20#精密鋼管批發零售

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　　20#精(jing)密(mi)鋼管熱(re)處理工藝

　　精密鋼管前奏

　　真(zhen)(zhen)空退火優質彈簧鋼(gang)、工具鋼(gang)、精密鋼(gang)管的絲材(cai)，不銹鋼(gang)制品及鈦(tai)(tai)合金(jin)材(cai)，作(zuo)光亮退火均可采(cai)(cai)用(yong)(yong)真(zhen)(zhen)空處(chu)理。退火溫度(du)愈(yu)低(di)，則要求真(zhen)(zhen)空度(du)愈(yu)高。為防止鉻的蒸(zheng)發及加(jia)速熱傳(chuan)導，一般采(cai)(cai)用(yong)(yong)載氣加(jia)熱(保溫)法，并(bing)注意對(dui)不銹鋼(gang)和鈦(tai)(tai)合金(jin)不宜(yi)用(yong)(yong)氮而(er)應采(cai)(cai)用(yong)(yong)氬氣。

　　精密鋼管過程

　　真(zhen)空淬(cui)(cui)(cui)火真(zhen)空淬(cui)(cui)(cui)火爐(lu)按冷(leng)(leng)卻(que)方(fang)法分為(wei)(wei)油(you)淬(cui)(cui)(cui)和(he)(he)氣(qi)(qi)(qi)淬(cui)(cui)(cui)兩(liang)類，按工(gong)(gong)位(wei)(wei)(wei)(wei)數分為(wei)(wei)單(dan)(dan)室(shi)(shi)(shi)(shi)(shi)式(shi)(shi)和(he)(he)雙室(shi)(shi)(shi)(shi)(shi)式(shi)(shi)，904山\畏嘲均屬(shu)周期式(shi)(shi)作(zuo)業(ye)(ye)爐(lu)。真(zhen)空油(you)淬(cui)(cui)(cui)爐(lu)都是(shi)雙室(shi)(shi)(shi)(shi)(shi)的(de)(de)，后室(shi)(shi)(shi)(shi)(shi)置電加(jia)(jia)熱(re)(re)元(yuan)件(jian)，前(qian)室(shi)(shi)(shi)(shi)(shi)的(de)(de)下方(fang)置油(you)槽。工(gong)(gong)件(jian)完成(cheng)加(jia)(jia)熱(re)(re)、保(bao)溫(wen)(wen)后移(yi)入前(qian)室(shi)(shi)(shi)(shi)(shi)，關閉中(zhong)門(men)后向前(qian)室(shi)(shi)(shi)(shi)(shi)充入惰性氣(qi)(qi)(qi)至大約2.66%26times;lO ～1.01%26times;10 Pa(200～760mm汞(gong)柱)，入油(you)。油(you)淬(cui)(cui)(cui)易(yi)引起工(gong)(gong)件(jian)表(biao)面變(bian)質(zhi)。由于表(biao)面活(huo)性大，在(zai)短暫(zan)的(de)(de)高溫(wen)(wen)油(you)膜作(zuo)用(yong)下即可發生(sheng)顯(xian)著薄層(ceng)滲碳，此外，碳黑和(he)(he)油(you)在(zai)表(biao)面的(de)(de)粘附對簡化熱(re)(re)處理(li)流(liu)程很(hen)不(bu)利(li)。真(zhen)空淬(cui)(cui)(cui)火技(ji)術的(de)(de)發展主(zhu)要在(zai)于研制性能優良、工(gong)(gong)位(wei)(wei)(wei)(wei)單(dan)(dan)一(yi)的(de)(de)氣(qi)(qi)(qi)冷(leng)(leng)淬(cui)(cui)(cui)火爐(lu)。