電熱合金使用的溫度劃分

電熱合金的最高使用溫度是指電熱元件外表在枯燥空氣中允許到達的最高溫度。當電熱元件呈放開狀態(tài)加熱時，電熱元件外表溫度比爐膛溫度高約50~100℃。呈封閉狀態(tài)加熱時，電工熱元件外表溫度比爐100~150℃。依據最高使用溫度，可以把電熱合金分為四個等級：超高溫級電熱合金、高溫級電熱合金、中溫級電熱合金、低溫級電熱合金。超高溫級電熱合金超高溫級電熱合金的使用溫度為1400℃。它用于制造工作溫度為1200~1300系。為了保證合金在高溫時的使用性能，這一組合金中含有較高的鉻22%~28%6%~8%，還含有少量的鈷、鉬、鈮、鈦和微量的釔、鑭、鈰等元素。這組合金中包括利用粉末冶金法制造的鋼胚、加工制造的電熱合金線、帶材。超高溫電熱合金主要用于工作溫度在1200~1300爐、粉末冶金制品燒結爐、陶瓷煅燒爐和高溫熱處理爐等的電熱元件。屬于超高溫級的電熱合金牌號有：0Cr26Al7.5；0Cr27Al7Mo2，0Cr24Al6R,0Cr22Al6CoRe和用粉末冶金法煉制的0Cr22Al5.8、0Cr23Al6。高溫級電熱合金高溫級電熱合金的使用溫度為 1300℃，主要用于制造溫度在1100~1200℃加熱爐用電熱元件。這一組電熱合金也都屬于鐵鉻鋁系列。該組合金中鉻、鋁含量稍低于超高級合金，含鉻22%~25%，鋁4%~6%，也含有少量鉬、鈮、鈷、鈦和稀土元素。高溫級電熱合金主要用于制造淬火、正火、退火、固溶處理等熱處理爐的電熱元件和銅、鋁以及其合金熔化爐的電熱元件。屬于高溫級電熱合金牌號有0Cr25Al5、0Cr21Al6Nb、0Cr23Al6等。中溫級電熱合金中溫級電熱合金使用溫度為1100℃，主要用于制造工作溫度為850~950℃加熱爐用電熱元件，例如高溫回火爐、溶鋁爐以及家用電器等。這一組電熱合金具有比較好的塑性，在常溫下可加工制成外形簡單的電熱元件。屬于此類的電熱合金牌號有：鎳鉻系合金Cr30Ni70；Cr20Ni80，鐵鉻鋁系列合金 0Cr23Al5，0Cr20Al3，0Cr19Al5，0Cr21Al6等。低溫級電熱合金950度在800~750℃以下的加熱爐用電熱元件，例如低溫回火爐，烘干Cr15Ni60，Cr20Ni35，Cr20Ni25合金和鐵鉻鋁系合金的1Cr13Al4，0Cr19Al3等。電熱合金的以上分組是依據在大氣條件下使用時依據溫度劃分的。假設電熱元件的工作環(huán)境介質發(fā)生變化，則其使用溫度應相應調整。鐵鉻鋁合金的特點優(yōu)良的抗氧化性能，其使用溫度可到達1400℃，這一溫度遠遠高于鎳鉻和鎳鉻鐵合金。由于合金中含鋁量高，是合金具有高的電阻率，最高的到達1.60μΩ·m。高電阻率可以有效地將電能轉換為熱能，還可以節(jié)約電熱材料。鐵鉻鋁的價格廉價，僅為鎳鉻合金的20%-25%，這就為大量使用制造了條件。鐵鉻鋁合金的缺點是鐵素體合金存在常溫脆性、475℃脆性、1000℃以上高溫脆性。由于高溫脆性帶來高溫強度低，最終導致電熱元件的使用壽命短。這種合金的可焊性很差，難修復。鐵鉻鋁的這些缺點通過的生產方法即粉末冶金可以得到肯定的改善，但不能完全消退。鐵鉻鋁合金主要用作工業(yè)電爐的加熱元件，用量90%左右。電阻率μΩ?m,20電阻率μΩ?m,20℃Mpa延長率%反復彎曲次數h/℃1.25±0.081.23±0.06 1.42±0.071.42±0.07 1.45±0.071.53±0.07588-735637-784637-784637-784637-784686-784≥16≥12≥12≥12≥12≥10≥5≥5≥5≥5≥5≥5--≥80/1250≥80/1300≥80/1300≥50/1350≥50/1350比熱J/g.0.4900.4900.5200.4940.4940.494KJ/m.h℃52.746.963.246.146.145.2a×10-6/ ℃15.4 13.5 14.7 16.0 16.0 16.0(20-1000℃)硬度HB 200-260 200-260 200-260 200-260 200-260 200-260顯微組織 鐵素體 鐵素體 鐵素體 鐵素體 鐵素體 鐵素體磁性 磁性 磁性 磁性 磁性 磁性 磁性牌號1Cr13A141Cr21A140Cr21A160Cr25A150Cr21A16Nb0Cr27A17Mo2Cr12.0-15.017.0-21.019.0-22.023.0-26.021.0-23.026.5-27.8主要AI4.0-6.02.0-4.05.0-7.04.5-6.55.0-7.06.0-7.0化學Fe余量余量余量余量余量余量成 Re適量適量適量適量適量適量分%參加量參加量Nb:0.5Mo:1.8-2.2元件最高使用溫度℃95011001250125013501400熔點℃145015001500150015101520g/cm37.407.357.167.107.107.10二、鐵鉻鋁系列直徑及其特性〔換算表1〕直徑直徑截面每米0Cr21Al4電阻率μΩ?m1.23±0.060Cr21Al6Nb電阻率μΩ?m1.45±0.070Cr27Al7Mo2電阻率(mm)(mm2)(cm2/m)每米積外表積20oC 每千克每米長20oC 每千每米μΩ?m 1.53±0.0720oC 每千每米電阻度重量每米克長每米克長(Ω/m)(m/kg)(kg/m)電阻度重量重量(Ω/m)(m/kg)(kg/m)電阻度(Ω/m)(m/kg)(kg/m)0.100.00783.14156.6174520.0000573184.6179330.0000558194.8179330.00005580.120.01133.77108.8120330.0000831128.2124530.0000803135.3124530.00008030.150.01774.7169.676920.00013082.179700.00012580.679700.0001250.170.02275.3454.259880.00016763.962050.00016167.462050.0001610.190.02845.9743.447850.00020951.149680.00020154.049680.0002010.210.03466.6035.539370.00025441.940660.00024644.240660.0002460.250.04917.8525.127700.00036129.528700.00034931.228700.0003490.270.05738.4821.523750.00042125.024600.00040726.724600.0004070.290.06619.1118.620580.00048622.021310.00046923.221320.0004690.310.07559.7416.318020.00055519.218660.00053620.318660.0005360.350.096211.0012.814140.00070715.114640.00068315.914640.0006830.400.125712.579.7910820.00092411.5411210.00089212.1911210.0008920.450.159014.147.738550.001179.128860.0011299.628860.0011290