20#精密鋼管批發零售

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　　20#精密鋼管熱處(chu)理工藝

　　精密鋼管前奏

　　真空(kong)退火優質彈簧(huang)鋼、工具鋼、精密鋼管的絲材，不(bu)銹鋼制品及鈦(tai)合(he)金材，作光亮退火均可采用(yong)真空(kong)處理。退火溫度愈低，則(ze)要求(qiu)真空(kong)度愈高。為防止(zhi)鉻的蒸發及加速熱傳導(dao)，一(yi)般采用(yong)載氣(qi)加熱(保溫)法，并注(zhu)意對不(bu)銹鋼和(he)鈦(tai)合(he)金不(bu)宜用(yong)氮而應采用(yong)氬氣(qi)。

　　精密鋼管過程

　　真(zhen)(zhen)空淬(cui)(cui)(cui)(cui)(cui)火真(zhen)(zhen)空淬(cui)(cui)(cui)(cui)(cui)火爐(lu)(lu)(lu)按冷(leng)卻方法分(fen)為油(you)(you)(you)(you)淬(cui)(cui)(cui)(cui)(cui)和氣(qi)(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)兩類，按工位(wei)(wei)數分(fen)為單室(shi)(shi)式(shi)(shi)和雙室(shi)(shi)式(shi)(shi)，904山(shan)\畏嘲均屬周(zhou)期(qi)(qi)式(shi)(shi)作業爐(lu)(lu)(lu)。真(zhen)(zhen)空油(you)(you)(you)(you)淬(cui)(cui)(cui)(cui)(cui)爐(lu)(lu)(lu)都(dou)是(shi)雙室(shi)(shi)的(de)(de)(de)，后室(shi)(shi)置電加熱(re)(re)(re)(re)元件(jian)，前室(shi)(shi)的(de)(de)(de)下方置油(you)(you)(you)(you)槽。工件(jian)完(wan)成加熱(re)(re)(re)(re)、保溫(wen)后移入(ru)前室(shi)(shi)，關(guan)閉中(zhong)門(men)后向前室(shi)(shi)充入(ru)惰(duo)(duo)性(xing)氣(qi)(qi)(qi)(qi)至大約2.66%26times;lO ～1.01%26times;10 Pa(200～760mm汞柱)，入(ru)油(you)(you)(you)(you)。油(you)(you)(you)(you)淬(cui)(cui)(cui)(cui)(cui)易引起工件(jian)表面(mian)變(bian)質。由于(yu)(yu)(yu)(yu)表面(mian)活性(xing)大，在(zai)短暫(zan)的(de)(de)(de)高(gao)溫(wen)油(you)(you)(you)(you)膜作用(yong)下即可發(fa)生顯著薄層滲碳(tan)，此外(wai)，碳(tan)黑(hei)和油(you)(you)(you)(you)在(zai)表面(mian)的(de)(de)(de)粘附對簡化熱(re)(re)(re)(re)處(chu)理(li)流程很不(bu)利(li)。真(zhen)(zhen)空淬(cui)(cui)(cui)(cui)(cui)火技(ji)術的(de)(de)(de)發(fa)展(zhan)(zhan)主要在(zai)于(yu)(yu)(yu)(yu)研制(zhi)性(xing)能(neng)優良、工位(wei)(wei)單一(yi)的(de)(de)(de)氣(qi)(qi)(qi)(qi)冷(leng)淬(cui)(cui)(cui)(cui)(cui)火爐(lu)(lu)(lu)。前述雙室(shi)(shi)式(shi)(shi)爐(lu)(lu)(lu)亦可用(yong)于(yu)(yu)(yu)(yu)氣(qi)(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)(在(zai)前室(shi)(shi)噴(pen)(pen)氣(qi)(qi)(qi)(qi)冷(leng)卻)，但雙工位(wei)(wei)式(shi)(shi)的(de)(de)(de)操作使(shi)大批量(liang)裝爐(lu)(lu)(lu)的(de)(de)(de)生產(chan)發(fa)生困難，也(ye)易在(zai)高(gao)溫(wen)移動中(zhong)引起工件(jian)變(bian)形或(huo)改(gai)變(bian)工件(jian)方位(wei)(wei)增加淬(cui)(cui)(cui)(cui)(cui)火變(bian)形。單一(yi)工位(wei)(wei)的(de)(de)(de)氣(qi)(qi)(qi)(qi)冷(leng)淬(cui)(cui)(cui)(cui)(cui)火爐(lu)(lu)(lu)是(shi)在(zai)加熱(re)(re)(re)(re)保溫(wen)完(wan)成后在(zai)加熱(re)(re)(re)(re)室(shi)(shi)內噴(pen)(pen)氣(qi)(qi)(qi)(qi)冷(leng)卻。氣(qi)(qi)(qi)(qi)冷(leng)的(de)(de)(de)冷(leng)速不(bu)如油(you)(you)(you)(you)冷(leng)快(kuai)，也(ye)低于(yu)(yu)(yu)(yu)傳統淬(cui)(cui)(cui)(cui)(cui)火法中(zhong)的(de)(de)(de)熔(rong)鹽等(deng)溫(wen)、分(fen)級淬(cui)(cui)(cui)(cui)(cui)火。因而，不(bu)斷提高(gao)噴(pen)(pen)冷(leng)室(shi)(shi)壓(ya)(ya)(ya)力，增大流量(liang)，以及采(cai)用(yong)摩(mo)爾質量(liang)比氮和氬小的(de)(de)(de)惰(duo)(duo)性(xing)氣(qi)(qi)(qi)(qi)體氦和氫，是(shi)當今真(zhen)(zhen)空淬(cui)(cui)(cui)(cui)(cui)火技(ji)術發(fa)展(zhan)(zhan)的(de)(de)(de)主流。70年代后期(qi)(qi)將氮氣(qi)(qi)(qi)(qi)噴(pen)(pen)冷(leng)的(de)(de)(de)壓(ya)(ya)(ya)力從(1～2)%26times;10Pa提高(gao)到(5～6)%26times;10Pa，使(shi)冷(leng)卻能(neng)力接近于(yu)(yu)(yu)(yu)常壓(ya)(ya)(ya)下的(de)(de)(de)油(you)(you)(you)(you)冷(leng)。80年代中(zhong)期(qi)(qi)出現超高(gao)壓(ya)(ya)(ya)氣(qi)(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)，用(yong)(10～20)%26times;10Pa的(de)(de)(de)氦，冷(leng)卻能(neng)力等(deng)于(yu)(yu)(yu)(yu)或(huo)略高(gao)于(yu)(yu)(yu)(yu)油(you)(you)(you)(you)淬(cui)(cui)(cui)(cui)(cui)，已進(jin)入(ru)工業實用(yong)。90年代初(chu)采(cai)用(yong)40%26times;10Pa的(de)(de)(de)氫氣(qi)(qi)(qi)(qi)，接近水淬(cui)(cui)(cui)(cui)(cui)的(de)(de)(de)冷(leng)卻能(neng)力，尚處(chu)于(yu)(yu)(yu)(yu)起步階(jie)段。工業發(fa)達國家已進(jin)展(zhan)(zhan)到以高(gao)壓(ya)(ya)(ya)(5～6)%26times;10。Pa氣(qi)(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)為主體，而中(zhong)國產(chan)氣(qi)(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)一(yi)些金屬的(de)(de)(de)蒸氣(qi)(qi)(qi)(qi)壓(ya)(ya)(ya)(理(li)論值(zhi))與溫(wen)度的(de)(de)(de)關(guan)系則尚處(chu)于(yu)(yu)(yu)(yu)一(yi)般加壓(ya)(ya)(ya)氣(qi)(qi)(qi)(qi)淬(cui)(cui)(cui)(cui)(cui)(2%26times;10Pa)型階(jie)段。

