鋼管(guan)坯料在(zai)穿孔(kong)和擴(kuo)孔(kong)時(shi)，必(bi)須滿足以下條件：在(zai)一次(ci)行(xing)程中，孔(kong)的擴(kuo)大不應(ying)超(chao)(chao)過5倍(bei)；擴(kuo)孔(kong)時(shi)的延伸系數(shu)不應(ying)超(chao)(chao)過1.45;穿孔(kong)時(shi)的延伸系數(shu)不應(ying)超(chao)(chao)過1.60。

采用擴(kuo)孔(kong)工(gong)藝(yi)的(de)(de)(de)(de)效果隨著穿(chuan)孔(kong)機(ji)噸(dun)位或擴(kuo)孔(kong)芯棒(bang)直(zhi)徑的(de)(de)(de)(de)減小而(er)(er)增加(jia)。在這種情況下(xia)，擴(kuo)孔(kong)工(gong)藝(yi)可以用到擠(ji)(ji)壓筒的(de)(de)(de)(de)整個長度(du)擴(kuo)孔(kong)頭擴(kuo)孔(kong)的(de)(de)(de)(de)坯料。所以，對于10~25MN擠(ji)(ji)壓機(ji)的(de)(de)(de)(de)擠(ji)(ji)壓穿(chuan)孔(kong)芯棒(bang)穿(chuan)孔(kong)車間，立式穿(chuan)（擴(kuo)）孔(kong)機(ji)的(de)(de)(de)(de)選擇應該是更簡單的(de)(de)(de)(de)擴(kuo)孔(kong)機(ji)，而(er)(er)不(bu)是穿(chuan)孔(kong)機(ji)。

 對于直徑(jing)超過150mm的(de)孔(kong)，采用擴(kuo)孔(kong)工藝是(shi)不合(he)適的(de)，因(yin)為這(zhe)就(jiu)需要(yao)使坯料的(de)鉆孔(kong)直徑(jing)超過35mm,因(yin)而(er)增加了金屬消耗，或(huo)者是(shi)需要(yao)進行2次擴(kuo)孔(kong)。其結果是(shi)使擠壓(ya)生(sheng)產(chan)線(xian)的(de)部分設備閑置，降低了整條(tiao)生(sheng)產(chan)線(xian)的(de)生(sheng)產(chan)的(de)影(ying)響效率。

 最直(zhi)接影(ying)響(xiang)穿(chuan)(chuan)(chuan)（擴(kuo)(kuo)）孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)料(liao)(liao)同(tong)心(xin)度的(de)(de)因(yin)(yin)素是(shi)穿(chuan)(chuan)(chuan)（擴(kuo)(kuo)）孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)料(liao)(liao)與穿(chuan)(chuan)(chuan)（擴(kuo)(kuo)）孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內襯(chen)之間(jian)的(de)(de)間(jian)隙。穿(chuan)(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，由于(yu)實心(xin)坯(pi)(pi)(pi)料(liao)(liao)在(zai)穿(chuan)(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內預先經過(guo)鐓粗(cu)(cu)工序(xu)，因(yin)(yin)此(ci)(ci)當鐓粗(cu)(cu)壞料(liao)(liao)的(de)(de)鐓粗(cu)(cu)變形程度足夠時，鐓粗(cu)(cu)后(hou)坯(pi)(pi)(pi)料(liao)(liao)與穿(chuan)(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內襯(chen)的(de)(de)牙孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)和(he)擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)工藝之間(jian)的(de)(de)間(jian)隙，基本上應等于(yu)零，在(zai)這種情況下(xia)，穿(chuan)(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)料(liao)(liao)與穿(chuan)(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內襯(chen)之間(jian)的(de)(de)間(jian)隙對(dui)(dui)于(yu)穿(chuan)(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)后(hou)空(kong)心(xin)坯(pi)(pi)(pi)同(tong)心(xin)度的(de)(de)影(ying)響(xiang)非(fei)常小。而當擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，由于(yu)預鉆(zhan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)料(liao)(liao)在(zai)擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內不進(jin)行(xing)預先鐓粗(cu)(cu)，因(yin)(yin)此(ci)(ci)，當預鉆(zhan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)料(liao)(liao)進(jin)行(xing)擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，預鉆(zhan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)空(kong)心(xin)坯(pi)(pi)(pi)料(liao)(liao)外徑與擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內襯(chen)之間(jian)的(de)(de)間(jian)隙使擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)過(guo)程的(de)(de)穩定(ding)性降(jiang)低(di)，因(yin)(yin)而直(zhi)接影(ying)響(xiang)到(dao)(dao)擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)后(hou)空(kong)心(xin)坯(pi)(pi)(pi)的(de)(de)同(tong)心(xin)度。在(zai)擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，對(dui)(dui)于(yu)坯(pi)(pi)(pi)料(liao)(liao)與擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內襯(chen)之間(jian)的(de)(de)間(jian)隙應當特別引起注(zhu)意，并且(qie)(qie)應盡(jin)可能地(di)做到(dao)(dao)最小，且(qie)(qie)做到(dao)(dao)精確(que)。這是(shi)確(que)保(bao)擴(kuo)(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)后(hou)空(kong)心(xin)坯(pi)(pi)(pi)同(tong)心(xin)度的(de)(de)關鍵。

另外，有資料(liao)認(ren)為(wei)(wei)(wei)碳鋼(gang)和低合金鋼(gang)穿孔時(shi)的(de)(de)延(yan)伸(shen)(shen)系數(shu)不(bu)應(ying)大于1.6,不(bu)銹(xiu)鋼(gang)不(bu)應(ying)超過1.5,而擴(kuo)孔時(shi)不(bu)銹(xiu)鋼(gang)的(de)(de)延(yan)伸(shen)(shen)系數(shu)不(bu)應(ying)大于1.3。圖2-23所示為(wei)(wei)(wei)空心坯(pi)獲(huo)得方法對(dui)不(bu)銹(xiu)鋼(gang)擠壓(ya)管壁厚均(jun)勻度的(de)(de)影響。坯(pi)料(liao)直(zhi)徑(jing)為(wei)(wei)(wei)229mm,穿孔芯棒(bang)和擴(kuo)孔頭的(de)(de)直(zhi)徑(jing)為(wei)(wei)(wei)112mm。前者(zhe) L/d,≈5,生產(chan)的(de)(de)不(bu)銹(xiu)鋼(gang)管規格(ge)為(wei)(wei)(wei) ф127mm x10mm;后者(zhe)L/d,≈6,生產(chan)的(de)(de)不(bu)銹(xiu)鋼(gang)管規格(ge)為(wei)(wei)(wei)ф127mmx4mm.圖2-24所示為(wei)(wei)(wei)55MN 擠壓(ya)機(ji)210mm、280mm和315mm擠壓(ya)筒的(de)(de)芯棒(bang)直(zhi)徑(jing)和空心坯(pi)長度之(zhi)間(jian)的(de)(de)關系。