將板、帶鋼在輥式冷彎(wan)成型(xing)機上，經若干架次相對旋轉的成型輥（水平輥、立輥、組合輥）連續彎曲變形以得到要求的形狀尺寸的冷彎型鋼的過程稱為輥式冷彎成型。輥式冷彎成型是金屬壓力加工工藝的一種，其成型過程如圖5-9所示。平板坯的特定部位經漸次彎曲成角度a2、a2、α3、···an,最后成為所要求的斷面。輥式冷彎成型與型鋼熱軋不同之處是，其各道次金屬橫截面積從理論上可視為不變。這種變形也不同于非穩態變形的沖壓成型，從一個角度彎至下一道的某一角度，在板坯全長上不是同時成型的，而是經過一個平緩過渡后，逐漸彎成需要的角度。

 輥(gun)(gun)式冷彎(wan)(wan)(wan)(wan)(wan)成(cheng)(cheng)(cheng)型(xing)(xing)(xing)和(he)普通(tong)軋(ya)制過(guo)(guo)(guo)程一(yi)(yi)樣，冷彎(wan)(wan)(wan)(wan)(wan)成(cheng)(cheng)(cheng)型(xing)(xing)(xing)時(shi)帶(dai)(dai)坯(pi)任意斷面(mian)(mian)(mian)上的金屬(shu)流動是穩定的，不(bu)(bu)隨(sui)時(shi)間(jian)而變(bian)化，相鄰兩道次之(zhi)間(jian)帶(dai)(dai)坯(pi)進(jin)入軋(ya)輥(gun)(gun)位置，如圖(tu)5-10所(suo)示，彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)角由上一(yi)(yi)道次的αn-1增(zeng)(zeng)大(da)到下(xia)(xia)(xia)一(yi)(yi)道次的αn,彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)圓弧半徑由rn-1,減小為(wei)rn.由于板坯(pi)前(qian)(qian)(qian)端(duan)(duan)部(bu)(bu)上拾，彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)角增(zeng)(zeng)大(da)，而產(chan)(chan)生(sheng)(sheng)的張力(li)作用于邊(bian)部(bu)(bu)，在(zai)(zai)相對(dui)(dui)旋轉(zhuan)的軋(ya)輥(gun)(gun)的作用下(xia)(xia)(xia)，板帶(dai)(dai)坯(pi)沿軋(ya)制方(fang)向前(qian)(qian)(qian)進(jin)并(bing)實現彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)變(bian)形(xing)(xing)(xing)。實現板坯(pi)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)變(bian)形(xing)(xing)(xing)的軋(ya)輥(gun)(gun)工作部(bu)(bu)分(fen)稱為(wei)軋(ya)槽(cao)(cao)（輥(gun)(gun)槽(cao)(cao)），由兩個(ge)和(he)兩個(ge)以上通(tong)過(guo)(guo)(guo)軋(ya)輥(gun)(gun)軸(zhou)平(ping)面(mian)(mian)(mian)所(suo)構(gou)成(cheng)(cheng)(cheng)的軋(ya)槽(cao)(cao)斷面(mian)(mian)(mian)變(bian)形(xing)(xing)(xing)區(qu)稱為(wei)孔(kong)型(xing)(xing)(xing)。因此，輥(gun)(gun)式冷彎(wan)(wan)(wan)(wan)(wan)成(cheng)(cheng)(cheng)型(xing)(xing)(xing)亦(yi)可(ke)視為(wei)板坯(pi)經(jing)若干孔(kong)型(xing)(xing)(xing)實現彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)的穩態變(bian)形(xing)(xing)(xing)過(guo)(guo)(guo)程。從(cong)上一(yi)(yi)道輥(gun)(gun)軸(zhou)平(ping)面(mian)(mian)(mian)（孔(kong)型(xing)(xing)(xing)）到下(xia)(xia)(xia)一(yi)(yi)道輥(gun)(gun)軸(zhou)平(ping)面(mian)(mian)(mian)（孔(kong)型(xing)(xing)(xing)）間(jian)距離L稱為(wei)平(ping)緩過(guo)(guo)(guo)渡(du)區(qu)長(chang)度。L的大(da)小與(yu)機架間(jian)距有關(guan)，L愈(yu)大(da)變(bian)形(xing)(xing)(xing)愈(yu)緩和(he)。而平(ping)緩過(guo)(guo)(guo)渡(du)區(qu)又可(ke)細分(fen)為(wei)L1和(he)L2兩個(ge)區(qu)（見圖(tu)5-11).