冷(leng)拔三通成形(xing)(xing)是(shi)將大于三通直(zhi)徑(jing)(jing)的(de)(de)(de)(de)管(guan)(guan)(guan)坯(pi)(pi)(pi)，壓扁約至冷(leng)拔三通直(zhi)徑(jing)(jing)的(de)(de)(de)(de)尺寸(cun)，在(zai)拉伸支(zhi)管(guan)(guan)(guan)的(de)(de)(de)(de)部位(wei)開一個(ge)孔；管(guan)(guan)(guan)坯(pi)(pi)(pi)經加熱，放入(ru)成形(xing)(xing)模(mo)中，并在(zai)管(guan)(guan)(guan)坯(pi)(pi)(pi)內(nei)裝入(ru)拉伸支(zhi)管(guan)(guan)(guan)的(de)(de)(de)(de)沖模(mo)；在(zai)壓力的(de)(de)(de)(de)作(zuo)用下(xia)管(guan)(guan)(guan)坯(pi)(pi)(pi)被徑(jing)(jing)向(xiang)壓縮，在(zai)徑(jing)(jing)向(xiang)壓縮的(de)(de)(de)(de)過(guo)(guo)程中金屬(shu)向(xiang)支(zhi)管(guan)(guan)(guan)方向(xiang)流動(dong)并在(zai)沖模(mo)的(de)(de)(de)(de)拉伸下(xia)形(xing)(xing)成支(zhi)管(guan)(guan)(guan)。整個(ge)過(guo)(guo)程是(shi)通過(guo)(guo)管(guan)(guan)(guan)坯(pi)(pi)(pi)的(de)(de)(de)(de)徑(jing)(jing)向(xiang)壓縮和支(zhi)管(guan)(guan)(guan)部位(wei)的(de)(de)(de)(de)拉伸過(guo)(guo)程而成形(xing)(xing)。與液壓脹形(xing)(xing)冷(leng)拔三通不同(tong)的(de)(de)(de)(de)是(shi)，冷(leng)拔三通支(zhi)管(guan)(guan)(guan)的(de)(de)(de)(de)金屬(shu)是(shi)由管(guan)(guan)(guan)坯(pi)(pi)(pi)的(de)(de)(de)(de)徑(jing)(jing)向(xiang)運動(dong)進(jin)行補償(chang)的(de)(de)(de)(de)，所以也稱為徑(jing)(jing)向(xiang)補償(chang)工(gong)藝。

由于(yu)采(cai)用加熱后壓(ya)制冷(leng)拔(ba)(ba)三通(tong)(tong)，材(cai)料(liao)成(cheng)形(xing)(xing)所需要的(de)(de)設備噸位(wei)降低。熱壓(ya)冷(leng)拔(ba)(ba)三通(tong)(tong)對材(cai)料(liao)的(de)(de)適應(ying)性較(jiao)寬，適用于(yu)低碳鋼(gang)(gang)、合(he)金鋼(gang)(gang)、不銹鋼(gang)(gang)的(de)(de)材(cai)料(liao)；特別是大(da)直徑和管壁偏(pian)厚的(de)(de)冷(leng)拔(ba)(ba)三通(tong)(tong)，通(tong)(tong)常采(cai)用這種(zhong)成(cheng)形(xing)(xing)工藝。

冷拔三通(tong)對接形式(shi)分類：

1、對(dui)焊式冷拔三(san)通：就是和連接管(guan)件(jian)對(dui)接后(hou)焊接的冷拔三(san)通。 

2、承插式冷拔三通(tong)：就(jiu)是(shi)把(ba)連接管件插入三通(tong)各端部后(hou)焊接或熔(rong)接的冷拔三通(tong)。

3、卡套式冷拔三通：就是(shi)各端部是(shi)卡套接頭，把(ba)管(guan)件插入后再緊固的冷拔三通。

4、螺(luo)紋式冷拔三通(tong)：以螺(luo)紋方式連(lian)接管件的冷拔三通(tong)。