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不鏽鋼鑄件縮松的原因有哪些

發布時間:2018-04-12點擊量:84

不鏽鋼鑄件縮松的原因有多種:由于不鏽鋼鑄件斷面過厚,造成補縮不良形成縮孔。不鏽鋼鑄件壁厚不均勻,在壁厚部分熱節處産生縮孔或縮松。 由于不鏽鋼鑄孔直徑太小形成鑄孔的砂芯被高溫金屬液加熱後,長期處于高溫狀态,降低了不鏽鋼鑄孔表面金屬的凝固速度,同時,砂芯為氣體或大氣壓提供了信道,導緻了孔壁産生縮孔和繡松。 不鏽鋼鑄件的凹角圓角半徑太小,使尖角處型砂傳熱能力降低,凹角處凝固速度下降,同時由于尖角處型砂受熱作用強,發氣壓力大,析出的氣體可向未凝固的金屬液滲入,導緻鑄件産生氣縮孔。熔煉方面的原因:不鏽鋼 液體金屬的含氣量太高,導緻在不鏽鋼鑄件冷卻過程中以氣泡形式析出,阻止鄰近的液體金屬向該處流動進行補縮,産生縮孔或縮松。 當灰鑄鐵碳當量太低時,将使鐵水凝固時共晶石墨析出量減少,降低了石墨化膨脹的作用,使凝固收縮增加,同時也降低鐵水的流動性。認而降低鐵水的自補縮能力,使鑄件容易産生縮孔或縮松。 當鐵水含磷量或含硫量偏高時,磷是擴大凝固溫度範圍的元素,同時形成大量的低熔點磷共晶,凝固時減少了補縮能力。硫是阻礙石墨化的元素,硫還能降低鐵水的流動性。同時,鐵水氧化嚴重,也降低液體金屬的流動性,使鑄件産生縮孔或縮松。 孕育鑄鐵或球墨鑄鐵在澆注前用矽鐵等孕育劑進行孕育處理時,如果孕育不良,将導緻鐵水凝固時析出大量的滲碳體,從而使凝固收縮增加,産生縮孔的局部必然會出現縮松.産生的機理是一樣的,鑄件在凝固的過程中,最後冷卻部位得不到補縮即會産生.There are many reasons for the shrinkage of stainless steel castings: due to the excessive thickness of the stainless steel castings, the shrinkage is bad and the shrinkage cavity is formed. The wall thickness of stainless steel castings is uneven, and shrinkage cavity or porosity is formed at the hot part of the wall thickness. As the diameter of the stainless steel is too small, the sand core formed by the casting hole is heated by high temperature metal liquid for a long time, and it is in a high temperature state for a long time, which reduces the solidification speed of the metal on the surface of the stainless steel casting hole. At the same time, the sand core provides the channel for gas or atmospheric pressure, resulting in the shrinkage and embroidery of the hole wall. The angular radius of the concave angle of the stainless steel castings is too small to reduce the heat transfer ability of the molding sand and the solidification speed at the concave corner. At the same time, the gas pressure is strong and the gas can be permeated into the non solidified metal fluid because of the sharp corner of the molding sand. The reason for melting is that the gas content of the stainless steel liquid metal is too high, which causes the precipitation of the stainless steel castings in the form of bubbles in the cooling process, and prevents the adjacent liquid metal from flowing to the place to make up, resulting in shrinkage or shrinkage. When the carbon equivalent of gray cast iron is too low, the precipitation of eutectic ink will be reduced, the effect of graphitization expansion is reduced, the solidification shrinkage is increased, and the fluidity of molten iron is also reduced. It is believed that the self shrinking ability of molten iron can be reduced, resulting in shrinkage or porosity. When the phosphorus content or sulfur content of molten iron is high, phosphorus is an element that expands the range of solidification temperature, and forms a large number of low melting point phosphorus eutectic, which reduces the filling capacity. Sulfur is a hindrance to graphitization, and sulfur can also reduce the fluidity of molten iron. At the same time, the oxidation of molten iron is serious, which also reduces the fluidity of liquid metal and causes shrinkage or porosity of castings. When inoculating cast iron or spheroidal graphite cast iron before pouring with ferrosilicon and other inoculants for inoculation, if the inoculation is bad, a large number of carburized carburized bodies will be precipitated when the molten iron is solidified, which makes the shrinkage of the solidification increase, and the part of the shrinkage will inevitably shrink. The mechanism is the same, the casting is cooled in the solidification process. When the parts are not made up, they will come into being.

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