.500.196315.716.266940.001447.387170.0013947.797170.0013940.600.28318.854.354800.002085.134980.002015.414980.002010.700.38522.03.203530.002833.773660.002733.983660.002730.800.50325.12.452700.0036972.882800.003573.042800.003570.900.63628.31.932130.0046752.282210.004522.412210.004521.000.78531.41.571730.0057701.85179.50.005571.95179.50.005571.201.13137.71.091200.0083131.282124.50.008031.35124.50.008031.401.53944.00.79988.40.011310.94291.50.010930.99491.50.010931.603.0150.30.61267.70.014770.72170.10.014270.76170.10.014271.802.5456.50.48353.560.018670.57055.50.018030.60155.50.018032.003.1462.80.39243.330.023080.46244.80.02290.48744.80.02292.203.8069.10.32435.800.027930.38137.00.02700.40237.00.02702.504.9178.50.25127.710.036090.29528.70.03490.31228.70.03492.806.1688.00.20022.080.045280.23522.90.04370.24822.90.04373.007.0794.20.174019.250.051960.20519.920.0520.21619.920.0523.509.62110.00.127814.140.070710.151014.640.06830.15914.640.06834.0012.57125.70.097910.820.092390.115411.210.08920.121811.210.08924.5015.90141.40.07738.550.11690.09128.860.11290.09628.860.11295.0019.63157.10.06266.930.14430.07387.170.13940.07797.170.13945.5023.80172.80.05185.720.17490.06105.920.16900.06445.920.16906.0028.30188.50.04354.810.20800.05134.980.2010.05414.980.2016.5033.202040.03714.090.24400.04374.240.2360.04614.240.2367.0038.502200.03203.530.28300.03773.660.2730.03983.660.273三、鐵鉻鋁系列直徑及其特性〔換算表2〕直徑截面每米直徑截面每米1Cr13Al4(mm)積 外表積電阻率0Cr25Al5電阻率0Cr21Al6電阻率(mm2)(cm2/m)μΩ?m 1.25±0.08 μΩ?m 1.42±0.07 μΩ?m 1.42±0.0720oC 每千 20oC 每千 20oC 每千每米克長每米重量每米克長每米重量每米克長每米重量電阻度

(kg/m) 電阻度 (kg/m) 電阻度 (kg/m)(Ω/m)(m/kg)(Ω/m)(m/kg)(Ω/m)(m/kg)0.100.00783.14159.2172060.0000581180.6179330.0000558180.6179050.00005580.120.01133.77110.5119490.0000836125.6124530.0000803125.6123600.00008090.150.01774.7170.776470.00013180.479700.00012580.478910.0001280.170.02275.3455.159540.00016862.662050.00016162.661530.0001630.190.02845.9744.147660.00021050.149590.00020150.149180.0002030.210.03466.6036.139010.00025641.040660.00024641.040370.0002480.250.04917.8525.527530.00036328.928700.00034628.928440.0003520.270.05738.4821.823600.00042424.824600.00040724.824370.0004100.290.06619.1118.920460.00048921.521320.00046921.521130.0004730.310.07559.7416.617900.00055918.818660.00053618.818490.0005410.350.096211.0013.014050.00071214.814640.00068314.814520.0006890.400.125712.579.9510750.00093011.311210.00089211.311110.0009000.450.159014.147.868500.0011778.938860.0011298.938780.0011380.500.196315.716.376880.0014537.237170.0013947.237110.0014060.600.28318.854.424800.0020925.024980.002015.024940.0020260.700.38522.03.253510.0028483.693660.002733.693620.0027510.800.50325.12.492690.0037202.832800.003572.832780.0036010.900.63628.31.962120.0047082.232210.004522.232200.0045541.000.78531.41.591720.0058121.808179.50.005571.808177.90.0056201.201.13137.71.111190.0083691.256124.50.008031.256123.50.0080981.401.53944.00.81287.80.0011390.92291.50.010930.92290.80.011021.603.0150.30.62267.20.014880.70670.10.014270.70669.50.014391.802.5456.50.49153.10.018830.55855.50.018030.55854.90.018192.003.1462.80.39843.00.023250.45244.80.02230.45244.50.022482.203.8069.10.32935.50.028130.37437.00.02700.37