將板、帶鋼在輥式冷彎成型機上，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)式冷彎(wan)(wan)(wan)(wan)(wan)成(cheng)型(xing)和(he)(he)普通軋(ya)(ya)(ya)制過(guo)程一(yi)(yi)樣(yang)，冷彎(wan)(wan)(wan)(wan)(wan)成(cheng)型(xing)時帶(dai)(dai)坯(pi)(pi)(pi)任意(yi)斷面(mian)上的金屬流動是穩(wen)定的，不隨時間而(er)(er)(er)變(bian)化，相(xiang)鄰兩道次之間帶(dai)(dai)坯(pi)(pi)(pi)進入軋(ya)(ya)(ya)輥(gun)位(wei)置，如圖5-10所(suo)示，彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)角(jiao)由上一(yi)(yi)道次的αn-1增(zeng)大(da)到(dao)下一(yi)(yi)道次的αn,彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)圓(yuan)弧半(ban)徑由rn-1,減小為rn.由于板(ban)(ban)坯(pi)(pi)(pi)前(qian)(qian)(qian)端部(bu)上拾(shi)，彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)角(jiao)增(zeng)大(da)，而(er)(er)(er)產(chan)生的張(zhang)力(li)作用于邊(bian)(bian)部(bu)，在(zai)相(xiang)對旋(xuan)轉的軋(ya)(ya)(ya)輥(gun)的作用下，板(ban)(ban)帶(dai)(dai)坯(pi)(pi)(pi)沿(yan)軋(ya)(ya)(ya)制方(fang)向(xiang)前(qian)(qian)(qian)進并實現(xian)(xian)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)變(bian)形(xing)(xing)(xing)。實現(xian)(xian)板(ban)(ban)坯(pi)(pi)(pi)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)變(bian)形(xing)(xing)(xing)的軋(ya)(ya)(ya)輥(gun)工作部(bu)分稱(cheng)為軋(ya)(ya)(ya)槽(cao)（輥(gun)槽(cao)），由兩個(ge)和(he)(he)兩個(ge)以上通過(guo)軋(ya)(ya)(ya)輥(gun)軸(zhou)(zhou)平(ping)(ping)面(mian)所(suo)構成(cheng)的軋(ya)(ya)(ya)槽(cao)斷面(mian)變(bian)形(xing)(xing)(xing)區(qu)(qu)(qu)稱(cheng)為孔(kong)(kong)型(xing)。因此，輥(gun)式冷彎(wan)(wan)(wan)(wan)(wan)成(cheng)型(xing)亦(yi)可視為板(ban)(ban)坯(pi)(pi)(pi)經(jing)若干孔(kong)(kong)型(xing)實現(xian)(xian)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)的穩(wen)態變(bian)形(xing)(xing)(xing)過(guo)程。從(cong)上一(yi)(yi)道輥(gun)軸(zhou)(zhou)平(ping)(ping)面(mian)（孔(kong)(kong)型(xing)）到(dao)下一(yi)(yi)道輥(gun)軸(zhou)(zhou)平(ping)(ping)面(mian)（孔(kong)(kong)型(xing)）間距離L稱(cheng)為平(ping)(ping)緩(huan)過(guo)渡(du)(du)區(qu)(qu)(qu)長(chang)度。L的大(da)小與(yu)機架(jia)間距有關，L愈(yu)大(da)變(bian)形(xing)(xing)(xing)愈(yu)緩(huan)和(he)(he)。而(er)(er)(er)平(ping)(ping)緩(huan)過(guo)渡(du)(du)區(qu)(qu)(qu)又可細(xi)分為L1和(he)(he)L2兩個(ge)區(qu)(qu)(qu)（見圖5-11).板(ban)(ban)坯(pi)(pi)(pi)從(cong)前(qian)(qian)(qian)道孔(kong)(kong)型(xing)（對應(ying)(ying)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)角(jiao)an-1)進入下道孔(kong)(kong)型(xing)（對應(ying)(ying)彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)角(jiao)αn),開(kai)始時坯(pi)(pi)(pi)料(liao)前(qian)(qian)(qian)端部(bu)分與(yu)軋(ya)(ya)(ya)輥(gun)下軋(ya)(ya)(ya)槽(cao)接(jie)觸(chu)，在(zai)坯(pi)(pi)(pi)料(liao)中形(xing)(xing)(xing)成(cheng)數值不大(da)的彈(dan)性應(ying)(ying)力(li)。軋(ya)(ya)(ya)件(jian)前(qian)(qian)(qian)行與(yu)上軋(ya)(ya)(ya)槽(cao)接(jie)觸(chu)，在(zai)上下軋(ya)(ya)(ya)槽(cao)作用下產(chan)生塑性彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)，即板(ban)(ban)坯(pi)(pi)(pi)在(zai)輥(gun)軸(zhou)(zhou)平(ping)(ping)面(mian)前(qian)(qian)(qian)（未通過(guo)an孔(kong)(kong)型(xing)）已開(kai)始了塑性彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)變(bian)形(xing)(xing)(xing)，原來(lai)平(ping)(ping)直的邊(bian)(bian)部(bu)產(chan)生縱向(xiang)扭曲(qu)(qu)，形(xing)(xing)(xing)成(cheng)復雜的曲(qu)(qu)線表面(mian)。坯(pi)(pi)(pi)料(liao)的橫截面(mian)形(xing)(xing)(xing)狀逐漸按孔(kong)(kong)型(xing)輪廓形(xing)(xing)(xing)狀變(bian)化。彎(wan)(wan)(wan)(wan)(wan)折處金屬連續經(jing)受(shou)彈(dan)性到(dao)彈(dan)塑性變(bian)形(xing)(xing)(xing)。隨彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)角(jiao)增(zeng)大(da)，彎(wan)(wan)(wan)(wan)(wan)曲(qu)(qu)圓(yuan)弧半(ban)徑減小，彎(wan)(wan)(wan)(wan)(wan)折處切向(xiang)正應(ying)(ying)力(li)和(he)(he)彎(wan)(wan)(wan)(wan)(wan)矩增(zeng)加(jia)，在(zai)板(ban)(ban)坯(pi)(pi)(pi)料(liao)前(qian)(qian)(qian)端已變(bian)形(xing)(xing)(xing)部(bu)分與(yu)軋(ya)(ya)(ya)輥(gun)壓(ya)緊軋(ya)(ya)(ya)件(jian)的共同作用下，板(ban)(ban)坯(pi)(pi)(pi)邊(bian)(bian)部(bu)出(chu)現(xian)(xian)拉應(ying)(ying)力(li)，引(yin)起邊(bian)(bian)部(bu)拉伸，板(ban)(ban)坯(pi)(pi)(pi)通過(guo)軋(ya)(ya)(ya)輥(gun)軸(zhou)(zhou)平(ping)(ping)面(mian)之后（通過(guo)孔(kong)(kong)型(xing)后），原來(lai)產(chan)生縱向(xiang)扭曲(qu)(qu)的邊(bian)(bian)部(bu)被拉平(ping)(ping)，輥(gun)軸(zhou)(zhou)平(ping)(ping)面(mian)前(qian)(qian)(qian)變(bian)形(xing)(xing)(xing)區(qu)(qu)(qu)長(chang)度不再增(zeng)加(jia)而(er)(er)(er)保持長(chang)度不變(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(liao)橫(heng)截面(mian)各個直線(xian)部(bu)分受(shou)縱(zong)向拉伸或壓(ya)縮(suo)變形，與(yu)之相鄰(lin)的曲線(xian)部(bu)分受(shou)彎曲變形，弄清(qing)板(ban)坯(pi)在(zai)相鄰(lin)兩道次間彎曲變形行(xing)為，對于(yu)制定(ding)成(cheng)型方案和設(she)計孔(kong)型具有一定(ding)的意義。

