The Nodular Graphite Iron Castings furnace before the test is an indispensable part of its production process, it is directly related to the quality of ductile iron pieces. Timely and accurate judgment of the spheroidization of molten iron, you can quickly take measures to control the quality of ductile iron. Misjudgment before the furnace will result in a large number of castings scrapped, a waste of modeling man-hours, so the furnace before the timely and accurate judgment of the ball than the furnace test is much more important. Actual production commonly used in the furnace before the test of iron liquid ballification of the following methods.
1, the surface crust and flames judge method
Rare earth magnesium ductile iron containing low magnesium, and rare earth elements, iron surface and pure magnesium ductile iron is not the same, the surface is not so much oxide, the flames are not so much and powerful. But when the additional 1/3 iron liquid when the liquid will escape the light and white flames, shaped like a candle. According to the number of flames, the height of the ball to determine the situation and magnesium residue, the higher the flames, the more powerful, that the ball good. Especially in the pouring, from the molten iron flow can be seen in the flames, such as the height of 25-50mm, that is good spheroidization; if the flames less than 15mm, the ball is poor. From the surface of the dyed iron Nodular Graphite Iron Castings after treatment, the formation of oxide film, and silver white rolling highlights, that is good for the ball. But the oxide film is too thick, it means that the molten iron temperature is low.
2, triangular test block method
At present, by observing the test block to determine the spheroidization is a commonly used method. The factory use of the test block a lot of shapes, sizes vary, the majority of factories using triangular test block.
3, casting process to determine
(1) Ductile iron molten iron poured into the mold, such as the pouring cup has been down to the concave, and the surface is very smooth, that the ball good; such as the upper part of the gate cup layer of hard shell, but also concave, Iron liquid temperature is low.
(2) in the pouring process, the sand surface of the surface of the round flat iron beans splashing pits (pits), indicating that the ball good.
4, black border identification method
After the ball is finished, the sample spoon is poured into a test piece with a thickness of about 10mm, cooled to dark red, and after quenching, if there is a black side on the upper surface of the test piece, it indicates that the ball is bad and the thicker the black The worse, resulting in recession, this time, such as iron liquid temperature can add additional alloy. From the test block can be seen: such as the test block around the arc-shaped, and the middle of the depression, and some also have a road wrinkles, it also means that the ball good; such as the test piece on the surface of the wheat-like point, then said Iron liquid oxidation, easy to decline. In this case, the furnace should be modified.
5, observe the solid state of molten iron
After the ballification treatment, remove a small amount of molten iron, pour into the Ф30mm cylindrical metal type, observed during the solidification of molten iron from the surface of the phenomenon of emission, and according to the amount of molten iron to determine the iron liquid ballification situation. Spheroidized good iron liquid, solid during the show a great expansion of the graphite, the surface of the molten iron in the beginning of the solidification of some decline in the surface of the shell after a small amount of molten iron from the case of gushing; and spheroidized iron Surface emission is less.
6, the rapid observation before the furnace
All of the above methods are the use of ductile iron a certain degree of indirect decision to determine the situation, but the production of various conditions vary widely, the method has limitations, and the rapid observation of the furnace can be more to avoid many factors Interference, direct observation of the ball situation.