不銹鋼(gang)的爐(lu)中釬焊一般(ban)是在某種保護性氣氛(fen)下(xia)或真空中進行，保護氣氛(fen)有氫(qing)氣、分(fen)解氨和氬氣。
干燥的氫氣或分解氨常用做爐中釬焊不(bu)銹鋼(gang)時的還原性保護氣氛，它們可還原不銹(xiu)鋼表面的氧化膜，并保護不銹鋼表面在釬焊時不再氧化。一般要求氫氣或分解氨的露點低于-40℃,但也要考慮保護氣體的露點要與釬焊溫度及母材的成分相適應。釬焊溫度越低、不銹鋼表面氧化膜越穩定，要求氫氣露點越低，見圖3-4。使用分解氨作保護氣氛時，必須保證NH3完全分解，避免殘余的NH3使不銹鋼表面氮化。
使用(yong)氫氣(qi)(qi)或(huo)(huo)(huo)分解(jie)氨(an)(an)作(zuo)(zuo)(zuo)保護氣(qi)(qi)氛的好(hao)處是：可(ke)實現(xian)釬(han)焊(han)爐的連續工(gong)(gong)作(zuo)(zuo)(zuo)，便于大批量(liang)生(sheng)產；釬(han)焊(han)過(guo)程中不需使用(yong)釬(han)劑，且焊(han)后工(gong)(gong)件光(guang)亮，無需任何焊(han)后工(gong)(gong)件表面清理工(gong)(gong)作(zuo)(zuo)(zuo)；可(ke)配合選(xuan)用(yong)的釬(han)料品種多(duo)；在批量(liang)生(sheng)產條件下焊(han)接成本低。但(dan)是使用(yong)氫氣(qi)(qi)或(huo)(huo)(huo)分解(jie)氨(an)(an)作(zuo)(zuo)(zuo)保護氣(qi)(qi)氛時(shi)要注意(yi)生(sheng)產安全，當(dang)空氣(qi)(qi)中混有4%~74%的氫氣(qi)(qi)或(huo)(huo)(huo)12.5%~27%氨(an)(an)氣(qi)(qi)時(shi)，會因燃燒而產生(sheng)爆(bao)炸(zha)。
作(zuo)為惰(duo)(duo)性氣(qi)體，氬(ya)(ya)氣(qi)可用作(zuo)爐中釬焊(han)不銹(xiu)鋼時的保護氣(qi)氛。與(yu)氫(qing)氣(qi)和分解氨不同(tong)，氬(ya)(ya)氣(qi)不具有還原性，只是利(li)用其(qi)惰(duo)(duo)性保護不銹(xiu)鋼表(biao)面在釬焊(han)過程中不氧(yang)化，所(suo)以(yi)不銹(xiu)鋼進爐釬焊(han)前(qian)必(bi)須徹(che)底(di)清除其(qi)表(biao)面的氧(yang)化膜，并且一般要求氬(ya)(ya)氣(qi)的露(lu)點低(di)于-40℃。
使用氬氣(qi)作保護氣(qi)氛一般(ban)是因為以下某種(zhong)(zhong)或多種(zhong)(zhong)原(yuan)因：①. 可采(cai)用含(han)高蒸汽壓元素的釬(han)(han)，如錳基釬(han)(han)料或含(han)錳較(jiao)多的釬(han)(han)料；②. 單件(jian)或小批量釬(han)(han)焊時，設備成(cheng)本低(di)；③. 不(bu)(bu)銹(xiu)(xiu)鋼(gang)與異種(zhong)(zhong)材釬(han)(han)焊時避(bi)免(mian)某些材料與爐內(nei)氣(qi)氛的反應，如在含(han)氫(qing)氣(qi)氛中釬(han)(han)焊連接(jie)不(bu)(bu)銹(xiu)(xiu)鋼(gang)與鈦合(he)金時，鈦金吸氫(qing)并與氫(qing)反應；④. 生(sheng)產過(guo)程安(an)全。
使用氬氣作保護氣氛時，常見的做法是將真空爐抽至高真空后（10-2~10-3Pa)充入少量氬氣，關閉爐體氣閥后升溫。或者在特制的密封容器內通人流動的氬氣，將空氣趕凈后，容器放入馬弗爐內加熱。也可在趕凈空氣后，關閉氣路，容器放人馬弗爐內加熱，但在升溫過
程(cheng)中(zhong)要隨時(shi)注意(yi)容(rong)(rong)器(qi)內的(de)(de)壓力，當容(rong)(rong)器(qi)內壓力超(chao)過大氣(qi)壓較多時(shi)應(ying)隨時(shi)放出一些氣(qi)體(ti)(ti)，以保證容(rong)(rong)器(qi)完好和生產安全。使用(yong)(yong)特(te)制的(de)(de)容(rong)(rong)器(qi)還有(you)另(ling)一個便利：當使用(yong)(yong)未經凈化的(de)(de)普通瓶裝(zhuang)氬氣(qi)時(shi)，可向(xiang)釬焊爐(lu)內通入少(shao)許BF3氣(qi)體(ti)(ti)釬劑(ji)，或加入少(shao)許氟(fu)硼(peng)酸(suan)鉀(jia)，氟(fu)硼(peng)酸(suan)鉀(jia)在800~900℃分(fen)解產生BF3.BF3可以去除金(jin)屬表面的(de)(de)氧化物，促進釬料(liao)的(de)(de)潤濕。氣(qi)體(ti)(ti)釬劑(ji)的(de)(de)使用(yong)(yong)濃度(du)一般控制在0.1%~0.001%(體(ti)(ti)積分(fen)數），避免焊后形(xing)成(cheng)殘渣。氟(fu)化物對人(ren)體(ti)(ti)有(you)害(hai)，要注意(yi)工作場地的(de)(de)通風(feng)。
