這類沉淀硬化不銹鋼的化學成分處于平衡狀態,Ms點(奧氏體開始轉變為馬氏體的起始溫度)低于室溫,因此從固溶處理溫度冷至室溫,鋼的組織主要是奧氏體組織,具有良好的韌性利于成形加工。但為了使其轉變成馬氏體,必須通過調整處理,調整處理的目的是通過碳和合金元素從奧氏體中析出提高鋼的Ms和M1點(奧氏體轉變為馬氏體的終止溫度),以利于馬氏體轉變。調整處理溫度對這種轉變產生較大影響。假如采用低的調整處理溫度(730~760℃),M1可升至室溫附近,在冷卻過程中,馬氏體轉變是完全的。


  如果(guo)采用高(gao)的(de)(de)(de)(de)調(diao)(diao)整(zheng)處(chu)理(li)(li)溫(wen)度(du)(930~955℃),因析(xi)出的(de)(de)(de)(de)碳較少,M1仍保(bao)持在(zai)攝氏(shi)(shi)(shi)(shi)零(ling)度(du)以(yi)下溫(wen)度(du),此(ci)時(shi)(shi)(shi)鋼(gang)(gang)不(bu)能完(wan)(wan)全轉(zhuan)變(bian)(bian)為馬(ma)氏(shi)(shi)(shi)(shi)體(ti)(ti),為了完(wan)(wan)全轉(zhuan)變(bian)(bian)成馬(ma)氏(shi)(shi)(shi)(shi)體(ti)(ti),必須施予(yu)冷處(chu)理(li)(li)工序。調(diao)(diao)整(zheng)處(chu)理(li)(li)溫(wen)度(du)愈高(gao),因固溶(rong)體(ti)(ti)中含碳量(liang)高(gao),所(suo)(suo)轉(zhuan)變(bian)(bian)成的(de)(de)(de)(de)馬(ma)氏(shi)(shi)(shi)(shi)體(ti)(ti)較低溫(wen)調(diao)(diao)整(zheng)處(chu)理(li)(li)所(suo)(suo)轉(zhuan)變(bian)(bian)成的(de)(de)(de)(de)馬(ma)氏(shi)(shi)(shi)(shi)體(ti)(ti)具(ju)(ju)有更高(gao)的(de)(de)(de)(de)強度(du)。此(ci)外,亦(yi)可(ke)(ke)借助(zhu)冷加工完(wan)(wan)成馬(ma)氏(shi)(shi)(shi)(shi)體(ti)(ti)轉(zhuan)變(bian)(bian)。這些(xie)馬(ma)氏(shi)(shi)(shi)(shi)體(ti)(ti)組織隨后(hou)在(zai)455~565℃時(shi)(shi)(shi)效(xiao)(xiao)(xiao)1~3h使之進一步強化。較高(gao)的(de)(de)(de)(de)時(shi)(shi)(shi)效(xiao)(xiao)(xiao)溫(wen)度(du),可(ke)(ke)提(ti)高(gao)鋼(gang)(gang)的(de)(de)(de)(de)韌(ren)性,但降低了可(ke)(ke)能達到的(de)(de)(de)(de)強度(du)和達此(ci)目的(de)(de)(de)(de)所(suo)(suo)需的(de)(de)(de)(de)時(shi)(shi)(shi)效(xiao)(xiao)(xiao)時(shi)(shi)(shi)間(jian)。對于(yu)大多數沉淀硬化不(bu)銹鋼(gang)(gang)在(zai)480~510℃時(shi)(shi)(shi)效(xiao)(xiao)(xiao),使用標(biao)準的(de)(de)(de)(de)時(shi)(shi)(shi)效(xiao)(xiao)(xiao)時(shi)(shi)(shi)間(jian),使之處(chu)于(yu)完(wan)(wan)全時(shi)(shi)(shi)效(xiao)(xiao)(xiao)或(huo)輕微過時(shi)(shi)(shi)效(xiao)(xiao)(xiao)狀態,可(ke)(ke)獲得最佳的(de)(de)(de)(de)強度(du)和韌(ren)性配合;在(zai)510℃以(yi)上溫(wen)度(du)時(shi)(shi)(shi)效(xiao)(xiao)(xiao),處(chu)于(yu)明顯(xian)的(de)(de)(de)(de)過時(shi)(shi)(shi)效(xiao)(xiao)(xiao)狀態,僅在(zai)要(yao)求具(ju)(ju)有較高(gao)韌(ren)性的(de)(de)(de)(de)情況(kuang)下使用。