前(qian)述雙室(shi)(shi)(shi)(shi)(shi)式(shi)(shi)爐(lu)亦可用(yong)于氣(qi)(qi)(qi)淬(cui)(cui)(cui)(在(zai)前(qian)室(shi)(shi)(shi)(shi)(shi)噴氣(qi)(qi)(qi)冷(leng)(leng)卻(que))，但雙工(gong)(gong)位(wei)(wei)(wei)(wei)式(shi)(shi)的(de)(de)操作(zuo)使大批(pi)量裝(zhuang)爐(lu)的(de)(de)生(sheng)產(chan)(chan)發生(sheng)困難(nan)，也易(yi)在(zai)高溫(wen)(wen)移(yi)動中(zhong)引起工(gong)(gong)件(jian)變(bian)形(xing)或(huo)(huo)改變(bian)工(gong)(gong)件(jian)方(fang)位(wei)(wei)(wei)(wei)增加(jia)(jia)淬(cui)(cui)(cui)火變(bian)形(xing)。單(dan)(dan)一(yi)工(gong)(gong)位(wei)(wei)(wei)(wei)的(de)(de)氣(qi)(qi)(qi)冷(leng)(leng)淬(cui)(cui)(cui)火爐(lu)是(shi)在(zai)加(jia)(jia)熱(re)(re)保(bao)溫(wen)(wen)完成(cheng)后在(zai)加(jia)(jia)熱(re)(re)室(shi)(shi)(shi)(shi)(shi)內噴氣(qi)(qi)(qi)冷(leng)(leng)卻(que)。氣(qi)(qi)(qi)冷(leng)(leng)的(de)(de)冷(leng)(leng)速不(bu)如油(you)冷(leng)(leng)快，也低于傳統淬(cui)(cui)(cui)火法中(zhong)的(de)(de)熔鹽等(deng)(deng)溫(wen)(wen)、分級淬(cui)(cui)(cui)火。因(yin)而，不(bu)斷(duan)提高噴冷(leng)(leng)室(shi)(shi)(shi)(shi)(shi)壓力(li)，增大流(liu)量，以(yi)及采用(yong)摩爾質(zhi)量比氮和(he)(he)氬小的(de)(de)惰性氣(qi)(qi)(qi)體(ti)氦(hai)(hai)和(he)(he)氫(qing)，是(shi)當今真(zhen)空淬(cui)(cui)(cui)火技(ji)術發展的(de)(de)主(zhu)流(liu)。70年代(dai)后期將氮氣(qi)(qi)(qi)噴冷(leng)(leng)的(de)(de)壓力(li)從(1～2)%26times;10Pa提高到(5～6)%26times;10Pa，使冷(leng)(leng)卻(que)能力(li)接近于常(chang)壓下的(de)(de)油(you)冷(leng)(leng)。80年代(dai)中(zhong)期出現超高壓氣(qi)(qi)(qi)淬(cui)(cui)(cui)，用(yong)(10～20)%26times;10Pa的(de)(de)氦(hai)(hai)，冷(leng)(leng)卻(que)能力(li)等(deng)(deng)于或(huo)(huo)略高于油(you)淬(cui)(cui)(cui)，已(yi)進入工(gong)(gong)業(ye)(ye)實用(yong)。90年代(dai)初(chu)采用(yong)40%26times;10Pa的(de)(de)氫(qing)氣(qi)(qi)(qi)，接近水淬(cui)(cui)(cui)的(de)(de)冷(leng)(leng)卻(que)能力(li)，尚(shang)處于起步(bu)階段。工(gong)(gong)業(ye)(ye)發達國家已(yi)進展到以(yi)高壓(5～6)%26times;10。Pa氣(qi)(qi)(qi)淬(cui)(cui)(cui)為(wei)(wei)主(zhu)體(ti)，而中(zhong)國產(chan)(chan)氣(qi)(qi)(qi)淬(cui)(cui)(cui)一(yi)些金屬(shu)的(de)(de)蒸氣(qi)(qi)(qi)壓(理(li)論值)與溫(wen)(wen)度的(de)(de)關系(xi)則尚(shang)處于一(yi)般加(jia)(jia)壓氣(qi)(qi)(qi)淬(cui)(cui)(cui)(2%26times;10Pa)型階段。

