將板、帶鋼在輥式冷彎成(cheng)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)(gun)(gun)(gun)(gun)式冷彎成(cheng)型(xing)和(he)普通(tong)軋(ya)(ya)(ya)(ya)(ya)制過(guo)程(cheng)一樣，冷彎成(cheng)型(xing)時帶坯(pi)(pi)(pi)(pi)(pi)(pi)任意斷(duan)(duan)面(mian)(mian)(mian)上的(de)(de)金屬(shu)流動是穩定的(de)(de)，不(bu)隨時間(jian)而變化，相(xiang)鄰(lin)兩(liang)(liang)道(dao)次(ci)之間(jian)帶坯(pi)(pi)(pi)(pi)(pi)(pi)進入軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)位置，如圖5-10所示，彎曲(qu)(qu)(qu)(qu)(qu)角(jiao)(jiao)由上一道(dao)次(ci)的(de)(de)αn-1增大到(dao)(dao)下一道(dao)次(ci)的(de)(de)αn,彎曲(qu)(qu)(qu)(qu)(qu)圓(yuan)弧半徑由rn-1,減小為(wei)(wei)(wei)rn.由于板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)前(qian)(qian)(qian)端(duan)部(bu)(bu)(bu)(bu)上拾，彎曲(qu)(qu)(qu)(qu)(qu)角(jiao)(jiao)增大，而產生的(de)(de)張力(li)作(zuo)用(yong)于邊(bian)部(bu)(bu)(bu)(bu)，在(zai)相(xiang)對(dui)旋轉的(de)(de)軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)的(de)(de)作(zuo)用(yong)下，板(ban)(ban)(ban)帶坯(pi)(pi)(pi)(pi)(pi)(pi)沿軋(ya)(ya)(ya)(ya)(ya)制方(fang)向(xiang)前(qian)(qian)(qian)進并實(shi)現(xian)彎曲(qu)(qu)(qu)(qu)(qu)變形(xing)。實(shi)現(xian)板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)彎曲(qu)(qu)(qu)(qu)(qu)變形(xing)的(de)(de)軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)工作(zuo)部(bu)(bu)(bu)(bu)分稱為(wei)(wei)(wei)軋(ya)(ya)(ya)(ya)(ya)槽(cao)（輥(gun)(gun)(gun)(gun)(gun)槽(cao)），由兩(liang)(liang)個(ge)和(he)兩(liang)(liang)個(ge)以上通(tong)過(guo)軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)所構(gou)成(cheng)的(de)(de)軋(ya)(ya)(ya)(ya)(ya)槽(cao)斷(duan)(duan)面(mian)(mian)(mian)變形(xing)區(qu)稱為(wei)(wei)(wei)孔(kong)(kong)(kong)(kong)型(xing)。因此(ci)，輥(gun)(gun)(gun)(gun)(gun)式冷彎成(cheng)型(xing)亦可視為(wei)(wei)(wei)板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)經若干(gan)孔(kong)(kong)(kong)(kong)型(xing)實(shi)現(xian)彎曲(qu)(qu)(qu)(qu)(qu)的(de)(de)穩態變形(xing)過(guo)程(cheng)。從上一道(dao)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)（孔(kong)(kong)(kong)(kong)型(xing)）到(dao)(dao)下一道(dao)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)（孔(kong)(kong)(kong)(kong)型(xing)）間(jian)距離(li)L稱為(wei)(wei)(wei)平(ping)(ping)(ping)(ping)緩過(guo)渡區(qu)長度。L的(de)(de)大小與(yu)(yu)機架間(jian)距有關，L愈(yu)(yu)大變形(xing)愈(yu)(yu)緩和(he)。而平(ping)(ping)(ping)(ping)緩過(guo)渡區(qu)又可細分為(wei)(wei)(wei)L1和(he)L2兩(liang)(liang)個(ge)區(qu)（見圖5-11).板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)從前(qian)(qian)(qian)道(dao)孔(kong)(kong)(kong)(kong)型(xing)（對(dui)應(ying)(ying)彎曲(qu)(qu)(qu)(qu)(qu)角(jiao)(jiao)an-1)進入下道(dao)孔(kong)(kong)(kong)(kong)型(xing)（對(dui)應(ying)(ying)彎曲(qu)(qu)(qu)(qu)(qu)角(jiao)(jiao)αn),開(kai)(kai)始時坯(pi)(pi)(pi)(pi)(pi)(pi)料(liao)(liao)前(qian)(qian)(qian)端(duan)部(bu)(bu)(bu)(bu)分與(yu)(yu)軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)下軋(ya)(ya)(ya)(ya)(ya)槽(cao)接(jie)觸，在(zai)坯(pi)(pi)(pi)(pi)(pi)(pi)料(liao)(liao)中(zhong)形(xing)成(cheng)數(shu)值不(bu)大的(de)(de)彈(dan)性(xing)應(ying)(ying)力(li)。軋(ya)(ya)(ya)(ya)(ya)件(jian)前(qian)(qian)(qian)行與(yu)(yu)上軋(ya)(ya)(ya)(ya)(ya)槽(cao)接(jie)觸，在(zai)上下軋(ya)(ya)(ya)(ya)(ya)槽(cao)作(zuo)用(yong)下產生塑(su)性(xing)彎曲(qu)(qu)(qu)(qu)(qu)，即板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)在(zai)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)前(qian)(qian)(qian)（未通(tong)過(guo)an孔(kong)(kong)(kong)(kong)型(xing)）已開(kai)(kai)始了(le)塑(su)性(xing)彎曲(qu)(qu)(qu)(qu)(qu)變形(xing)，原(yuan)來平(ping)(ping)(ping)(ping)直的(de)(de)邊(bian)部(bu)(bu)(bu)(bu)產生縱(zong)向(xiang)扭曲(qu)(qu)(qu)(qu)(qu)，形(xing)成(cheng)復雜(za)的(de)(de)曲(qu)(qu)(qu)(qu)(qu)線表面(mian)(mian)(mian)。坯(pi)(pi)(pi)(pi)(pi)(pi)料(liao)(liao)的(de)(de)橫截(jie)面(mian)(mian)(mian)形(xing)狀逐漸按孔(kong)(kong)(kong)(kong)型(xing)輪(lun)廓形(xing)狀變化。彎折處(chu)金屬(shu)連(lian)續經受彈(dan)性(xing)到(dao)(dao)彈(dan)塑(su)性(xing)變形(xing)。隨彎曲(qu)(qu)(qu)(qu)(qu)角(jiao)(jiao)增大，彎曲(qu)(qu)(qu)(qu)(qu)圓(yuan)弧半徑減小，彎折處(chu)切向(xiang)正應(ying)(ying)力(li)和(he)彎矩(ju)增加，在(zai)板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)料(liao)(liao)前(qian)(qian)(qian)端(duan)已變形(xing)部(bu)(bu)(bu)(bu)分與(yu)(yu)軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)壓緊軋(ya)(ya)(ya)(ya)(ya)件(jian)的(de)(de)共同作(zuo)用(yong)下，板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)邊(bian)部(bu)(bu)(bu)(bu)出現(xian)拉(la)應(ying)(ying)力(li)，引起邊(bian)部(bu)(bu)(bu)(bu)拉(la)伸，板(ban)(ban)(ban)坯(pi)(pi)(pi)(pi)(pi)(pi)通(tong)過(guo)軋(ya)(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)之后(hou)（通(tong)過(guo)孔(kong)(kong)(kong)(kong)型(xing)后(hou)），原(yuan)來產生縱(zong)向(xiang)扭曲(qu)(qu)(qu)(qu)(qu)的(de)(de)邊(bian)部(bu)(bu)(bu)(bu)被拉(la)平(ping)(ping)(ping)(ping)，輥(gun)(gun)(gun)(gun)(gun)軸(zhou)(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)前(qian)(qian)(qian)變形(xing)區(qu)長度不(bu)再增加而保持長度不(bu)變（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.

