封頭(tou)(tou)是指用(yong)(yong)以封閉容器端部使其內外(wai)介(jie)質(zhi)隔離的(de)(de)元件，又稱端蓋。圓(yuan)筒形(xing)(xing)(xing)(xing)(xing)容器的(de)(de)封頭(tou)(tou)一般都(dou)是迥轉殼體。按(an)封頭(tou)(tou)表面(mian)的(de)(de)形(xing)(xing)(xing)(xing)(xing)狀(zhuang)可(ke)分為凸形(xing)(xing)(xing)(xing)(xing)、錐形(xing)(xing)(xing)(xing)(xing)、平(ping)板形(xing)(xing)(xing)(xing)(xing)和組(zu)合形(xing)(xing)(xing)(xing)(xing)。凸形(xing)(xing)(xing)(xing)(xing)封頭(tou)(tou)是指外(wai)表面(mian)形(xing)(xing)(xing)(xing)(xing)狀(zhuang)為凸面(mian)的(de)(de)封頭(tou)(tou)，如半球形(xing)(xing)(xing)(xing)(xing)、橢圓(yuan)形(xing)(xing)(xing)(xing)(xing)、碟形(xing)(xing)(xing)(xing)(xing)和無折邊球形(xing)(xing)(xing)(xing)(xing)封頭(tou)(tou)等。有的(de)(de)氣(qi)瓶采(cai)用(yong)(yong)凸面(mian)向內的(de)(de)組(zu)合形(xing)(xing)(xing)(xing)(xing)底封頭(tou)(tou)，既可(ke)強度(du)，又能滿(man)足(zu)安然使用(yong)(yong)的(de)(de)需求。  

封(feng)(feng)頭是(shi)容器(qi)的一個(ge)部件，是(shi)以焊(han)接方式連接筒體。（如(ru)下(xia)圖(tu)）根據幾何(he)形(xing)(xing)(xing)狀的不同，可分(fen)(fen)為球(qiu)形(xing)(xing)(xing)、橢圓形(xing)(xing)(xing)、碟形(xing)(xing)(xing)、球(qiu)冠(guan)(guan)形(xing)(xing)(xing)、錐殼(ke)和(he)平(ping)蓋等幾種(zhong)(zhong)，其中球(qiu)形(xing)(xing)(xing)、橢圓形(xing)(xing)(xing)、碟形(xing)(xing)(xing)、球(qiu)冠(guan)(guan)型封(feng)(feng)頭又統稱為凸形(xing)(xing)(xing)封(feng)(feng)頭。在焊(han)接上(shang)分(fen)(fen)為對(dui)焊(han)封(feng)(feng)頭，承(cheng)插焊(han)封(feng)(feng)頭。用于(yu)各(ge)種(zhong)(zhong)容器(qi)設備，如(ru)儲(chu)罐、換熱器(qi)、塔、反應釜(fu)、鍋(guo)爐和(he)分(fen)(fen)離設備等。材(cai)質有碳鋼(gang)（A3、20#、Q235、Q345B、16Mn等）、不銹鋼(gang)（304、321、304L、316、316L等）、合(he)金鋼(gang)（15Mo315CrMoV35CrMoV45CrMo）、鋁、鈦、銅、鎳(nie)及鎳(nie)合(he)金等。