固溶处理温度对Fe-Mn-Al-C铁素体基轻质钢耐蚀性能的影响

利用光学显微镜、扫描电镜、X射线衍射仪等研究了热轧态、850、950和1 050 ℃固溶处理Fe-Mn-Al-C铁素体基轻质钢的微观组织。通过测试固溶处理试样的极化曲线和阻抗曲线,以及观察试样在3.5%NaCl溶液中腐蚀后的表面状态,分析其耐蚀性。结果表明,试样经850 ℃固溶处理后的组织为铁素体+κ碳化物;950 ℃固溶处理后组织为铁素体+奥氏体+少量κ碳化物;1050 ℃固溶处理后组织为铁素体+奥氏体。随固溶处理温度的升高,试样中κ碳化物逐渐粗化直至全部溶解,950 ℃时发生奥氏体转变且晶粒有所增大,但1050 ℃时奥氏体的含量却略有降低。950 ℃固溶处理试样在3.5%NaCl溶液中的耐蚀性最佳,其自腐蚀电流密度为3.102×10^-6 A/cm²,钝化膜的电阻R_p值为3944 Ω。经过240 h腐蚀浸泡后,950 ℃固溶处理试样的腐蚀速率最低,这主要是由于其组织中奥氏体含量相对较高、铁素体和κ碳化物含量相对较低以及铁素体中Al元素含量较高所致。

Influence of solution temperature on corrosion resistance of Fe-Mn-Al-C ferrite based light weight steel

Microstructure of a Fe-Mn-Al-C ferrite based lightweight steel after hot-rolling and solution treatment at 850, 950 and 1050 ℃, respectively, were analysed by means of OM, SEM and X-ray diffractometer. The corrosion resistance of the solution treated samples were studied by obtaining the polarization curves, impedance curves and the surface states corrosion in 3.5%NaCl solution. The results show that the microstructure after solution treatment at 850, 950 and 1050 ℃ are ferrite+ κ carbide, ferrite+ austenite+ a little κ carbide and ferrite+ austenite, respectively. With the solution treatment temperature increasing, κ carbides coarse gradually until dissolve completely, austenite forms and the grain grows, but the amount of the austenite decreases slightly. The best corrosion resistance in 3.5%NaCl solution is obtained after solution treatment at 950 ℃, which self corrosion current density is 3.102×10^-6 A/cm² and resistance R_p value of passivation film is 3944 Ω, the corrosion rate is lowest after corrosion test for 240 h. All of that is mainly due to the higher content of austenite and Al in ferrite as well as the lower content of ferrite and κ carbide.