Ductile Iron Casting Brackets

Cast iron brackets are usually made by ductile iron ASTM A536 Class 60-40-18 and 65-45-12. The weights are from several kilogram to ten kilograms. Small size to middle size with middle machining requirements. Why are most of cast iron brackets made by ductile iron, not by gray iron? It is because cast iron brackets are used on the trucks and vehicles, so they have to have good tensile strength and elongation. Of course, for the most of civil uses, the gray iron brackets are also good choices for the lower costs. The most suitable casting process for the cast iron brackets are the automatic molding line, which can assure the good quality and large production rate. The second choice should be shell molding process. Although the price of shell molding is higher than automatic molding line, the shell molding has better quality, surface quality and complex structures. Most important is, shell molding are suitable to small volume of cast iron brackets. The green sand floor molding is cheaper, but it is not suitable for cast iron brackets because of quality issues. As for the cast iron brackets, the most important consideration is not the surface quality, the prices, the machining precision, the painting, but the material quality and inside defects. The material quality means the tensile strength, elongation and the nodularity percentage. Bad materials will cause the danger in application. The most of compensation was caused by the material issues. The inside defects are also the important issue for cast iron brackets. Some positions are easy to have defects. Most of defects are shrinkage. Shrinkage is very harmful for iron brackets. So, you could inspect them by dissect the castings or X-ray flaw detector. Some clients want to inspect the shrinkage by ultrasonic flaw-detecting machine, but according to our experiences, the ultrasonic detectors are not suitable for iron castings, because they can not distinguish the low density, shrinkage and sand holes. Low density is allowable for a certain level to cast iron brackets.