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对含不同百分比 Si、Mn、Cu、Ni 及杂质的21/4Cr-1 M_0钢,分别在425℃、450℃和475℃,54000、20000及5000h 作分级等温时效试验,讨论了分级及等温脆化与化学成分妁关系。结果概述如下:(1)经过步冷处理的50%断面转变温度和40ft-1b 转变温度与脆化因子 K_2=(2si+Mn+Cu+Ni)·;=(10P+5Sb+4Sn+As)×10~2有很好的相关性,因此,减少 Si、Mn、Cn、Ni 及杂质含量会有效地降低回火脆性。(2)从 K_2和方程可以精确的估计给定温度 T℃,th 高温回火脆化处理后50%断面转变温度和40ft-1b 转变温度的变化情况。(3)假定在425℃使用的石油化设备寿命为20年,锻件韧性是40TT≤10或38℃,300mm 厚的21/4Cr-1M。钢锻件的化学成分将控制如下:40TT≤10℃,≤13.0,k_2≤14.340TT≤38℃,X≤17.5,k2_≤19.3
For 21 / 4Cr-1M_0 steel with different percentages of Si, Mn, Cu, Ni and impurities, the isothermal aging tests at 425 ℃, 450 ℃ and 475 ℃, 54000, 20000 and 5000h were conducted respectively. The classification and isothermal brittleness Chemical and chemical composition 妁 relations. The results are summarized as follows: (1) 50% cross-section transition temperature and 40ft-1b transition temperature and embrittlement factor K 2 = (2si + Mn + Cu + Ni) · = (10P + 5Sb + 4Sn + As) 10 ~ 2 have a good correlation, therefore, to reduce Si, Mn, Cn, Ni and impurities will effectively reduce the temper embrittlement. (2) From K 2 and equation, we can accurately estimate the change of 50% cross-section transition temperature and 40ft-1b transition temperature after high-temperature temper embrittlement treatment at given temperature T ℃, th. (3) It is assumed that the service life of petrochemical equipment used at 425 ° C is 20 years. Forging toughness is 21 / 4Cr-1M for 40TT ≤10 or 38 ° C and 300 mm thickness. The chemical composition of the steel forgings will be controlled as follows: 40TT≤10 ℃, ≤13.0, k_2≤14.340TT≤38 ℃, X≤17.5, k2_≤19.3