is a casting process, are made from rare earth magnesium nodulizing agent, cupola and grey are the same.
Small make up today to tell you something about what factors affect the ductile casting
the production of the product.
A, property of ductile cast iron, graphite shape, matrix was 1, graphite shape: ductile cast iron, as the name implies, one of the most representative graphite spheroidal shape.
The quality of ductile iron are typically spheroidization rate to assess.
Graphite more roundness, small, distribution more uniform, the fragmentation effect of matrix and the stress concentration caused by the smaller, the better the performance of ductile iron.
According to GB/T9441 nodular cast iron metallographic examination requirements, graphite shape is divided into six levels, level 3 or more qualified, spheroidization rate to reach more than 75%.
2, the matrix organization: ductile iron matrix organization varies according to the brand.
Ball iron matrix was mainly composed of ferrite and pearlite, also includes a small number of cementite, phosphorus eutectic.
Casting ferrite content more, less pearlite content, good toughness, low intensity;
The opposite high strength, toughness is poor.
I plant commonly used QT400 -
10 brands in ferritic ductile iron as the main substrate, pearlite content to control below 20%.
Cementite, phosphorus eutectic plant in these two groups in the use of ductile iron is harmful organization must be controlled under 2%, otherwise the casting strength and toughness is poor.
The following are two matrix image of the organization.
Second, the cause of unqualified microstructure: ductile iron parts unqualified microstructure is mainly embodied in the graphite spheroidizing, matrix was wrong form or form the two aspects.
1, the main cause of the graphite spheroidizing bad: bad chemical composition control, hinder the graphitizing elements too much;
Inoculation, spheroidizing process control is bad;
Molten iron cooling too quickly;
Pouring time is too long, etc.
2, the cause of pearlite in matrix exceeds bid: hot metal pouring control is bad.
The cause of cementite overweight: casting cooling too quickly;
Poor chemical composition control, such as low silicon content in hot metal;
Nodularizer too much;
Inoculation is bad;
The causes of excessive phosphorus eutectic is: P element content exceeds bid.
Organization is unqualified after the aluminum alloy casting remedy: if casting adverse or phosphorus eutectic graphite spheroidizing, late is beyond repair, so it is necessary to effective quality control of production process.
If cast pearlite and cementite in overweight, can also through the low temperature, high temperature annealing heat treatment means such as remedy.
Above is the reason why on ductile casting processing products is unqualified, hope can help to you.
Today small make up to you at this point, let's see you next time.
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