板坯(pi)從(cong)前(qian)(qian)(qian)道孔(kong)型(xing)(xing)(xing)（對(dui)(dui)應(ying)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)角an-1)進(jin)入下(xia)(xia)(xia)道孔(kong)型(xing)(xing)(xing)（對(dui)(dui)應(ying)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)角αn),開(kai)始時(shi)坯(pi)料(liao)前(qian)(qian)(qian)端(duan)(duan)部(bu)(bu)分(fen)與(yu)軋(ya)輥(gun)(gun)下(xia)(xia)(xia)軋(ya)槽(cao)(cao)接(jie)觸(chu)，在(zai)(zai)坯(pi)料(liao)中(zhong)形(xing)(xing)(xing)成(cheng)(cheng)(cheng)數(shu)值不(bu)(bu)大(da)的彈性(xing)(xing)(xing)(xing)應(ying)力(li)。軋(ya)件(jian)前(qian)(qian)(qian)行與(yu)上軋(ya)槽(cao)(cao)接(jie)觸(chu)，在(zai)(zai)上下(xia)(xia)(xia)軋(ya)槽(cao)(cao)作用下(xia)(xia)(xia)產(chan)(chan)生(sheng)(sheng)塑性(xing)(xing)(xing)(xing)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)，即板坯(pi)在(zai)(zai)輥(gun)(gun)軸(zhou)平(ping)面(mian)(mian)(mian)前(qian)(qian)(qian)（未通(tong)過(guo)(guo)(guo)an孔(kong)型(xing)(xing)(xing)）已開(kai)始了塑性(xing)(xing)(xing)(xing)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)變(bian)形(xing)(xing)(xing)，原來平(ping)直的邊(bian)部(bu)(bu)產(chan)(chan)生(sheng)(sheng)縱向扭曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)，形(xing)(xing)(xing)成(cheng)(cheng)(cheng)復(fu)雜(za)的曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)線表面(mian)(mian)(mian)。坯(pi)料(liao)的橫截(jie)面(mian)(mian)(mian)形(xing)(xing)(xing)狀逐漸按孔(kong)型(xing)(xing)(xing)輪(lun)廓形(xing)(xing)(xing)狀變(bian)化。彎(wan)(wan)(wan)(wan)(wan)折處金屬(shu)連(lian)續(xu)經(jing)受彈性(xing)(xing)(xing)(xing)到彈塑性(xing)(xing)(xing)(xing)變(bian)形(xing)(xing)(xing)。隨(sui)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)角增(zeng)(zeng)大(da)，彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)圓弧半徑減小，彎(wan)(wan)(wan)(wan)(wan)折處切向正應(ying)力(li)和(he)彎(wan)(wan)(wan)(wan)(wan)矩增(zeng)(zeng)加(jia)，在(zai)(zai)板坯(pi)料(liao)前(qian)(qian)(qian)端(duan)(duan)已變(bian)形(xing)(xing)(xing)部(bu)(bu)分(fen)與(yu)軋(ya)輥(gun)(gun)壓緊軋(ya)件(jian)的共同作用下(xia)(xia)(xia)，板坯(pi)邊(bian)部(bu)(bu)出(chu)現拉應(ying)力(li)，引起邊(bian)部(bu)(bu)拉伸，板坯(pi)通(tong)過(guo)(guo)(guo)軋(ya)輥(gun)(gun)軸(zhou)平(ping)面(mian)(mian)(mian)之(zhi)后（通(tong)過(guo)(guo)(guo)孔(kong)型(xing)(xing)(xing)后），原來產(chan)(chan)生(sheng)(sheng)縱向扭曲(qu)(qu)(qu)(qu)(qu)(qu)(qu)的邊(bian)部(bu)(bu)被拉平(ping)，輥(gun)(gun)軸(zhou)平(ping)面(mian)(mian)(mian)前(qian)(qian)(qian)變(bian)形(xing)(xing)(xing)區(qu)長(chang)度不(bu)(bu)再增(zeng)(zeng)加(jia)而保(bao)持長(chang)度不(bu)(bu)變(bian)（L)。

