不銹(xiu)鋼的爐中(zhong)釬焊一般是在(zai)某種保護(hu)性氣(qi)氛(fen)下或真空(kong)中(zhong)進行，保護(hu)氣(qi)氛(fen)有氫(qing)氣(qi)、分解氨(an)和氬氣(qi)。
干燥的氫氣或分解氨常用做爐中釬焊不銹鋼時的還原性保護氣氛，它們可還原不(bu)銹鋼表面的氧化膜，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(shi)用氫(qing)氣(qi)(qi)或分解氨(an)作(zuo)保(bao)護氣(qi)(qi)氛的好處是(shi)：可(ke)實現釬(han)焊(han)(han)爐的連(lian)續工作(zuo)，便于大批(pi)(pi)量生(sheng)產(chan)；釬(han)焊(han)(han)過程中不(bu)需使(shi)用釬(han)劑(ji)，且焊(han)(han)后工件光亮，無需任何(he)焊(han)(han)后工件表面清理工作(zuo)；可(ke)配合(he)選用的釬(han)料品種多；在批(pi)(pi)量生(sheng)產(chan)條(tiao)件下焊(han)(han)接成本低。但是(shi)使(shi)用氫(qing)氣(qi)(qi)或分解氨(an)作(zuo)保(bao)護氣(qi)(qi)氛時要注意生(sheng)產(chan)安全，當空氣(qi)(qi)中混有4%~74%的氫(qing)氣(qi)(qi)或12.5%~27%氨(an)氣(qi)(qi)時，會(hui)因燃燒而(er)產(chan)生(sheng)爆炸。
作為惰(duo)性(xing)氣(qi)體，氬氣(qi)可(ke)用(yong)作爐(lu)中(zhong)釬(han)焊(han)不銹鋼(gang)時的(de)保護(hu)氣(qi)氛。與氫(qing)氣(qi)和分解氨不同，氬氣(qi)不具有還原性(xing)，只是利用(yong)其(qi)(qi)惰(duo)性(xing)保護(hu)不銹鋼(gang)表面在釬(han)焊(han)過程中(zhong)不氧(yang)化，所以不銹鋼(gang)進(jin)爐(lu)釬(han)焊(han)前必(bi)須徹底清除其(qi)(qi)表面的(de)氧(yang)化膜，并且一般要(yao)求氬氣(qi)的(de)露(lu)點低于-40℃。
使用氬氣作保(bao)護氣氛一(yi)般是(shi)因(yin)為以下某種或(huo)多種原因(yin)：①. 可(ke)采用含高蒸(zheng)汽壓元(yuan)素的釬，如錳基釬料(liao)或(huo)含錳較多的釬料(liao)；②. 單件或(huo)小(xiao)批量釬焊時，設備成本(ben)低；③. 不(bu)銹(xiu)鋼與(yu)異種材釬焊時避免某些材料(liao)與(yu)爐內氣氛的反應，如在含氫氣氛中釬焊連接不(bu)銹(xiu)鋼與(yu)鈦合金時，鈦金吸氫并與(yu)氫反應；④. 生產過程安(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
程中要隨時(shi)(shi)注(zhu)意(yi)容器(qi)(qi)內的壓力，當(dang)容器(qi)(qi)內壓力超過大氣(qi)(qi)壓較多時(shi)(shi)應隨時(shi)(shi)放出一(yi)(yi)些氣(qi)(qi)體(ti)，以保證容器(qi)(qi)完好和生產(chan)安全(quan)。使(shi)用特制(zhi)的容器(qi)(qi)還有另(ling)一(yi)(yi)個便利(li)：當(dang)使(shi)用未經凈化的普通瓶裝氬氣(qi)(qi)時(shi)(shi)，可(ke)向釬(han)(han)焊(han)爐(lu)內通入少(shao)許(xu)BF3氣(qi)(qi)體(ti)釬(han)(han)劑，或加入少(shao)許(xu)氟(fu)硼酸鉀(jia)，氟(fu)硼酸鉀(jia)在(zai)800~900℃分解產(chan)生BF3.BF3可(ke)以去除金屬表面的氧化物，促進(jin)釬(han)(han)料的潤濕(shi)。氣(qi)(qi)體(ti)釬(han)(han)劑的使(shi)用濃度一(yi)(yi)般控制(zhi)在(zai)0.1%~0.001%(體(ti)積分數），避免焊(han)后(hou)形成殘渣。氟(fu)化物對(dui)人體(ti)有害，要注(zhu)意(yi)工(gong)作場地(di)的通風。
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(zhong)(zhong)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)時(shi)(shi)(shi)(shi)影響釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)接(jie)頭(tou)性(xing)能，特(te)別是力學性(xing)能的(de)主(zhu)要工藝(yi)參數(shu)包釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)、保(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)(shi)(shi)(shi)間(jian)(jian)。釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)一(yi)(yi)(yi)般(ban)選擇在(zai)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)液(ye)相(xiang)線溫(wen)(wen)(wen)(wen)(wen)度(du)(du)以(yi)上(shang)50~100℃,保(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)(shi)(shi)(shi)間(jian)(jian)在(zai)5~10min.當工件較大時(shi)(shi)(shi)(shi)，可在(zai)升溫(wen)(wen)(wen)(wen)(wen)過程(cheng)中(zhong)(zhong)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)固相(xiang)線溫(wen)(wen)(wen)(wen)(wen)度(du)(du)以(yi)下某(mou)(mou)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)保(bao)溫(wen)(wen)(wen)(wen)(wen)一(yi)(yi)(yi)段(duan)時(shi)(shi)(shi)(shi)間(jian)(jian)，確(que)保(bao)工件溫(wen)(wen)(wen)(wen)(wen)度(du)(du)均勻。使用鎳(nie)(nie)基(ji)(ji)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)時(shi)(shi)(shi)(shi)，除了(le)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)和保(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)(shi)(shi)(shi)間(jian)(jian)外，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)隙(xi)(xi)也是接(jie)頭(tou)強(qiang)度(du)(du)和塑性(xing)的(de)決定因(yin)素之(zhi)一(yi)(yi)(yi)。