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利用光学显微镜、透射电镜 (TEM)和X射线能量散射仪 (EDAX) ,对V N和V Ti N两种低碳微合金钢在薄板坯连铸连轧工艺中微观组织的演变进行了检验。在 5道次轧制过程中的第 4道次轧制后 ,V N钢的晶粒尺寸由原始粗大的晶粒 (≈ 1mm)减小到约 5 0 μm ,V Ti N钢减小到 2 2 μm。V Ti N钢最终平均铁素体晶粒尺寸为 4 8～ 6 6 μm ,略小于V N钢的晶粒尺寸(5 3～ 7 2 μm)。V N钢仅在 10 5 0℃均热之后观察到了VN第二相 ,而在 12 0 0℃和 110 0℃均热后没有发现VN存在。V Ti N钢在浇铸和均热期间 (12 0 0℃、110 0℃和 10 5 0℃ ) ,V Ti N颗粒已经形成。而V N钢仅在 10 5 0℃均热期间才析出AlN颗粒 ,并与MnS或MnS和VN复合析出有关。在V Ti N钢中没有检测到AlN。在两种钢的最终产品中均发现了含V的细小析出物 (小于10nm) ,但在V Ti N钢中出现的频率比V N钢低 ,最终板材中的细小析出物对弥散强化起主要作用 ,可以获得良好韧性、良好延展性的高强度性能 (LYS≈ 4 6 0～ 5 6 0MPa) ,与常规控制轧制生产的类似产品相比 ,具有一定的竞争性。但V N钢中加入Ti后 ,降低了屈服强度 ,这是由于奥氏体中形成了V Ti(N)颗粒 ,减少了可在铁素体中形成富V细小析出物的V、N量的结果。
The evolution of microstructure of VN and V Ti N low carbon microalloyed steels in the process of thin slab casting and rolling was tested by optical microscope, transmission electron microscopy (TEM) and energy dispersive X-ray diffractometer (EDAX). After the 4 pass rolling in a 5-pass rolling, the grain size of the VN steel decreases from the original coarse grains (≈1 mm) to about 50 μm and the V Ti N steel decreases to 2 2 μm. The final average ferrite grain size of V Ti N steel was 48-6 6 μm, slightly smaller than the grain size of V N steel (53-372 μm). The VN second phase was observed only for VN steel after soaking at 10500C, while no VN was found after soaking at 120 ° C and 110 ° C. V Ti N steel has been formed during the casting and soaking (1200 ° C, 110 ° C and 105 ° C). However, the VN steel only precipitated AlN particles during soaking at 105 ℃, and was related to the composite precipitation of MnS or MnS and VN. No AlN was detected in V Ti N steel. Fine precipitates containing V (less than 10 nm) were found in both steel final products, but in V Ti N steels the frequency was lower than in VN steels and the fine precipitates in the final sheet played a major role in dispersion strengthening (LYS≈460 ~ 560MPa) with good ductility and good ductility, which is competitive with the similar products produced by conventional controlled rolling. However, the addition of Ti to VN steels reduces the yield strength due to the formation of V Ti (N) particles in the austenite and reduces the V and N content that can form V-rich precipitates in the ferrite .