 這是平緩過渡區第一階段，整個過程中彎曲角單方向增大（從（an-1增至an+Δan),見圖5-12,并且坯料中性層彎曲圓弧半徑從rn-1減小至rn.通過軸平面后，變形區長度仍有增加，形成平緩過渡區第二階段，彎曲角從an+Δan減小為αn.坯料前端出現彈性變形特征，內應力重新分布，第二階段長度不再增加（L2),在此長度范圍內整個橫截面上內應力彼此相等，呈現第一類殘應力特征。成型過程繼續下去，平緩過渡區保持形狀尺寸不變，其長度通常小于兩機架間距離。

 彎曲角變化呈S形，分為三段。在平緩過渡區任一位置上彎曲角大小可用下式表示.

坯(pi)料橫(heng)截面各個直線(xian)部(bu)分受縱向拉伸或壓縮變形(xing)，與之相鄰的曲線(xian)部(bu)分受彎曲變形(xing)，弄清板(ban)坯(pi)在相鄰兩道次(ci)間彎曲變形(xing)行為，對于制定成型方案和設(she)計(ji)孔型具(ju)有(you)一定的意義。

為將板帶材經連(lian)續(xu)輥(gun)彎(wan)變(bian)形加工成(cheng)合格冷(leng)(leng)彎(wan)型(xing)(xing)鋼而進行的成(cheng)型(xing)(xing)方(fang)法及工具(ju)的設(she)計(ji)稱為冷(leng)(leng)彎(wan)成(cheng)型(xing)(xing)輥(gun)孔型(xing)(xing)設(she)計(ji)。冷(leng)(leng)彎(wan)成(cheng)型(xing)(xing)輥(gun)孔型(xing)(xing)設(she)計(ji)的依(yi)據是：冷(leng)(leng)彎(wan)型(xing)(xing)材產品標(biao)準、成(cheng)型(xing)(xing)材料的性能、技術要求、生產機組配置(zhi)及主要參數。

1. 孔型設計的要求

 ①. 能(neng)夠生產(chan)出符合技術(shu)要求的產(chan)品斷面形狀及尺寸精度。

 ②. 產品在全長上無水平(ping)垂(chui)直瓢曲及縱向(xiang)扭轉(zhuan)。

 ③. 彎折處減薄及(ji)斷(duan)面殘(can)余應力最小，產品無(wu)邊波、皺折及(ji)裂紋(wen)。

 ④. 金屬出人孔型順(shun)利，軋(ya)輥安(an)裝調整方便。

 ⑤. 孔(kong)型組合(he)配置合(he)理、孔(kong)型磨損小、輥耗低、能耗小。

 ⑥. 操作方便，可達最(zui)大機組生(sheng)產率。

2. 冷彎(wan)成(cheng)型輥孔型設計步驟

 ①. 確定坯(pi)料寬度。

 ②. 確定(ding)型鋼對水平輥中心線的位置。

 ③. 選(xuan)擇型(xing)鋼成(cheng)型(xing)基(ji)本中心線（簡稱基(ji)軸）及(ji)基(ji)準線段。

 ④. 確定(ding)型鋼過(guo)渡斷面(mian)數量和形狀（俗(su)稱花形圖）。

 ⑤. 畫斷面配輥(gun)圖和單個軋(ya)輥(gun)及輥(gun)片(pian)圖。

 ⑥. 導衛及(ji)輔助工具(ju)設計及(ji)圖(tu)紙的繪制。

 ⑦. 必要的校核。