為將(jiang)板帶材(cai)(cai)經連續輥彎(wan)變(bian)形(xing)加工(gong)成(cheng)(cheng)合格冷彎(wan)型(xing)(xing)(xing)(xing)鋼而(er)進行的成(cheng)(cheng)型(xing)(xing)(xing)(xing)方法及工(gong)具的設(she)計(ji)稱為冷彎(wan)成(cheng)(cheng)型(xing)(xing)(xing)(xing)輥孔型(xing)(xing)(xing)(xing)設(she)計(ji)。冷彎(wan)成(cheng)(cheng)型(xing)(xing)(xing)(xing)輥孔型(xing)(xing)(xing)(xing)設(she)計(ji)的依據是(shi)：冷彎(wan)型(xing)(xing)(xing)(xing)材(cai)(cai)產(chan)品標準、成(cheng)(cheng)型(xing)(xing)(xing)(xing)材(cai)(cai)料的性能、技術要求、生產(chan)機組配置及主(zhu)要參數。

1. 孔(kong)型設計的要求

 ①. 能夠生產出(chu)符合技術要(yao)求的產品斷(duan)面形狀及(ji)尺寸精度。

 ②. 產品在全長上無(wu)水平垂直(zhi)瓢曲及縱向扭轉。

 ③. 彎折(zhe)處減薄及斷(duan)面殘余(yu)應(ying)力最小，產品無邊(bian)波、皺折(zhe)及裂紋。

 ④. 金屬(shu)出人孔型順(shun)利，軋輥安裝調整方便。

 ⑤. 孔型組合(he)配置合(he)理(li)、孔型磨損小(xiao)、輥耗(hao)低、能耗(hao)小(xiao)。

 ⑥. 操作方便，可達(da)最大(da)機組生(sheng)產率。

2. 冷彎成型(xing)輥孔型(xing)設計步驟

 ①. 確(que)定坯料寬度。

 ②. 確定型鋼對水平輥中心(xin)線的位置。

 ③. 選擇型(xing)鋼(gang)成型(xing)基本中心線（簡稱基軸）及基準線段。

 ④. 確定型鋼(gang)過渡斷面數(shu)量和形狀（俗(su)稱(cheng)花(hua)形圖）。

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

 ⑥. 導衛及(ji)輔助工具設(she)計(ji)及(ji)圖紙的繪制(zhi)。

 ⑦. 必要(yao)的校核(he)。