　　結果(guo)真空(kong)(kong)滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)為真空(kong)(kong)滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)一淬(cui)火工(gong)藝曲線。在(zai)(zai)真空(kong)(kong)中加熱到滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)溫度并(bing)保溫使(shi)表面(mian)凈(jing)化、活化之后(hou)，通(tong)(tong)入(ru)稀薄滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)富化氣(qi)(見控制氣(qi)氛(fen)熱處理)，在(zai)(zai)大約1330Pa(10T0rr)負壓下(xia)進(jin)行滲(shen)(shen)入(ru)，然后(hou)停(ting)氣(qi)(降壓)進(jin)行擴散。滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)后(hou)的精密鋼管淬(cui)火采用一次淬(cui)火法，即先停(ting)電，通(tong)(tong)氮冷(leng)卻工(gong)件至臨界點A，、以下(xia)，使(shi)內部發生(sheng)相變，再(zai)停(ting)氣(qi)、開泵，升溫到Ac1，～Accm之間(jian)。淬(cui)冷(leng)方法可采用氣(qi)冷(leng)或油(you)冷(leng)。后(hou)者(zhe)為奧氏體化后(hou)移入(ru)前室，充氮至常(chang)(chang)壓，入(ru)油(you)。真空(kong)(kong)滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)的溫度一般高于(yu)普通(tong)(tong)氣(qi)體滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)，常(chang)(chang)采用920～1040℃滲(shen)(shen)入(ru)和擴散可按所示(shi)分(fen)兩階段，也可用脈沖式(shi)通(tong)(tong)氣(qi)、停(ting)氣(qi)，多段式(shi)的滲(shen)(shen)一擴相間(jian)，效(xiao)果(guo)更(geng)好。由于(yu)溫度高，尤其表面(mian)潔凈(jing)、有活性，真空(kong)(kong)滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)層(ceng)形成(cheng)速(su)度比普通(tong)(tong)氣(qi)體、液體和固(gu)體滲(shen)(shen)碳(tan)(tan)(tan)(tan)(tan)快(kuai)，如要(yao)求滲(shen)(shen)層(ceng)為1mm時，在(zai)(zai)927℃只(zhi)需(xu)5h，而1033℃僅需(xu)1h。

　　精密(mi)鋼管硬度與變形(xing)

　　取兩塊式樣，一塊用于研究不(bu)同(tong)形變程(cheng)度對硬度的影(ying)(ying)響(xiang)，另(ling)一塊研究不(bu)同(tong)溫度對性能(neng)的影(ying)(ying)響(xiang)。

　　冷(leng)(leng)變形(xing)強(qiang)(qiang)化(hua)(hua)(hua)在實際生(sheng)產中(zhong)具有(you)(you)重(zhong)要(yao)的(de)(de)(de)意義。首先這是一(yi)(yi)種重(zhong)要(yao)的(de)(de)(de)強(qiang)(qiang)化(hua)(hua)(hua)材(cai)料的(de)(de)(de)手(shou)段，尤其對(dui)用(yong)(yong)熱(re)處理不能強(qiang)(qiang)化(hua)(hua)(hua)的(de)(de)(de)材(cai)料來(lai)說，顯得更為重(zhong)要(yao)。其次，冷(leng)(leng)變形(xing)強(qiang)(qiang)化(hua)(hua)(hua)有(you)(you)利于(yu)金屬的(de)(de)(de)變形(xing)均勻。因為精密鋼管(guan)的(de)(de)(de)變形(xing)部(bu)分產生(sheng)硬化(hua)(hua)(hua)，將使變形(xing)向未變形(xing)或(huo)變形(xing)較少的(de)(de)(de)部(bu)分繼(ji)(ji)續發展。第(di)三，冷(leng)(leng)變形(xing)強(qiang)(qiang)化(hua)(hua)(hua)可以提高構件在使用(yong)(yong)過程中(zhong)的(de)(de)(de)安全性，構件一(yi)(yi)旦超載，產生(sheng)塑性變形(xing)，由于(yu)強(qiang)(qiang)化(hua)(hua)(hua)作用(yong)(yong)，可防(fang)止構件突(tu)然斷裂。但是，冷(leng)(leng)變形(xing)強(qiang)(qiang)化(hua)(hua)(hua)也給精密鋼管(guan)的(de)(de)(de)繼(ji)(ji)續變形(xing)帶來(lai)困難，甚(shen)至(zhi)出現裂紋。因此(ci)，在精密鋼管(guan)變形(xing)和加工(gong)過程中(zhong)常進行"中(zhong)間(jian)退火"，以消除它的(de)(de)(de)不利影響。