20#精密鋼管批發零售

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　　20#精密鋼管(guan)熱(re)處(chu)理工藝(yi)

　　精密鋼管前奏

　　真(zhen)空(kong)退火(huo)優質彈(dan)簧(huang)鋼(gang)、工具鋼(gang)、精密鋼(gang)管的絲材，不銹(xiu)鋼(gang)制(zhi)品及鈦合(he)金材，作光亮退火(huo)均可采(cai)用真(zhen)空(kong)處理。退火(huo)溫度愈低(di)，則要求真(zhen)空(kong)度愈高。為防止鉻(ge)的蒸發(fa)及加速熱傳導，一般采(cai)用載氣加熱(保(bao)溫)法，并注意對不銹(xiu)鋼(gang)和鈦合(he)金不宜用氮而(er)應采(cai)用氬(ya)氣。

　　精密鋼管過程

　　真空淬(cui)(cui)(cui)(cui)(cui)火(huo)真空淬(cui)(cui)(cui)(cui)(cui)火(huo)爐(lu)按(an)(an)冷(leng)(leng)卻(que)(que)(que)方法(fa)分為油(you)(you)淬(cui)(cui)(cui)(cui)(cui)和(he)氣(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)兩類，按(an)(an)工位數分為單室(shi)(shi)(shi)式和(he)雙(shuang)(shuang)室(shi)(shi)(shi)式，904山\畏嘲均屬周期式作(zuo)業爐(lu)。真空油(you)(you)淬(cui)(cui)(cui)(cui)(cui)爐(lu)都是(shi)(shi)雙(shuang)(shuang)室(shi)(shi)(shi)的(de)(de)，后室(shi)(shi)(shi)置(zhi)電(dian)加(jia)熱(re)元件(jian)，前室(shi)(shi)(shi)的(de)(de)下(xia)(xia)方置(zhi)油(you)(you)槽(cao)。工件(jian)完成加(jia)熱(re)、保(bao)溫(wen)后移入(ru)前室(shi)(shi)(shi)，關閉中(zhong)(zhong)門后向前室(shi)(shi)(shi)充入(ru)惰性氣(qi)(qi)(qi)至大約2.66%26times;lO ～1.01%26times;10 Pa(200～760mm汞柱)，入(ru)油(you)(you)。油(you)(you)淬(cui)(cui)(cui)(cui)(cui)易引起工件(jian)表(biao)面變(bian)(bian)質。由于(yu)(yu)表(biao)面活性大，在(zai)短(duan)暫的(de)(de)高(gao)(gao)溫(wen)油(you)(you)膜作(zuo)用(yong)下(xia)(xia)即可發(fa)生顯著薄層滲碳，此外，碳黑和(he)油(you)(you)在(zai)表(biao)面的(de)(de)粘(zhan)附對(dui)簡化(hua)熱(re)處(chu)理流程很不利。真空淬(cui)(cui)(cui)(cui)(cui)火(huo)技(ji)術(shu)(shu)的(de)(de)發(fa)展(zhan)主(zhu)要在(zai)于(yu)(yu)研制性能(neng)優(you)良、工位單一的(de)(de)氣(qi)(qi)(qi)冷(leng)(leng)淬(cui)(cui)(cui)(cui)(cui)火(huo)爐(lu)。前述雙(shuang)(shuang)室(shi)(shi)(shi)式爐(lu)亦可用(yong)于(yu)(yu)氣(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)(在(zai)前室(shi)(shi)(shi)噴(pen)氣(qi)(qi)(qi)冷(leng)(leng)卻(que)(que)(que))，但雙(shuang)(shuang)工位式的(de)(de)操(cao)作(zuo)使大批量裝(zhuang)爐(lu)的(de)(de)生產(chan)發(fa)生困難，也易在(zai)高(gao)(gao)溫(wen)移動中(zhong)(zhong)引起工件(jian)變(bian)(bian)形或(huo)改(gai)變(bian)(bian)工件(jian)方位增(zeng)加(jia)淬(cui)(cui)(cui)(cui)(cui)火(huo)變(bian)(bian)形。單一工位的(de)(de)氣(qi)(qi)(qi)冷(leng)(leng)淬(cui)(cui)(cui)(cui)(cui)火(huo)爐(lu)是(shi)(shi)在(zai)加(jia)熱(re)保(bao)溫(wen)完成后在(zai)加(jia)熱(re)室(shi)(shi)(shi)內噴(pen)氣(qi)(qi)(qi)冷(leng)(leng)卻(que)(que)(que)。氣(qi)(qi)(qi)冷(leng)(leng)的(de)(de)冷(leng)(leng)速(su)不如油(you)(you)冷(leng)(leng)快，也低于(yu)(yu)傳統淬(cui)(cui)(cui)(cui)(cui)火(huo)法(fa)中(zhong)(zhong)的(de)(de)熔鹽等(deng)溫(wen)、分級淬(cui)(cui)(cui)(cui)(cui)火(huo)。因而(er)，不斷提高(gao)(gao)噴(pen)冷(leng)(leng)室(shi)(shi)(shi)壓(ya)(ya)力，增(zeng)大流量，以(yi)及采用(yong)摩爾質量比(bi)氮和(he)氬小的(de)(de)惰性氣(qi)(qi)(qi)體氦(hai)和(he)氫，是(shi)(shi)當今真空淬(cui)(cui)(cui)(cui)(cui)火(huo)技(ji)術(shu)(shu)發(fa)展(zhan)的(de)(de)主(zhu)流。70年代后期將(jiang)氮氣(qi)(qi)(qi)噴(pen)冷(leng)(leng)的(de)(de)壓(ya)(ya)力從(1～2)%26times;10Pa提高(gao)(gao)到(5～6)%26times;10Pa，使冷(leng)(leng)卻(que)(que)(que)能(neng)力接近于(yu)(yu)常壓(ya)(ya)下(xia)(xia)的(de)(de)油(you)(you)冷(leng)(leng)。80年代中(zhong)(zhong)期出現(xian)超高(gao)(gao)壓(ya)(ya)氣(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)，用(yong)(10～20)%26times;10Pa的(de)(de)氦(hai)，冷(leng)(leng)卻(que)(que)(que)能(neng)力等(deng)于(yu)(yu)或(huo)略高(gao)(gao)于(yu)(yu)油(you)(you)淬(cui)(cui)(cui)(cui)(cui)，已進(jin)入(ru)工業實用(yong)。90年代初采用(yong)40%26times;10Pa的(de)(de)氫氣(qi)(qi)(qi)，接近水(shui)淬(cui)(cui)(cui)(cui)(cui)的(de)(de)冷(leng)(leng)卻(que)(que)(que)能(neng)力，尚處(chu)于(yu)(yu)起步階段。工業發(fa)達國家已進(jin)展(zhan)到以(yi)高(gao)(gao)壓(ya)(ya)(5～6)%26times;10。Pa氣(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)為主(zhu)體，而(er)中(zhong)(zhong)國產(chan)氣(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)一些金屬的(de)(de)蒸氣(qi)(qi)(qi)壓(ya)(ya)(理論值(zhi))與溫(wen)度的(de)(de)關系則(ze)尚處(chu)于(yu)(yu)一般加(jia)壓(ya)(ya)氣(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)(2%26times;10Pa)型(xing)階段。

