冷彎成型產品在(zai)生產加工時一定要(yao)注意產品的彈性變形(xing)和在(zai)成型過程(cheng)中(zhong)形(xing)成的張力(li)，主要(yao)特(te)點如下(xia)：
1. 產(chan)品(pin)的彈性變(bian)形(xing)
冷(leng)彎產品質量很大程度上取決于冷(leng)彎成(cheng)(cheng)型(xing)機(ji)的(de)(de)精度。欲正確調整冷(leng)彎成(cheng)(cheng)型(xing)機(ji)，必須要(yao)預先確定(ding)金屬對輥的(de)(de)壓力與輥縫(feng)之間(jian)的(de)(de)變(bian)(bian)(bian)化關(guan)系，即彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)情況。成(cheng)(cheng)型(xing)機(ji)的(de)(de)彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)由工作輥、軸(zhou)(zhou)承(cheng)及軸(zhou)(zhou)承(cheng)座、機(ji)架牌坊、壓下(xia)裝(zhuang)置等的(de)(de)彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)和(he)安裝(zhuang)間(jian)隙組成(cheng)(cheng)。研究(jiu)表明(ming)，當總(zong)負載(zai)不大時(shi)，軋(ya)輥彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)僅占總(zong)彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)的(de)(de)25%;而當載(zai)荷大時(shi)（達200kN),成(cheng)(cheng)型(xing)輥彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)占總(zong)彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)的(de)(de)70%。可見成(cheng)(cheng)型(xing)輥的(de)(de)彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)是成(cheng)(cheng)型(xing)機(ji)彈(dan)性(xing)(xing)變(bian)(bian)(bian)形(xing)中的(de)(de)主要(yao)部分(fen)。
生產實際及理論計算表明，對(dui)于（1~4)mm×(400~1500)mm冷(leng)彎成(cheng)型機，當冷(leng)彎集中載荷為200kN時，成(cheng)型輥彈性變形達1.49mm.
成型機彈(dan)(dan)(dan)(dan)(dan)性(xing)(xing)變(bian)形(xing)對產品(pin)質量的影(ying)響可(ke)在(zai)成型輥(gun)孔型設(she)計中設(she)置輥(gun)縫時(shi)加(jia)以補償。它應等于金屬(shu)料厚度與彈(dan)(dan)(dan)(dan)(dan)跳間距(ju)差值。另(ling)外，冷(leng)彎(wan)(wan)生產實(shi)(shi)踐及理(li)論研(yan)究表(biao)明，冷(leng)彎(wan)(wan)過程中除(chu)塑(su)性(xing)(xing)變(bian)形(xing)外，還存在(zai)彈(dan)(dan)(dan)(dan)(dan)性(xing)(xing)變(bian)形(xing)和(he)彈(dan)(dan)(dan)(dan)(dan)塑(su)性(xing)(xing)變(bian)形(xing)共(gong)存的狀(zhuang)況，當金屬(shu)移出孔型后，彎(wan)(wan)曲角(jiao)要(yao)發生變(bian)化(hua)。如圖5-16(a)所(suo)示，設(she)計彎(wan)(wan)曲角(jiao)為β,移出孔型后會回(hui)(hui)彈(dan)(dan)(dan)(dan)(dan)γ角(jiao)度，因(yin)此欲得精確形(xing)狀(zhuang)產品(pin)，成品(pin)道(dao)次(ci)應考慮過量彎(wan)(wan)角(jiao)度，以彌(mi)補回(hui)(hui)彈(dan)(dan)(dan)(dan)(dan)，見(jian)圖5-16(b).實(shi)(shi)踐證明，材料彈(dan)(dan)(dan)(dan)(dan)性(xing)(xing)極限越(yue)(yue)(yue)大，回(hui)(hui)彈(dan)(dan)(dan)(dan)(dan)就越(yue)(yue)(yue)大，材料越(yue)(yue)(yue)厚回(hui)(hui)彈(dan)(dan)(dan)(dan)(dan)越(yue)(yue)(yue)大，彎(wan)(wan)曲臂(bei)越(yue)(yue)(yue)長(chang)回(hui)(hui)彈(dan)(dan)(dan)(dan)(dan)越(yue)(yue)(yue)大，彎(wan)(wan)曲角(jiao)越(yue)(yue)(yue)多回(hui)(hui)彈(dan)(dan)(dan)(dan)(dan)也(ye)會越(yue)(yue)(yue)大。
此外工藝過(guo)(guo)程的(de)不(bu)(bu)同(tong)(tong)，材料彎(wan)曲時應(ying)力、應(ying)變狀態不(bu)(bu)同(tong)(tong)，回(hui)彈量亦不(bu)(bu)同(tong)(tong)。一般認為，對于簡單斷面冷彎(wan)型(xing)鋼，由于彎(wan)折(zhe)處及邊部存在拉(la)應(ying)力，回(hui)彈較小(xiao)，所以一般可(ke)不(bu)(bu)取過(guo)(guo)量彎(wan)角度，或者僅(jin)考慮30'~1°即可(ke)。而對于波紋(wen)型(xing)鋼，中(zhong)心波要(yao)考慮向內過(guo)(guo)彎(wan)1°,邊波要(yao)大30'。
2. 機組張(zhang)力
在(zai)(zai)冷彎成(cheng)(cheng)型(xing)(xing)機組(zu)上，帶(dai)鋼(gang)前進的(de)驅(qu)動(dong)力(li)是(shi)通過驅(qu)動(dong)輥(gun)(gun)和帶(dai)鋼(gang)之間的(de)摩擦力(li)傳遞(di)的(de)。為了在(zai)(zai)成(cheng)(cheng)型(xing)(xing)過程中形成(cheng)(cheng)張力(li)、不產生堆(dui)鋼(gang)、使成(cheng)(cheng)型(xing)(xing)后型(xing)(xing)鋼(gang)平(ping)直，成(cheng)(cheng)型(xing)(xing)輥(gun)(gun)的(de)平(ping)均輥(gun)(gun)徑(jing)要加(jia)工成(cheng)(cheng)從(cong)(cong)第一(yi)架(jia)開始(shi)逐漸增大的(de)趨勢(shi)，即Dn+1稍(shao)大于Dn,使后一(yi)架(jia)對前一(yi)架(jia)有一(yi)個拉伸作用(yong)。由于直徑(jing)增加(jia)其線速度就會增加(jia)，因此在(zai)(zai)架(jia)次之間就形成(cheng)(cheng)了張力(li)，從(cong)(cong)而帶(dai)鋼(gang)能平(ping)直地運行(xing)。
Dn+1=(1.005~1.010)Dn
式中 Dn 第n架成型輥(gun)平(ping)均(jun)直徑；
Dn+1 第n+1架成型輥平均直徑。