在真空爐中釬焊不銹鋼是一種常用且理想的方法。釬焊不銹鋼時一般要求真空度達到10-2～10-3Pa,并且要求真空爐的氣體泄漏率小于10-2Pa/s.使用真空爐釬焊不銹鋼的好處是：可避免不銹鋼的氧化；可避免釬焊爐內氣氛對母材的不良影響；真空爐升、降溫速度慢，工件不變形或變形量很小；無論以何種方式添加釬料均不會在接頭內形成氣孔；無需消耗保護氣體；無需氣體凈化裝置；無安全隱患；帶有充氣及快冷風扇置的真空爐同樣具有較高的生產率，并可實現釬焊與焊后工件熱處理的結合。
在氫氣或分解氨氣氛爐中釬焊不銹鋼可使用紫銅、銅基、銀基、錳基、鎳基和金基釬料。在氬氣氛爐中釬焊不銹鋼可使用銅基、銀基、錳基、金基釬料。在真空爐中釬焊不銹鋼可采用紫銅、不含易蒸發元素（Zn、Cd)或僅含少量高蒸汽壓元素（Mn)的銅基和銀基釬料、鎳基釬料和金基釬料。使用鎳基釬料釬焊不銹鋼薄件時，要選擇對母材溶蝕傾向小的釬料。
爐中釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)時(shi)(shi)影響釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)接頭(tou)性(xing)(xing)(xing)能(neng)，特別是(shi)力學性(xing)(xing)(xing)能(neng)的(de)主要工(gong)藝(yi)參數包釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)度(du)(du)(du)(du)、保(bao)溫(wen)(wen)時(shi)(shi)間(jian)(jian)(jian)。釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)度(du)(du)(du)(du)一(yi)般選擇在(zai)(zai)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)液相線溫(wen)(wen)度(du)(du)(du)(du)以上(shang)50~100℃,保(bao)溫(wen)(wen)時(shi)(shi)間(jian)(jian)(jian)在(zai)(zai)5~10min.當(dang)工(gong)件(jian)較(jiao)大時(shi)(shi)，可(ke)在(zai)(zai)升(sheng)溫(wen)(wen)過(guo)程中釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)固(gu)相線溫(wen)(wen)度(du)(du)(du)(du)以下(xia)某溫(wen)(wen)度(du)(du)(du)(du)保(bao)溫(wen)(wen)一(yi)段時(shi)(shi)間(jian)(jian)(jian)，確保(bao)工(gong)件(jian)溫(wen)(wen)度(du)(du)(du)(du)均勻(yun)。使用(yong)鎳基釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)時(shi)(shi)，除了(le)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)度(du)(du)(du)(du)和(he)保(bao)溫(wen)(wen)時(shi)(shi)間(jian)(jian)(jian)外(wai)，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)(jian)隙(xi)也是(shi)接頭(tou)強(qiang)度(du)(du)(du)(du)和(he)塑(su)性(xing)(xing)(xing)的(de)決定因素之(zhi)一(yi)。圖3-5、圖3-6顯示了(le)三種鎳基釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)不(bu)銹(xiu)鋼時(shi)(shi)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)接頭(tou)強(qiang)度(du)(du)(du)(du)與釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)(jian)隙(xi)的(de)關(guan)系(xi)。為降低釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)的(de)熔點，鎳基釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)中含有(you)較(jiao)多的(de)硼(peng)(peng)、硅(gui)、磷(lin)(lin)，它們在(zai)(zai)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)組織(zhi)中以脆(cui)性(xing)(xing)(xing)的(de)硼(peng)(peng)化(hua)物(wu)、硅(gui)化(hua)物(wu)、磷(lin)(lin)化(hua)物(wu)形式存(cun)在(zai)(zai)。釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)時(shi)(shi)在(zai)(zai)一(yi)定的(de)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)度(du)(du)(du)(du)和(he)保(bao)溫(wen)(wen)時(shi)(shi)間(jian)(jian)(jian)下(xia)，當(dang)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)(jian)隙(xi)小于某一(yi)數值，硼(peng)(peng)、硅(gui)、磷(lin)(lin)向(xiang)母材擴(kuo)散充(chong)分(fen)(fen)，凝(ning)固(gu)后釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)組織(zhi)為鎳基固(gu)溶體，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)強(qiang)度(du)(du)(du)(du)高、塑(su)性(xing)(xing)(xing)好(hao)，此數值稱作該釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)(liao)在(zai)(zai)此釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)度(du)(du)(du)(du)和(he)保(bao)溫(wen)(wen)時(shi)(shi)間(jian)(jian)(jian)下(xia)的(de)最(zui)大釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)間(jian)(jian)(jian)隙(xi)。當(dang)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)(jian)隙(xi)超過(guo)最(zui)大間(jian)(jian)(jian)隙(xi)，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)中硼(peng)(peng)、硅(gui)、磷(lin)(lin)向(xiang)母材擴(kuo)散不(bu)充(chong)分(fen)(fen)，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)中會存(cun)在(zai)(zai)脆(cui)性(xing)(xing)(xing)化(hua)合物(wu)，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)的(de)強(qiang)度(du)(du)(du)(du)和(he)塑(su)性(xing)(xing)(xing)都會下(xia)降。而(er)且在(zai)(zai)一(yi)定范圍(wei)內，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)越寬，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)中脆(cui)性(xing)(xing)(xing)相越多，接頭(tou)的(de)強(qiang)度(du)(du)(du)(du)和(he)塑(su)性(xing)(xing)(xing)越低。
在(zai)釬(han)(han)焊(han)實(shi)際部件時，有(you)時部件加工精度(du)或裝配(pei)精度(du)很(hen)難(nan)保(bao)(bao)(bao)證(zheng)釬(han)(han)縫間隙(xi)很(hen)小，適當地提(ti)高(gao)釬(han)(han)焊(han)溫(wen)(wen)度(du)或延(yan)長(chang)保(bao)(bao)(bao)溫(wen)(wen)時間可增大(da)(da)(da)最大(da)(da)(da)釬(han)(han)焊(han)間隙(xi)，見圖(tu)3-7。當在(zai)高(gao)溫(wen)(wen)下長(chang)時間保(bao)(bao)(bao)溫(wen)(wen)造成母材(cai)晶粒過分長(chang)大(da)(da)(da)或釬(han)(han)料對母材(cai)溶蝕(shi)過度(du)時，也可在(zai)焊(han)后接(jie)頭(tou)冷卻到某一較低溫(wen)(wen)度(du)保(bao)(bao)(bao)溫(wen)(wen)，通(tong)過擴散消除釬(han)(han)縫中的脆性相(xiang)而增大(da)(da)(da)最大(da)(da)(da)釬(han)(han)焊(han)間隙(xi)，見圖(tu)3-8。但(dan)由于磷原子較大(da)(da)(da)，向(xiang)母材(cai)中擴散困難(nan)，這些措施對Ni-Cr-P和Ni-P這類(lei)釬(han)(han)料作用(yong)不(bu)大(da)(da)(da)。
爐中釬焊時為控制釬料不流到接頭外其他部位或造成工件與卡具的粘連，可在防止釬料潤濕處涂止焊劑。釬焊不銹鋼時可以用TiO2、Y2O3或云母粉與乙醇混和后做止焊劑。