坯料橫截面各個直線部(bu)分(fen)(fen)受(shou)縱向拉伸或壓(ya)縮變形(xing)，與之(zhi)相(xiang)鄰的曲(qu)線部(bu)分(fen)(fen)受(shou)彎(wan)(wan)曲(qu)變形(xing)，弄清板坯在相(xiang)鄰兩道次間彎(wan)(wan)曲(qu)變形(xing)行為，對于制定(ding)(ding)成型方案(an)和設計孔型具(ju)有(you)一定(ding)(ding)的意義。

為將板帶材經連續輥(gun)彎(wan)(wan)變形加工成合格(ge)冷彎(wan)(wan)型(xing)鋼而進行的(de)成型(xing)方法及(ji)工具的(de)設(she)計(ji)(ji)稱(cheng)為冷彎(wan)(wan)成型(xing)輥(gun)孔型(xing)設(she)計(ji)(ji)。冷彎(wan)(wan)成型(xing)輥(gun)孔型(xing)設(she)計(ji)(ji)的(de)依據是：冷彎(wan)(wan)型(xing)材產品標準、成型(xing)材料的(de)性能、技(ji)術要求、生產機(ji)組配置(zhi)及(ji)主要參數。

1. 孔(kong)型設計的(de)要求

 ①. 能夠(gou)生產出符合技術要求(qiu)的(de)產品斷(duan)面(mian)形狀及尺寸精度。

 ②. 產品在全長上無水(shui)平垂直瓢曲及縱向扭轉。

 ③. 彎折處減薄及(ji)斷面殘余應力最小(xiao)，產品(pin)無邊波、皺折及(ji)裂紋。

 ④. 金屬出人孔型順利，軋輥(gun)安(an)裝調(diao)整方(fang)便。

 ⑤. 孔型組合配(pei)置(zhi)合理、孔型磨損小、輥耗低、能耗小。

 ⑥. 操(cao)作方便，可(ke)達(da)最(zui)大機組生產(chan)率。

2. 冷彎成型(xing)輥孔型(xing)設計步驟

 ①. 確定坯料(liao)寬度(du)。

 ②. 確定(ding)型鋼(gang)對(dui)水(shui)平(ping)輥(gun)中心線(xian)的(de)位置。

 ③. 選(xuan)擇型鋼成型基本中心線（簡稱基軸）及基準線段。

 ④. 確(que)定型鋼過渡斷面數量(liang)和(he)形狀（俗稱花形圖）。

 ⑤. 畫斷面(mian)配(pei)輥(gun)圖和單個軋輥(gun)及輥(gun)片圖。

 ⑥. 導衛及(ji)輔助工具設(she)計及(ji)圖紙(zhi)的(de)繪制。

 ⑦. 必(bi)要的校核。