圖3-5、圖3-6顯示(shi)了(le)三種鎳(nie)(nie)基(ji)(ji)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)不銹鋼時(shi)(shi)(shi)(shi)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)接(jie)頭(tou)強(qiang)度(du)(du)與釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)隙(xi)(xi)的(de)關(guan)系。為(wei)降(jiang)低(di)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)的(de)熔點，鎳(nie)(nie)基(ji)(ji)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)中(zhong)(zhong)含有較多的(de)硼(peng)(peng)、硅(gui)、磷(lin)(lin)，它們在(zai)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)組(zu)織中(zhong)(zhong)以(yi)脆(cui)性(xing)的(de)硼(peng)(peng)化(hua)(hua)物、硅(gui)化(hua)(hua)物、磷(lin)(lin)化(hua)(hua)物形式存在(zai)。釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)時(shi)(shi)(shi)(shi)在(zai)一(yi)(yi)(yi)定的(de)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)和保(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)(shi)(shi)(shi)間(jian)(jian)下，當釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)隙(xi)(xi)小于某(mou)(mou)一(yi)(yi)(yi)數(shu)值，硼(peng)(peng)、硅(gui)、磷(lin)(lin)向(xiang)母材擴散充分，凝固后釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)組(zu)織為(wei)鎳(nie)(nie)基(ji)(ji)固溶體，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)強(qiang)度(du)(du)高(gao)、塑性(xing)好(hao)，此數(shu)值稱作(zuo)該(gai)釬(han)(han)(han)(han)(han)(han)(han)(han)(han)料(liao)在(zai)此釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)和保(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)(shi)(shi)(shi)間(jian)(jian)下的(de)最(zui)大釬(han)(han)(han)(han)(han)(han)(han)(han)(han)焊(han)(han)間(jian)(jian)隙(xi)(xi)。當釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)間(jian)(jian)隙(xi)(xi)超(chao)過最(zui)大間(jian)(jian)隙(xi)(xi)，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)中(zhong)(zhong)硼(peng)(peng)、硅(gui)、磷(lin)(lin)向(xiang)母材擴散不充分，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)中(zhong)(zhong)會存在(zai)脆(cui)性(xing)化(hua)(hua)合物，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)的(de)強(qiang)度(du)(du)和塑性(xing)都會下降(jiang)。而且在(zai)一(yi)(yi)(yi)定范圍內，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)越(yue)寬，釬(han)(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)中(zhong)(zhong)脆(cui)性(xing)相(xiang)越(yue)多，接(jie)頭(tou)的(de)強(qiang)度(du)(du)和塑性(xing)越(yue)低(di)。
在釬(han)(han)(han)(han)焊實際部件(jian)時(shi)，有時(shi)部件(jian)加工精(jing)度(du)(du)或(huo)裝(zhuang)配精(jing)度(du)(du)很難保(bao)證釬(han)(han)(han)(han)縫(feng)間隙很小，適當地提高釬(han)(han)(han)(han)焊溫(wen)(wen)(wen)(wen)度(du)(du)或(huo)延長保(bao)溫(wen)(wen)(wen)(wen)時(shi)間可增(zeng)(zeng)大(da)最(zui)大(da)釬(han)(han)(han)(han)焊間隙，見圖(tu)3-7。當在高溫(wen)(wen)(wen)(wen)下長時(shi)間保(bao)溫(wen)(wen)(wen)(wen)造成母(mu)材晶粒過分長大(da)或(huo)釬(han)(han)(han)(han)料對母(mu)材溶(rong)蝕過度(du)(du)時(shi)，也可在焊后接頭冷(leng)卻(que)到(dao)某一較低溫(wen)(wen)(wen)(wen)度(du)(du)保(bao)溫(wen)(wen)(wen)(wen)，通(tong)過擴(kuo)散消除釬(han)(han)(han)(han)縫(feng)中的(de)脆性相(xiang)而增(zeng)(zeng)大(da)最(zui)大(da)釬(han)(han)(han)(han)焊間隙，見圖(tu)3-8。但(dan)由于磷原子(zi)較大(da)，向母(mu)材中擴(kuo)散困難，這(zhe)些措施對Ni-Cr-P和Ni-P這(zhe)類釬(han)(han)(han)(han)料作用不大(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。