　　結果真(zhen)(zhen)空(kong)滲(shen)碳(tan)(tan)為真(zhen)(zhen)空(kong)滲(shen)碳(tan)(tan)一(yi)淬火工藝(yi)曲線。在真(zhen)(zhen)空(kong)中加熱(re)到(dao)滲(shen)碳(tan)(tan)溫(wen)(wen)度并保溫(wen)(wen)使表面凈化(hua)、活化(hua)之(zhi)后(hou)，通(tong)(tong)入稀薄滲(shen)碳(tan)(tan)富化(hua)氣(qi)(qi)(qi)(見控制氣(qi)(qi)(qi)氛熱(re)處理)，在大(da)約(yue)1330Pa(10T0rr)負壓下進(jin)行滲(shen)入，然后(hou)停(ting)(ting)氣(qi)(qi)(qi)(降壓)進(jin)行擴(kuo)散(san)。滲(shen)碳(tan)(tan)后(hou)的精密鋼管淬火采用一(yi)次淬火法(fa)，即先停(ting)(ting)電，通(tong)(tong)氮冷(leng)卻(que)工件至臨(lin)界點A，、以下，使內(nei)部發生相(xiang)變，再停(ting)(ting)氣(qi)(qi)(qi)、開泵，升溫(wen)(wen)到(dao)Ac1，～Accm之(zhi)間。淬冷(leng)方法(fa)可采用氣(qi)(qi)(qi)冷(leng)或油冷(leng)。后(hou)者為奧(ao)氏體化(hua)后(hou)移(yi)入前室，充氮至常(chang)壓，入油。真(zhen)(zhen)空(kong)滲(shen)碳(tan)(tan)的溫(wen)(wen)度一(yi)般高于(yu)普通(tong)(tong)氣(qi)(qi)(qi)體滲(shen)碳(tan)(tan)，常(chang)采用920～1040℃滲(shen)入和擴(kuo)散(san)可按所示(shi)分兩階段(duan)，也(ye)可用脈沖式通(tong)(tong)氣(qi)(qi)(qi)、停(ting)(ting)氣(qi)(qi)(qi)，多段(duan)式的滲(shen)一(yi)擴(kuo)相(xiang)間，效果更好(hao)。由于(yu)溫(wen)(wen)度高，尤其表面潔凈、有活性，真(zhen)(zhen)空(kong)滲(shen)碳(tan)(tan)層形成速度比普通(tong)(tong)氣(qi)(qi)(qi)體、液體和固(gu)體滲(shen)碳(tan)(tan)快，如要求(qiu)滲(shen)層為1mm時，在927℃只(zhi)需(xu)(xu)5h，而1033℃僅(jin)需(xu)(xu)1h。

