鈦及(ji)鈦合金因其優異的綜合性能(neng),廣泛應用(yong)于(yu)航(hang)空(kong)、航(hang)天(tian)、艦船、石(shi)油(you)、化工(gong)(gong)、制(zhi)鹽、制(zhi)堿、冶(ye)金等行(xing)業。目前PTA項(xiang)目使用(yong)的鈦管(guan)(guan)材(cai)主要(yao)(yao)為Gr.2(TA2)純(chun)鈦管(guan)(guan),這(zhe)類管(guan)(guan)材(cai)塑性好,冷加(jia)工(gong)(gong)變(bian)形量(liang)可達80%,但在實(shi)際生產過(guo)程中(zhong),需要(yao)(yao)根據(ju)(ju)設備(bei)能(neng)力狀況選(xuan)(xuan)擇(ze)合適(shi)的變(bian)形量(liang)進行(xing)冷加(jia)工(gong)(gong),經冷加(jia)工(gong)(gong)的管(guan)(guan)材(cai)真空(kong)熱(re)處(chu)理后可繼續(xu)加(jia)工(gong)(gong),最終達到(dao)GB/T 3625、ASME SB338標(biao)準或技(ji)術標(biao)準要(yao)(yao)求。研究(jiu)人員針對(dui)PTA項(xiang)目用(yong)Gr.2(TA2)Φ19mm×1.25mm×Lmm純(chun)鈦管(guan)(guan),依(yi)據(ju)(ju)技(ji)術標(biao)準要(yao)(yao)求,制(zhi)定冷加(jia)工(gong)(gong)工(gong)(gong)藝(yi),研究(jiu)軋(ya)制(zhi)變(bian)形量(liang)及(ji)熱(re)處(chu)理溫度對(dui)管(guan)(guan)材(cai)組(zu)織(zhi)及(ji)性能(neng)的影(ying)響,從(cong)而選(xuan)(xuan)取合適(shi)的變(bian)形量(liang)及(ji)熱(re)處(chu)理溫度,為純(chun)鈦管(guan)(guan)材(cai)批(pi)量(liang)化生產獲得穩定的組(zu)織(zhi)和力學性能(neng)提供參考。
實驗用原材(cai)料為Gr.2(TA2)純鈦,化學成(cheng)(cheng)分(fen)符(fu)合產品(pin)的技(ji)術(shu)要求(qiu)。鑄錠經鍛造(zao)、棒坯(pi)鉆孔、包套擠壓(ya)、除銅酸洗得到(dao)冷軋管坯(pi)。冷變形采用常規冷軋管機進行多道次(ci)軋制(zhi),軋制(zhi)單道次(ci)變形量(liang)控制(zhi)在35%~65%,最終(zhong)得到(dao)Φ19mm×1.25mm成(cheng)(cheng)品(pin)管材(cai),成(cheng)(cheng)品(pin)管材(cai)室溫力(li)學性能應滿(man)足(zu)Rm≥400MPa,Rp0.2=290~400MPa,A≥23%, 其余各項檢測(ce)要求(qiu)滿(man)足(zu)ASME SB338標(biao)準要求(qiu)。
設計48%、60%兩(liang)種(zhong)變形(xing)量進行(xing)冷加(jia)工(gong)(gong),加(jia)工(gong)(gong)后的(de)管材經不同溫(wen)度(500、550、600 和700℃)保溫(wen)120min真空退(tui)火,采用OLYMPUSMPG3顯微鏡觀察縱向(xiang)顯微組織,WAW-1000拉伸試(shi)驗機測試(shi)室溫(wen)力學(xue)性能。試(shi)驗結果(guo)表(biao)明:
(1)冷加工(gong)變(bian)形量為48%,經500℃熱處(chu)理,局部出(chu)現少量等(deng)軸(zhou)晶,90%以(yi)上(shang)為加工(gong)態組織,經550℃熱處(chu)理,可獲得晶粒(li)尺(chi)寸小于5μm的細小等(deng)軸(zhou)晶。冷加工(gong)變(bian)形量達到60%時,經500℃熱處(chu)理,可獲得晶粒(li)尺(chi)寸小于5μm的細小等(deng)軸(zhou)晶。
(2)管材經48%、60%變(bian)(bian)形量冷加工后,采用(yong)不(bu)同熱(re)處(chu)理制度真空退火,由室溫力(li)學性(xing)能(neng)(neng)測試結(jie)果(guo)可以看出:同一(yi)變(bian)(bian)形量條件下(xia)(xia),隨(sui)溫度升高,強(qiang)度降低(di),塑性(xing)增加,當溫度達(da)到700℃時,強(qiang)度大幅降低(di),超出標準要(yao)求下(xia)(xia)限。同一(yi)熱(re)處(chu)理溫度條件下(xia)(xia),隨(sui)變(bian)(bian)形量增大,強(qiang)度降低(di),塑性(xing)增加,然(ran)而,熱(re)處(chu)理溫度為500℃、48%變(bian)(bian)形量條件下(xia)(xia),屈服強(qiang)度遠超出標準要(yao)求值上(shang)限,而60%變(bian)(bian)形量條件下(xia)(xia),各項性(xing)能(neng)(neng)均較(jiao)好(hao)。
(3)冷加(jia)工變(bian)形(xing)量(liang)為(wei)48%,熱(re)(re)處理溫(wen)度選(xuan)擇550~600℃。冷加(jia)工變(bian)形(xing)量(liang)為(wei)60%,熱(re)(re)處理溫(wen)度選(xuan)擇500~600℃,均可(ke)獲得滿意(yi)的力學性能和顯微組(zu)織(zhi)。
