混凝土泵管(guan)的(de)(de)(de)轉變(bian)(bian)溫度(du)、轉變(bian)(bian)時間和(he)組織(zhi)特征各習相(xiang)(xiang)(xiang)同(tong)(tong)。即便(bian)同(tong)(tong)一鋼(gang)種,只要(yao)*終(zhong)用途不(bu)同(tong)(tong),所要(yao)求的(de)(de)(de)組織(zhi)和(he)性能(neng)也不(bu)盡相(xiang)(xiang)(xiang)同(tong)(tong)。二次(ci)冷(leng)(leng)卻是(shi)指從(cong)相(xiang)(xiang)(xiang)變(bian)(bian)開始溫度(du)到(dao)相(xiang)(xiang)(xiang)變(bian)(bian)結束溫度(du)范(fan)(fan)圍內的(de)(de)(de)冷(leng)(leng)卻制。二次(ci)冷(leng)(leng)卻的(de)(de)(de)目的(de)(de)(de)是(shi)通(tong)過(guo)(guo)控制相(xiang)(xiang)(xiang)變(bian)(bian)時的(de)(de)(de)冷(leng)(leng)卻速度(du)和(he)停止控冷(leng)(leng)的(de)(de)(de)溫度(du)控制相(xiang)(xiang)(xiang)變(bian)(bian)過(guo)(guo)程,以保證(zheng)鋼(gang)材快(kuai)冷(leng)(leng)后得到(dao)所要(yao)求的(de)(de)(de)金相(xiang)(xiang)(xiang)組織(zhi)性能(neng)。二次(ci)冷(leng)(leng)卻(空冷(leng)(leng))是(shi)指相(xiang)(xiang)(xiang)變(bian)(bian)后至室溫范(fan)(fan)圍內的(de)(de)(de)冷(leng)(leng)卻。而對于鋪在空冷(leng)(leng)過(guo)(guo)程中會發生(sheng)(sheng)碳(tan)(tan)氮化(hua)(hua)物析出,對生(sheng)(sheng)成的(de)(de)(de)貝氏體產生(sheng)(sheng)回火效果。對于髙碳(tan)(tan)鋼(gang)或髙碳(tan)(tan)合金鋼(gang)相(xiang)(xiang)(xiang)變(bian)(bian)后空冷(leng)(leng)時將使快(kuai)冷(leng)(leng)中,析出的(de)(de)(de)過(guo)(guo)飽和(he)碳(tan)(tan)化(hua)(hua)物繼(ji)續(xu)彌散析出。如相(xiang)(xiang)(xiang)變(bian)(bian)完成后仍采用工(gong)藝,就可(ke)以阻止碳(tan)(tan)化(hua)(hua)物析出,保持其碳(tan)(tan)化(hua)(hua)物固溶狀態,鞏固溶強化(hua)(hua)的(de)(de)(de)目的(de)(de)(de)。