Mn-Si元素对340MPa热浸镀锌钢板力学性能和浸润性的影响研究
发布时间：2019-03-03 18:31
【摘要】：近些年来,汽车车身轻量化逐渐成为汽车行业主要发展方向。采用先进高强钢,不但能够使钢板变薄,而且在减轻车身重量的同时保证其较高的安全性,同时,在钢板表面镀一层锌可以有效的提高钢板的耐腐蚀性能,延长其使用效率。本文针对一种典型(340MPa级别)热镀锌钢板,研究在不同工艺条件下,其Mn-Si元素的强化机理,并分析了Mn、Si元素的添加对热浸镀锌钢板的氧化行为、抑制层形貌及镀层质量的影响规律。并运用预氧化-还原工艺研究其对热浸镀锌钢板浸润性的影响规律,主要研究结果如下:(1)随Si含量提高,屈服强度变化不大,但抗拉强度提高明显。当Si含量由0.01%提高至0.18%时,主要发生Si、Mn的内氧化,抑制层分布连续且均匀;而当Si含量继续提高至0.49%时,提高了发生外氧化的几率,抑制层尺寸出现明显分化;当Si含量提高至0.93%时,在亚表层出现的Si、Mn氧化物明显减少,主要发生外氧化,出现较大面积的裸露基体,而且Fe-Al相分布较为稀疏。(2)随Mn含量提高,抗拉强度呈增加趋势,Mn含量由1.22%提高至1.46%时,抗拉强度的提高尤为明显。当Mn含量由0.84%提高至1.22%时,氧化物数量和尺寸有所增大,形成的抑制层分布密集,完整地覆盖于钢基体表面,观察不到裸露的基体,镀层均匀致密;当Mn含量提高至1.46%时,氧化物形貌发生改变,氧化物的密度大大增加,形成了一层Si、Mn氧化物膜,抑制层在部分区域出现缺失,出现裸露的基体,锌晶粒间的漏镀区域显著增大,这将造成涂镀性能恶化。与Mn元素相比,Si对涂镀性能的影响更大。(3)随露点升高,氧化类型由外氧化向内氧化过渡。在单一露点条件下,热镀锌钢板抑制层均匀性和致密性很差;而在预氧化-还原工艺条件下,其抑制层分布密度及均匀性提高,但是在某些晶界处,仍出现Fe-Al相分布稀疏或者缺失。预氧化-还原工艺可以在一定程度上改变氧化行为,从而有利于抑制层的形成。但是,沿晶界分布的外氧化依旧存在,难以保证完全内氧化的发生。
[Abstract]:In recent years, automobile body lightweight has gradually become the main development direction of automobile industry. The use of advanced high strength steel can not only make the steel plate thinner, but also reduce the body weight and ensure its high safety. At the same time, zinc coating on the surface of the steel plate can effectively improve the corrosion resistance of the steel plate and prolong its service efficiency. In this paper, the strengthening mechanism of Mn-Si element in a typical (340MPa grade) hot dip galvanized steel sheet was studied under different process conditions, and the oxidation behavior of Mn,Si element addition on hot dip galvanized steel plate was analyzed. The influence of coating morphology and coating quality on the surface morphology of the coating was studied. The influence of pre-oxidation-reduction process on the wettability of hot dip galvanized steel plate was studied. The main results are as follows: (1) with the increase of Si content, the yield strength does not change much, but the tensile strength increases obviously. When the content of Si increased from 0.01% to 0.18%, the internal oxidation of Si,Mn occurred, and the distribution of the inhibition layer was continuous and uniform. When the content of Si continues to increase to 0.49%, the probability of external oxidation is increased and the size of the inhibition layer is obviously differentiated. When the content of Si was increased to 0.93%, the content of Si,Mn oxide in subsurface layer decreased obviously, and there was a large area of exposed matrix, and the distribution of Fe-Al phase was sparse. (2) with the increase of Mn content, there was a large area of bare matrix. (2) with the increase of Mn content, the content of Mn increased. The tensile strength increased, especially when the content of Mn increased from 1.22% to 1.46%. When the content of Mn increased from 0.84% to 1.22%, the amount and size of oxide increased, and the formation of the inhibition layer was dense and completely covered on the surface of the steel substrate. The bare substrate was not observed, and the coating was homogeneous and dense. When the content of Mn increased to 1.46%, the morphology of oxide changed and the density of oxide increased greatly. A layer of Si,Mn oxide film was formed. The leakage zone between zinc grains increases significantly, which will result in the deterioration of coating properties. The effect of Si on coating properties is greater than that of Mn. (3) with the increase of dew point, the oxidation type changes from external oxidation to internal oxidation. Under the condition of single dew point, the uniformity and compactness of the inhibition layer of hot-dip galvanized steel sheet are very poor. Under the condition of pre-oxidation-reduction process, the density and uniformity of the inhibition layer increase, but at some grain boundaries, the Fe-Al phase distribution is still sparse or missing. The pre-oxidation-reduction process can change the oxidation behavior to a certain extent, which is beneficial to inhibit the formation of the layer. However, the external oxidation along the grain boundary still exists, and it is difficult to guarantee the occurrence of complete internal oxidation.
