تأثير جوانه‌زا و مدول ريختگي بر ريزساختار انجمادي چدن آستنيتي منگنزي با گرافيت كروي

Effect of Inoculation and Casting Modulus on the as Cast Microstructure of Austenitic Manganese Iron with Nodular Graphite

در اﯾﻦ ﻣﻘﺎﻟﻪ، اﺛﺮ ﻣﯿﺰان و ﻧﺤﻮه اﻓﺰودن ﺟﻮاﻧﻪزا و ﺿﺨﺎﻣﺖ ﻗﻄﻌﻪ ﺑﺮ رﯾﺰﺳﺎﺧﺘﺎر اﻧﺠﻤﺎدي ﭼﺪن ﻧﺸﮑﻦ آﺳﺘﻨﯿﺘﯽ ﺑﺎ ﻣﻘﺪار اﺳﻤﯽ 5 درﺻﺪ وزﻧﯽ ﻣﻨﮕﻨﺰ ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﺑﻪ اﯾﻦ ﻣﻨﻈﻮر ﺑﻌﺪ از ﻋﻤﻞ ﻧﺸﮑﻦﺳﺎزي ﭼﺪن ﻣﺬاب ﺑﺎ ﻓﺮوﺳﯿﻠﯿﮑﻮﻣﻨﯿﺰﯾﻢ، ﻋﻤﻠﯿﺎت ﺟﻮاﻧﻪزاﯾﯽ ﺑﺎ ﻓﺮوﺳﯿﻠﯿﺴﯿﻢ زﯾﺮﮐﻮﻧﯿﻢدار اﻧﺠﺎم ﺷﺪ. ﺟﻮاﻧﻪزاﯾﯽ ﺑﻪ دو روش اﺻﻠﯽ، اﻓﺰودن در ﭘﺎﺗﯿﻞ و اﻓﺰودن ﺣﯿﻦ ﺑﺎررﯾﺰي در ﻣﻘﺎدﯾﺮ ﻣﺨﺘﻠﻒ )ﺻﻔﺮ، 0/2 ،0/1 و 0/3 درﺻﺪ وزﻧﯽ( اﻧﺠﺎم ﺷﺪ. ﻫﻤﭽﻨﯿﻦ رﯾﺨﺘﻪﮔﺮي در ﻗﺎﻟﺐ ﻣﺎﺳﻪاي ﺑﺎ ﭼﺴﺐ ﺳﯿﻠﯿﮑﺎت ﺳﺪﯾﻢ و ﺑﻪ ﺷﮑﻞ ﭘﻠﻪاي ﺑﺎ ﺿﺨﺎﻣﺖﻫﺎي 10 ،5 و 20 ﻣﯿﻠﯽﻣﺘﺮ اﻧﺠﺎم ﺷﺪ. ﺑﺮرﺳﯽﻫﺎي رﯾﺰﺳﺎﺧﺘﺎري و ﺳﺨﺘﯽ ﺗﻮﺳﻂ ﻣﯿﮑﺮوﺳﮑﻮپﻫﺎي ﻧﻮري و اﻟﮑﺘﺮوﻧﯽ روﺑﺸﯽ، آﻧﺎﻟﯿﺰ EDS و آﻧﺎﻟﯿﺰ ﺗﺼﻮﯾﺮي MIP4 و ﺳﺨﺘﯽ ﺳﻨﺠﯽ راﮐﻮلﺳﯽ اﻧﺠﺎم ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ رﯾﺰﺳﺎﺧﺘﺎر رﯾﺨﺘﮕﯽ اﯾﻦ ﭼﺪن ﺷﺎﻣﻞ ﮔﺮاﻓﯿﺖﻫﺎي ﮐﺮوي و ﮐﺎرﺑﯿﺪﻫﺎي ﯾﻮﺗﮑﺘﯿﮏ در زﻣﯿﻨﻪ ﭘﺮﻟﯿﺘﯽ اﺳﺖ. ﺑﺎ ﮐﺎﻫﺶ ﺿﺨﺎﻣﺖ ﻧﻤﻮﻧﻪﻫﺎ، ﻣﻘﺪار ﮐﺎرﺑﯿﺪ ﯾﻮﺗﮑﺘﯿﮏ و ﺗﻌﺪاد ﮔﺮاﻓﯿﺖﻫﺎ، اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ و ﻣﻘﺪار ﭘﺮﻟﯿﺖ و اﻧﺪازه ﮔﺮاﻓﯿﺖﻫﺎ ﮐﺎﻫﺶ ﻣﯽﯾﺎﺑﺪ. ﺑﺮاي ﺗﻤﺎﻣﯽ ﺿﺨﺎﻣﺖﻫﺎي ﺟﺪاره ﻣﺸﺎﻫﺪه ﺷﺪ ﮐﻪ ﺑﺎ ﺟﻮاﻧﻪزﻧﯽ، ﻣﻘﺪار ﮐﺎرﺑﯿﺪ ﯾﻮﺗﮑﺘﯿﮏ و اﻧﺪازه ﮔﺮاﻓﯿﺖﻫﺎ ﮐﺎﻫﺶ ﯾﺎﻓﺘﻪ اﺳﺖ و در ﻣﻘﺎﺑﻞ، ﺗﻌﺪاد و ﻣﻘﺪار ﮐﺮهﻫﺎي ﮔﺮاﻓﯿﺖﻫﺎي اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﻧﺸﺎن داده ﺷﺪ ﮐﻪ ﺟﻮاﻧﻪزﻧﯽ در ﺣﯿﻦ ﺑﺎررﯾﺰي ﻣﻮﺛﺮﺗﺮ از ﺟﻮاﻧﻪزﻧﯽ در ﭘﺎﺗﯿﻞ اﺳﺖ.

In this paper, the effects of grain refiner amount, its addition method and the casting modulus (wall thickness) on the solidification microstructure of austenitic nodular graphite cast iron with 5 weight percent manganese were investigated. For this purpose, the inoculation was performed with ferrosilicon zirconium after spheroidizing with ferrosilicon magnesium. The grain refiner additions were performed using two basic method, ladle inoculation and pouring stream inoculation in different amounts (0, 0.1, 0.2 and 0.3% by weight). In addition, the casting process was performed in the step form sand-sodium silicate binder mold with 5, 10 and 20 mm thicknesses. Microstructural evaluations and hardness measuring were achieved using the optical and electron microscopes, EDS, MIP4 visual analysis and Rockwell C test method. The results showed that the as cast microstructure of the cast iron consists of nodular graphite and eutectic carbide at the pearlitic matrix. The amount of eutectic carbides and graphite nodule count increase and the amount of pearlite and the size of the graphite’s decrease by decreasing the mold thickness. For all casting modulus (wall thicknesses), the inoculation process decreases the amount of eutectic carbide and graphite size and increases the graphite nodule count and its volume fraction. In addition, it was observed that the pouring stream inoculation is more effective than the ladle inoculation.