冷却速率对无取向硅钢中夹杂物析出行为的影响

Effect of Cooling Rate on Precipitating Behavior of Inclusions in Non-Oriented Silicon Steel

借助高温激光共聚焦显微镜实时观察了无取向硅钢（/%：0.001 8C,0.76Si,0.24Mn,0.074P,0.003S,0.001 Al,0.005 60,0.001 1N）连铸坯切取的试样从1 400℃以5～40℃/s的速率冷却至600℃时组织变化,并在实时观察后用非水溶液电解提取和分析了试样中的夹杂物。结果表明,冷却至987～1 020℃（高温）和830～636℃（低温）两阶段,分别开始有新相析出,并分别于952～918℃和804～636℃析出结束。第一（高温）阶段,随冷却速率增加,新相的开始、结束析出温度均升高,但析出温度区间减小;第二（低温）阶段,随冷却速率增加新相的开始、结束析出温度均降低,但析出温度区间增大;此外在较低冷却速率下,高温阶段有利于新相充分析出,在较高冷却速率下,低温阶段有利于新相充分析出;随着冷却速率增加,夹杂物抑制晶粒长大的效果逐渐减少,试样平均晶粒尺寸先是减少,并在10℃/s时达到最小,而后单调、快速增加。因此,应该选择5℃/s以下或者20℃/s以上的冷却速率,并尽可能避免生成0.21～0.50μm MnS、AlN以及冷却后期析出的CuxS夹杂物,使成品获得较好的磁性能。

Change of structure in specimen cutting from casting slab of non-oriented silicon steel （/% ： 0. 001 8C, 0. 76Si, 0. 24Mn, 0. 074P, 0. 003S, 0. 001A1, 0.005 60,0. 001 IN） cooling from 1 400 ℃ to 600 ℃ with 5 -40 ℃/s rate has been observed at real-time by using a high temperature confocal microscope, and after observation the inclusions in specimen are extracted and analyzed by non-aqueous solution electrolytic method. Results show that steel cooling to the two precipitation period i.e. beginning precipitated at 987 - 1 020 ℃ （higher temperature） and 830 -636℃ （lower tempera- ture） and finishing precipitated at 952 -918℃ and 804 ～ 636 ℃ there are new phases respectively precipitated; in first （higher temperature） period with increasing cooling rate the beginning and finishing temperature of new phases all increase but the precipitated temperature period decreases, at second （lower temperature） period with increasing cooling rate the be- ginning and finishing precipitated temperature of new phases all decrease but the precipitated temperature period increases, beside at lower cooling rate the higher precipitated temperature period is favorable to sufficient precipitation of new phases, and at higher cooling rate the lower precipitated temperature period is favorable to sufficient precipitation of new phases; with increasing cooling rate the inhibition effect of inclusions on grain growth gradually decreases, the average grain size of steel first decreases and comes down to minimum value with cooling rate 10 ℃/s, then monotonically and quickly increa- ses. Therefore the cooling rate less than 5 ℃/s or more than 20 ℃/s should be selected to avoid forming 0. 21 -0. 50 μm MnS and A1N, as well as CuxS inclusions precipitated in cooling later stage to get better magnetic performance.