How to quickly identify the quality of the ductile iron pipe fittings before a, furnace inspection before the ball is cast iron is an indispensable part of the production process, it is directly related to the quality of ductile cast iron.
Timely, accurate judgment of spheroidal graphite iron liquid, can quickly take measures to control the quality of ductile iron.
Before furnace misjudgment will cause a lot of the casting
scrap, waste modelling working hours, so timely, accurate judgment before furnace spheroidizing is more important than furnace after inspection.
In front of the furnace is commonly used in the actual production of iron liquid spheroidizing method has the following kinds.
1, pouring process judgment (
Ductile iron liquid poured into the mold, such as flood basin has been down concave shrinkage, and the surface is very smooth, show spheroidizing order;
Such as pouring basin knot a layer of crust and upper are concave, suggests that the low temperature of molten irons.
In the process of casting, sand mould surface has splash the circular flat iron beans of pitting,
That spheroidizing is good.
2, the surface crust and flame judgment method and soil magnesium nodular cast iron magnesium content is low, and rare earth elements, liquid iron surface and pure magnesium nodular cast iron, the surface no enough scale, the flame is not so much.
But when adding a third iron liquid level can escape micron and white * * flame, like a candle flame.
According to the height of the flame quantity, judge the spheroidizing and residual amount of magnesium, the flame is higher, the more powerful, spheroidizing is good.
Especially when pouring, * * fire can be seen in the iron flow, such as height of 25 ~ ffice: smarttags '/ & gt;
50 mm, is spheroidizing is good;
If the flame is lower than 15 mm, the spheroidizing is poorer.
Of ductile iron liquid iron from the surface, the formation of oxide film, rolling window and have a silvery white, is for the spheroidizing is good.
But said the iron oxide film is too thick, the liquid temperature is low.
3, triangular block method at present, through the observation to judge the spheroidizing block is a kind of widely used methods.
GeChang used block shape many, different size, most factories using triangle block.
According to my factory production characteristics, casting size and thickness, selection of triangular cross-section of block size of 12.
Also some plant adopts circular test piece, such as 15 mm, 25 mm, Ф Ф Ф 30 mm.
Iron liquid principle is finished with sampling spoon by 200 mm below the surface of the liquid iron is poured into a block and cold to the dark red Fang Keshui quenching cooling ball a good piece of cylindrical is much bigger than gray cast iron appearance clean palace are usually on both sides of the triangle block vertical casting sand have shrinkage in lie at the top of the block or both sides have a shrinkage in cooling type break block, spheroidizing good try, a silvery white or silver porcelain fracture among white clear if osteoporosis fracture is silvery white and radial pattern table ball agent addition amount on the high side of carbide block at this time more trendy specimens made 'clap' the embrittlement of the tap is off and hit the mouth of a strong new calcium carbide smell so good when pouring to float silicon) if an silver and uniform distribution of small black spots if broken color crystal, the Ming defeated (
See the table)
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Table the two identification methods of spheroidization quality triangle sample description: 1)
Spheroidizing good triangular block that can have calcium carbide after quenching water interrupt immediately escape.
Depth of the white iron and nodular cast iron type, type and composition of fluid, so did not give the data in the table, the rare earth magnesium nodular cast iron chill depth is not obvious.
4, after the black border check ball handling, ladle pouring with sample block about a 10 mm thick, cool to dark red, quenching on patrol, such as found on the block surface has a dark side, said spheroidizing, and the thicker the black border, the spheroidizing, produce a recession, at this time, such as high temperature of iron liquid can be adding alloy.
Can see from the test block, such as around the block into a circular arc shape, and the middle sag, some wrinkles, also said spheroidizing good;
Such as block on the surface of wheat skin point, said iron melt oxidation, easy to recession.
In this case, the response to the stove.
5, observe the molten iron solidification condition after spheroidizing, take out a small amount of liquid iron, poured into the Ф 30 mm cylindrical metal type, observed during solidification of iron liquid poured out from the surface phenomenon, and according to the flow to judge the liquid iron spheroidization iron liquid quantity.
During spheroidizing good iron liquid and solid show a lot of graphite expansion force, at the beginning of the solidification of liquid iron surface some decline, after surface crust with a small amount of iron liquid by watchcase gushed out;
The spheroidizing bad gushed out small number of liquid iron surface.
Before furnace 6, fast metallographic observation methods above is a feature is the use of nodular cast iron indirectly judge the spheroidizing, but the production of all kinds of conditions change, described methods have limitations, but in front of furnace fast metallographic observation can avoid the interference of many factors, more ground directly observed spheroidizing.
Second, the metallographic inspection after the furnace (
Metallographic examination after mainly observe microstructure such as graphite morphology and characteristics of metal matrix was inclusion through metallographic analysis can break a solid base for the change of casting quality.
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