浙(zhe)江至(zhi)德鋼業(ye)有限公司技術人員(yuan)，根據公司車間生產工藝及(ji)檢驗發現不銹鋼管擠壓時(shi)，使用的空心坯可(ke)以由以下三種方法(fa)獲(huo)得：

 1. 在實心坯料上，直(zhi)接鉆一(yi)個直(zhi)徑(jing)比擠壓芯棒(bang)直(zhi)徑(jing)略大的(de)孔。這種方法用于(yu)得(de)到(dao)直(zhi)徑(jing)為50mm以下(xia)的(de)孔。

 2. 在實心坯(pi)料上，先(xian)預鉆一(yi)個直徑為20~30mm的小(xiao)孔(kong)，然后在擴(kuo)孔(kong)機(ji)上將孔(kong)擴(kuo)大到指定(ding)的尺(chi)寸。這(zhe)種方法用于得到50~100mm的孔(kong)。

 3. 實(shi)心坯料在(zai)穿孔機上直接穿孔，得到所要求尺寸的孔。這種方法用于大于100mm的孔。

  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(bu)銹(xiu)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(ya)機(ji)上，采(cai)用ф210mm、ф280mm和ф315mm 擠壓(ya)筒時(shi)的芯(xin)棒(bang)直徑(jing)空心坯長(chang)度之間(jian)的關(guan)系示(shi)于圖(tu)2-24。圖(tu)中有細線的區域表示(shi)可能的芯(xin)棒(bang)直徑(jing)與空心坯的長(chang)度的比(bi)值。采(cai)用坯料的孔工藝，將(jiang)使這個區域向(xiang)較小的空心坯長(chang)度方(fang)面(mian)明顯(xian)地縮(suo)小。在(zai)許多情(qing)況下，不銹鋼管縮(suo)小到一半。

 不(bu)銹鋼管坯料在穿孔(kong)和擴(kuo)孔(kong)時，必須(xu)滿足(zu)以(yi)下條件：在一次行程中，孔(kong)的擴(kuo)大不(bu)(bu)應超(chao)過5倍；擴(kuo)孔(kong)時的延伸系數不(bu)(bu)應超(chao)過1.45;穿孔(kong)時的延伸系數不(bu)(bu)應超(chao)過1.60。

采(cai)用擴(kuo)(kuo)(kuo)孔(kong)(kong)(kong)工(gong)藝的效果隨著穿(chuan)孔(kong)(kong)(kong)機(ji)噸位(wei)或(huo)擴(kuo)(kuo)(kuo)孔(kong)(kong)(kong)芯(xin)棒直徑的減小而增加。在這種情(qing)況(kuang)下，擴(kuo)(kuo)(kuo)孔(kong)(kong)(kong)工(gong)藝可以用到(dao)擠(ji)(ji)(ji)壓筒的整個長度擴(kuo)(kuo)(kuo)孔(kong)(kong)(kong)頭擴(kuo)(kuo)(kuo)孔(kong)(kong)(kong)的坯料。所以，對于10~25MN擠(ji)(ji)(ji)壓機(ji)的擠(ji)(ji)(ji)壓穿(chuan)孔(kong)(kong)(kong)芯(xin)棒穿(chuan)孔(kong)(kong)(kong)車(che)間，立式(shi)穿(chuan)（擴(kuo)(kuo)(kuo)）孔(kong)(kong)(kong)機(ji)的選擇應該是更(geng)簡(jian)單的擴(kuo)(kuo)(kuo)孔(kong)(kong)(kong)機(ji)，而不是穿(chuan)孔(kong)(kong)(kong)機(ji)。

 對于直(zhi)徑(jing)超(chao)過150mm的(de)孔(kong)，采用(yong)擴孔(kong)工(gong)藝(yi)是不合適(shi)的(de)，因(yin)為這就需要使坯料的(de)鉆孔(kong)直(zhi)徑(jing)超(chao)過35mm,因(yin)而增(zeng)加(jia)了金屬消耗，或者是需要進行(xing)2次擴孔(kong)。其結(jie)果(guo)是使擠壓生(sheng)(sheng)產線的(de)部分設(she)備(bei)閑(xian)置，降低(di)了整條生(sheng)(sheng)產線的(de)生(sheng)(sheng)產的(de)影響效率。

