不銹鋼的爐中(zhong)釬(han)焊一般是在某種保(bao)護性(xing)氣(qi)(qi)氛下或真空中(zhong)進行(xing)，保(bao)護氣(qi)(qi)氛有氫氣(qi)(qi)、分解(jie)氨和氬氣(qi)(qi)。
干燥的氫氣或分解氨常用做爐中釬焊不銹(xiu)鋼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(shi)(shi)用氫氣(qi)(qi)(qi)(qi)或分解(jie)氨(an)(an)作(zuo)保護氣(qi)(qi)(qi)(qi)氛(fen)的(de)好處是：可(ke)實現釬焊(han)爐的(de)連續工(gong)作(zuo)，便于大批量生(sheng)產(chan)；釬焊(han)過程(cheng)中不需使(shi)(shi)用釬劑(ji)，且焊(han)后(hou)工(gong)件光亮，無需任何焊(han)后(hou)工(gong)件表面清理工(gong)作(zuo)；可(ke)配(pei)合選用的(de)釬料品種多；在批量生(sheng)產(chan)條(tiao)件下焊(han)接成本低。但是使(shi)(shi)用氫氣(qi)(qi)(qi)(qi)或分解(jie)氨(an)(an)作(zuo)保護氣(qi)(qi)(qi)(qi)氛(fen)時要注意生(sheng)產(chan)安(an)全，當空氣(qi)(qi)(qi)(qi)中混有4%~74%的(de)氫氣(qi)(qi)(qi)(qi)或12.5%~27%氨(an)(an)氣(qi)(qi)(qi)(qi)時，會因燃燒而產(chan)生(sheng)爆炸。
作為惰性(xing)(xing)氣(qi)(qi)體，氬氣(qi)(qi)可(ke)用(yong)作爐(lu)中釬焊不(bu)銹(xiu)鋼時的(de)保護氣(qi)(qi)氛。與氫氣(qi)(qi)和分解(jie)氨不(bu)同，氬氣(qi)(qi)不(bu)具有還原性(xing)(xing)，只是利用(yong)其(qi)惰性(xing)(xing)保護不(bu)銹(xiu)鋼表面在釬焊過程中不(bu)氧化(hua)，所以不(bu)銹(xiu)鋼進爐(lu)釬焊前(qian)必須徹(che)底清除其(qi)表面的(de)氧化(hua)膜，并且一般(ban)要求氬氣(qi)(qi)的(de)露點低于-40℃。
使(shi)用氬氣作(zuo)保護(hu)氣氛一般是因為以下某種或多種原因：①. 可采用含高蒸汽壓元素的釬(han)(han)(han)，如錳基釬(han)(han)(han)料(liao)(liao)或含錳較多的釬(han)(han)(han)料(liao)(liao)；②. 單件或小批(pi)量釬(han)(han)(han)焊時，設備成本低；③. 不(bu)銹鋼與(yu)異種材釬(han)(han)(han)焊時避免某些材料(liao)(liao)與(yu)爐內(nei)氣氛的反(fan)應，如在含氫氣氛中釬(han)(han)(han)焊連接不(bu)銹鋼與(yu)鈦(tai)合金(jin)(jin)時，鈦(tai)金(jin)(jin)吸(xi)氫并與(yu)氫反(fan)應；④. 生產過(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
程中要隨(sui)時(shi)注意容器(qi)內的(de)壓力，當容器(qi)內壓力超過大氣(qi)(qi)壓較多時(shi)應隨(sui)時(shi)放出一(yi)些氣(qi)(qi)體(ti)，以(yi)保(bao)證(zheng)容器(qi)完好(hao)和(he)生(sheng)產安全。使用(yong)特制的(de)容器(qi)還有另一(yi)個便(bian)利：當使用(yong)未經凈化的(de)普通(tong)(tong)瓶裝氬(ya)氣(qi)(qi)時(shi)，可向(xiang)釬(han)(han)焊爐內通(tong)(tong)入少許(xu)(xu)BF3氣(qi)(qi)體(ti)釬(han)(han)劑(ji)，或加入少許(xu)(xu)氟(fu)硼(peng)酸(suan)鉀，氟(fu)硼(peng)酸(suan)鉀在800~900℃分(fen)(fen)解產生(sheng)BF3.BF3可以(yi)去除金屬表面的(de)氧化物(wu)(wu)，促進釬(han)(han)料的(de)潤濕。氣(qi)(qi)體(ti)釬(han)(han)劑(ji)的(de)使用(yong)濃度一(yi)般(ban)控制在0.1%~0.001%(體(ti)積(ji)分(fen)(fen)數），避(bi)免焊后形(xing)成殘渣。氟(fu)化物(wu)(wu)對人體(ti)有害，要注意工(gong)作(zuo)場地(di)的(de)通(tong)(tong)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(lu)中(zhong)釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)時(shi)影響釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)接頭性(xing)(xing)(xing)能(neng)，特別是力學性(xing)(xing)(xing)能(neng)的(de)(de)主要工藝參數(shu)(shu)包(bao)釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)、保(bao)(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)間(jian)(jian)。釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)一(yi)般(ban)選(xuan)擇(ze)在(zai)(zai)(zai)釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)液(ye)相線(xian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)以(yi)上50~100℃,保(bao)(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)間(jian)(jian)在(zai)(zai)(zai)5~10min.當工件(jian)較大時(shi)，可(ke)在(zai)(zai)(zai)升溫(wen)(wen)(wen)(wen)(wen)過(guo)程(cheng)中(zhong)釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)固(gu)相線(xian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)以(yi)下(xia)某溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)保(bao)(bao)溫(wen)(wen)(wen)(wen)(wen)一(yi)段時(shi)間(jian)(jian)，確(que)保(bao)(bao)工件(jian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)均勻。