　　結果真空(kong)滲(shen)(shen)(shen)(shen)碳(tan)(tan)為(wei)真空(kong)滲(shen)(shen)(shen)(shen)碳(tan)(tan)一淬(cui)(cui)火(huo)工藝曲線。在真空(kong)中加熱(re)到滲(shen)(shen)(shen)(shen)碳(tan)(tan)溫(wen)度(du)并(bing)保溫(wen)使表(biao)面凈(jing)化(hua)(hua)、活(huo)化(hua)(hua)之(zhi)后(hou)(hou)(hou)，通(tong)入(ru)(ru)(ru)稀薄(bo)滲(shen)(shen)(shen)(shen)碳(tan)(tan)富化(hua)(hua)氣(qi)(見控(kong)制氣(qi)氛熱(re)處(chu)理)，在大約(yue)1330Pa(10T0rr)負壓下進行滲(shen)(shen)(shen)(shen)入(ru)(ru)(ru)，然后(hou)(hou)(hou)停氣(qi)(降壓)進行擴散(san)。滲(shen)(shen)(shen)(shen)碳(tan)(tan)后(hou)(hou)(hou)的精密鋼管淬(cui)(cui)火(huo)采用一次淬(cui)(cui)火(huo)法，即先停電，通(tong)氮(dan)冷(leng)卻工件至臨界點A，、以下，使內部發(fa)生相變，再(zai)停氣(qi)、開泵，升溫(wen)到Ac1，～Accm之(zhi)間。淬(cui)(cui)冷(leng)方法可(ke)采用氣(qi)冷(leng)或(huo)油(you)冷(leng)。后(hou)(hou)(hou)者為(wei)奧氏體化(hua)(hua)后(hou)(hou)(hou)移入(ru)(ru)(ru)前室，充氮(dan)至常壓，入(ru)(ru)(ru)油(you)。真空(kong)滲(shen)(shen)(shen)(shen)碳(tan)(tan)的溫(wen)度(du)一般高于普(pu)通(tong)氣(qi)體滲(shen)(shen)(shen)(shen)碳(tan)(tan)，常采用920～1040℃滲(shen)(shen)(shen)(shen)入(ru)(ru)(ru)和擴散(san)可(ke)按所示(shi)分(fen)兩(liang)階段，也可(ke)用脈沖式通(tong)氣(qi)、停氣(qi)，多段式的滲(shen)(shen)(shen)(shen)一擴相間，效(xiao)果更好。由(you)于溫(wen)度(du)高，尤其表(biao)面潔凈(jing)、有活(huo)性(xing)，真空(kong)滲(shen)(shen)(shen)(shen)碳(tan)(tan)層形成速度(du)比(bi)普(pu)通(tong)氣(qi)體、液體和固體滲(shen)(shen)(shen)(shen)碳(tan)(tan)快，如要求滲(shen)(shen)(shen)(shen)層為(wei)1mm時，在927℃只需(xu)(xu)5h，而1033℃僅(jin)需(xu)(xu)1h。

