將板、帶鋼在輥(gun)式(shi)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)(gun)式冷(leng)彎(wan)(wan)成(cheng)(cheng)(cheng)型和(he)普(pu)通(tong)(tong)軋(ya)(ya)(ya)(ya)制過(guo)(guo)程一(yi)樣，冷(leng)彎(wan)(wan)成(cheng)(cheng)(cheng)型時(shi)帶坯(pi)(pi)(pi)任意(yi)斷(duan)面(mian)(mian)(mian)(mian)上(shang)的(de)(de)(de)(de)金屬(shu)流動是穩定的(de)(de)(de)(de)，不(bu)(bu)隨時(shi)間而(er)變(bian)(bian)(bian)化，相鄰兩(liang)道(dao)(dao)次(ci)之間帶坯(pi)(pi)(pi)進入軋(ya)(ya)(ya)(ya)輥(gun)(gun)位(wei)置，如圖5-10所(suo)示，彎(wan)(wan)曲(qu)角(jiao)由(you)(you)上(shang)一(yi)道(dao)(dao)次(ci)的(de)(de)(de)(de)αn-1增大(da)到(dao)下(xia)(xia)一(yi)道(dao)(dao)次(ci)的(de)(de)(de)(de)αn,彎(wan)(wan)曲(qu)圓弧半徑(jing)由(you)(you)rn-1,減小(xiao)(xiao)為rn.由(you)(you)于板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)前(qian)(qian)(qian)端部(bu)(bu)(bu)上(shang)拾，彎(wan)(wan)曲(qu)角(jiao)增大(da)，而(er)產生的(de)(de)(de)(de)張力(li)(li)作用于邊(bian)(bian)(bian)部(bu)(bu)(bu)，在(zai)相對旋(xuan)轉的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)輥(gun)(gun)的(de)(de)(de)(de)作用下(xia)(xia)，板(ban)(ban)(ban)(ban)帶坯(pi)(pi)(pi)沿軋(ya)(ya)(ya)(ya)制方向(xiang)(xiang)前(qian)(qian)(qian)進并實現(xian)彎(wan)(wan)曲(qu)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)。實現(xian)板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)彎(wan)(wan)曲(qu)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)輥(gun)(gun)工作部(bu)(bu)(bu)分(fen)(fen)(fen)稱(cheng)為軋(ya)(ya)(ya)(ya)槽(cao)（輥(gun)(gun)槽(cao)），由(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)(ya)輥(gun)(gun)軸(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)(mian)所(suo)構成(cheng)(cheng)(cheng)的(de)(de)(de)(de)軋(ya)(ya)(ya)(ya)槽(cao)斷(duan)面(mian)(mian)(mian)(mian)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)區稱(cheng)為孔(kong)型。因此(ci)，輥(gun)(gun)式冷(leng)彎(wan)(wan)成(cheng)(cheng)(cheng)型亦可視(shi)為板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)經(jing)若干孔(kong)型實現(xian)彎(wan)(wan)曲(qu)的(de)(de)(de)(de)穩態變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)過(guo)(guo)程。從上(shang)一(yi)道(dao)(dao)輥(gun)(gun)軸(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)(mian)（孔(kong)型）到(dao)下(xia)(xia)一(yi)道(dao)(dao)輥(gun)(gun)軸(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)(mian)（孔(kong)型）間距離L稱(cheng)為平(ping)(ping)(ping)(ping)緩過(guo)(guo)渡區長度(du)。L的(de)(de)(de)(de)大(da)小(xiao)(xiao)與(yu)機架間距有關(guan)，L愈大(da)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)愈緩和(he)。而(er)平(ping)(ping)(ping)(ping)緩過(guo)(guo)渡區又可細分(fen)(fen)(fen)為L1和(he)L2兩(liang)個(ge)區（見(jian)圖5-11).板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)從前(qian)(qian)(qian)道(dao)(dao)孔(kong)型（對應(ying)彎(wan)(wan)曲(qu)角(jiao)an-1)進入下(xia)(xia)道(dao)(dao)孔(kong)型（對應(ying)彎(wan)(wan)曲(qu)角(jiao)αn),開始時(shi)坯(pi)(pi)(pi)料前(qian)(qian)(qian)端部(bu)(bu)(bu)分(fen)(fen)(fen)與(yu)軋(ya)(ya)(ya)(ya)輥(gun)(gun)下(xia)(xia)軋(ya)(ya)(ya)(ya)槽(cao)接觸(chu)，在(zai)坯(pi)(pi)(pi)料中(zhong)形(xing)(xing)(xing)(xing)成(cheng)(cheng)(cheng)數(shu)值不(bu)(bu)大(da)的(de)(de)(de)(de)彈性(xing)(xing)應(ying)力(li)(li)。軋(ya)(ya)(ya)(ya)件前(qian)(qian)(qian)行(xing)與(yu)上(shang)軋(ya)(ya)(ya)(ya)槽(cao)接觸(chu)，在(zai)上(shang)下(xia)(xia)軋(ya)(ya)(ya)(ya)槽(cao)作用下(xia)(xia)產生塑(su)性(xing)(xing)彎(wan)(wan)曲(qu)，即板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)在(zai)輥(gun)(gun)軸(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)(mian)前(qian)(qian)(qian)（未通(tong)(tong)過(guo)(guo)an孔(kong)型）已(yi)開始了塑(su)性(xing)(xing)彎(wan)(wan)曲(qu)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)，原來(lai)平(ping)(ping)(ping)(ping)直的(de)(de)(de)(de)邊(bian)(bian)(bian)部(bu)(bu)(bu)產生縱向(xiang)(xiang)扭曲(qu)，形(xing)(xing)(xing)(xing)成(cheng)(cheng)(cheng)復雜的(de)(de)(de)(de)曲(qu)線表面(mian)(mian)(mian)(mian)。坯(pi)(pi)(pi)料的(de)(de)(de)(de)橫截面(mian)(mian)(mian)(mian)形(xing)(xing)(xing)(xing)狀(zhuang)逐(zhu)漸按孔(kong)型輪廓形(xing)(xing)(xing)(xing)狀(zhuang)變(bian)(bian)(bian)化。彎(wan)(wan)折處金屬(shu)連(lian)續(xu)經(jing)受彈性(xing)(xing)到(dao)彈塑(su)性(xing)(xing)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)。隨彎(wan)(wan)曲(qu)角(jiao)增大(da)，彎(wan)(wan)曲(qu)圓弧半徑(jing)減小(xiao)(xiao)，彎(wan)(wan)折處切向(xiang)(xiang)正應(ying)力(li)(li)和(he)彎(wan)(wan)矩增加，在(zai)板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)料前(qian)(qian)(qian)端已(yi)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)部(bu)(bu)(bu)分(fen)(fen)(fen)與(yu)軋(ya)(ya)(ya)(ya)輥(gun)(gun)壓緊軋(ya)(ya)(ya)(ya)件的(de)(de)(de)(de)共同作用下(xia)(xia)，板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)邊(bian)(bian)(bian)部(bu)(bu)(bu)出現(xian)拉(la)應(ying)力(li)(li)，引(yin)起邊(bian)(bian)(bian)部(bu)(bu)(bu)拉(la)伸(shen)，板(ban)(ban)(ban)(ban)坯(pi)(pi)(pi)通(tong)(tong)過(guo)(guo)軋(ya)(ya)(ya)(ya)輥(gun)(gun)軸(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)(mian)之后（通(tong)(tong)過(guo)(guo)孔(kong)型后），原來(lai)產生縱向(xiang)(xiang)扭曲(qu)的(de)(de)(de)(de)邊(bian)(bian)(bian)部(bu)(bu)(bu)被拉(la)平(ping)(ping)(ping)(ping)，輥(gun)(gun)軸(zhou)平(ping)(ping)(ping)(ping)面(mian)(mian)(mian)(mian)前(qian)(qian)(qian)變(bian)(bian)(bian)形(xing)(xing)(xing)(xing)區長度(du)不(bu)(bu)再增加而(er)保持長度(du)不(bu)(bu)變(bian)(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(ge)個直線(xian)部(bu)分受縱向拉伸或壓縮變形，與之相鄰的曲線(xian)部(bu)分受彎曲變形，弄清板(ban)坯(pi)在相鄰兩道次間(jian)彎曲變形行為(wei)，對(dui)于制定成型(xing)方案和設計孔型(xing)具有一定的意義。

