冷(leng)彎成(cheng)(cheng)型(xing)(xing)產品(pin)(pin)在生產加工(gong)時(shi)一定要注意產品(pin)(pin)的(de)彈(dan)性變形(xing)(xing)和在成(cheng)(cheng)型(xing)(xing)過程中形(xing)(xing)成(cheng)(cheng)的(de)張力(li)，主要特點如下：
1. 產品(pin)的彈性變(bian)形
冷(leng)彎(wan)產品質量很大(da)程度上取(qu)決于冷(leng)彎(wan)成(cheng)(cheng)(cheng)型(xing)機的(de)精度。欲(yu)正(zheng)確調整冷(leng)彎(wan)成(cheng)(cheng)(cheng)型(xing)機，必(bi)須要(yao)(yao)預先確定金屬對輥(gun)(gun)的(de)壓力與輥(gun)(gun)縫之間的(de)變化(hua)關系(xi)，即(ji)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)情況。成(cheng)(cheng)(cheng)型(xing)機的(de)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)由工作輥(gun)(gun)、軸承及軸承座、機架牌坊、壓下裝置(zhi)等(deng)的(de)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)和安裝間隙(xi)組成(cheng)(cheng)(cheng)。研究表明，當總(zong)(zong)負(fu)載不(bu)大(da)時，軋輥(gun)(gun)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)僅占總(zong)(zong)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)的(de)25%;而(er)當載荷大(da)時（達200kN),成(cheng)(cheng)(cheng)型(xing)輥(gun)(gun)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)占總(zong)(zong)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)的(de)70%。可見成(cheng)(cheng)(cheng)型(xing)輥(gun)(gun)的(de)彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)是成(cheng)(cheng)(cheng)型(xing)機彈(dan)(dan)性(xing)(xing)(xing)(xing)變形(xing)中(zhong)的(de)主要(yao)(yao)部分。
生產實際及理論(lun)計算表明，對于（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(bian)形達1.49mm.
成型(xing)機彈(dan)(dan)(dan)性(xing)變(bian)形對(dui)產(chan)品(pin)質(zhi)量的影響可在成型(xing)輥(gun)孔(kong)型(xing)設(she)計中(zhong)設(she)置輥(gun)縫時加以補(bu)償。它(ta)應等于(yu)金屬料厚度與彈(dan)(dan)(dan)跳間(jian)距差(cha)值。另外，冷彎(wan)(wan)生產(chan)實(shi)踐(jian)(jian)及理論研(yan)究表明(ming)，冷彎(wan)(wan)過程中(zhong)除塑(su)性(xing)變(bian)形外，還(huan)存(cun)在彈(dan)(dan)(dan)性(xing)變(bian)形和(he)彈(dan)(dan)(dan)塑(su)性(xing)變(bian)形共存(cun)的狀況，當金屬移出孔(kong)型(xing)后(hou)(hou)，彎(wan)(wan)曲(qu)(qu)角要(yao)發(fa)生變(bian)化。如圖5-16(a)所示(shi)，設(she)計彎(wan)(wan)曲(qu)(qu)角為(wei)β,移出孔(kong)型(xing)后(hou)(hou)會回(hui)彈(dan)(dan)(dan)γ角度，因(yin)此欲得精確形狀產(chan)品(pin)，成品(pin)道次應考慮過量彎(wan)(wan)角度，以彌補(bu)回(hui)彈(dan)(dan)(dan)，見(jian)圖5-16(b).實(shi)踐(jian)(jian)證明(ming)，材料彈(dan)(dan)(dan)性(xing)極限越(yue)(yue)(yue)大(da)(da)(da)，回(hui)彈(dan)(dan)(dan)就越(yue)(yue)(yue)大(da)(da)(da)，材料越(yue)(yue)(yue)厚回(hui)彈(dan)(dan)(dan)越(yue)(yue)(yue)大(da)(da)(da)，彎(wan)(wan)曲(qu)(qu)臂越(yue)(yue)(yue)長回(hui)彈(dan)(dan)(dan)越(yue)(yue)(yue)大(da)(da)(da)，彎(wan)(wan)曲(qu)(qu)角越(yue)(yue)(yue)多回(hui)彈(dan)(dan)(dan)也會越(yue)(yue)(yue)大(da)(da)(da)。
此外(wai)工藝過程(cheng)的(de)不(bu)同，材料彎(wan)曲時應力、應變狀態不(bu)同，回彈量亦不(bu)同。一般認為，對(dui)于(yu)(yu)簡單斷面冷彎(wan)型鋼，由于(yu)(yu)彎(wan)折處(chu)及邊部存(cun)在拉(la)應力，回彈較小，所以(yi)一般可(ke)(ke)不(bu)取過量彎(wan)角度，或(huo)者僅考(kao)慮30'~1°即可(ke)(ke)。而對(dui)于(yu)(yu)波(bo)紋型鋼，中心波(bo)要考(kao)慮向內過彎(wan)1°,邊波(bo)要大30'。
2. 機(ji)組張力
在冷彎成型(xing)機組上，帶(dai)鋼(gang)(gang)前進的驅動力是通過驅動輥(gun)和帶(dai)鋼(gang)(gang)之間(jian)的摩(mo)擦力傳遞(di)的。為了在成型(xing)過程中(zhong)形(xing)成張力、不產生(sheng)堆鋼(gang)(gang)、使成型(xing)后型(xing)鋼(gang)(gang)平直，成型(xing)輥(gun)的平均輥(gun)徑要加工成從(cong)(cong)第一(yi)(yi)架(jia)開始逐漸增(zeng)大(da)(da)的趨勢(shi)，即Dn+1稍大(da)(da)于Dn,使后一(yi)(yi)架(jia)對前一(yi)(yi)架(jia)有一(yi)(yi)個拉伸作用。由于直徑增(zeng)加其(qi)線速度就會增(zeng)加，因此在架(jia)次之間(jian)就形(xing)成了張力，從(cong)(cong)而帶(dai)鋼(gang)(gang)能平直地運行。
Dn+1=(1.005~1.010)Dn
式中 Dn 第n架成(cheng)型(xing)輥平均直徑(jing)；
Dn+1 第n+1架成型輥平均直徑。
