Casting of conventional elements carbon, silicon, manganese, sulfur, phosphorus, this is our traditional five elements.
Important factors directly affect the mechanical properties of casting
Main functions are as follows: 1, the element silicon is the beneficial elements in the casting, it like carbon, can promote the graphitization, add in the form of inoculant silicon effect more apparent.
For as-cast ball mill casting, increasing silicon content has a dual role, on the one hand, it make cementite and pearlite, phosphorus ternary eutectic decreases, ferrite increased, thus reduce the strength and hardness, improve casting plastic;
Silicon solid solution strengthening ferrite on the other hand, raising the yield point and hardness;
In the coagulation of silicon improve casting liquidity, increasing volume expansion;
Silicon can improve the heat resistance, corrosion resistance.
Increase of silicon, especially the breeding of silicon, can significantly control the amount of carbide, as a result, silicon is inhibition of manganese in nodular cast iron chilling tendency of strong elements.
Silicon within a certain range, which is beneficial to the improvement of strength and toughness, but make the anti-wear performance decreases.
So to take the right amount.
In general, gray casting silicon content in 1.
2% ~ 3.
0%, ductile casting silicon in 2.
0% ~ 3.
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2, elements, carbon is the most basic constituents of iron castings in.
It is mainly to distinguish the main basis of steel or iron, carbon content is greater than 1.
Iron is 7%, less than 1.
7% of the known as the steel, and, in the process of production, carbon affects the mechanical properties of casting.
In the casting of the carbon will promote the graphitization, reduce chilling tendency, namely, reduce the cementite and pearlite, phosphorus ternary eutectic, increase the ferrite, and thus reduce the hardness to improve processing performance;
The improvement of magnesium carbon promote absorption;
Improve spheroidizing, in order to achieve the desired effect;
In the coagulation of carbon to improve liquidity, increasing the volume expansion;
Carbon increase vibration absorption, anti-friction property, thermal conductivity.
But high carbon graphite floatation, deteriorate mechanical properties, low and easy to produce shrinkage cavity defects such as shrinkage.
So, castings of different quality requirements, reasonable selecting carbon content in general is a way to improve the quality of castings, such as: most of grey iron carbon content in 2.
6% ~ 3.
In the 3 6%, nodular cast iron.
5% ~ 3.
Carbon on the mechanical property of manganese in nodular cast iron effect is not obvious, general carbon is higher than 3.
Easy to appear when 9% graphite floatation, affects the quality of cast iron, carbon is lower than 3.
0%, does not favor the graphitization general control carbon in 3.
0% ~ 3.
It is advisable to 8%.
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3, manganese element is one of the important elements of castings, the amount of manganese, helps to generate texture structure, increase the rigidity and strength and abrasion resistance.
Manganese and sulfur are stable compounds, is hampering the graphitization element, when coexist with sulfur, the affinity of manganese and sulfur is bigger, will be combined into MnS compounds, such as in the appropriate temperature, unimpeded graphitizing effect not only, also can counteract sulfur, it plays the role in addition to sulfur.
Manganese reaches a certain amount, can make the castings with high intensity, high hardness, high density, and the advantages of wear-resisting, at this time of silicon also increase accordingly.
Manganese segregation in eutectic group boundary, under the as-cast breeds into carbide, increase the amount of manganese, will deteriorate mechanical properties.
So the content of manganese should generally low.
But manganese can stable austenite, prompting austenitic matrix form, can become weak magnetic nodular cast iron, with good abrasion resistance.
The manganese is dissolved in austenite, solid solution with iron to form the displacement type, and, because of the manganese to carbon is stronger than iron affinity, it organization carbon diffusion in solid solution and precipitation, the stability and expansion of austenitic area.
4, elemental sulfur is also a kind of impurity, is a harmful element.
In casting, sulfur and other element such as Mn, Mg, strong affinity, generate stable carbides, hinder the graphitization, consumption of iron liquid spheroidizing elements, forming the MgS, MnS, such as residue, due to the effect of consumption of the sulfur made effective residual spheroidizing element content is too low is to reduce the spheroidizing, also promote the formation of slag, such as subcutaneous blowhole defects.
Sulfur due to decrease the rate of spheroidizing, accelerate the spheroidizing decay and the formation of slag decreased mechanical properties or unstable.
Low content of sulfur elements should be removed, it should be.
In the ordinary gray iron, sulfur content is in commonly 0.
02% ~ 0.
15%, S&le in nodular cast iron;
02%, sometimes visible on the circumstances.
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