在軋制圓鋼斷面時孔型的側壁斜度往往允許的變形量有關系。孔型的側壁斜度越大，允許的變形量也越大。在軋制過程中，由于摩擦力的存在，孔型不斷磨損。變形量越大，孔型磨損越快。孔型的磨損直接影響到成品尺寸的精確度和表面的粗糙度。同時，孔型的磨損增加了換孔換輥時間，影響軋鋼機產量(liang)。由于孔型側(ce)壁斜度大，甚至(zhi)可(ke)以減少軋鋼機調整，這(zhe)不僅可(ke)以節約(yue)軋輥(gun)還(huan)可(ke)以節省(sheng)電能。

軋(ya)(ya)鋼機(ji)采用(yong)大斜度的(de)孔型(xing)可(ke)(ke)增加孔型(xing)的(de)共用(yong)性(xing)。比(bi)如大斜度的(de)箱型(xing)孔型(xing)，通過控制孔型(xing)的(de)充滿(man)程(cheng)度，可(ke)(ke)以軋(ya)(ya)出尺寸不同的(de)軋(ya)(ya)件(jian)。這(zhe)一點對(dui)于初軋(ya)(ya)機(ji)，開(kai)坯機(ji)以及型(xing)鋼軋(ya)(ya)機(ji)的(de)毛軋(ya)(ya)孔型(xing)尤為重(zhong)要。

生產(chan)圓(yuan)鋼的(de)(de)(de)孔(kong)(kong)型(xing)(xing)系統一(yi)(yi)般(ban)由延(yan)伸(shen)孔(kong)(kong)和(he)精軋(ya)(ya)(ya)(ya)孔(kong)(kong)兩部(bu)分組成,延(yan)伸(shen)孔(kong)(kong)的(de)(de)(de)主(zhu)要目(mu)的(de)(de)(de)是減小(xiao)軋(ya)(ya)(ya)(ya)件(jian)(jian)斷面(mian),并(bing)為軋(ya)(ya)(ya)(ya)件(jian)(jian)正(zheng)確、順(shun)利地進入精軋(ya)(ya)(ya)(ya)孔(kong)(kong)創造良好的(de)(de)(de)條件(jian)(jian)。除特殊(shu)要求外(wai)孔(kong)(kong)型(xing)(xing)的(de)(de)(de)角(jiao)部(bu)很少用(yong)折線，一(yi)(yi)般(ban)都做成圓(yuan)角(jiao)，孔(kong)(kong)型(xing)(xing)內圓(yuan)角(jiao)的(de)(de)(de)作用(yong)  可(ke)(ke)(ke)以防止(zhi)軋(ya)(ya)(ya)(ya)件(jian)(jian)角(jiao)部(bu)的(de)(de)(de)急劇冷卻；可(ke)(ke)(ke)以使槽(cao)底的(de)(de)(de)應(ying)力集中(zhong)減小(xiao)增加(jia)軋(ya)(ya)(ya)(ya)輥強度(du)：通過改(gai)(gai)變(bian)內圓(yuan)角(jiao)半(ban)徑，可(ke)(ke)(ke)以改(gai)(gai)變(bian)孔(kong)(kong)型(xing)(xing)的(de)(de)(de)實(shi)際面(mian)積和(he)尺寸(cun)，從而改(gai)(gai)變(bian)軋(ya)(ya)(ya)(ya)件(jian)(jian)在孔(kong)(kong)型(xing)(xing)中(zhong)的(de)(de)(de)充滿程度(du)，有(you)時還(huan)對軋(ya)(ya)(ya)(ya)件(jian)(jian)的(de)(de)(de)局部(bu)加(jia)工(gong)起一(yi)(yi)定的(de)(de)(de)作用(yong)。

孔型(xing)外(wai)(wai)圓角的(de)(de)作用  當軋(ya)(ya)(ya)(ya)件(jian)進入孔型(xing)不(bu)正(zheng)時(shi)，外(wai)(wai)圓角能防(fang)止軋(ya)(ya)(ya)(ya)件(jian)的(de)(de)一側受輥(gun)(gun)(gun)(gun)環切割；當軋(ya)(ya)(ya)(ya)件(jian)在(zai)孔型(xing)中(zhong)略有過(guo)充(chong)滿(man)現象時(shi)，即出現“耳子”時(shi)外(wai)(wai)圓角可(ke)使其避免(mian)有尖銳的(de)(de)折線(xian)，這樣可(ke)以防(fang)止軋(ya)(ya)(ya)(ya)件(jian)繼續(xu)軋(ya)(ya)(ya)(ya)制形(xing)成(cheng)(cheng)折疊(die)；對于異型(xing)軋(ya)(ya)(ya)(ya)孔，增(zeng)大(da)外(wai)(wai)圓角半徑也(ye)可(ke)使軋(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)的(de)(de)局部應力集中(zhong)減(jian)少，從而增(zeng)加(jia)軋(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)的(de)(de)強度。圓孔型(xing)系統中(zhong)變形(xing)較為均勻(yun)(yun)，軋(ya)(ya)(ya)(ya)制前后的(de)(de)斷面形(xing)狀(zhuang)過(guo)渡緩和，能防(fang)止產生局部應力；軋(ya)(ya)(ya)(ya)件(jian)斷面各(ge)處冷卻均勻(yun)(yun)；氧化鐵皮易于脫落；還可(ke)由(you)延伸孔型(xing)軋(ya)(ya)(ya)(ya)出成(cheng)(cheng)品圓鋼(gang)，減(jian)少了(le)軋(ya)(ya)(ya)(ya)輥(gun)(gun)(gun)(gun)數(shu)量和換輥(gun)(gun)(gun)(gun)次數(shu)。

當采用閉口(kou)型(xing)(xing)以(yi)及軋(ya)制某(mou)些異型(xing)(xing)鋼時(shi)，為(wei)(wei)了(le)控制軋(ya)件的(de)(de)(de)斷面(mian)形狀，要使用鎖口(kou)。在(zai)(zai)軋(ya)制某(mou)些簡單斷面(mian)型(xing)(xing)鋼時(shi)，其(qi)成品孔(kong)(kong)型(xing)(xing)的(de)(de)(de)外(wai)圓角半徑可(ke)以(yi)取小些，甚至為(wei)(wei)零。在(zai)(zai)同一孔(kong)(kong)型(xing)(xing)中軋(ya)制幾種厚度活高(gao)度差(cha)異較大的(de)(de)(de)軋(ya)件時(shi)，其(qi)鎖口(kou)長(chang)度必須大些，借以(yi)防(fang)止軋(ya)制較厚或較高(gao)的(de)(de)(de)軋(ya)件時(shi)金屬(shu)流入輥縫。用鎖口(kou)的(de)(de)(de)孔(kong)(kong)型(xing)(xing)，其(qi)相鄰孔(kong)(kong)型(xing)(xing)的(de)(de)(de)鎖口(kou)一般是上下交替(ti)出現的(de)(de)(de)。