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Home > Rapid identification method for nodular cast iron

Rapid identification method for spheroidization quality of nodular cast iron



Furnace inspection

It is an indispensable part in the production process of ductile cast iron. It is directly related to the quality of ductile iron castings. Timely and accurate judgment of the spheroidization of molten iron, we can take measures to control the quality of ductile cast iron. Misjudgment will result in a large number of casting scrap, waste molding. Therefore, the timely and accurate judgment of the furnace is more important than the post furnace inspection. In practical production, the method of checking the spheroidization of molten iron before the furnace is commonly used.

The crust and the flames of judgment

The rare earth magnesium nodular cast iron containing magnesium content is low, and rare earth elements, the surface of the molten iron and pure magnesium nodular cast iron is not the same, not so much the surface oxide, the flame is not so strong. But when adding 1/3 liquid iron liquid escapes and magnesium white * * flame, shaped like a candle. According to the number and height of the flame ball and judge the residual amount of magnesium, the flame is higher, more powerful, that ball is good. Especially in the pouring, from the molten iron flow can see * fire, such as the height of 25~ffice:smarttags "/>50mm, that is, the ball is good. If the flame is lower than 15mm, while the ball is poor. From the treated nodular cast iron liquid surface, the formation of oxide film, and the silver white rolling highlights, that is good for the ball. But the oxide film is too thick, it means that the low temperature of molten iron.

Triangular block method

At present, it is a common method to judge the spheroidization by observing the block. The test block of each plant has many shapes and sizes, and most factories adopt the triangle test block. According to the characteristics of our factory production, casting size and thickness, with triangular block section size is 12.5mm (bottom) * (50mm (high). Some factories use circular block, for example, with 15mm, with 25mm, with 30mm ranging. Liquid iron after sampling by the theory of molten iron at 200mm below the surface of the liquid is poured into the test block and cold to be dark red, water quenching, block ball good circle is much larger than that of grey cast iron appearance, clean and bright are usually vertical pouring and the sand river. Block on both sides of a horizontal pouring block top surface depression or depression on both sides of a specimen after cooling knock ball test, silvery white or grey white porcelain fracture tip clear middle loose if the fracture is silver white and radial pattern, while adding high ball produced more carbide. The test block into a "pat" snap test piece is broken and the new tap hammer mouth very strong smell of calcium carbide. So the best pouring floating silicon fertility if export silver gray, and uniform distribution of black dots in broken color crystal.

Casting process judgment

1). The ductile iron liquid is poured into the mold, such as pouring cup has been downward concave, and the surface is very smooth, that ball is good; if the pouring cup superstructure and a crust, is sinking, indicating the low temperature of liquid iron.

2). In the casting process, the circular part of the surface of the sand flat iron beans splash pits (PIT), that ball is good.

Black edge identification

The ball after the treatment, with a ladle pouring block 10mm thick, cooling to dark red, hit after quenching. If the block surface has a dark side, said the ball is bad, and the black side of the ball more thick, more bad, produce recession. At this point, such as the high temperature of molten iron alloy. From the block can also be seen as blocks around the arc shape, and the middle sag, some have a lot of wrinkles, also said the ball is good. If the block surface is like oatmeal, said liquid iron oxide, easy to decline. In this case, the furnace should be transformed.

Observe the solidification state of molten iron

The ball after the treatment, take out a small amount of liquid iron, poured into the 30mm diameter cylindrical metal type, observed during solidification of molten iron by surface emission phenomena, and to determine the liquid iron spheroidization according to the emission quantity of molten iron. The ball of molten iron good, solid period showed a lot of expanded graphite, the surface of the molten iron in the solidification start down a little, after a small amount of crusts on the surface of molten iron by case emission. And the number of the surface of the iron surface is less.

Rapid metallographic observation before furnace

All the above methods are used to indirectly determine the spheroidization of nodular cast iron. However, the production of a variety of conditions vary greatly, the method has limitations. However, the rapid metallographic observation before furnace can avoid the interference of many factors, and directly observe the spheroidization.