常壓鑄造條件下灰鑄鐵表面合金化的研究
發(fā)布時間：2019-02-23 17:12
【摘要】：鑄滲工藝因其成本低、生產(chǎn)周期短被常用于鑄件表面或局部強化,以改善鑄件表面耐磨、耐高溫、耐腐蝕等性能。但目前用得較多的是負壓鑄滲工藝,該工藝由于負壓的作用,其排氣效果好、不易產(chǎn)生氣孔缺陷,也可以不用粘結(jié)劑使預制合金層產(chǎn)生強度、不存在粘結(jié)劑分解所造成的氣孔、渣孔等缺陷。但其需要專用設備且工藝過程復雜、適用的鑄件有限,大部分鑄件仍是采用常壓鑄造工藝生產(chǎn)出來的,因此,解決常壓鑄造條件下的關鍵技術問題意義重大。常壓鑄滲工藝必須使用粘結(jié)劑才能使鑄滲前的預制合金層產(chǎn)生強度,粘結(jié)劑的加入會導致氣孔、渣孔形成,因此,如何優(yōu)化粘結(jié)劑,在保證強度的前提下,降低氣孔、渣孔的形成,是我們首先要解決的問題。在此基礎上,探索了合金粉末粒度、涂覆層厚度對鑄滲效果的影響規(guī)律,在常壓鑄造條件下獲得了質(zhì)量較好的表面鑄滲層,并分析鑄滲層的組織結(jié)構與成分,最后測試了鑄滲層的耐磨性。本文首先探討了四種典型粘結(jié)劑(水玻璃、磷酸二氫鋁、聚乙烯醇、聚乙烯醇縮丁醛)粘結(jié)強度、發(fā)氣量對灰鑄鐵表面合金化質(zhì)量的影響規(guī)律。其中水玻璃是四種粘結(jié)劑中最適合常壓鑄滲工藝的粘結(jié)劑,添加量為7 wt.%時,粘結(jié)強度適宜且發(fā)氣量小,鑄滲層質(zhì)量良好,滲層厚度為5 mm且組織致密、缺陷少。研究了合金粉末粒度、涂覆層厚度對鑄滲層厚度的影響,合金粉末粒度100目,涂覆層厚度4 m m為最優(yōu)參數(shù)。利用金相顯微鏡、掃描電子顯微鏡、X-射線衍射分析儀、能譜儀、硬度計等分析測試方法,對鑄滲層顯微組織結(jié)構、成分及硬度進行分析表征,可知鑄滲層存在三個明顯不同的區(qū)域。不同區(qū)域的顯微組織結(jié)構與成分因合金粉末與金屬液之間相互的擴散作用而存在明顯差異。同時,研究了厚度不同對鑄滲層組織結(jié)構以及三體磨料磨損性能的影響規(guī)律。滲層厚度大,其硬度高,耐磨性好,滲層厚度為5 mm時,表面平均硬度為840 HV,耐磨性為基體的2倍。
[Abstract]:Due to its low cost and short production cycle, casting infiltration process is often used to improve the surface wear resistance, high temperature resistance and corrosion resistance of castings. However, at present, the negative die-casting infiltration process is widely used. Due to the negative pressure, the process has good exhaust effect and is not easy to produce porosity defects. It can also make the prefabricated alloy layer produce strength without binder, and there is no porosity caused by the decomposition of binder. Defects such as slag holes But the special equipment is needed and the process is complicated, the suitable casting is limited, most castings are still produced by the normal pressure casting process, therefore, it is of great significance to solve the key technical problems under the normal pressure casting condition. The bonding agent must be used to produce the strength of the prefabricated alloy layer before casting infiltration, and the addition of binder will lead to the formation of pores and slag holes. Therefore, how to optimize the binder and reduce the porosity under the premise of ensuring the strength, The formation of slag hole is the problem that we must solve first. On this basis, the influence of alloy powder granularity and coating thickness on the cast infiltration effect was explored. The surface cast infiltration layer with good quality was obtained under normal pressure casting conditions, and the microstructure and composition of the cast infiltration layer were analyzed. Finally, the wear resistance of the cast layer was tested. In this paper, the effect of four typical binders (sodium silicate, aluminum dihydrogen phosphate, polyvinyl butyral) on the surface alloying quality of gray cast iron was studied. Water glass is the most suitable binder of four binders for normal die-casting infiltration process. When the amount of binder is 7 wt.%, the bond strength is suitable and the amount of gas is small, the quality of cast infiltrating layer is good, the thickness of infiltrating layer is 5 mm, the structure is compact and the defects are less. The effect of alloy powder particle size and coating thickness on the thickness of cast coating was studied. The optimum parameters were 100 mesh of alloy powder size and 4 mm of coating thickness. By means of metallographic microscope, scanning electron microscope, X-ray diffraction analyzer, energy spectrometer and hardness meter, the microstructure, composition and hardness of the cast infiltrated layer were analyzed and characterized. It can be seen that there are three distinct areas in the cast layer. The microstructure and composition of different regions are obviously different due to the diffusion between alloy powder and liquid metal. At the same time, the influence of different thickness on the microstructure and wear properties of three-body abrasive was studied. When the thickness of the layer is 5 mm, the average surface hardness is 840 HV, and the wear resistance is twice as high as that of the matrix.
