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(lian)續(xu)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)管(guan)(guan)(guan)時，荒管(guan)(guan)(guan)可(ke)(ke)(ke)以(yi)看做是(shi)(shi)(shi)在(zai)不(bu)(bu)同直徑(jing)(jing)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)間連(lian)續(xu)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)形成的(de)(de)(de)(de)，穿在(zai)不(bu)(bu)銹(xiu)鋼管(guan)(guan)(guan)中的(de)(de)(de)(de)芯(xin)棒(bang)可(ke)(ke)(ke)以(yi)看做是(shi)(shi)(shi)曲率(lv)半徑(jing)(jing)無(wu)窮大的(de)(de)(de)(de)內(nei)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)。浮動(dong)芯(xin)棒(bang)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)時，芯(xin)棒(bang)除受到軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)經(jing)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)傳遞(di)來的(de)(de)(de)(de)作(zuo)用力外(wai)，再(zai)無(wu)其他(ta)外(wai)力作(zuo)用。當軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)頭部經(jing)第(di)一(yi)機(ji)(ji)架(jia)(jia)(jia)咬入(ru)(ru)后(hou)(hou)，隨著軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)逐一(yi)走向后(hou)(hou)面(mian)(mian)的(de)(de)(de)(de)延(yan)伸機(ji)(ji)架(jia)(jia)(jia)，作(zuo)用在(zai)芯(xin)棒(bang)上(shang)的(de)(de)(de)(de)機(ji)(ji)架(jia)(jia)(jia)數相繼增(zeng)多，故芯(xin)棒(bang)速(su)(su)(su)(su)度不(bu)(bu)斷(duan)(duan)提高(gao)，這(zhe)(zhe)個階段稱(cheng)(cheng)為(wei)“咬入(ru)(ru)”階段；當軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)頭部進(jin)入(ru)(ru)最末機(ji)(ji)架(jia)(jia)(jia)后(hou)(hou)，整個軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)處在(zai)連(lian)續(xu)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)管(guan)(guan)(guan)機(ji)(ji)所(suo)有機(ji)(ji)架(jia)(jia)(jia)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)中，芯(xin)棒(bang)速(su)(su)(su)(su)度維(wei)持(chi)不(bu)(bu)變(bian)，稱(cheng)(cheng)為(wei)“穩定(ding)(ding)(ding)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)”階段；當軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)尾部離開第(di)一(yi)機(ji)(ji)架(jia)(jia)(jia)后(hou)(hou)，芯(xin)棒(bang)速(su)(su)(su)(su)度逐級提高(gao)，直到軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)結束，稱(cheng)(cheng)為(wei)“軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)出”階段。軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)工作(zuo)圓(yuan)周速(su)(su)(su)(su)度是(shi)(shi)(shi)按“穩定(ding)(ding)(ding)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)”狀態下(xia)設定(ding)(ding)(ding)的(de)(de)(de)(de)，軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)過(guo)程中軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)又是(shi)(shi)(shi)遵(zun)循著體積(ji)不(bu)(bu)變(bian)定(ding)(ding)(ding)律的(de)(de)(de)(de)。