【学位授予单位】：辽宁科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1;TG174.4
本文编号：2433987
[Abstract]:In recent years, automobile body lightweight has gradually become the main development direction of automobile industry. The use of advanced high strength steel can not only make the steel plate thinner, but also reduce the body weight and ensure its high safety. At the same time, zinc coating on the surface of the steel plate can effectively improve the corrosion resistance of the steel plate and prolong its service efficiency. In this paper, the strengthening mechanism of Mn-Si element in a typical (340MPa grade) hot dip galvanized steel sheet was studied under different process conditions, and the oxidation behavior of Mn,Si element addition on hot dip galvanized steel plate was analyzed. The influence of coating morphology and coating quality on the surface morphology of the coating was studied. The influence of pre-oxidation-reduction process on the wettability of hot dip galvanized steel plate was studied. The main results are as follows: (1) with the increase of Si content, the yield strength does not change much, but the tensile strength increases obviously. When the content of Si increased from 0.01% to 0.18%, the internal oxidation of Si,Mn occurred, and the distribution of the inhibition layer was continuous and uniform. When the content of Si continues to increase to 0.49%, the probability of external oxidation is increased and the size of the inhibition layer is obviously differentiated. When the content of Si was increased to 0.93%, the content of Si,Mn oxide in subsurface layer decreased obviously, and there was a large area of exposed matrix, and the distribution of Fe-Al phase was sparse. (2) with the increase of Mn content, there was a large area of bare matrix. (2) with the increase of Mn content, the content of Mn increased. The tensile strength increased, especially when the content of Mn increased from 1.22% to 1.46%. When the content of Mn increased from 0.84% to 1.22%, the amount and size of oxide increased, and the formation of the inhibition layer was dense and completely covered on the surface of the steel substrate. The bare substrate was not observed, and the coating was homogeneous and dense. When the content of Mn increased to 1.46%, the morphology of oxide changed and the density of oxide increased greatly. A layer of Si,Mn oxide film was formed. The leakage zone between zinc grains increases significantly, which will result in the deterioration of coating properties. The effect of Si on coating properties is greater than that of Mn. (3) with the increase of dew point, the oxidation type changes from external oxidation to internal oxidation. Under the condition of single dew point, the uniformity and compactness of the inhibition layer of hot-dip galvanized steel sheet are very poor. Under the condition of pre-oxidation-reduction process, the density and uniformity of the inhibition layer increase, but at some grain boundaries, the Fe-Al phase distribution is still sparse or missing. The pre-oxidation-reduction process can change the oxidation behavior to a certain extent, which is beneficial to inhibit the formation of the layer. However, the external oxidation along the grain boundary still exists, and it is difficult to guarantee the occurrence of complete internal oxidation.
【学位授予单位】：辽宁科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1;TG174.4
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