【摘要】：近些年來,汽車車身輕量化逐漸成為汽車行業(yè)主要發(fā)展方向。采用先進(jìn)高強(qiáng)鋼,不但能夠使鋼板變薄,而且在減輕車身重量的同時(shí)保證其較高的安全性,同時(shí),在鋼板表面鍍一層鋅可以有效的提高鋼板的耐腐蝕性能,延長其使用效率。本文針對一種典型(340MPa級別)熱鍍鋅鋼板,研究在不同工藝條件下,其Mn-Si元素的強(qiáng)化機(jī)理,并分析了Mn、Si元素的添加對熱浸鍍鋅鋼板的氧化行為、抑制層形貌及鍍層質(zhì)量的影響規(guī)律。并運(yùn)用預(yù)氧化-還原工藝研究其對熱浸鍍鋅鋼板浸潤性的影響規(guī)律,主要研究結(jié)果如下:(1)隨Si含量提高,屈服強(qiáng)度變化不大,但抗拉強(qiáng)度提高明顯。當(dāng)Si含量由0.01%提高至0.18%時(shí),主要發(fā)生Si、Mn的內(nèi)氧化,抑制層分布連續(xù)且均勻;而當(dāng)Si含量繼續(xù)提高至0.49%時(shí),提高了發(fā)生外氧化的幾率,抑制層尺寸出現(xiàn)明顯分化;當(dāng)Si含量提高至0.93%時(shí),在亞表層出現(xiàn)的Si、Mn氧化物明顯減少,主要發(fā)生外氧化,出現(xiàn)較大面積的裸露基體,而且Fe-Al相分布較為稀疏。(2)隨Mn含量提高,抗拉強(qiáng)度呈增加趨勢,Mn含量由1.22%提高至1.46%時(shí),抗拉強(qiáng)度的提高尤為明顯。當(dāng)Mn含量由0.84%提高至1.22%時(shí),氧化物數(shù)量和尺寸有所增大,形成的抑制層分布密集,完整地覆蓋于鋼基體表面,觀察不到裸露的基體,鍍層均勻致密;當(dāng)Mn含量提高至1.46%時(shí),氧化物形貌發(fā)生改變,氧化物的密度大大增加,形成了一層Si、Mn氧化物膜,抑制層在部分區(qū)域出現(xiàn)缺失,出現(xiàn)裸露的基體,鋅晶粒間的漏鍍區(qū)域顯著增大,這將造成涂鍍性能惡化。與Mn元素相比,Si對涂鍍性能的影響更大。(3)隨露點(diǎn)升高,氧化類型由外氧化向內(nèi)氧化過渡。在單一露點(diǎn)條件下,熱鍍鋅鋼板抑制層均勻性和致密性很差;而在預(yù)氧化-還原工藝條件下,其抑制層分布密度及均勻性提高,但是在某些晶界處,仍出現(xiàn)Fe-Al相分布稀疏或者缺失。預(yù)氧化-還原工藝可以在一定程度上改變氧化行為,從而有利于抑制層的形成。但是,沿晶界分布的外氧化依舊存在,難以保證完全內(nèi)氧化的發(fā)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.
【學(xué)位授予單位】：遼寧科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG142.1;TG174.4

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