冷彎(wan)成(cheng)型(xing)產(chan)品在生產(chan)加工(gong)時一定(ding)要注意產(chan)品的(de)(de)彈性(xing)變形和在成(cheng)型(xing)過程中形成(cheng)的(de)(de)張力，主要特點如下：
1. 產(chan)品的彈性變形(xing)
冷(leng)(leng)彎(wan)產品(pin)質量(liang)很大程度上(shang)取決于冷(leng)(leng)彎(wan)成(cheng)(cheng)(cheng)型(xing)(xing)機的(de)(de)(de)精(jing)度。欲正確調整冷(leng)(leng)彎(wan)成(cheng)(cheng)(cheng)型(xing)(xing)機，必(bi)須要預先確定金屬對輥(gun)的(de)(de)(de)壓力與(yu)輥(gun)縫之間的(de)(de)(de)變(bian)(bian)(bian)(bian)化(hua)關(guan)系，即彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)情況。成(cheng)(cheng)(cheng)型(xing)(xing)機的(de)(de)(de)彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)由工作輥(gun)、軸(zhou)承(cheng)及軸(zhou)承(cheng)座、機架牌坊、壓下裝(zhuang)置等(deng)的(de)(de)(de)彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)和安裝(zhuang)間隙組成(cheng)(cheng)(cheng)。研究表明(ming)，當總負載(zai)不(bu)大時(shi)，軋輥(gun)彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)僅占總彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)的(de)(de)(de)25%;而(er)當載(zai)荷大時(shi)（達200kN),成(cheng)(cheng)(cheng)型(xing)(xing)輥(gun)彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)占總彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)的(de)(de)(de)70%。可見成(cheng)(cheng)(cheng)型(xing)(xing)輥(gun)的(de)(de)(de)彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)是成(cheng)(cheng)(cheng)型(xing)(xing)機彈(dan)性(xing)變(bian)(bian)(bian)(bian)形(xing)(xing)中的(de)(de)(de)主要部分。
生產實際(ji)及理(li)論計算(suan)表明，對(dui)于(yu)（1~4)mm×(400~1500)mm冷(leng)彎(wan)成(cheng)型(xing)機，當(dang)冷(leng)彎(wan)集中(zhong)載荷為200kN時，成(cheng)型(xing)輥彈性(xing)變(bian)形達(da)1.49mm.
成型(xing)(xing)機彈性變形對產(chan)(chan)品質量(liang)的影響(xiang)可在(zai)成型(xing)(xing)輥(gun)孔型(xing)(xing)設計中設置輥(gun)縫時加以(yi)補償(chang)。它應等(deng)于金屬料(liao)厚度與彈跳間距差值。另外(wai)，冷彎(wan)(wan)(wan)生產(chan)(chan)實(shi)踐及理(li)論研究表明，冷彎(wan)(wan)(wan)過程中除塑性變形外(wai)，還存在(zai)彈性變形和(he)彈塑性變形共存的狀況(kuang)，當金屬移出(chu)孔型(xing)(xing)后，彎(wan)(wan)(wan)曲(qu)(qu)角(jiao)要發生變化。如圖5-16(a)所示，設計彎(wan)(wan)(wan)曲(qu)(qu)角(jiao)為β,移出(chu)孔型(xing)(xing)后會(hui)回(hui)(hui)(hui)彈γ角(jiao)度，因此欲(yu)得(de)精確形狀產(chan)(chan)品，成品道次應考慮過量(liang)彎(wan)(wan)(wan)角(jiao)度，以(yi)彌補回(hui)(hui)(hui)彈，見圖5-16(b).實(shi)踐證明，材料(liao)彈性極限越(yue)大，回(hui)(hui)(hui)彈就越(yue)大，材料(liao)越(yue)厚回(hui)(hui)(hui)彈越(yue)大，彎(wan)(wan)(wan)曲(qu)(qu)臂越(yue)長回(hui)(hui)(hui)彈越(yue)大，彎(wan)(wan)(wan)曲(qu)(qu)角(jiao)越(yue)多(duo)回(hui)(hui)(hui)彈也(ye)會(hui)越(yue)大。
此外工(gong)藝(yi)過(guo)程的不(bu)同，材料彎(wan)曲時應力(li)、應變狀態不(bu)同，回彈量亦不(bu)同。一(yi)般認為，對(dui)于簡(jian)單斷面冷彎(wan)型(xing)鋼(gang)，由于彎(wan)折處及邊部存在拉(la)應力(li)，回彈較小，所以一(yi)般可不(bu)取過(guo)量彎(wan)角(jiao)度，或者(zhe)僅考慮30'~1°即(ji)可。而對(dui)于波(bo)紋型(xing)鋼(gang)，中心波(bo)要考慮向內過(guo)彎(wan)1°,邊波(bo)要大(da)30'。
2. 機組張力
在冷彎成(cheng)型(xing)(xing)(xing)機(ji)組上，帶鋼前進的(de)驅(qu)動力是(shi)通過(guo)驅(qu)動輥(gun)和帶鋼之間(jian)的(de)摩擦力傳遞的(de)。為了(le)在成(cheng)型(xing)(xing)(xing)過(guo)程中形成(cheng)張(zhang)力、不產生堆鋼、使(shi)成(cheng)型(xing)(xing)(xing)后型(xing)(xing)(xing)鋼平直，成(cheng)型(xing)(xing)(xing)輥(gun)的(de)平均輥(gun)徑要加工成(cheng)從第一(yi)架開始逐漸增(zeng)大(da)的(de)趨勢，即Dn+1稍(shao)大(da)于Dn,使(shi)后一(yi)架對(dui)前一(yi)架有一(yi)個(ge)拉伸作用(yong)。由于直徑增(zeng)加其線速(su)度(du)就(jiu)會增(zeng)加，因此(ci)在架次(ci)之間(jian)就(jiu)形成(cheng)了(le)張(zhang)力，從而帶鋼能(neng)平直地運行。
Dn+1=(1.005~1.010)Dn
式中(zhong) Dn 第n架成(cheng)型輥平(ping)均直徑；
Dn+1 第n+1架成型輥平均直徑。
