全浮動芯棒連續軋管機簡稱MM(Mandrel Mill),一般設有8個機架。軋制過程中對芯棒速度不加以控制，芯棒由被輾軋金屬的摩擦力帶動自由跟隨管子通過軋機，芯棒的運行速度是不受控的；軋制過程中芯棒的運行速度隨著各機架的咬入、拋鋼有波動，從而引起管子壁厚的波動；軋制結束后，芯棒隨荒管軋出至連軋機后的輸出輥道。在軋制中薄壁管時芯棒的全長幾乎都在荒管內，如圖4-3所示。帶有芯棒的荒管橫移至脫棒線，由脫棒機將芯棒從荒管中抽出以便冷卻、潤滑后循環使用。浮動芯棒連續軋管機的特點是軋制節奏快，每分鐘可軋4支甚至更多的不(bu)銹(xiu)鋼管；但荒管的壁厚精度稍低，設有脫棒機其工藝流程較長，芯棒的長度接近于管子的長度；適合生產較小規格的無縫不銹鋼管。比較有代表性的浮動芯棒連續軋管機有德國米爾海姆廠的RK2機組和我國寶鋼的ф140mm機組。

  連續(xu)(xu)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)管(guan)時，荒管(guan)可以(yi)看做是(shi)(shi)(shi)在(zai)(zai)不(bu)(bu)(bu)同(tong)直(zhi)徑(jing)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)間連續(xu)(xu)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)形成(cheng)的(de)(de)(de)(de)，穿在(zai)(zai)不(bu)(bu)(bu)銹鋼管(guan)中的(de)(de)(de)(de)芯(xin)(xin)(xin)棒(bang)(bang)(bang)可以(yi)看做是(shi)(shi)(shi)曲(qu)率半徑(jing)無窮(qiong)大(da)的(de)(de)(de)(de)內軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)。浮動芯(xin)(xin)(xin)棒(bang)(bang)(bang)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)時，芯(xin)(xin)(xin)棒(bang)(bang)(bang)除(chu)受(shou)到軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)經軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)傳遞來的(de)(de)(de)(de)作用力外(wai)，再無其(qi)(qi)他外(wai)力作用。當軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)頭部經第一機(ji)(ji)(ji)(ji)架(jia)(jia)咬入(ru)后(hou)(hou)，隨著軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)逐一走(zou)向后(hou)(hou)面(mian)的(de)(de)(de)(de)延(yan)伸機(ji)(ji)(ji)(ji)架(jia)(jia)，作用在(zai)(zai)芯(xin)(xin)(xin)棒(bang)(bang)(bang)上(shang)的(de)(de)(de)(de)機(ji)(ji)(ji)(ji)架(jia)(jia)數(shu)相繼(ji)增(zeng)多(duo)，故芯(xin)(xin)(xin)棒(bang)(bang)(bang)速(su)度(du)(du)不(bu)(bu)(bu)斷提高(gao)，這(zhe)個(ge)(ge)階(jie)(jie)段(duan)稱(cheng)為(wei)“咬入(ru)”階(jie)(jie)段(duan)；當軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)頭部進入(ru)最末機(ji)(ji)(ji)(ji)架(jia)(jia)后(hou)(hou)，整個(ge)(ge)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)處在(zai)(zai)連續(xu)(xu)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)管(guan)機(ji)(ji)(ji)(ji)所(suo)有機(ji)(ji)(ji)(ji)架(jia)(jia)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)中，芯(xin)(xin)(xin)棒(bang)(bang)(bang)速(su)度(du)(du)維(wei)持(chi)不(bu)(bu)(bu)變(bian)，稱(cheng)為(wei)“穩定(ding)(ding)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)”階(jie)(jie)段(duan)；當軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)尾部離開(kai)第一機(ji)(ji)(ji)(ji)架(jia)(jia)后(hou)(hou)，芯(xin)(xin)(xin)棒(bang)(bang)(bang)速(su)度(du)(du)逐級提高(gao)，直(zhi)到軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)結束，稱(cheng)為(wei)“軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)出”階(jie)(jie)段(duan)。軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)工作圓周(zhou)速(su)度(du)(du)是(shi)(shi)(shi)按“穩定(ding)(ding)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)”狀態下設定(ding)(ding)的(de)(de)(de)(de)，軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)過程中軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)又是(shi)(shi)(shi)遵循著體積(ji)不(bu)(bu)(bu)變(bian)定(ding)(ding)律的(de)(de)(de)(de)。然而(er)由(you)芯(xin)(xin)(xin)棒(bang)(bang)(bang)引起的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)(jian)(jian)速(su)度(du)(du)的(de)(de)(de)(de)升(sheng)高(gao)，使(shi)流(liu)入(ru)后(hou)(hou)面(mian)機(ji)(ji)(ji)(ji)架(jia)(jia)的(de)(de)(de)(de)金(jin)屬(shu)必然增(zeng)多(duo)，也就是(shi)(shi)(shi)說，后(hou)(hou)面(mian)的(de)(de)(de)(de)機(ji)(ji)(ji)(ji)架(jia)(jia)由(you)芯(xin)(xin)(xin)棒(bang)(bang)(bang)送人了比(bi)其(qi)(qi)設定(ding)(ding)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)圓周(zhou)速(su)度(du)(du)所(suo)允許的(de)(de)(de)(de)還要多(duo)的(de)(de)(de)(de)金(jin)屬(shu)，這(zhe)就出現了使(shi)斷面(mian)積(ji)增(zeng)大(da)的(de)(de)(de)(de)金(jin)屬(shu)積(ji)累(lei)。這(zhe)種(zhong)逐步流(liu)入(ru)的(de)(de)(de)(de)附加金(jin)屬(shu)造成(cheng)的(de)(de)(de)(de)較(jiao)大(da)斷面(mian)，盡管(guan)在(zai)(zai)最后(hou)(hou)的(de)(de)(de)(de)機(ji)(ji)(ji)(ji)架(jia)(jia)上(shang)得到了加工，但仍然導致在(zai)(zai)荒管(guan)的(de)(de)(de)(de)一些部位上(shang)直(zhi)徑(jing)變(bian)大(da)和壁(bi)厚(hou)(hou)變(bian)厚(hou)(hou)，這(zhe)種(zhong)現象稱(cheng)為(wei)“竹(zhu)節”。原則上(shang)講(jiang)可能(neng)在(zai)(zai)整根不(bu)(bu)(bu)銹鋼管(guan)上(shang)均出現“竹(zhu)節”。顯然“竹(zhu)節”現象屬(shu)縱向壁(bi)厚(hou)(hou)不(bu)(bu)(bu)均，對隨后(hou)(hou)的(de)(de)(de)(de)張減機(ji)(ji)(ji)(ji)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)(zhi)(zhi)(zhi)是(shi)(shi)(shi)不(bu)(bu)(bu)利(li)的(de)(de)(de)(de)，應盡可能(neng)防止。