為(wei)將(jiang)板帶材經連續輥彎變形加工成合格冷彎型(xing)(xing)鋼而進行(xing)的(de)成型(xing)(xing)方法(fa)及工具的(de)設(she)計(ji)稱(cheng)為(wei)冷彎成型(xing)(xing)輥孔型(xing)(xing)設(she)計(ji)。冷彎成型(xing)(xing)輥孔型(xing)(xing)設(she)計(ji)的(de)依(yi)據是(shi)：冷彎型(xing)(xing)材產(chan)品標準(zhun)、成型(xing)(xing)材料的(de)性能(neng)、技術要(yao)求、生(sheng)產(chan)機組配置(zhi)及主要(yao)參數。

1. 孔(kong)型設(she)計的要求(qiu)

 ①. 能夠生產(chan)出符合技(ji)術要求的(de)產(chan)品斷(duan)面(mian)形狀及(ji)尺(chi)寸(cun)精度。

 ②. 產品在全長上無(wu)水(shui)平垂直瓢曲及(ji)縱向扭轉。

 ③. 彎折(zhe)處減薄及斷面殘余應力最小(xiao)，產品(pin)無邊波(bo)、皺折(zhe)及裂紋。

 ④. 金屬出人孔型順利，軋輥安裝調(diao)整方便。

 ⑤. 孔型(xing)組合配置合理、孔型(xing)磨損(sun)小、輥耗低、能耗小。

 ⑥. 操作方便(bian)，可達(da)最大機組生產率。

2. 冷(leng)彎成型(xing)輥孔(kong)型(xing)設(she)計步驟

 ①. 確定坯料寬度。

 ②. 確定型鋼對(dui)水平輥中(zhong)心線(xian)的位置。

 ③. 選(xuan)擇(ze)型鋼(gang)成型基(ji)本中心線（簡稱基(ji)軸）及基(ji)準線段。

 ④. 確定型鋼過渡斷面數量和(he)形狀（俗(su)稱花形圖）。

 ⑤. 畫斷面配輥(gun)圖和單個軋輥(gun)及(ji)輥(gun)片(pian)圖。

 ⑥. 導衛及輔助(zhu)工(gong)具設計及圖紙的繪制。

 ⑦. 必要的校核。