【學位授予單位】：西南科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG174.445
本文編號：2429040
[Abstract]:Due to its low cost and short production cycle, casting infiltration process is often used to improve the surface wear resistance, high temperature resistance and corrosion resistance of castings. However, at present, the negative die-casting infiltration process is widely used. Due to the negative pressure, the process has good exhaust effect and is not easy to produce porosity defects. It can also make the prefabricated alloy layer produce strength without binder, and there is no porosity caused by the decomposition of binder. Defects such as slag holes But the special equipment is needed and the process is complicated, the suitable casting is limited, most castings are still produced by the normal pressure casting process, therefore, it is of great significance to solve the key technical problems under the normal pressure casting condition. The bonding agent must be used to produce the strength of the prefabricated alloy layer before casting infiltration, and the addition of binder will lead to the formation of pores and slag holes. Therefore, how to optimize the binder and reduce the porosity under the premise of ensuring the strength, The formation of slag hole is the problem that we must solve first. On this basis, the influence of alloy powder granularity and coating thickness on the cast infiltration effect was explored. The surface cast infiltration layer with good quality was obtained under normal pressure casting conditions, and the microstructure and composition of the cast infiltration layer were analyzed. Finally, the wear resistance of the cast layer was tested. In this paper, the effect of four typical binders (sodium silicate, aluminum dihydrogen phosphate, polyvinyl butyral) on the surface alloying quality of gray cast iron was studied. Water glass is the most suitable binder of four binders for normal die-casting infiltration process. When the amount of binder is 7 wt.%, the bond strength is suitable and the amount of gas is small, the quality of cast infiltrating layer is good, the thickness of infiltrating layer is 5 mm, the structure is compact and the defects are less. The effect of alloy powder particle size and coating thickness on the thickness of cast coating was studied. The optimum parameters were 100 mesh of alloy powder size and 4 mm of coating thickness. By means of metallographic microscope, scanning electron microscope, X-ray diffraction analyzer, energy spectrometer and hardness meter, the microstructure, composition and hardness of the cast infiltrated layer were analyzed and characterized. It can be seen that there are three distinct areas in the cast layer. The microstructure and composition of different regions are obviously different due to the diffusion between alloy powder and liquid metal. At the same time, the influence of different thickness on the microstructure and wear properties of three-body abrasive was studied. When the thickness of the layer is 5 mm, the average surface hardness is 840 HV, and the wear resistance is twice as high as that of the matrix.
【學位授予單位】：西南科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG174.445
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