  為了防(fang)止(zhi)或減(jian)少(shao)“竹(zhu)節”形成，孔型設計分(fen)配壓下(xia)量時，在保證總(zong)延伸不變(bian)的前(qian)提下(xia)，適當(dang)增(zeng)加(jia)前(qian)幾架(jia)壓下(xia)量。這樣，就可(ke)(ke)在后面幾個機(ji)架(jia)中使芯(xin)棒(bang)速(su)(su)度的躍增(zeng)得到減(jian)弱，從(cong)而減(jian)輕芯(xin)棒(bang)速(su)(su)度變(bian)化(hua)(hua)的影響。良(liang)好的芯(xin)棒(bang)潤滑有利(li)于延伸和降(jiang)低能耗，也可(ke)(ke)以減(jian)少(shao)竹(zhu)節的形成。還(huan)可(ke)(ke)以采用電控技術防(fang)止(zhi)竹(zhu)節的產生(sheng)，由電子計算機(ji)進(jin)行預設定，軋輥轉速(su)(su)按要求變(bian)化(hua)(hua)，當(dang)軋件通過時對(dui)軋輥轉速(su)(su)進(jin)行校準，使各機(ji)架(jia)的出口(kou)速(su)(su)度與芯(xin)棒(bang)速(su)(su)度的變(bian)化(hua)(hua)相適應。

  盡管(guan)(guan)對“竹節”現象采取了(le)不少措施并取得了(le)一定的(de)效果(guo)，但軋(ya)(ya)制(zhi)條件的(de)變化(hua)依然(ran)存在，且(qie)(qie)成品(pin)管(guan)(guan)的(de)尺寸精度始終(zhong)不如限動(dong)芯(xin)棒(bang)(bang)(bang)軋(ya)(ya)機。此外，芯(xin)棒(bang)(bang)(bang)長，使制(zhi)造費用(yong)加大(da)，制(zhi)造困(kun)難，且(qie)(qie)長芯(xin)棒(bang)(bang)(bang)的(de)重(zhong)量也很大(da)，不銹(xiu)鋼(gang)管(guan)(guan)帶(dai)著過重(zhong)的(de)芯(xin)棒(bang)(bang)(bang)在輥道上運行將會導致不銹(xiu)鋼(gang)管(guan)(guan)表(biao)面損(sun)傷(shang)。故目前浮動(dong)芯(xin)棒(bang)(bang)(bang)連續(xu)軋(ya)(ya)管(guan)(guan)機均用(yong)于小型機組(zu)，至今(jin)這種機組(zu)僅能(neng)生產直徑小于177.8mm以(yi)下的(de)不銹(xiu)鋼(gang)管(guan)(guan)。浮動(dong)芯(xin)棒(bang)(bang)(bang)連續(xu)軋(ya)(ya)管(guan)(guan)機機組(zu)在20世(shi)紀70年代之前比較(jiao)盛行。