將板、帶鋼在輥式冷彎(wan)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)(gun)(gun)(gun)(gun)式冷(leng)(leng)彎(wan)(wan)(wan)成(cheng)型(xing)(xing)和(he)普通(tong)(tong)軋(ya)(ya)(ya)制過(guo)(guo)程(cheng)一(yi)樣，冷(leng)(leng)彎(wan)(wan)(wan)成(cheng)型(xing)(xing)時帶(dai)(dai)坯(pi)(pi)(pi)(pi)任意斷面(mian)上(shang)的(de)(de)金(jin)屬流動是穩定(ding)的(de)(de)，不(bu)(bu)隨時間(jian)而(er)變(bian)(bian)化(hua)，相(xiang)鄰兩(liang)道次(ci)之間(jian)帶(dai)(dai)坯(pi)(pi)(pi)(pi)進(jin)入軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)位置，如圖5-10所(suo)示，彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)角(jiao)(jiao)由(you)(you)(you)上(shang)一(yi)道次(ci)的(de)(de)αn-1增(zeng)(zeng)大到(dao)下(xia)一(yi)道次(ci)的(de)(de)αn,彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)圓弧半(ban)徑(jing)由(you)(you)(you)rn-1,減(jian)小為(wei)rn.由(you)(you)(you)于板(ban)坯(pi)(pi)(pi)(pi)前(qian)端部(bu)(bu)(bu)上(shang)拾(shi)，彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)角(jiao)(jiao)增(zeng)(zeng)大，而(er)產(chan)(chan)生(sheng)的(de)(de)張力作用于邊部(bu)(bu)(bu)，在(zai)(zai)(zai)相(xiang)對(dui)(dui)旋(xuan)轉的(de)(de)軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)的(de)(de)作用下(xia)，板(ban)帶(dai)(dai)坯(pi)(pi)(pi)(pi)沿(yan)軋(ya)(ya)(ya)制方向前(qian)進(jin)并實(shi)現(xian)彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)變(bian)(bian)形(xing)(xing)(xing)(xing)。實(shi)現(xian)板(ban)坯(pi)(pi)(pi)(pi)彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)變(bian)(bian)形(xing)(xing)(xing)(xing)的(de)(de)軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)工作部(bu)(bu)(bu)分稱為(wei)軋(ya)(ya)(ya)槽(cao)（輥(gun)(gun)(gun)(gun)(gun)槽(cao)），由(you)(you)(you)兩(liang)個(ge)和(he)兩(liang)個(ge)以上(shang)通(tong)(tong)過(guo)(guo)軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)平(ping)(ping)(ping)面(mian)所(suo)構成(cheng)的(de)(de)軋(ya)(ya)(ya)槽(cao)斷面(mian)變(bian)(bian)形(xing)(xing)(xing)(xing)區(qu)稱為(wei)孔(kong)(kong)(kong)型(xing)(xing)。因此，輥(gun)(gun)(gun)(gun)(gun)式冷(leng)(leng)彎(wan)(wan)(wan)成(cheng)型(xing)(xing)亦可視為(wei)板(ban)坯(pi)(pi)(pi)(pi)經(jing)若干孔(kong)(kong)(kong)型(xing)(xing)實(shi)現(xian)彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)的(de)(de)穩態變(bian)(bian)形(xing)(xing)(xing)(xing)過(guo)(guo)程(cheng)。從上(shang)一(yi)道輥(gun)(gun)(gun)(gun)(gun)軸(zhou)平(ping)(ping)(ping)面(mian)（孔(kong)(kong)(kong)型(xing)(xing)）到(dao)下(xia)一(yi)道輥(gun)(gun)(gun)(gun)(gun)軸(zhou)平(ping)(ping)(ping)面(mian)（孔(kong)(kong)(kong)型(xing)(xing)）間(jian)距離L稱為(wei)平(ping)(ping)(ping)緩(huan)過(guo)(guo)渡(du)(du)區(qu)長(chang)度。L的(de)(de)大小與(yu)機架間(jian)距有關，L愈大變(bian)(bian)形(xing)(xing)(xing)(xing)愈緩(huan)和(he)。而(er)平(ping)(ping)(ping)緩(huan)過(guo)(guo)渡(du)(du)區(qu)又(you)可細分為(wei)L1和(he)L2兩(liang)個(ge)區(qu)（見圖5-11).板(ban)坯(pi)(pi)(pi)(pi)從前(qian)道孔(kong)(kong)(kong)型(xing)(xing)（對(dui)(dui)應彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)角(jiao)(jiao)an-1)進(jin)入下(xia)道孔(kong)(kong)(kong)型(xing)(xing)（對(dui)(dui)應彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)角(jiao)(jiao)αn),開(kai)始(shi)(shi)時坯(pi)(pi)(pi)(pi)料前(qian)端部(bu)(bu)(bu)分與(yu)軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)下(xia)軋(ya)(ya)(ya)槽(cao)接(jie)觸，在(zai)(zai)(zai)坯(pi)(pi)(pi)(pi)料中形(xing)(xing)(xing)(xing)成(cheng)數值(zhi)不(bu)(bu)大的(de)(de)彈(dan)性(xing)應力。軋(ya)(ya)(ya)件(jian)前(qian)行與(yu)上(shang)軋(ya)(ya)(ya)槽(cao)接(jie)觸，在(zai)(zai)(zai)上(shang)下(xia)軋(ya)(ya)(ya)槽(cao)作用下(xia)產(chan)(chan)生(sheng)塑(su)性(xing)彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)，即板(ban)坯(pi)(pi)(pi)(pi)在(zai)(zai)(zai)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)平(ping)(ping)(ping)面(mian)前(qian)（未通(tong)(tong)過(guo)(guo)an孔(kong)(kong)(kong)型(xing)(xing)）已開(kai)始(shi)(shi)了塑(su)性(xing)彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)變(bian)(bian)形(xing)(xing)(xing)(xing)，原來平(ping)(ping)(ping)直的(de)(de)邊部(bu)(bu)(bu)產(chan)(chan)生(sheng)縱向扭曲(qu)(qu)(qu)(qu)，形(xing)(xing)(xing)(xing)成(cheng)復雜的(de)(de)曲(qu)(qu)(qu)(qu)線表(biao)面(mian)。坯(pi)(pi)(pi)(pi)料的(de)(de)橫截面(mian)形(xing)(xing)(xing)(xing)狀逐(zhu)漸按孔(kong)(kong)(kong)型(xing)(xing)輪廓形(xing)(xing)(xing)(xing)狀變(bian)(bian)化(hua)。彎(wan)(wan)(wan)折處(chu)金(jin)屬連續經(jing)受彈(dan)性(xing)到(dao)彈(dan)塑(su)性(xing)變(bian)(bian)形(xing)(xing)(xing)(xing)。隨彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)角(jiao)(jiao)增(zeng)(zeng)大，彎(wan)(wan)(wan)曲(qu)(qu)(qu)(qu)圓弧半(ban)徑(jing)減(jian)小，彎(wan)(wan)(wan)折處(chu)切向正應力和(he)彎(wan)(wan)(wan)矩增(zeng)(zeng)加(jia)，在(zai)(zai)(zai)板(ban)坯(pi)(pi)(pi)(pi)料前(qian)端已變(bian)(bian)形(xing)(xing)(xing)(xing)部(bu)(bu)(bu)分與(yu)軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)壓緊軋(ya)(ya)(ya)件(jian)的(de)(de)共(gong)同作用下(xia)，板(ban)坯(pi)(pi)(pi)(pi)邊部(bu)(bu)(bu)出現(xian)拉(la)(la)應力，引起邊部(bu)(bu)(bu)拉(la)(la)伸(shen)，板(ban)坯(pi)(pi)(pi)(pi)通(tong)(tong)過(guo)(guo)軋(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)(gun)軸(zhou)平(ping)(ping)(ping)面(mian)之后（通(tong)(tong)過(guo)(guo)孔(kong)(kong)(kong)型(xing)(xing)后），原來產(chan)(chan)生(sheng)縱向扭曲(qu)(qu)(qu)(qu)的(de)(de)邊部(bu)(bu)(bu)被拉(la)(la)平(ping)(ping)(ping)，輥(gun)(gun)(gun)(gun)(gun)軸(zhou)平(ping)(ping)(ping)面(mian)前(qian)變(bian)(bian)形(xing)(xing)(xing)(xing)區(qu)長(chang)度不(bu)(bu)再增(zeng)(zeng)加(jia)而(er)保持長(chang)度不(bu)(bu)變(bian)(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)料橫截面各個直線(xian)部分受縱向拉伸(shen)或壓縮變形，與之相鄰的曲線(xian)部分受彎曲變形，弄清板坯(pi)在相鄰兩道次間彎曲變形行為，對于制定(ding)成型(xing)方(fang)案和設(she)計(ji)孔型(xing)具有一(yi)定(ding)的意義(yi)。

