The first type of iron to ever be cast, grey iron, has had a long and illustrious history in our world. The earliest cast iron products were made in China, circa the 5th century BC. At that time, iron was cast into the form of weapons, simple pots, ploughshares and shot. Also, between the 9th and 4th centuries BC, people developed malleable iron casting. Malleable cast iron was much easier to manipulate. It is likely that the Chinese shared their cast iron process along the Silk Road. Despite this, Western Europeans didn’t begin iron casting until the 15th century AD. Artisans used the cast process to make heavy cannons for the British Royal Navy, per the instruction of Henry VIII.
Grey Iron Castings
Grey Iron Castings – OSCO Industries, Inc..
A few centuries later, in 1707, a British man named Abraham Darby discovered a way to cast iron pots with thinner walls. He used this to make cast iron cookware. Using the same method, other manufacturers made cast iron shields and some body armor parts. This use of iron casting for armor was popular through the mid-1700s.
In the 1770s, James Watt developed an atmospheric steam engine, updated from an earlier one by Thomas Newcomen, Watt’s steam engine made gray iron casting easier and the parts produced more accurate and higher strength.
Before steel, people used grey iron castings as structural components of bridges. They made the switch to steel in the early 1800s, as steel has much higher tensile strength and hardness. The use of grey cast iron proved more successful in the construction of buildings like textile mills. The iron construction helped prevent fires. Textile mills benefited from this in particular because they were filled with combustible fibers and flammable dust. The iron helped so much that, eventually, manufacturers began making their equipment from cast iron as well.
Throughout the last century, gray iron castings continued to be popular. In 1967, for example, gray iron was being cast at about two and a half times the volume of other cast metals. That year, manufacturers cast upwards of 14 million tons of gray iron products.
Today, though gray iron is among the oldest irons, it is still routinely cast. This is a testament to its usefulness. Within the last decade, manufacturers have greatly increased the dimensional control with which they can cast grey iron. They’ve also been able to improve the quality of thin sections. Dimensional control and product quality will only improve in the coming years, as manufacturers continue to perfect these practices. To make better parts, manufacturers are also working on mold surface treatments that allow them to skip post-casting mold blasting procedures. Skipping this step translates to quicker and less expensive casting. As always, they’re also looking into ways to strengthen gray iron.