Usually, a small amount of spheroidizing agent (usually magnesium, rare earth magnesium alloy, or rare earth alloy containing cerium) and inoculant (usually ferrosilicon) is added to the molten iron prior to casting, resulting in the formation of spheroidal graphite after solidification of the molten iron. This kind of cast iron has higher strength and toughness than other cast irons. It can sometimes replace cast steel and malleable cast iron (malleablecastiron), and has been widely used in the machine building industry.
In 1947, ductile iron was used abroad for industrial production.
A. castings shall be subject to 100% dimensional inspection.
B. visual inspection, magnetic particle (MT), ultrasonic (UT) and radiographic (RT) nondestructive testing. Each RT delivery specification is ASTM-F186.
Because of the slow cooling of the cross section and the long solidification time of the metal liquid, the casting easily causes shrinkage of the internal casting. In order to obtain high tensile strength, yield strength and elongation of the past, have Cast Ferritic Nodular Iron, heat treatment temperature depends on the cast structure in the existence of free cementite and pearlite, and the use of 900-950 high temperature heat treatment. But the production cost is high, the process is complex, and the production cycle is long, which brings great difficulties to the production organization and delivery time, which requires the casting under the ferrite matrix. Therefore, the difficulty of producing this kind of material is mainly concentrated in the following aspects:
A. casting is the radiographic examination of the designated area and how to solve the internal shrinkage of the casting;
B, how to ensure more than 90% of the as cast ferrite matrix?;
C. how does the material have sufficient tensile strength and yield strength?;
How does D. obtain sufficient elongation (> 18%) after alloying treatment to obtain the desired elongation?;
E. uses the best alloying process