Development

It is believed that early attempts to soften hard castings by reheating them, and the collection and publication of the results of these operations in 1722, by Reaumur, which led to the taking out of patents on the process by Lucas in 1804, comprised the early history of the malleable-iron industry Seth Boyden of Newark, New Jersey, produced the first malleable iron in America. It is recorded that in 1828, The Franklin Institute of Philadelphia, Pennsylvania, awarded him a premium for the best specimens of annealed cast iron. These were mainly harness trimmings.

Before 1890, the secrets of the process of malleableizing were closely guarded, which accounts for its slow growth, but since then great advances have been made both in quality and tonnage, due to a better knowledge of the principles involved. As the industry now stands it is farthest advanced in the United States. It is estimated that for the year 1907 the output for all Europe was but 50,000 tons as compared with a production of 980,000 tons in America for the same year.

It is rather surprising that, while there is more skill required to produce malleables - and there are several extra operations - the price is so little in advance of that for gray iron. This is accounted for in part by the large number of castings ordered from a given pattern.

Comparative Characteristics Of Metal

An idea of the value of this material is best obtained by a comparison of its properties with those of similar substances. Thus, gray-iron castings range from those nearly black in fracture, to white, with all degrees of softness up to glass hardness. They may be strong or weak and still serve their purpose. The desirable characteristics of the gray-iron casting is its extreme resistance to compression. Where great shock is to be cared for, great massiveness is required.

The steel casting has the highest strength of any cast metal: it may be deformed considerably without danger, and is cheaper than a corresponding forging.

The malleable casting is the connecting link between the two above mentioned. It is stronger than the gray casting but not as strong as cast steel. It can be bent or twisted considerably without breaking, and approaches gray iron in compressive strength; but its most valuable characteristic is resistance to shock. This property is best illustrated by the car coupler, a large number of drop tests having shown the value of the malleable coupler as compared with one of cast steel.