First, the furnace before the test
Casting furnace before the test is an indispensable part of its production process, it is directly related to the quality of Nodular Graphite Iron Castings pieces. Timely and accurate judgment of the spheroidization of molten iron, you can quickly take measures to control the quality of Nodular Graphite Iron Castings. Misjudgment before the furnace will result in a large number of castings scrapped, waste modeling man-hour, so the furnace before the timely and accurate judgment of the ball than the furnace inspection is much more important. Actual production commonly used in the furnace before the test of iron liquid ballification of the following methods.
1 surface crust and flames judgment method
Rare earth magnesium Nodular Graphite Iron Castings containing low amount of magnesium, and rare earth elements, iron surface and pure magnesium Nodular Graphite Iron Castings 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 magnesium light and white flames, shaped like 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 fire, such as the height of 25 ~ ffice: smarttags "/> 50mm, that is good ball; if the flame is less than 15mm, the ball is poor. After the Nodular Graphite Iron Castings iron surface to see the formation of oxide film, and silver-white rolling highlights, that is good for the ball, but the oxide film is too thick, then the liquid temperature is low.
2 triangular test block method
At present, by observing the test block to determine the ballification is a commonly used method. The size of the test block used in the factory, the size of the different, the majority of factories using triangular test block. According to the characteristics of our production, the size and thickness of the castings, the cross-sectional area of the triangular specimen is 12.5mm (bottom) × 50mm (high), and some factories adopt round test blocks such as Ф15mm, Ф25mm and Ф30mm. After the liquid is finished with a sample spoon from the surface of the molten iron 200mm below the liquid and poured into the test block and cold to dark red side of the water can be quenched by the ball good ball than the gray cast iron is much larger appearance of clean and bright sand is usually Vertical pouring on both sides of the test block on both sides of the retraction of the top of the block or on both sides of the shrinkage of the test block cooling after the ball break good test, was silver or silver gray porcelain fracture tip white mouth clear middle of the loose if broken Silver-white and radial pattern of the ball is added to the high amount of carbide generated more time at this time when the test block issued a "pat" of the crack sound of the test piece flick is broken and the new mouth is very strong calcium carbide Odor so the best pouring when the floating silicon if the mouth was silver-gray and evenly distributed black spots if the broken crystal
3 to determine the casting process
(1) Nodular Graphite Iron Castings 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) During the pouring process, the sand-shaped surface splashing round flat iron beans with pitting (pits), indicating that the ball is 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, after quenching, if found on the surface of the test piece has a black side, then the ball is bad, and the thicker black The worse the worse, resulting in a 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 a wheat-like point, then said Iron liquid oxidation, easy to decline. In this case, the furnace should be modified.
5 observe the solidification 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. The ball of good iron liquid, solid during the show a great expansion of the graphite, iron liquid surface 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 stove before the rapid metallographic observation
All of the above methods are the use of Nodular Graphite Iron Castings 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.