鈦法蘭熱加工注意細節!
熱加(jia)工(gong),主要是(shi)鍛造、軋制和擠壓是(shi)半成品及產(chan)品的(de)(de)基本生產(chan)手(shou)段。鑒于鈦法蘭組織結構對熱加(jia)工(gong)工(gong)藝具(ju)毛根強的(de)(de)敏感性,因此正確選擇和掌握工(gong)藝參數不僅對保(bao)證(zheng)產(chan)品的(de)(de)外形(xing)尺寸精度十分重要,同(tong)時對產(chan)品的(de)(de)內在質量也是(shi)關鍵因素(su)。
和一般金屬結構材料相(xiang)比,鈦法蘭的(de)(de)(de)熱加工(gong)(gong)(gong)特點是變(bian)(bian)形(xing)(xing)(xing)(xing)抗力(li)大(da),變(bian)(bian)形(xing)(xing)(xing)(xing)溫(wen)度(du)范圍(wei)狹窄。六方晶(jing)體結構的(de)(de)(de)鈦,不易(yi)變(bian)(bian)形(xing)(xing)(xing)(xing)。為提(ti)高塑性,就需將金屬加熱到相(xiang)變(bian)(bian)點以上的(de)(de)(de)b相(xiang)區,進(jin)行所謂b加工(gong)(gong)(gong)。但(dan)(dan)由于鈦法蘭過熱傾向大(da),高溫(wen)加熱將引起(qi)b晶(jing)粒急劇長大(da),但(dan)(dan)若變(bian)(bian)形(xing)(xing)(xing)(xing)量不足,冷(leng)卻后(hou)形(xing)(xing)(xing)(xing)成粗(cu)大(da)魏氏(shi)組(zu)織(zhi)則(ze)會明(ming)顯降(jiang)低合金的(de)(de)(de)期性與疲勞強度(du),而(er)月這種過熱組(zu)織(zhi)在(zai)隨后(hou)的(de)(de)(de)熱處(chu)理中艱以消除,因此目前(qian)生產中對(dui)(dui)(dui)成品(pin)或成品(pin)前(qian)一火(huo)的(de)(de)(de)熱加工(gong)(gong)(gong)起(qi)始溫(wen)度(du)規定不用過臨界(jie)點Tb。由于鈦法蘭的(de)(de)(de)變(bian)(bian)形(xing)(xing)(xing)(xing)抗力(li)對(dui)(dui)(dui)變(bian)(bian)形(xing)(xing)(xing)(xing)溫(wen)度(du)的(de)(de)(de)降(jiang)低或變(bian)(bian)形(xing)(xing)(xing)(xing)速率的(de)(de)(de)提(ti)高非常敏感,以至停鍛溫(wen)度(du)也不能過低。這兩方面因素(su)的(de)(de)(de)約(yue)束,使大(da)多數鈦法蘭的(de)(de)(de)成品(pin)加工(gong)(gong)(gong)溫(wen)度(du)范圍(wei)限制在(zai)800一950℃之間,掌握起(qi)來很不容易(yi)。但(dan)(dan)對(dui)(dui)(dui)鑄錠的(de)(de)(de)開坯,溫(wen)度(du)范圍(wei)可以擴大(da)到850一1150℃,在(zai)隨后(hou)火(huo)次的(de)(de)(de)加工(gong)(gong)(gong)過程中,再逐次降(jiang)低溫(wen)度(du)。
鈦法蘭合金導(dao)熱(re)性差,在快速變(bian)形(xing)時,工(gong)件(jian)心部(bu)溫升快,因熱(re)量傳(chuan)遞慢(man)而(er)容易造成(cheng)過(guo)熱(re),而(er)工(gong)件(jian)表面溫度則(ze)較(jiao)低,又易形(xing)成(cheng)表面裂紋(wen),故加工(gong)過(guo)程中需(xu)注(zhu)意掌握變(bian)形(xing)速率和變(bian)形(xing)量。