　　精密鋼管(guan)硬(ying)度與(yu)變(bian)形

　　取兩塊(kuai)(kuai)式(shi)樣，一(yi)塊(kuai)(kuai)用于研究不同形變程度(du)對(dui)硬(ying)度(du)的(de)影響，另一(yi)塊(kuai)(kuai)研究不同溫度(du)對(dui)性能的(de)影響。

　　冷變(bian)(bian)(bian)形(xing)(xing)強(qiang)化(hua)(hua)在實際生(sheng)產中具有重要(yao)的(de)(de)意義。首先這是(shi)一種重要(yao)的(de)(de)強(qiang)化(hua)(hua)材(cai)料(liao)的(de)(de)手(shou)段，尤其(qi)對用(yong)熱處理不能強(qiang)化(hua)(hua)的(de)(de)材(cai)料(liao)來說，顯(xian)得更為重要(yao)。其(qi)次，冷變(bian)(bian)(bian)形(xing)(xing)強(qiang)化(hua)(hua)有利于(yu)金(jin)屬的(de)(de)變(bian)(bian)(bian)形(xing)(xing)均勻。因(yin)為精(jing)密(mi)鋼管(guan)的(de)(de)變(bian)(bian)(bian)形(xing)(xing)部分產生(sheng)硬(ying)化(hua)(hua)，將使變(bian)(bian)(bian)形(xing)(xing)向(xiang)未(wei)變(bian)(bian)(bian)形(xing)(xing)或(huo)變(bian)(bian)(bian)形(xing)(xing)較少的(de)(de)部分繼續發(fa)展。第(di)三(san)，冷變(bian)(bian)(bian)形(xing)(xing)強(qiang)化(hua)(hua)可以(yi)提高構件(jian)在使用(yong)過程中的(de)(de)安(an)全性(xing)，構件(jian)一旦(dan)超(chao)載，產生(sheng)塑性(xing)變(bian)(bian)(bian)形(xing)(xing)，由于(yu)強(qiang)化(hua)(hua)作用(yong)，可防止構件(jian)突然斷裂。但(dan)是(shi)，冷變(bian)(bian)(bian)形(xing)(xing)強(qiang)化(hua)(hua)也給精(jing)密(mi)鋼管(guan)的(de)(de)繼續變(bian)(bian)(bian)形(xing)(xing)帶(dai)來困難，甚至出(chu)現裂紋。因(yin)此，在精(jing)密(mi)鋼管(guan)變(bian)(bian)(bian)形(xing)(xing)和加工過程中常進行"中間退火(huo)"，以(yi)消(xiao)除它的(de)(de)不利影(ying)響。