电热合金使用的温度划分

电热合金的最高使用温度是指电热元件外表在枯燥空气中允许到达的最高温度。当电热元件呈放开状态加热时，电热元件外表温度比炉膛温度高约50~100℃。呈封闭状态加热时，电工热元件外表温度比炉100~150℃。依据最高使用温度，可以把电热合金分为四个等级：超高温级电热合金、高温级电热合金、中温级电热合金、低温级电热合金。超高温级电热合金超高温级电热合金的使用温度为1400℃。它用于制造工作温度为1200~1300系。为了保证合金在高温时的使用性能，这一组合金中含有较高的铬22%~28%6%~8%，还含有少量的钴、钼、铌、钛和微量的钇、镧、鈰等元素。这组合金中包括利用粉末冶金法制造的钢胚、加工制造的电热合金线、带材。超高温电热合金主要用于工作温度在1200~1300炉、粉末冶金制品烧结炉、陶瓷煅烧炉和高温热处理炉等的电热元件。属于超高温级的电热合金牌号有：0Cr26Al7.5；0Cr27Al7Mo2，0Cr24Al6R,0Cr22Al6CoRe和用粉末冶金法炼制的0Cr22Al5.8、0Cr23Al6。高温级电热合金高温级电热合金的使用温度为 1300℃，主要用于制造温度在1100~1200℃加热炉用电热元件。这一组电热合金也都属于铁铬铝系列。该组合金中铬、铝含量稍低于超高级合金，含铬22%~25%，铝4%~6%，也含有少量钼、铌、钴、钛和稀土元素。高温级电热合金主要用于制造淬火、正火、退火、固溶处理等热处理炉的电热元件和铜、铝以及其合金熔化炉的电热元件。属于高温级电热合金牌号有0Cr25Al5、0Cr21Al6Nb、0Cr23Al6等。中温级电热合金中温级电热合金使用温度为1100℃，主要用于制造工作温度为850~950℃加热炉用电热元件，例如高温回火炉、溶铝炉以及家用电器等。这一组电热合金具有比较好的塑性，在常温下可加工制成外形简单的电热元件。属于此类的电热合金牌号有：镍铬系合金Cr30Ni70；Cr20Ni80，铁铬铝系列合金 0Cr23Al5，0Cr20Al3，0Cr19Al5，0Cr21Al6等。低温级电热合金950度在800~750℃以下的加热炉用电热元件，例如低温回火炉，烘干Cr15Ni60，Cr20Ni35，Cr20Ni25合金和铁铬铝系合金的1Cr13Al4，0Cr19Al3等。电热合金的以上分组是依据在大气条件下使用时依据温度划分的。假设电热元件的工作环境介质发生变化，则其使用温度应相应调整。铁铬铝合金的特点优良的抗氧化性能，其使用温度可到达1400℃，这一温度远远高于镍铬和镍铬铁合金。由于合金中含铝量高，是合金具有高的电阻率，最高的到达1.60μΩ·m。高电阻率可以有效地将电能转换为热能，还可以节约电热材料。铁铬铝的价格廉价，仅为镍铬合金的20%-25%，这就为大量使用制造了条件。铁铬铝合金的缺点是铁素体合金存在常温脆性、475℃脆性、1000℃以上高温脆性。由于高温脆性带来高温强度低，最终导致电热元件的使用寿命短。这种合金的可焊性很差，难修复。铁铬铝的这些缺点通过的生产方法即粉末冶金可以得到肯定的改善，但不能完全消退。铁铬铝合金主要用作工业电炉的加热元件，用量90%左右。电阻率µΩ?m,20电阻率µΩ?m,20℃Mpa延长率%反复弯曲次数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比热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显微组织 铁素体 铁素体 铁素体 铁素体 铁素体 铁素体磁性 磁性 磁性 磁性 磁性 磁性 磁性牌号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化学Fe余量余量余量余量余量余量成 Re适量适量适量适量适量适量分%参加量参加量Nb:0.5Mo:1.8-2.2元件最高使用温度℃95011001250125013501400熔点℃145015001500150015101520g/cm37.407.357.167.107.107.10二、铁铬铝系列直径及其特性〔换算表1〕直径直径截面每米0Cr21Al4电阻率μΩ•m1.23±0.060Cr21Al6Nb电阻率μΩ•m1.45±0.070Cr27Al7Mo2电阻率(mm)(mm2)(cm2/m)每米积外表积20ºC 每千克每米长20ºC 每千每米μΩ•m 1.53±0.0720ºC 每千每米电阻度重量每米克长每米克长(Ω/m)(m/kg)(kg/m)电阻度重量重量(Ω/m)(m/kg)(kg/m)电阻度(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、铁铬铝系列直径及其特性〔换算表2〕直径截面每米直径截面每米1Cr13Al4(mm)积 外表积电阻率0Cr25Al5电阻率0Cr21Al6电阻率(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 每千每米克长每米重量每米克长每米重量每米克长每米重量电阻度

(kg/m) 电阻度 (kg/m) 电阻度 (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