為將板帶材經連續輥(gun)彎變形加工成(cheng)(cheng)合格冷彎型鋼而進(jin)行的(de)成(cheng)(cheng)型方法及工具的(de)設(she)計(ji)稱為冷彎成(cheng)(cheng)型輥(gun)孔型設(she)計(ji)。冷彎成(cheng)(cheng)型輥(gun)孔型設(she)計(ji)的(de)依據是：冷彎型材產品標準、成(cheng)(cheng)型材料的(de)性能、技(ji)術要求、生產機組配(pei)置及主(zhu)要參數。

1. 孔型設計的要(yao)求(qiu)

 ①. 能夠(gou)生產出符合技術要求(qiu)的產品斷面(mian)形狀(zhuang)及尺寸(cun)精度。

 ②. 產品在全長(chang)上無(wu)水平(ping)垂直瓢曲及縱(zong)向扭轉。

 ③. 彎折處減薄及斷面(mian)殘余應(ying)力最小(xiao)，產品無邊波、皺折及裂紋。

 ④. 金(jin)屬出(chu)人孔(kong)型順利，軋輥安裝調整方便(bian)。

 ⑤. 孔型(xing)組合配置(zhi)合理、孔型(xing)磨損(sun)小(xiao)、輥耗(hao)低、能(neng)耗(hao)小(xiao)。

 ⑥. 操作方便(bian)，可達最大機組生產率(lv)。

2. 冷彎(wan)成(cheng)型輥孔型設(she)計(ji)步驟(zou)

 ①. 確定(ding)坯料寬度。

 ②. 確定型(xing)鋼對(dui)水平輥中心線的位置。

 ③. 選(xuan)擇型(xing)鋼成(cheng)型(xing)基本中心線（簡稱基軸(zhou)）及基準線段。

 ④. 確定型鋼過渡斷面數(shu)量和形狀（俗稱花形圖(tu)）。

 ⑤. 畫斷面配輥圖和單個軋(ya)輥及輥片圖。

 ⑥. 導(dao)衛(wei)及輔助工具設(she)計及圖紙的繪(hui)制。

 ⑦. 必要的校核。