使用鎳(nie)基(ji)(ji)(ji)釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)時(shi)，除了釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)和保(bao)(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)間(jian)(jian)外，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)間(jian)(jian)隙(xi)也是接頭強(qiang)度(du)(du)(du)(du)和塑(su)性(xing)(xing)(xing)的(de)(de)決定(ding)因(yin)素之一(yi)。圖3-5、圖3-6顯示了三種鎳(nie)基(ji)(ji)(ji)釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)不銹(xiu)鋼時(shi)釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)接頭強(qiang)度(du)(du)(du)(du)與釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)間(jian)(jian)隙(xi)的(de)(de)關(guan)系。為(wei)降低釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)的(de)(de)熔點(dian)，鎳(nie)基(ji)(ji)(ji)釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)中(zhong)含有較多的(de)(de)硼(peng)(peng)(peng)、硅(gui)、磷(lin)，它們在(zai)(zai)(zai)釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)組(zu)(zu)織中(zhong)以(yi)脆(cui)(cui)性(xing)(xing)(xing)的(de)(de)硼(peng)(peng)(peng)化(hua)(hua)(hua)物、硅(gui)化(hua)(hua)(hua)物、磷(lin)化(hua)(hua)(hua)物形(xing)式(shi)存(cun)在(zai)(zai)(zai)。釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)時(shi)在(zai)(zai)(zai)一(yi)定(ding)的(de)(de)釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)和保(bao)(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)間(jian)(jian)下(xia)，當釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)間(jian)(jian)隙(xi)小于某一(yi)數(shu)(shu)值(zhi)，硼(peng)(peng)(peng)、硅(gui)、磷(lin)向母(mu)材擴散充(chong)分，凝(ning)固(gu)后釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)組(zu)(zu)織為(wei)鎳(nie)基(ji)(ji)(ji)固(gu)溶體(ti)，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)強(qiang)度(du)(du)(du)(du)高、塑(su)性(xing)(xing)(xing)好，此數(shu)(shu)值(zhi)稱作該釬(han)(han)(han)(han)(han)(han)(han)(han)料(liao)(liao)在(zai)(zai)(zai)此釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)和保(bao)(bao)溫(wen)(wen)(wen)(wen)(wen)時(shi)間(jian)(jian)下(xia)的(de)(de)最大釬(han)(han)(han)(han)(han)(han)(han)(han)焊(han)間(jian)(jian)隙(xi)。當釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)間(jian)(jian)隙(xi)超過(guo)最大間(jian)(jian)隙(xi)，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)中(zhong)硼(peng)(peng)(peng)、硅(gui)、磷(lin)向母(mu)材擴散不充(chong)分，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)中(zhong)會(hui)存(cun)在(zai)(zai)(zai)脆(cui)(cui)性(xing)(xing)(xing)化(hua)(hua)(hua)合物，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)的(de)(de)強(qiang)度(du)(du)(du)(du)和塑(su)性(xing)(xing)(xing)都會(hui)下(xia)降。而且在(zai)(zai)(zai)一(yi)定(ding)范圍內，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)越(yue)(yue)寬，釬(han)(han)(han)(han)(han)(han)(han)(han)縫(feng)(feng)(feng)(feng)中(zhong)脆(cui)(cui)性(xing)(xing)(xing)相越(yue)(yue)多，接頭的(de)(de)強(qiang)度(du)(du)(du)(du)和塑(su)性(xing)(xing)(xing)越(yue)(yue)低。
在(zai)(zai)釬(han)焊(han)實際部(bu)(bu)件時(shi)(shi)，有時(shi)(shi)部(bu)(bu)件加(jia)工精(jing)度(du)或裝(zhuang)配精(jing)度(du)很難(nan)保(bao)(bao)證釬(han)縫間隙(xi)很小，適當地提高釬(han)焊(han)溫度(du)或延長保(bao)(bao)溫時(shi)(shi)間可(ke)增(zeng)大最大釬(han)焊(han)間隙(xi)，見圖(tu)3-7。當在(zai)(zai)高溫下長時(shi)(shi)間保(bao)(bao)溫造(zao)成母(mu)材(cai)晶(jing)粒過(guo)分(fen)長大或釬(han)料對母(mu)材(cai)溶蝕(shi)過(guo)度(du)時(shi)(shi)，也(ye)可(ke)在(zai)(zai)焊(han)后接頭冷卻到(dao)某(mou)一較(jiao)低溫度(du)保(bao)(bao)溫，通過(guo)擴散消除釬(han)縫中的(de)脆性(xing)相(xiang)而(er)增(zeng)大最大釬(han)焊(han)間隙(xi)，見圖(tu)3-8。但由于磷原子(zi)較(jiao)大，向母(mu)材(cai)中擴散困難(nan)，這(zhe)些措施對Ni-Cr-P和Ni-P這(zhe)類釬(han)料作用(yong)不大。
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。