 最直接(jie)影(ying)響穿(chuan)(chuan)（擴(kuo)）孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)(pi)(pi)料(liao)同(tong)心(xin)度(du)(du)的(de)(de)因素是(shi)穿(chuan)(chuan)（擴(kuo)）孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)(pi)(pi)料(liao)與(yu)(yu)穿(chuan)(chuan)（擴(kuo)）孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)襯之(zhi)間(jian)(jian)的(de)(de)間(jian)(jian)隙。穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，由(you)于(yu)(yu)實心(xin)坯(pi)(pi)(pi)(pi)(pi)料(liao)在(zai)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)預先(xian)經過鐓(dui)(dui)(dui)(dui)粗(cu)工序(xu)，因此(ci)當(dang)鐓(dui)(dui)(dui)(dui)粗(cu)壞料(liao)的(de)(de)鐓(dui)(dui)(dui)(dui)粗(cu)變形程(cheng)度(du)(du)足(zu)夠時，鐓(dui)(dui)(dui)(dui)粗(cu)后(hou)坯(pi)(pi)(pi)(pi)(pi)料(liao)與(yu)(yu)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)襯的(de)(de)牙孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)和(he)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)工藝之(zhi)間(jian)(jian)的(de)(de)間(jian)(jian)隙，基(ji)本上應(ying)等于(yu)(yu)零，在(zai)這種情況(kuang)下，穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)(pi)(pi)料(liao)與(yu)(yu)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)襯之(zhi)間(jian)(jian)的(de)(de)間(jian)(jian)隙對于(yu)(yu)穿(chuan)(chuan)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)后(hou)空(kong)心(xin)坯(pi)(pi)(pi)(pi)(pi)同(tong)心(xin)度(du)(du)的(de)(de)影(ying)響非(fei)常(chang)小。而(er)(er)當(dang)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，由(you)于(yu)(yu)預鉆孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)(pi)(pi)料(liao)在(zai)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)不進行(xing)預先(xian)鐓(dui)(dui)(dui)(dui)粗(cu)，因此(ci)，當(dang)預鉆孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)坯(pi)(pi)(pi)(pi)(pi)料(liao)進行(xing)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，預鉆孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)空(kong)心(xin)坯(pi)(pi)(pi)(pi)(pi)料(liao)外徑與(yu)(yu)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)襯之(zhi)間(jian)(jian)的(de)(de)間(jian)(jian)隙使擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)過程(cheng)的(de)(de)穩定性降(jiang)低，因而(er)(er)直接(jie)影(ying)響到擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)后(hou)空(kong)心(xin)坯(pi)(pi)(pi)(pi)(pi)的(de)(de)同(tong)心(xin)度(du)(du)。在(zai)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)時，對于(yu)(yu)坯(pi)(pi)(pi)(pi)(pi)料(liao)與(yu)(yu)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)筒(tong)內(nei)(nei)(nei)襯之(zhi)間(jian)(jian)的(de)(de)間(jian)(jian)隙應(ying)當(dang)特別(bie)引起注意，并且(qie)應(ying)盡可能地做(zuo)到最小，且(qie)做(zuo)到精(jing)確(que)。這是(shi)確(que)保(bao)擴(kuo)孔(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)后(hou)空(kong)心(xin)坯(pi)(pi)(pi)(pi)(pi)同(tong)心(xin)度(du)(du)的(de)(de)關鍵。

另外，有資料認為(wei)(wei)碳鋼(gang)(gang)和低合金鋼(gang)(gang)穿孔時(shi)的(de)延(yan)伸(shen)(shen)系數不(bu)應(ying)大于1.6,不(bu)銹(xiu)(xiu)鋼(gang)(gang)不(bu)應(ying)超過(guo)1.5,而擴孔時(shi)不(bu)銹(xiu)(xiu)鋼(gang)(gang)的(de)延(yan)伸(shen)(shen)系數不(bu)應(ying)大于1.3。圖2-23所示為(wei)(wei)空心(xin)坯(pi)獲得方(fang)法對不(bu)銹(xiu)(xiu)鋼(gang)(gang)擠(ji)(ji)壓管(guan)壁厚(hou)均勻度的(de)影響(xiang)。坯(pi)料直(zhi)(zhi)徑(jing)為(wei)(wei)229mm,穿孔芯棒和擴孔頭的(de)直(zhi)(zhi)徑(jing)為(wei)(wei)112mm。前者 L/d,≈5,生(sheng)產(chan)的(de)不(bu)銹(xiu)(xiu)鋼(gang)(gang)管(guan)規格(ge)(ge)為(wei)(wei) ф127mm x10mm;后者L/d,≈6,生(sheng)產(chan)的(de)不(bu)銹(xiu)(xiu)鋼(gang)(gang)管(guan)規格(ge)(ge)為(wei)(wei)ф127mmx4mm.圖2-24所示為(wei)(wei)55MN 擠(ji)(ji)壓機(ji)210mm、280mm和315mm擠(ji)(ji)壓筒的(de)芯棒直(zhi)(zhi)徑(jing)和空心(xin)坯(pi)長度之間(jian)的(de)關系。