  半奧(ao)氏(shi)體(ti)(ti)沉淀(dian)硬化(hua)不銹(xiu)鋼(gang)的代表(biao)鋼(gang)種有(you)07Cr7Ni7A1、07Cr15Ni7Mo2Al。該類鋼(gang)中(zhong)均含有(you)15%~17%的Cr并含有(you)Ni、Mo等元素(su),因此具有(you)足夠的不銹(xiu)性,而且其(qi)耐(nai)蝕性在一些介(jie)質(zhi)中(zhong)與(yu)18-8型奧(ao)氏(shi)體(ti)(ti)不銹(xiu)鋼(gang)相(xiang)當(dang)或(huo)相(xiang)近。該類鋼(gang)一般以(yi)固溶狀態供貨,其(qi)金相(xiang)組織基(ji)本(ben)為奧(ao)氏(shi)體(ti)(ti),并含有(you)5%~20%的鐵素(su)體(ti)(ti)。奧(ao)氏(shi)體(ti)(ti)塑(su)性好,容易(yi)進(jin)行(xing)(xing)(xing)冷加(jia)工成形(xing)和焊接,待(dai)加(jia)工成形(xing)后再(zai)進(jin)行(xing)(xing)(xing)特殊(shu)的中(zhong)間處(chu)理,使奧(ao)氏(shi)體(ti)(ti)轉變為低碳(tan)馬(ma)氏(shi)體(ti)(ti),并通過時效處(chu)理,進(jin)行(xing)(xing)(xing)沉淀(dian)硬化(hua)來達到更高(gao)的強度。


  07Cr15Ni7Mo2Al鋼(gang)的綜(zong)合(he)性(xing)能優(you)于07Cr17Ni7Al鋼(gang),因此(ci)在化學工業中應(ying)用(yong)較廣,主要用(yong)于制(zhi)造耐蝕(shi)(shi)性(xing)好并且具有高強度的各種(zhong)容器(qi)、管道、彈(dan)簧等,其耐蝕(shi)(shi)性(xing)優(you)于馬氏體(ti)不銹鋼(gang)、馬氏體(ti)沉(chen)淀硬化不銹鋼(gang)和馬氏體(ti)時效(xiao)鋼(gang)。


  在固溶狀態下,07Cr7Ni7A1和07Cr15Ni7Mo2Al鋼具有(you)奧氏體組織結構時,能夠承受(shou)冷(leng)(leng)加(jia)(jia)(jia)工(gong)(gong)(gong)(gong)變形,但是這兩(liang)種鋼都(dou)具有(you)冷(leng)(leng)加(jia)(jia)(jia)工(gong)(gong)(gong)(gong)硬化(hua)傾向,因此冷(leng)(leng)軋(ya)、冷(leng)(leng)沖壓等多采用道次少、壓下量大、增加(jia)(jia)(jia)多次中間固溶處理(li)的(de)(de)工(gong)(gong)(gong)(gong)藝方法來進行加(jia)(jia)(jia)工(gong)(gong)(gong)(gong)。熱(re)加(jia)(jia)(jia)工(gong)(gong)(gong)(gong)較容(rong)易,合適的(de)(de)加(jia)(jia)(jia)工(gong)(gong)(gong)(gong)溫度(du)為950~1150℃。半奧氏體沉淀硬化(hua)不銹(xiu)鋼的(de)(de)熱(re)處理(li)工(gong)(gong)(gong)(gong)藝較為復雜,且要(yao)求非常嚴格。只有(you)按照(zhao)規定的(de)(de)工(gong)(gong)(gong)(gong)藝規范(溫度(du)、時間、冷(leng)(leng)卻(que)速度(du))予以控制,才(cai)能獲得較佳的(de)(de)力學性能。


  該類鋼焊接性良好,可采用(yong)電弧焊、氬弧焊,焊前不需預熱,焊后(hou)需進(jin)行固溶退火處理(li)。








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