然(ran)而由(you)芯(xin)棒(bang)引起的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)件(jian)速(su)(su)(su)(su)度的(de)(de)(de)(de)升高(gao)，使流入(ru)(ru)后(hou)(hou)面(mian)(mian)機(ji)(ji)架(jia)(jia)(jia)的(de)(de)(de)(de)金(jin)(jin)屬必然(ran)增(zeng)多，也就是(shi)(shi)(shi)說，后(hou)(hou)面(mian)(mian)的(de)(de)(de)(de)機(ji)(ji)架(jia)(jia)(jia)由(you)芯(xin)棒(bang)送人了比其設定(ding)(ding)(ding)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)圓(yuan)周速(su)(su)(su)(su)度所(suo)允許的(de)(de)(de)(de)還(huan)要多的(de)(de)(de)(de)金(jin)(jin)屬，這(zhe)(zhe)就出現了使斷(duan)(duan)面(mian)(mian)積(ji)增(zeng)大的(de)(de)(de)(de)金(jin)(jin)屬積(ji)累。這(zhe)(zhe)種逐步(bu)流入(ru)(ru)的(de)(de)(de)(de)附(fu)加金(jin)(jin)屬造(zao)成的(de)(de)(de)(de)較大斷(duan)(duan)面(mian)(mian)，盡(jin)管(guan)(guan)(guan)在(zai)最后(hou)(hou)的(de)(de)(de)(de)機(ji)(ji)架(jia)(jia)(jia)上(shang)得到了加工，但仍然(ran)導致(zhi)在(zai)荒管(guan)(guan)(guan)的(de)(de)(de)(de)一(yi)些部位上(shang)直徑(jing)(jing)變(bian)大和壁(bi)厚(hou)變(bian)厚(hou)，這(zhe)(zhe)種現象稱(cheng)(cheng)為(wei)“竹(zhu)節”。原則上(shang)講可(ke)(ke)(ke)能在(zai)整根不(bu)(bu)銹(xiu)鋼管(guan)(guan)(guan)上(shang)均出現“竹(zhu)節”。顯然(ran)“竹(zhu)節”現象屬縱向壁(bi)厚(hou)不(bu)(bu)均，對隨后(hou)(hou)的(de)(de)(de)(de)張減(jian)機(ji)(ji)軋(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)制(zhi)是(shi)(shi)(shi)不(bu)(bu)利的(de)(de)(de)(de)，應盡(jin)可(ke)(ke)(ke)能防止(zhi)。

  為了防止(zhi)或(huo)減(jian)(jian)少(shao)“竹節”形成(cheng)，孔型(xing)設計分配壓下(xia)量(liang)時(shi)(shi)，在保(bao)證總延伸(shen)不(bu)變(bian)(bian)的(de)(de)前提下(xia)，適當增(zeng)加前幾架壓下(xia)量(liang)。這樣，就可在后面幾個機架中(zhong)使芯棒速(su)度的(de)(de)躍增(zeng)得到減(jian)(jian)弱(ruo)，從而(er)減(jian)(jian)輕芯棒速(su)度變(bian)(bian)化的(de)(de)影響。良好(hao)的(de)(de)芯棒潤(run)滑有利于延伸(shen)和降低能耗，也可以減(jian)(jian)少(shao)竹節的(de)(de)形成(cheng)。還可以采(cai)用電(dian)(dian)控技術防止(zhi)竹節的(de)(de)產(chan)生(sheng)，由電(dian)(dian)子計算機進(jin)行預(yu)設定，軋輥轉速(su)按要求變(bian)(bian)化，當軋件通過時(shi)(shi)對軋輥轉速(su)進(jin)行校準，使各機架的(de)(de)出口速(su)度與芯棒速(su)度的(de)(de)變(bian)(bian)化相適應(ying)。

  盡管(guan)(guan)對“竹節”現(xian)象(xiang)采取了(le)不(bu)少(shao)措施(shi)并取得了(le)一定的效果，但軋制(zhi)條(tiao)件(jian)的變化依然存在(zai)，且成(cheng)品管(guan)(guan)的尺寸(cun)精度始終不(bu)如限動(dong)芯(xin)棒(bang)軋機(ji)。此外，芯(xin)棒(bang)長，使(shi)制(zhi)造(zao)(zao)費用(yong)加大(da)(da)，制(zhi)造(zao)(zao)困(kun)難(nan)，且長芯(xin)棒(bang)的重(zhong)(zhong)量也很大(da)(da)，不(bu)銹鋼(gang)管(guan)(guan)帶著過重(zhong)(zhong)的芯(xin)棒(bang)在(zai)輥(gun)道(dao)上運行將會導致(zhi)不(bu)銹鋼(gang)管(guan)(guan)表面損(sun)傷(shang)。故目前浮動(dong)芯(xin)棒(bang)連(lian)續軋管(guan)(guan)機(ji)均用(yong)于小(xiao)型機(ji)組，至今這種(zhong)機(ji)組僅能(neng)生(sheng)產直徑(jing)小(xiao)于177.8mm以下的不(bu)銹鋼(gang)管(guan)(guan)。浮動(dong)芯(xin)棒(bang)連(lian)續軋管(guan)(guan)機(ji)機(ji)組在(zai)20世紀70年(nian)代(dai)之前比(bi)較盛行。