　　精密鋼管(guan)硬度與變形(xing)

　　取兩塊式樣，一塊用于研究(jiu)不同(tong)形變(bian)程度(du)對(dui)硬度(du)的(de)影響，另一塊研究(jiu)不同(tong)溫(wen)度(du)對(dui)性能的(de)影響。

　　冷(leng)(leng)變(bian)(bian)形(xing)(xing)(xing)強(qiang)(qiang)化(hua)在實際生(sheng)產中具有重(zhong)(zhong)要(yao)的(de)(de)(de)(de)(de)(de)(de)意義。首先(xian)這是(shi)一種重(zhong)(zhong)要(yao)的(de)(de)(de)(de)(de)(de)(de)強(qiang)(qiang)化(hua)材料(liao)(liao)的(de)(de)(de)(de)(de)(de)(de)手(shou)段，尤(you)其(qi)對用熱處理不能強(qiang)(qiang)化(hua)的(de)(de)(de)(de)(de)(de)(de)材料(liao)(liao)來(lai)(lai)說，顯得更(geng)為重(zhong)(zhong)要(yao)。其(qi)次，冷(leng)(leng)變(bian)(bian)形(xing)(xing)(xing)強(qiang)(qiang)化(hua)有利于金屬的(de)(de)(de)(de)(de)(de)(de)變(bian)(bian)形(xing)(xing)(xing)均(jun)勻(yun)。因為精(jing)(jing)密鋼管(guan)(guan)的(de)(de)(de)(de)(de)(de)(de)變(bian)(bian)形(xing)(xing)(xing)部(bu)分產生(sheng)硬化(hua)，將使變(bian)(bian)形(xing)(xing)(xing)向未變(bian)(bian)形(xing)(xing)(xing)或(huo)變(bian)(bian)形(xing)(xing)(xing)較少的(de)(de)(de)(de)(de)(de)(de)部(bu)分繼續發展。第三(san)，冷(leng)(leng)變(bian)(bian)形(xing)(xing)(xing)強(qiang)(qiang)化(hua)可以提高構件(jian)在使用過(guo)程(cheng)中的(de)(de)(de)(de)(de)(de)(de)安全性，構件(jian)一旦超(chao)載，產生(sheng)塑(su)性變(bian)(bian)形(xing)(xing)(xing)，由于強(qiang)(qiang)化(hua)作用，可防止構件(jian)突然斷裂。但是(shi)，冷(leng)(leng)變(bian)(bian)形(xing)(xing)(xing)強(qiang)(qiang)化(hua)也給精(jing)(jing)密鋼管(guan)(guan)的(de)(de)(de)(de)(de)(de)(de)繼續變(bian)(bian)形(xing)(xing)(xing)帶來(lai)(lai)困難，甚至出現裂紋(wen)。因此，在精(jing)(jing)密鋼管(guan)(guan)變(bian)(bian)形(xing)(xing)(xing)和加工過(guo)程(cheng)中常進行(xing)"中間退(tui)火"，以消(xiao)除它的(de)(de)(de)(de)(de)(de)(de)不利影響。